Most of us are aware of some degree of warming; winters are warmer and spring comes earlier. But in the Arctic, warming is more than twice as great as here in Europe and in summertime, torrents of melt water now plunge from Greenland's kilometre-high glaciers. The complete dissolution of Greenland's icy mountains will take time, but by then the sea will have risen seven metres, enough to make uninhabitable all of the low lying coastal cities of the world, including London, Venice, Calcutta, New York and Tokyo. Even a two metre rise is enough to put most of southern Florida under water.
The floating ice of the Arctic Ocean is even more vulnerable to warming; in 30 years, its white reflecting ice, the area of the US, may become dark sea that absorbs the warmth of summer sunlight, and further hastens the end of the Greenland ice. The North Pole, goal of so many explorers, will then be no more than a point on the ocean surface.
Not only the Arctic is changing; climatologists warn a four-degree rise in temperature is enough to eliminate the vast Amazon forests in a catastrophe for their people, their biodiversity, and for the world, which would lose one of its great natural air conditioners.
The scientists who form the Intergovernmental Panel on Climate Change reported in 2001 that global temperature would rise between two and six degrees Celsius by 2100. Their grim forecast was made perceptible by last summer's excessive heat; and according to Swiss meteorologists, the Europe-wide hot spell that killed over 20,000 was wholly different from any previous heat wave. The odds against it being a mere deviation from the norm were 300,000 to one. It was a warning of worse to come.
What makes global warming so serious and so urgent is that the great Earth system, Gaia, is trapped in a vicious circle of positive feedback. Extra heat from any source, whether from greenhouse gases, the disappearance of Arctic ice or the Amazon forest, is amplified, and its effects are more than additive. It is almost as if we had lit a fire to keep warm, and failed to notice, as we piled on fuel, that the fire was out of control and the furniture had ignited. When that happens, little time is left to put out the fire before it consumes the house. Global warming, like a fire, is accelerating and almost no time is left to act.
So what should we do? We can just continue to enjoy a warmer 21st century while it lasts, and make cosmetic attempts, such as the Kyoto Treaty, to hide the political embarrassment of global warming, and this is what I fear will happen in much of the world. When, in the 18th century, only one billion people lived on Earth, their impact was small enough for it not to matter what energy source they used.
But with six billion, and growing, few options remain; we can not continue drawing energy from fossil fuels and there is no chance that the renewables, wind, tide and water power can provide enough energy and in time. If we had 50 years or more we might make these our main sources. But we do not have 50 years; the Earth is already so disabled by the insidious poison of greenhouse gases that even if we stop all fossil fuel burning immediately, the consequences of what we have already done will last for 1,000 years. Every year that we continue burning carbon makes it worse for our descendants and for civilisation.
Worse still, if we burn crops grown for fuel this could hasten our decline. Agriculture already uses too much of the land needed by the Earth to regulate its climate and chemistry. A car consumes 10 to 30 times as much carbon as its driver; imagine the extra farmland required to feed the appetite of cars.
By all means, let us use the small input from renewables sensibly, but only one immediately available source does not cause global warming and that is nuclear energy. True, burning natural gas instead of coal or oil releases only half as much carbon dioxide, but unburnt gas is 25 times as potent a greenhouse agent as is carbon dioxide. Even a small leakage would neutralise the advantage of gas.
The prospects are grim, and even if we act successfully in amelioration, there will still be hard times, as in war, that will stretch our grandchildren to the limit. We are tough and it would take more than the climate catastrophe to eliminate all breeding pairs of humans; what is at risk is civilisation. As individual animals we are not so special, and in some ways are like a planetary disease, but through civilisation we redeem ourselves and become a precious asset for the Earth; not least because through our eyes the Earth has seen herself in all her glory.
There is a chance we may be saved by an unexpected event such as a series of volcanic eruptions severe enough to block out sunlight and so cool the Earth. But only losers would bet their lives on such poor odds. Whatever doubts there are about future climates, there are no doubts that greenhouse gases and temperatures both are rising.
We have stayed in ignorance for many reasons; important among them is the denial of climate change in the US where governments have failed to give their climate scientists the support they needed. The Green lobbies, which should have given priority to global warming, seem more concerned about threats to people than with threats to the Earth, not noticing that we are part of the Earth and wholly dependent upon its well being. It may take a disaster worse than last summer's European deaths to wake us up.
Opposition to nuclear energy is based on irrational fear fed by Hollywood-style fiction, the Green lobbies and the media. These fears are unjustified, and nuclear energy from its start in 1952 has proved to be the safest of all energy sources. We must stop fretting over the minute statistical risks of cancer from chemicals or radiation. Nearly one third of us will die of cancer anyway, mainly because we breathe air laden with that all pervasive carcinogen, oxygen. If we fail to concentrate our minds on the real danger, which is global warming, we may die even sooner, as did more than 20,000 unfortunates from overheating in Europe last summer.
I find it sad and ironic that the UK, which leads the world in the quality of its Earth and climate scientists, rejects their warnings and advice, and prefers to listen to the Greens. But I am a Green and I entreat my friends in the movement to drop their wrongheaded objection to nuclear energy.
Even if they were right about its dangers, and they are not, its worldwide use as our main source of energy would pose an insignificant threat compared with the dangers of intolerable and lethal heat waves and sea levels rising to drown every coastal city of the world. We have no time to experiment with visionary energy sources; civilisation is in imminent danger and has to use nuclear - the one safe, available, energy source - now or suffer the pain soon to be inflicted by our outraged planet.
Friday, July 4, 2008
Global Warming(contd...)
Global warming has started affecting the Indian coastline with statistics suggesting a rising trend of 2.5 mm/year in the sea level in the region.
"The government is aware of the implication of the sea level rise due to projected climate change," Namo Narain Meena, Minister of state for Environment and Forests told Rajya Sabha in a written reply.
"Observations recorded by Indian Space Research Organisation (ISRO)/department of Space (DOS) on the mean sea level along the Indian coast show a long-term rising trend of about 1 mm/year," he said.
A high-level coordination committee, chaired by Prime Minister Manmohan Singh has been set up for assessment, adaptation and mitigation of climate change while the National Environment Policy 2006 addresses the issue of global warming, the minister said.
An "expert committee on impacts of climate change" was set up in May last year to study the impact of anthropogenic climate change on India and to identify the measures that may be needed to address its vulnerability, he said.
"The government is aware of the implication of the sea level rise due to projected climate change," Namo Narain Meena, Minister of state for Environment and Forests told Rajya Sabha in a written reply.
"Observations recorded by Indian Space Research Organisation (ISRO)/department of Space (DOS) on the mean sea level along the Indian coast show a long-term rising trend of about 1 mm/year," he said.
A high-level coordination committee, chaired by Prime Minister Manmohan Singh has been set up for assessment, adaptation and mitigation of climate change while the National Environment Policy 2006 addresses the issue of global warming, the minister said.
An "expert committee on impacts of climate change" was set up in May last year to study the impact of anthropogenic climate change on India and to identify the measures that may be needed to address its vulnerability, he said.
Anna University results
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The results seems to have out.The results can also be seen at these sites:http://www.worldcolleges.info/results-all/index.php
http://www.webdunia.com
The results seems to have out.The results can also be seen at these sites:http://www.worldcolleges.info/results-all/index.php
http://www.webdunia.com
Thursday, July 3, 2008
Global Warming
I need to ask for the reader's indulgence, as this post is not about autism, except insofar as determining the merit of correlations has become a perseveration of mine. You see, it is trivial to come up with naive correlations of autism trends vs. practically anything about the modern world. The administrative prevalence of autism has been increasing almost always since records have been kept. Concurrent upward trends of nearly anything, from vaccines to environmental pollution, from trans fats to electromagnetic radiation, and so on, are easy to come by.In my latest post at LB/RB I suggested that instead of correlating trends in a naive manner, we could attempt to correlate the residuals of time regression models of each trend. A residual is a delta or difference between an observed value and a modeled value. (Here's a concise explanation).When modeling real world phenomena, regression models will never (or almost never) be perfect fits. For all sorts of reasons, even if simply random fluctuation, there will be deviations from a modeled trend. If there's a causative relationship between two trends, the residuals of (or deviations from) corresponding close-fitting regression models should correlate with one another as well. By this I don't mean that the residuals should always be in the same direction; but they should be in the same direction more often than not, in average.The nice thing about this technique is that it is completely accessible to anyone with Excel installed. It can also be illustrated graphically, as the reader will see.So it occurred to me to test this idea in a different field of science where there's controversy over correlation vs. causation. I thought global warming would be a great candidate. After all, the spoof about a decrease in the number of pirates correlating with many other arbitrary trends appears to originate in the global warming debate (see this).To summarize what I found, there is a strong and statistically significant correlation between cumulative human CO2 emissions and northern hemisphere temperature anomalies. Because of the methodology used, I'm quite confident this cannot be explained by coincidence, data collection errors, solar output as a confound, or causation in the opposite direction.Now, I fully recognize that I'm only superficially familiar with the debate over anthropogenic global warming. I am also not versed in climatology. Therefore, I cannot be entirely sure that this type of analysis hasn't been done before. Google and Google Scholar searches didn't seem to turn up anything, and given the importance of the topic, I thought it was not only prudent but necessary to put this evidence out there. As always, scrutiny and discussion are welcome.Northern hemisphere temperature data from 1850 to 2004 was obtained from the Climatic Research Unit of the University of East Anglia, UK.Global CO2 emission data was obtained from CDIAC. I did not use CO2 atmospheric concentration data because temperature increases can theoretically cause this concentration to increase. Human emissions are what we're interested in. More specifically, I calculated cumulative CO2 emissions for every year since 1850. Greenhouse temperature anomalies are presumably caused by the total amount of CO2 in the atmosphere, not by the emissions in any given year. Since CO2 stays in the atmosphere for 50 to 200 years (source) modeling the cumulative human contribution of CO2 should be adequate enough.Figure 1 (click to enlarge) is a graph of the general time trends of these two sets of data. It also shows the modeled trend lines we will use to calculate residuals. In this analysis we're using third-order polynomial models. They seem to give a considerably closer fit than second-order polynomial models. I calculated the residuals and built a scatter graph matching cumulative CO2 (X axis) and temperature (Y axis) residuals for each year from 1850 to 2004. As expected, the slope of a linear regression of the scatter was positive (1.9x10-5) and statistically significant (95% confidence interval 1.13x10-5 to 2.66x10-5).[Note: Instructions on how to calculate the slope confidence interval of a linear regression with Excel can be found here.]I suspected, however, that there should be lag between cumulative CO2 fluctuations and temperature fluctuations. It presumably takes some time for heat to be trapped. I proceeded to create a moving average trend line of the temperature residuals. It did in fact have a similar shape to the cumulative CO2 residuals graph, but it appeared to lag it by about 10 years. The reader should be able to roughly see this lag in Figure 1. So I re-ran the whole analysis by only considering the years 1850 to 1997 and correlating CO2 residuals with residuals of temperature 10 years later. The correlation between these two sets of data is remarkable. Let's start with a bar graph of both sets of residuals, Figure 2.Figure 2 is a good graph to get a subjective sense of the correlation. Let's see if the math confirms this. Figure 3 is the scatter graph of the residuals. The slope of a linear regression of the scatter is 2.6x10-5, and it is statistically significant (95% confidence interval 1.88x10-5 to 3.33x10-5). Even the 99.99999999% confidence interval is entirely positive. Unless anthropogenic global warming is a reality, there is no apparent reason why the residuals of cumulative human CO2 emissions should correlate so well with the residuals of temperature 10 years later throughout the last 150 years.The slope of the scatter is actually more steep than expected, if you consider the naive correlation between cumulative CO2 emissions and temperature. There are probably several reasons for this. The one I believe to be the most likely is that over time CO2 does get removed from the atmosphere. Adding this consideration to the analysis should produce a more accurate slope. The other potential reasons don't bode so well for our species.
Wednesday, July 2, 2008
SDk
Since the MPSDK 1.2 was launched on Jul. 24 during Open Source Convention in Portland, we met some users and customers asking about Linux version. MPSDK is a multiple platform/OS based software stack, but we don't have Linux version in current release because the project was started several years ago major on PC (laptop) which was not common for user to select Linux.
Now Linux is more used in mobile device with improved usibility. Intel is also contributing to build the next generation mobile platform of UMPC and MID. Linux will be an important platform extension for MPSDK. The team will work to make it happen for MPSDK Linux version, like power, display, connectivity, bandwidth management, etc. The consistent programming interface with Windows will also simplify application development and save cost for porting.
As an open source project, any feedback or input is welcome to help us improve the features as well as usage.
Now Linux is more used in mobile device with improved usibility. Intel is also contributing to build the next generation mobile platform of UMPC and MID. Linux will be an important platform extension for MPSDK. The team will work to make it happen for MPSDK Linux version, like power, display, connectivity, bandwidth management, etc. The consistent programming interface with Windows will also simplify application development and save cost for porting.
As an open source project, any feedback or input is welcome to help us improve the features as well as usage.
Wetlands impact
Tune in to WYPR 88.1 FM in Baltimore at 9:35 a.m. tomorrow morning (Wednesday, May 14) to hear my next "Environment in Focus" radio show. This segment will be called "Wetlands and Global Warming."
If you aren't going to be listening to your radio at that time, you can listen anytime by clicking here.
The program will talk about the research of two scientists who are conducting cutting-edge studies on wetlands on opposite sides of the Chesapeake Bay: Brian Needelman of the University of Maryland, who's working at the Blackwater Wildlife Refuge on the Eastern Shore; and Carl Mitchell of the Smithsonian Environmental Research Center, whose studying Kirkpatrick Marsh south of Annapolis.
Needelman (below) proposes that building wetlands would be a great tool in fighting global warming. Marsh grass absorbs carbon dioxide as it grows. So if polluters (like power companies) were required to build large new wetlands, that might "offset" some of the damage done by their pollution.
Brian Needelman at the Blackwater National Wildlife Refuge on Maryland's Eastern Shore. (Sun photo by Doug Kapustin)
But Mitchell (below) raises warnings about the possibility that building vast new marshes could worsen mercury contamination in fish. That may sound odd, because wetlands are often seen as purely good in an ecological sense. But Mitchell and other researchers are documenting how marshes transform air pollution from coal-fired power plants into methylmercury, which accumulates in fish and can cause brain damage in people.
If you aren't going to be listening to your radio at that time, you can listen anytime by clicking here.
The program will talk about the research of two scientists who are conducting cutting-edge studies on wetlands on opposite sides of the Chesapeake Bay: Brian Needelman of the University of Maryland, who's working at the Blackwater Wildlife Refuge on the Eastern Shore; and Carl Mitchell of the Smithsonian Environmental Research Center, whose studying Kirkpatrick Marsh south of Annapolis.
Needelman (below) proposes that building wetlands would be a great tool in fighting global warming. Marsh grass absorbs carbon dioxide as it grows. So if polluters (like power companies) were required to build large new wetlands, that might "offset" some of the damage done by their pollution.
Brian Needelman at the Blackwater National Wildlife Refuge on Maryland's Eastern Shore. (Sun photo by Doug Kapustin)
But Mitchell (below) raises warnings about the possibility that building vast new marshes could worsen mercury contamination in fish. That may sound odd, because wetlands are often seen as purely good in an ecological sense. But Mitchell and other researchers are documenting how marshes transform air pollution from coal-fired power plants into methylmercury, which accumulates in fish and can cause brain damage in people.
Greenhouse Gardening
Some of my favorite and earliest memories are those of being around greenhouses. I remember visiting my Granddad every weekend in London, England. He lived in an apartment in London and all the residents had their own little garden out the back. My granddad had built a fish pond and greenhouse in his little garden, both were well used. And the best thing about going to visit Granddad for Sunday dinners was that the first thing I got to do was run out to his little garden and feed the big goldfish in his pond. I knew that he kept the goldfish food and garden pond supplies up high on a shelf just above the greenhouse bench that was inside his greenhouse, so I would reach for the food and head over to the garden pond to feed the fish. They were huge, and were trained to “kiss” your fingers when you gently floated you hand on the surface of the water! My parents also rented a small plot of land when I was growing up in England where my siblings and I spent many evenings playing while they dug, planted and weeded their vegetable patch. We had a greenhouse that enabled us to get the seedlings going, and would provide us with amazingly fresh vegetables that were bursting with flavor all year through!
It’s not surprising that my love affair with greenhouses has continued into my adult life! Owning a greenhouse has been a way of providing my own children with quality, fresh and mostly organic fruits and vegetables. It is important to know that there is a little bit of knowledge required to cultivating plants in a greenhouse environment; it is a little bit more involved that just putting up a protective structure in your garden and throwing some plants in there! You need a greenhouse plan. These are some of the elements that must be considered in order to really get the maximum potential out of your greenhouse or sunroom: the type of greenhouse you want whether it be a cold house, portable greenhouse, hobby greenhouse a greenhouse kit or a large or a mini greenhouse, the greenhouse construction and it’s foundation type, which greenhouse equipment you will need, which type of greenhouse covering or glazing is best suited to you, and the type of watering, humidity control, heating and air circulation systems that are best suited to your sunroom or greenhouse gardening needs.
First Decide Whether you Want to have Cold House or a Heated Greenhouse.
A cold house is the simplest of greenhouses, it is not equipped with any artificial means of heat and thus the growing season is shortened when the outside temperature drops below freezing. It is not possible to grow frost sensitive plants between late fall and the middle of spring unless you provide heat (which would not make it a cold house!). A cold house does extend the growing season from that of the outdoors by trapping the heat from the sun during the day. And it provides a cozy respite for you to work away from the elements of wind and rain, it also protects plants from these same elements too. When you install a heater into your cold house it becomes a true greenhouse and it transforms the hobby of gardening into a year-round hobby. The minimum temperature required to grow greenhouse plants through the winter is 45° F (7.2°C), so be sure to allow for this extra cost for heating to be included in your monthly budget. Also, be sure that when you begin planning for your greenhouse construction that you build it as near as possible to your house as this will reduce costs for digging and installation of electrical wires (and plumbing if you need that too). It is also better for quick access during the winter months if you have your greenhouse closer to your house.
Choosing between a Portable Greenhouse, Hobby Greenhouse a Greenhouse Kit, Sun Room Kit or a Large or a Mini Greenhouse
There is truly a wide variety of different styles and types of greenhouses on the market today. Each is suited to a different need or want and degree of seriousness for greenhouse gardening. When you build a greenhouse from scratch with a foundation you are probably a serious gardener with great expectations from your greenhouse. But, for the less serious greenhouse gardener there are smaller versions of greenhouses and sunrooms available that come in the form of portable greenhouses, a hobby greenhouse or mini greenhouses. Each online greenhouse manufacturer and distributor will have their own specifications and recommendations for each and it is best that you do your own research to decide which is best for you.
A Greenhouse Foundation is Truly the “Foundation” of any Sunroom!
A greenhouse is a structure that creates a protected environment for plants to grow in, thus extending the productive lives of plants. It is therefore important that someone intent upon greenhouse gardening learns as much as possible about maximizing the uses of his or her sunroom. The first step in greenhouse construction is ensuring that your greenhouse or greenhouse kit will be solid and functional for many years to come is to make sure that it has a good and solid foundation. It is important to decide whether you want a concrete foundation or whether you want to have a soil foundation. A soil base in a greenhouse has many advantages, and allows you to grow larger plants straight from the ground. Just make sure that the drainage in the area that you are going to build your greenhouse is good, and test the soil to make sure that it contains good nutrient rich soil. If you need to replace the soil, it is better to do so before you begin construction of the greenhouse rather than after! In order to prevent the floor, or the soil, in your greenhouse foundation from freezing or getting cooler during the winter season it is important to insulate the perimeter of your foundation with a 1- 2 inch Styrofoam board that goes about 2 feet deep all around the outside edge of your foundation.
The Best Type of Greenhouse Covering or Glazing
The next most important consideration for the functionality and long term endurance of greenhouses is the glazing that you use. The glazing is usually the most expensive part of your greenhouse, but this is the feature that will let the very important light that makes your plants grow into your sunroom. Different types of glazes will give you different growing effects. The most common types of glazes are plastic sheets or glass. Most greenhouse kits are easily available at online stores and they come with polycarbonate plastic glaze. Always make sure that the greenhouse covering or glazing you choose is UV stabilized in order to better protect your plants. It is important to know whether you are getting single, double or triple thick glaze as you should avoid the single-pane glazes. Single-pane glass or plastic gets too hot in the summer and too cold in the winter, thus it will not be of much benefit to your greenhouse growing environment. Double pane or triple pane glazes will suffice much better and will last many years longer. Always remember that cheap upfront can be expensive later on!
Light and Photosynthesis
Photosynthesis is the name given to the process that converts light into energy (or into sugar in the case of plants). In order for photosynthesis to occur the following requirements must be provided: light, a temperature that is optimally between 32°F (0°C) and 100°F (37.7°C), carbon dioxide (CO2) and water. The key to greenhouse gardening is to keep all of these factors in optimum balance, and by doing so it is possible to maximize plant growth. The glazing that you choose to cover your greenhouse can greatly affect the photosynthesis process. Studies have shown that plants grow better under glass or plastic that is not clear. Glazings that have smoky appearance to them; that you cannot see through clearly, are advantageous as they scatter the light that enters a greenhouse. This gives a more even distribution of light and thus gives more total light to plants. When light goes through clear glass shadows are created in a greenhouse, which causes some plants to get more light than others.
This is an important consideration if you are looking to maximize growth for all plants in your green house. The best type of material for diffusing light is fiberglass, then polyethylenes, polycarbonates and finally acrylics. Glass is not good for diffusing light; it is also not as resistant to breakages and temperature fluctuations.
A Word about Greenhouse Kits and Sunroom Kits
Greenhouse kits and sunroom kits offer a wonderful alternative for people who don’t have the expertise or the time to build their own green house from scratch. A green house kit is a new phenomenon of the last few years and because of the fact that most people have very busy schedules these days it is no wonder that their sales are sky rocketing! They are also very easy to source at online garden stores and are usually cheaper on the internet too. Most online garden supplies stores offer very good technical support to help you through the greenhouse construction experience! Most greenhouse kits and sunroom kits are constructed with aluminum, PVC or wooden frames. Just remember that the reason you bought a kit was probably due to lack of time to build one from scratch, and keep in mind that all outside wood structures need regular maintenance, i.e. staining or painting. So it is recommended that you buy aluminum or PVC if you want maintenance free! If you do want to go with an aluminum frame be sure to ask if there are thermal breaks in it, these will make sure that the outside metal is not in direct contact with the inside metal which will help ensure that the inside of your greenhouse stays as warm as possible during the winter months.
Watering Needs for Greenhouse Plants
As it does not rain inside greenhouses watering is a very important thing for greenhouse owners to remember! But, watering inside a green house is not just as simple as just watering your greenhouse plants everyday. Within soil there are small open air pores that roots depend on for supplying them with nutritious gases. When you water your plants these small air spaces get filled up with water and it, in effect, causes suffocation for roots. When roots suffocate, plants wilt and the most common reaction by gardeners for wilting plants is more watering! Just remember that the watering needs inside a greenhouse are different from the watering needs of your outside garden. Because the green house environment is enclosed a fair amount of moisture does get trapped and thus, less watering is usually required. The best rule for watering plants in your greenhouse or sunroom is: always check the soil before you water, if the soil is dry then you should go ahead and water. And, remember that plants, just like people, do not like being watered with cold water. For plants the ideal water temperature is between 65°F and 80°F (18.3°C and 26.7°C). Anything above 80°F (26.7°C) is too hot!
There are many different alternatives available for watering your greenhouse plants. Among your choices are irrigation systems, drip system, misters, water sensors and a gardener’s best friend the good old watering can. Irrigation systems are wonderful for those periods of time that you plan on being away; there is nothing worse than coming home to dead plants in your green house because your best friend forgot to water them while you were away! A good selection of all of these watering systems is available at online gardening and greenhouse supply stores.
Humidity Requirements in a Greenhouse
All plants have small open pores in their leaves through which gases such as oxygen, and CO2 pass. Water vapor is also emitted through these pores as plants do not use all of the water that they soak up. The accumulation of water vapor is called humidity and relative humidity is the term that describes the quantity of water vapor present in the air. Air temperature affects the amount of water vapor in the air and it is this relationship between air temperature and the quantity of water vapor present that gives us the term relative; for example: the quantity of vapor present is relative to the current air temperature! It is possible to measure the humidity of air with an instrument called a hygrometer.
It is important to know what the humidity is in a greenhouse as most plants grow best between a certain range of relative humidity. The best range or humidity for green house plants is between 45 and 60 percent. Knowing your relative humidity also enables you to control your greenhouse growing environment as humidity that is too high (above 80%) encourages the growth of mould both on plants and within your greenhouse. Plant moulds will destroy plants and will cause rot to occur in any wooden structures within your sunspace (which can be very detrimental if you have a wood frame greenhouse or sunroom or if you have wood shelving or a wood green house bench). Moulds are also usually a great concern as they cause disease.
It is more common for greenhouses to have a problem with high humidity rather than low humidity. If you have a high humidity problem in your green house some remedies are: to increase circulation by installing a fan, water earlier in the day to help prevent evening humidity problems (as moulds grow at night time), water only when the plants need it, buy an air-to-air heat exchanger which exchanges warm moist air with cool and dry air, or put in a ventilation system by which moist air can escape. If the humidity in your greenhouse or sunroom is too low it is much easier to fix than a high humidity problem. The easiest and best solution is to water more often. It is also very easy to buy greenhouse humidifiers that will easily increase your sun room humidity. These types of humidifiers are easily available at online green house supply stores.
Carbon Dioxide in the Greenhouse Environment
My seven year old son came home from school recently and announced “Mom, did you know that trees make oxygen from carbon dioxide?” It was a great time to teach him a lesson about how plants use carbon dioxide (CO2) and how they emit oxygen as the end result of this chemical exchange or reaction.
Since the early 1900’s scientists have been able to measure the amount of CO2 that is present in the air. It was discovered that the normal level of carbon dioxide in the air is about 300 parts per million (ppm). CO2 is essential to photosynthesis and thus it must be present in the air at least in at least 300 ppm in order for plants to grow properly. When CO2 is deficient in the air plants simply do not grow, their growth is very slow and stunted. It is also actually possible to speed plant growth up by increasing CO2 levels in the air. The simple addition of CO2 to the air is as good as adding fertilizer to your plants. Most plants grow with a yield increase of ten to thirty percent when the CO2 levels are between 1,200 to 1,500 parts per million. Note that anything above 2,000 ppm is not used by plants and it will not increase their growth beyond that point.
The reason that we need to know about CO2 is that depletion of CO2 can be and usually is a big problem in greenhouses and sunrooms. When plants are raised in a sealed environment as usually happens when you keep all the vents and windows closed in the winters, it is very easy for them to deplete the air of CO2. Plants that are raised in our residences have access to the CO2 that we and our pets breathe out as a waste product and to the air that comes in through open doors and windows. But, in the crowded plant environment of a sealed greenhouse or sunroom CO2 can actually be depleted within one day if measures are not taken against this!
The first action to help with reducing CO2 depletion for plants in green houses is to realize that a plant produces oxygen through it’s leaves, and the oxygen actually sits on and around the leaves unless the gentle breezes of nature comes by and blows it away! Then the leaf pores are introduced to the CO2 that the breeze just circulated to them and they are able to access it as the oxygen is no longer “blocking” their pores. We know, of course, that nature’s gentle breezes do not enter sealed greenhouses! Thus, we need to create some type of a “breeze” system within our greenhouses to circulate the oxygen away from the leaf surfaces and introduce the CO2 that is in other areas of the greenhouse. The simplest way to do this is to introduce a fan to your green house or sun room; either a floor fan or a ceiling fan works very well! Note: that you can turn the fans off at night as plants do not utilize CO2 in the absence of light.
A second step is to consistently introduce organic matter to your soil as the microbes and bacteria in decomposing matter is living and breathing and provides the air with it’s waste product; which just happens to be CO2! The amount of CO2 that organic matter introduces can also be depleted quickly, so the installation of fans is still necessary. It is also interesting to note that some people with a bigger greenhouse space that permits the keeping of a rabbit in a hutch or chickens in a cage will do so in order to supply their greenhouse plants with extra CO2! The most important thing to remember here is that you will need to allow for the extra work of cleaning out a rabbit hutch or a chicken cage as they get quite smelly quickly and the excess ammonia in the air will not be good for your plants or pleasant for you either! So if you’ve ever entertained the idea of having a pet rabbit for either you or your kids this may be your chance providing you are prepared to clean out a cage about once every 5-8 days. (or this could be a great opportunity to teach an older child some responsibility and add a chore to their list!)
Proper Balance of pH Levels for Maximum Greenhouse Plant Growth
Healthy soil is required for good plant production and healthy soil is created when it has a proper pH! There are a few aspects to creating and maintaining healthy soil and a proper pH balance. If the pH level is off balance then it is impossible for the critical nutrients necessary for plant health to survive in soil. The pH describes what the level of acidity is in your soil. The pH scale is based on a scale of 1-14, with 7 being the mid-point or the neutral point. Soil that is from pH 0 to pH 7 is considered acidic, and soil that is from pH 7 to pH 14 is considered alkaline, or basic. It is best to keep your soil as close to 7 as possible.
Greenhouse gardeners are wise to test the pH levels in their soil and pH test kits are easily available at online green house supply stores. If your soil is too acidic (low pH) it is best to add limestone or wood to your soil, and if it is too alkaline (high pH) it is best to add compost material (avoid manure), sulfur or acidifying plant foods that are available commercially. A properly balanced pH will ensure that the correct nutrients are available for your plants to properly root and utilize the minerals in the soil that are required for maximum growth. It also ensures that the healthy and beneficial microbes that live in soil can survive and help plants grow. Healthy microbes are important in controlling diseases and they also feed on bad microbes such as parasites too. When good microbes cannot survive in soil the bad microbes will take over and thus there is a greater chance of disease and pests entering the greenhouse environment. This is not unlike the good bacteria/bad bacteria that live in the human bowels, we need to keep these in balance too in order to prevent disease from entering the human body!
Heating Needs in a Greenhouse
Scientists have proven that the optimal growing temperature for most plants is between 50°F (10°C) and 85°F (29.4°C). This is a big temperature range and your consistent temperature target is really dependent upon the type of plants that you are growing in your greenhouse. If you have mostly seedlings then it is useful to note that seedlings thrive in warmer temperatures. If you have mostly mature plants then aim for a cooler temperature target. If the temperature gets above 85°F (29.4°C) then you will get plant growth problems such as slower growth and flower drop which will prevent flowers from setting and producing fruit. If temperatures get too low you will see much of the same problems as when the temperature gets too high. Temperature is vitally important to plants as it affects everything in their life cycle; photosynthesis, cell division, water intake, nutrient uptake, etc. It is thus, vitally important that we manage the temperature in a greenhouse so that we can assist our plants to grow at their maximum potential.
Here are four ways to supply a heat source to greenhouses; portable heaters, hot water pipes, wired in electrical heat or solar heating. Each has their own benefits and each has their downfall! Portable heaters are a wonderfully quick and easy way to add heat to a greenhouse or sunroom; they can be powered by natural gas, electricity, propane, wood, oil or kerosene. The biggest downfall with the gas, oil, wood or kerosene heaters is that whenever you burn them they emit gases that are harmful to plants so you absolutely must have some kind of a ventilation system that carries these emissions away and out of your greenhouse. Be careful that your venting system is not in direct contact with the skin on your greenhouse if it is made out of plastic as the heat from the ventilation system can melt the skin or in cases of excessive heat could actually cause it to melt! Also, check on the recommended size of heater for the size of your greenhouse. Most manufacturers will give you a recommendation for the maximum and minimum heating space that their heaters will heat.
Hot water systems are best installed by professional welders and plumbers. They are often custom made to fit the size of your greenhouse and usually consist of a system of pipes that run around the inside walls of your sunroom. They are attached to a water intake system and a pump that circulates the water through the pipes. Although the initial heating of the water in the pipes is a little costly, once the water in the pipes is hot it retains its heat very well which is where the cost reduction in hot water systems comes into place.
Electric heating in a greenhouse is an amazing concept in “how to very easily heat a greenhouse” – you turn the dial! The only problem is that electric heat in a greenhouse can get very, very expensive in the winter. The other major problem that you need to consider with electric heating is what your back up plan will be if there is a power outage. Remember that if you lose power in the middle of a winter freeze you could actually lose all of your plants overnight! The best device for “watching” greenhouse temperatures is a ‘temperature alarm’ that is made specifically for greenhouses. This nifty little device will set off an alarm as soon as the temperature in your greenhouse or sun room goes below a level that you preset into it. When this happens you will know that either your power has gone out or you just need to turn up the heat! In cases of power outages perhaps the best back up plan is to purchase your very own generator that can power a portable heater or two inside the green house or sunroom until the power comes back. Another very wise investment is to purchase some solar heating panels for your greenhouse, these will generate enough heat through a power outage in the winter to prevent freezing, although they will not usually generate enough heat to keep a greenhouse warm through a long freeze. Solar heating panels will prevent you from losing the majority of your plants in a short power outage during a freeze.
Solar heating is a very cost efficient way of heating your greenhouse if you set it up properly and design your green house to use solar heating efficiently. The most important thing to consider when first designing your sunroom or green house construction is to decide upon it’s location in your garden. To maximize the usage of the sun’s energy it is best that you orientate your greenhouse to have its long side face within 20 degrees of either side of true south. And in order to utilize larger solar panels it is best to have the greenhouse be 2 or 3 times longer than it is wide. Other ways to ensure solar heating is maximized is to make sure your greenhouse is airtight, so that it doesn’t lose it’s heat through leaks. Make sure that your glaze is double or triple glazing to help reduce heat loss. Insulate the walls of the greenhouse to prevent heat loss, this is especially useful on the north wall where most heat loss will occur; and the easiest way to insulate this wall is to buy bubble insulation in rolls (the kind of bubble wrap that packages come wrapped in for protection in the mail). Some green house supply stores carry clear bubble greenhouse insulation. Spray a glue adhesive to the inside of your glazing and press your pre-cut bubble insulation up against the adhesive until it sticks. Earlier in this article we talked about insulating the foundation of your greenhouse with 1-2 inch thick styrofoam board, and this is another way to prevent heat loss from your greenhouse – especially if you choose to go with solar heating panels.
Selecting the Right Seeds and Plants for Your Greenhouse
When it comes to selecting seeds and plants for your greenhouse the biggest deciding factor is your personal choice! You will need to set up your greenhouse interior to accommodate the types of plants that you choose though. For example if you choose to grow plants that require a trellis you will have to install some trellises. Some examples of plants that grow well with a trellis are peas, runner beans, tomatos, cucumbers, watermelon, winter squash, nasturtiums, passionflower, bougainvillea and sweet peas. Some crops are harvested only once and then they are done; for example onions, carrots and radishes. Other crops that need harvesting many times; for example leaf lettuce, strawberries, broccoli and brussel sprouts should be placed in easy to reach places, like at the edges of beds.
Buy a good book on greenhouse gardening so as to learn about the different temperature, water, humidity and pH level requirements of different plants and then make your final selections of seeds and plants. A greenhouse gardener’s book will also help you with the best layouts for your plants and seedlings.
As a final note on buying seeds and plants for your greenhouse please be aware that it is very advantageous to buy them from online greenhouse supply stores and online seed catalogues as they are coming directly from “the source” in most cases! This means that the seeds and plants are usually fresher and have been stored correctly while in storage as a lot of online stores are based directly from farms and growing facilities. The selection and varieties of seeds and plants that are available at online stores are unequalled. You will be delighted with the selection and the information that is available for each plant or seed selection that you choose at online green house supply stores and seed or plant catalogues. Customer service at these stores is also exceptional. Most online gardening stores offer free shipping once an order hits a certain dollar amount too!
Buying a Green house is Investing in a Therapeutic Activity!
There is nothing like “getting down with the dirt” to really melt away the stress of a busy day. Gardening is a cleansing and therapeutic way to spend your time, it enables us to get in touch with nature, and it’s no wonder that it is one of the most popular leisure activities that people list in their resumes and on questionnaires. I have a doctor friend who advises his patients to run barefoot on the beach to unwind and let stresses melt away, I find that gardening and greenhouse gardening does the same thing for me!
If you invest some time in researching greenhouse construction, types of greenhouses and sunrooms available such as greenhouse kits, sun room kits, hobby greenhouses, large or mini greenhouses and portable green houses you will be sure to start an adventure of a lifetime! Remember to learn all that you can about greenhouse equipment, which type of greenhouse covering or glazing is best suited to you, and the type of watering, humidity control, heating and air circulation systems that are best suited to your sunroom or greenhouse gardening needs. Time invested in greenhouse gardening before you actually start your green house construction will be time well spent, and will ensure that you get maximum stress relief and enjoyment out of your greenhouse hobby!!
It’s not surprising that my love affair with greenhouses has continued into my adult life! Owning a greenhouse has been a way of providing my own children with quality, fresh and mostly organic fruits and vegetables. It is important to know that there is a little bit of knowledge required to cultivating plants in a greenhouse environment; it is a little bit more involved that just putting up a protective structure in your garden and throwing some plants in there! You need a greenhouse plan. These are some of the elements that must be considered in order to really get the maximum potential out of your greenhouse or sunroom: the type of greenhouse you want whether it be a cold house, portable greenhouse, hobby greenhouse a greenhouse kit or a large or a mini greenhouse, the greenhouse construction and it’s foundation type, which greenhouse equipment you will need, which type of greenhouse covering or glazing is best suited to you, and the type of watering, humidity control, heating and air circulation systems that are best suited to your sunroom or greenhouse gardening needs.
First Decide Whether you Want to have Cold House or a Heated Greenhouse.
A cold house is the simplest of greenhouses, it is not equipped with any artificial means of heat and thus the growing season is shortened when the outside temperature drops below freezing. It is not possible to grow frost sensitive plants between late fall and the middle of spring unless you provide heat (which would not make it a cold house!). A cold house does extend the growing season from that of the outdoors by trapping the heat from the sun during the day. And it provides a cozy respite for you to work away from the elements of wind and rain, it also protects plants from these same elements too. When you install a heater into your cold house it becomes a true greenhouse and it transforms the hobby of gardening into a year-round hobby. The minimum temperature required to grow greenhouse plants through the winter is 45° F (7.2°C), so be sure to allow for this extra cost for heating to be included in your monthly budget. Also, be sure that when you begin planning for your greenhouse construction that you build it as near as possible to your house as this will reduce costs for digging and installation of electrical wires (and plumbing if you need that too). It is also better for quick access during the winter months if you have your greenhouse closer to your house.
Choosing between a Portable Greenhouse, Hobby Greenhouse a Greenhouse Kit, Sun Room Kit or a Large or a Mini Greenhouse
There is truly a wide variety of different styles and types of greenhouses on the market today. Each is suited to a different need or want and degree of seriousness for greenhouse gardening. When you build a greenhouse from scratch with a foundation you are probably a serious gardener with great expectations from your greenhouse. But, for the less serious greenhouse gardener there are smaller versions of greenhouses and sunrooms available that come in the form of portable greenhouses, a hobby greenhouse or mini greenhouses. Each online greenhouse manufacturer and distributor will have their own specifications and recommendations for each and it is best that you do your own research to decide which is best for you.
A Greenhouse Foundation is Truly the “Foundation” of any Sunroom!
A greenhouse is a structure that creates a protected environment for plants to grow in, thus extending the productive lives of plants. It is therefore important that someone intent upon greenhouse gardening learns as much as possible about maximizing the uses of his or her sunroom. The first step in greenhouse construction is ensuring that your greenhouse or greenhouse kit will be solid and functional for many years to come is to make sure that it has a good and solid foundation. It is important to decide whether you want a concrete foundation or whether you want to have a soil foundation. A soil base in a greenhouse has many advantages, and allows you to grow larger plants straight from the ground. Just make sure that the drainage in the area that you are going to build your greenhouse is good, and test the soil to make sure that it contains good nutrient rich soil. If you need to replace the soil, it is better to do so before you begin construction of the greenhouse rather than after! In order to prevent the floor, or the soil, in your greenhouse foundation from freezing or getting cooler during the winter season it is important to insulate the perimeter of your foundation with a 1- 2 inch Styrofoam board that goes about 2 feet deep all around the outside edge of your foundation.
The Best Type of Greenhouse Covering or Glazing
The next most important consideration for the functionality and long term endurance of greenhouses is the glazing that you use. The glazing is usually the most expensive part of your greenhouse, but this is the feature that will let the very important light that makes your plants grow into your sunroom. Different types of glazes will give you different growing effects. The most common types of glazes are plastic sheets or glass. Most greenhouse kits are easily available at online stores and they come with polycarbonate plastic glaze. Always make sure that the greenhouse covering or glazing you choose is UV stabilized in order to better protect your plants. It is important to know whether you are getting single, double or triple thick glaze as you should avoid the single-pane glazes. Single-pane glass or plastic gets too hot in the summer and too cold in the winter, thus it will not be of much benefit to your greenhouse growing environment. Double pane or triple pane glazes will suffice much better and will last many years longer. Always remember that cheap upfront can be expensive later on!
Light and Photosynthesis
Photosynthesis is the name given to the process that converts light into energy (or into sugar in the case of plants). In order for photosynthesis to occur the following requirements must be provided: light, a temperature that is optimally between 32°F (0°C) and 100°F (37.7°C), carbon dioxide (CO2) and water. The key to greenhouse gardening is to keep all of these factors in optimum balance, and by doing so it is possible to maximize plant growth. The glazing that you choose to cover your greenhouse can greatly affect the photosynthesis process. Studies have shown that plants grow better under glass or plastic that is not clear. Glazings that have smoky appearance to them; that you cannot see through clearly, are advantageous as they scatter the light that enters a greenhouse. This gives a more even distribution of light and thus gives more total light to plants. When light goes through clear glass shadows are created in a greenhouse, which causes some plants to get more light than others.
This is an important consideration if you are looking to maximize growth for all plants in your green house. The best type of material for diffusing light is fiberglass, then polyethylenes, polycarbonates and finally acrylics. Glass is not good for diffusing light; it is also not as resistant to breakages and temperature fluctuations.
A Word about Greenhouse Kits and Sunroom Kits
Greenhouse kits and sunroom kits offer a wonderful alternative for people who don’t have the expertise or the time to build their own green house from scratch. A green house kit is a new phenomenon of the last few years and because of the fact that most people have very busy schedules these days it is no wonder that their sales are sky rocketing! They are also very easy to source at online garden stores and are usually cheaper on the internet too. Most online garden supplies stores offer very good technical support to help you through the greenhouse construction experience! Most greenhouse kits and sunroom kits are constructed with aluminum, PVC or wooden frames. Just remember that the reason you bought a kit was probably due to lack of time to build one from scratch, and keep in mind that all outside wood structures need regular maintenance, i.e. staining or painting. So it is recommended that you buy aluminum or PVC if you want maintenance free! If you do want to go with an aluminum frame be sure to ask if there are thermal breaks in it, these will make sure that the outside metal is not in direct contact with the inside metal which will help ensure that the inside of your greenhouse stays as warm as possible during the winter months.
Watering Needs for Greenhouse Plants
As it does not rain inside greenhouses watering is a very important thing for greenhouse owners to remember! But, watering inside a green house is not just as simple as just watering your greenhouse plants everyday. Within soil there are small open air pores that roots depend on for supplying them with nutritious gases. When you water your plants these small air spaces get filled up with water and it, in effect, causes suffocation for roots. When roots suffocate, plants wilt and the most common reaction by gardeners for wilting plants is more watering! Just remember that the watering needs inside a greenhouse are different from the watering needs of your outside garden. Because the green house environment is enclosed a fair amount of moisture does get trapped and thus, less watering is usually required. The best rule for watering plants in your greenhouse or sunroom is: always check the soil before you water, if the soil is dry then you should go ahead and water. And, remember that plants, just like people, do not like being watered with cold water. For plants the ideal water temperature is between 65°F and 80°F (18.3°C and 26.7°C). Anything above 80°F (26.7°C) is too hot!
There are many different alternatives available for watering your greenhouse plants. Among your choices are irrigation systems, drip system, misters, water sensors and a gardener’s best friend the good old watering can. Irrigation systems are wonderful for those periods of time that you plan on being away; there is nothing worse than coming home to dead plants in your green house because your best friend forgot to water them while you were away! A good selection of all of these watering systems is available at online gardening and greenhouse supply stores.
Humidity Requirements in a Greenhouse
All plants have small open pores in their leaves through which gases such as oxygen, and CO2 pass. Water vapor is also emitted through these pores as plants do not use all of the water that they soak up. The accumulation of water vapor is called humidity and relative humidity is the term that describes the quantity of water vapor present in the air. Air temperature affects the amount of water vapor in the air and it is this relationship between air temperature and the quantity of water vapor present that gives us the term relative; for example: the quantity of vapor present is relative to the current air temperature! It is possible to measure the humidity of air with an instrument called a hygrometer.
It is important to know what the humidity is in a greenhouse as most plants grow best between a certain range of relative humidity. The best range or humidity for green house plants is between 45 and 60 percent. Knowing your relative humidity also enables you to control your greenhouse growing environment as humidity that is too high (above 80%) encourages the growth of mould both on plants and within your greenhouse. Plant moulds will destroy plants and will cause rot to occur in any wooden structures within your sunspace (which can be very detrimental if you have a wood frame greenhouse or sunroom or if you have wood shelving or a wood green house bench). Moulds are also usually a great concern as they cause disease.
It is more common for greenhouses to have a problem with high humidity rather than low humidity. If you have a high humidity problem in your green house some remedies are: to increase circulation by installing a fan, water earlier in the day to help prevent evening humidity problems (as moulds grow at night time), water only when the plants need it, buy an air-to-air heat exchanger which exchanges warm moist air with cool and dry air, or put in a ventilation system by which moist air can escape. If the humidity in your greenhouse or sunroom is too low it is much easier to fix than a high humidity problem. The easiest and best solution is to water more often. It is also very easy to buy greenhouse humidifiers that will easily increase your sun room humidity. These types of humidifiers are easily available at online green house supply stores.
Carbon Dioxide in the Greenhouse Environment
My seven year old son came home from school recently and announced “Mom, did you know that trees make oxygen from carbon dioxide?” It was a great time to teach him a lesson about how plants use carbon dioxide (CO2) and how they emit oxygen as the end result of this chemical exchange or reaction.
Since the early 1900’s scientists have been able to measure the amount of CO2 that is present in the air. It was discovered that the normal level of carbon dioxide in the air is about 300 parts per million (ppm). CO2 is essential to photosynthesis and thus it must be present in the air at least in at least 300 ppm in order for plants to grow properly. When CO2 is deficient in the air plants simply do not grow, their growth is very slow and stunted. It is also actually possible to speed plant growth up by increasing CO2 levels in the air. The simple addition of CO2 to the air is as good as adding fertilizer to your plants. Most plants grow with a yield increase of ten to thirty percent when the CO2 levels are between 1,200 to 1,500 parts per million. Note that anything above 2,000 ppm is not used by plants and it will not increase their growth beyond that point.
The reason that we need to know about CO2 is that depletion of CO2 can be and usually is a big problem in greenhouses and sunrooms. When plants are raised in a sealed environment as usually happens when you keep all the vents and windows closed in the winters, it is very easy for them to deplete the air of CO2. Plants that are raised in our residences have access to the CO2 that we and our pets breathe out as a waste product and to the air that comes in through open doors and windows. But, in the crowded plant environment of a sealed greenhouse or sunroom CO2 can actually be depleted within one day if measures are not taken against this!
The first action to help with reducing CO2 depletion for plants in green houses is to realize that a plant produces oxygen through it’s leaves, and the oxygen actually sits on and around the leaves unless the gentle breezes of nature comes by and blows it away! Then the leaf pores are introduced to the CO2 that the breeze just circulated to them and they are able to access it as the oxygen is no longer “blocking” their pores. We know, of course, that nature’s gentle breezes do not enter sealed greenhouses! Thus, we need to create some type of a “breeze” system within our greenhouses to circulate the oxygen away from the leaf surfaces and introduce the CO2 that is in other areas of the greenhouse. The simplest way to do this is to introduce a fan to your green house or sun room; either a floor fan or a ceiling fan works very well! Note: that you can turn the fans off at night as plants do not utilize CO2 in the absence of light.
A second step is to consistently introduce organic matter to your soil as the microbes and bacteria in decomposing matter is living and breathing and provides the air with it’s waste product; which just happens to be CO2! The amount of CO2 that organic matter introduces can also be depleted quickly, so the installation of fans is still necessary. It is also interesting to note that some people with a bigger greenhouse space that permits the keeping of a rabbit in a hutch or chickens in a cage will do so in order to supply their greenhouse plants with extra CO2! The most important thing to remember here is that you will need to allow for the extra work of cleaning out a rabbit hutch or a chicken cage as they get quite smelly quickly and the excess ammonia in the air will not be good for your plants or pleasant for you either! So if you’ve ever entertained the idea of having a pet rabbit for either you or your kids this may be your chance providing you are prepared to clean out a cage about once every 5-8 days. (or this could be a great opportunity to teach an older child some responsibility and add a chore to their list!)
Proper Balance of pH Levels for Maximum Greenhouse Plant Growth
Healthy soil is required for good plant production and healthy soil is created when it has a proper pH! There are a few aspects to creating and maintaining healthy soil and a proper pH balance. If the pH level is off balance then it is impossible for the critical nutrients necessary for plant health to survive in soil. The pH describes what the level of acidity is in your soil. The pH scale is based on a scale of 1-14, with 7 being the mid-point or the neutral point. Soil that is from pH 0 to pH 7 is considered acidic, and soil that is from pH 7 to pH 14 is considered alkaline, or basic. It is best to keep your soil as close to 7 as possible.
Greenhouse gardeners are wise to test the pH levels in their soil and pH test kits are easily available at online green house supply stores. If your soil is too acidic (low pH) it is best to add limestone or wood to your soil, and if it is too alkaline (high pH) it is best to add compost material (avoid manure), sulfur or acidifying plant foods that are available commercially. A properly balanced pH will ensure that the correct nutrients are available for your plants to properly root and utilize the minerals in the soil that are required for maximum growth. It also ensures that the healthy and beneficial microbes that live in soil can survive and help plants grow. Healthy microbes are important in controlling diseases and they also feed on bad microbes such as parasites too. When good microbes cannot survive in soil the bad microbes will take over and thus there is a greater chance of disease and pests entering the greenhouse environment. This is not unlike the good bacteria/bad bacteria that live in the human bowels, we need to keep these in balance too in order to prevent disease from entering the human body!
Heating Needs in a Greenhouse
Scientists have proven that the optimal growing temperature for most plants is between 50°F (10°C) and 85°F (29.4°C). This is a big temperature range and your consistent temperature target is really dependent upon the type of plants that you are growing in your greenhouse. If you have mostly seedlings then it is useful to note that seedlings thrive in warmer temperatures. If you have mostly mature plants then aim for a cooler temperature target. If the temperature gets above 85°F (29.4°C) then you will get plant growth problems such as slower growth and flower drop which will prevent flowers from setting and producing fruit. If temperatures get too low you will see much of the same problems as when the temperature gets too high. Temperature is vitally important to plants as it affects everything in their life cycle; photosynthesis, cell division, water intake, nutrient uptake, etc. It is thus, vitally important that we manage the temperature in a greenhouse so that we can assist our plants to grow at their maximum potential.
Here are four ways to supply a heat source to greenhouses; portable heaters, hot water pipes, wired in electrical heat or solar heating. Each has their own benefits and each has their downfall! Portable heaters are a wonderfully quick and easy way to add heat to a greenhouse or sunroom; they can be powered by natural gas, electricity, propane, wood, oil or kerosene. The biggest downfall with the gas, oil, wood or kerosene heaters is that whenever you burn them they emit gases that are harmful to plants so you absolutely must have some kind of a ventilation system that carries these emissions away and out of your greenhouse. Be careful that your venting system is not in direct contact with the skin on your greenhouse if it is made out of plastic as the heat from the ventilation system can melt the skin or in cases of excessive heat could actually cause it to melt! Also, check on the recommended size of heater for the size of your greenhouse. Most manufacturers will give you a recommendation for the maximum and minimum heating space that their heaters will heat.
Hot water systems are best installed by professional welders and plumbers. They are often custom made to fit the size of your greenhouse and usually consist of a system of pipes that run around the inside walls of your sunroom. They are attached to a water intake system and a pump that circulates the water through the pipes. Although the initial heating of the water in the pipes is a little costly, once the water in the pipes is hot it retains its heat very well which is where the cost reduction in hot water systems comes into place.
Electric heating in a greenhouse is an amazing concept in “how to very easily heat a greenhouse” – you turn the dial! The only problem is that electric heat in a greenhouse can get very, very expensive in the winter. The other major problem that you need to consider with electric heating is what your back up plan will be if there is a power outage. Remember that if you lose power in the middle of a winter freeze you could actually lose all of your plants overnight! The best device for “watching” greenhouse temperatures is a ‘temperature alarm’ that is made specifically for greenhouses. This nifty little device will set off an alarm as soon as the temperature in your greenhouse or sun room goes below a level that you preset into it. When this happens you will know that either your power has gone out or you just need to turn up the heat! In cases of power outages perhaps the best back up plan is to purchase your very own generator that can power a portable heater or two inside the green house or sunroom until the power comes back. Another very wise investment is to purchase some solar heating panels for your greenhouse, these will generate enough heat through a power outage in the winter to prevent freezing, although they will not usually generate enough heat to keep a greenhouse warm through a long freeze. Solar heating panels will prevent you from losing the majority of your plants in a short power outage during a freeze.
Solar heating is a very cost efficient way of heating your greenhouse if you set it up properly and design your green house to use solar heating efficiently. The most important thing to consider when first designing your sunroom or green house construction is to decide upon it’s location in your garden. To maximize the usage of the sun’s energy it is best that you orientate your greenhouse to have its long side face within 20 degrees of either side of true south. And in order to utilize larger solar panels it is best to have the greenhouse be 2 or 3 times longer than it is wide. Other ways to ensure solar heating is maximized is to make sure your greenhouse is airtight, so that it doesn’t lose it’s heat through leaks. Make sure that your glaze is double or triple glazing to help reduce heat loss. Insulate the walls of the greenhouse to prevent heat loss, this is especially useful on the north wall where most heat loss will occur; and the easiest way to insulate this wall is to buy bubble insulation in rolls (the kind of bubble wrap that packages come wrapped in for protection in the mail). Some green house supply stores carry clear bubble greenhouse insulation. Spray a glue adhesive to the inside of your glazing and press your pre-cut bubble insulation up against the adhesive until it sticks. Earlier in this article we talked about insulating the foundation of your greenhouse with 1-2 inch thick styrofoam board, and this is another way to prevent heat loss from your greenhouse – especially if you choose to go with solar heating panels.
Selecting the Right Seeds and Plants for Your Greenhouse
When it comes to selecting seeds and plants for your greenhouse the biggest deciding factor is your personal choice! You will need to set up your greenhouse interior to accommodate the types of plants that you choose though. For example if you choose to grow plants that require a trellis you will have to install some trellises. Some examples of plants that grow well with a trellis are peas, runner beans, tomatos, cucumbers, watermelon, winter squash, nasturtiums, passionflower, bougainvillea and sweet peas. Some crops are harvested only once and then they are done; for example onions, carrots and radishes. Other crops that need harvesting many times; for example leaf lettuce, strawberries, broccoli and brussel sprouts should be placed in easy to reach places, like at the edges of beds.
Buy a good book on greenhouse gardening so as to learn about the different temperature, water, humidity and pH level requirements of different plants and then make your final selections of seeds and plants. A greenhouse gardener’s book will also help you with the best layouts for your plants and seedlings.
As a final note on buying seeds and plants for your greenhouse please be aware that it is very advantageous to buy them from online greenhouse supply stores and online seed catalogues as they are coming directly from “the source” in most cases! This means that the seeds and plants are usually fresher and have been stored correctly while in storage as a lot of online stores are based directly from farms and growing facilities. The selection and varieties of seeds and plants that are available at online stores are unequalled. You will be delighted with the selection and the information that is available for each plant or seed selection that you choose at online green house supply stores and seed or plant catalogues. Customer service at these stores is also exceptional. Most online gardening stores offer free shipping once an order hits a certain dollar amount too!
Buying a Green house is Investing in a Therapeutic Activity!
There is nothing like “getting down with the dirt” to really melt away the stress of a busy day. Gardening is a cleansing and therapeutic way to spend your time, it enables us to get in touch with nature, and it’s no wonder that it is one of the most popular leisure activities that people list in their resumes and on questionnaires. I have a doctor friend who advises his patients to run barefoot on the beach to unwind and let stresses melt away, I find that gardening and greenhouse gardening does the same thing for me!
If you invest some time in researching greenhouse construction, types of greenhouses and sunrooms available such as greenhouse kits, sun room kits, hobby greenhouses, large or mini greenhouses and portable green houses you will be sure to start an adventure of a lifetime! Remember to learn all that you can about greenhouse equipment, which type of greenhouse covering or glazing is best suited to you, and the type of watering, humidity control, heating and air circulation systems that are best suited to your sunroom or greenhouse gardening needs. Time invested in greenhouse gardening before you actually start your green house construction will be time well spent, and will ensure that you get maximum stress relief and enjoyment out of your greenhouse hobby!!
Tuesday, July 1, 2008
Gbl warm(contd..)
Of buckets and blogs
Filed under:
Oceans
Instrumental Record
Climate Science— gavin @ 10:44 AM
This last week has been an interesting one for observers of how climate change is covered in the media and online. On Wednesday an interesting paper (Thompson et al) was published in Nature, pointing to a clear artifact in the sea surface temperatures in 1945 and associating it with the changing mix of fleets and measurement techniques at the end of World War II. The mainstream media by and large got the story right - puzzling anomaly tracked down, corrections in progress after a little scientific detective work, consequences minor - even though a few headline writers got a little carried away in equating a specific dip in 1945 ocean temperatures with the more gentle 1940s-1970s cooling that is seen in the land measurements. However, some blog commentaries have gone completely overboard on the implications of this study in ways that are very revealing of their underlying biases.
The best commentary came from John Nielsen-Gammon's new blog where he described very clearly how the uncertainties in data - both the known unknowns and unknown unknowns - get handled in practice (read that and then come back). Stoat, quite sensibly, suggested that it's a bit early to be expressing an opinion on what it all means. But patience is not one of the blogosphere's virtues and so there was no shortage of people extrapolating wildly to support their pet hobbyhorses. This in itself is not so unusual; despite much advice to the contrary, people (the media and bloggers) tend to weight new individual papers that make the news far more highly than the balance of evidence that really underlies assessments like the IPCC. But in this case, the addition of a little knowledge made the usual extravagances a little more scientific-looking and has given it some extra steam.
Filed under:
Oceans
Instrumental Record
Climate Science— gavin @ 10:44 AM
This last week has been an interesting one for observers of how climate change is covered in the media and online. On Wednesday an interesting paper (Thompson et al) was published in Nature, pointing to a clear artifact in the sea surface temperatures in 1945 and associating it with the changing mix of fleets and measurement techniques at the end of World War II. The mainstream media by and large got the story right - puzzling anomaly tracked down, corrections in progress after a little scientific detective work, consequences minor - even though a few headline writers got a little carried away in equating a specific dip in 1945 ocean temperatures with the more gentle 1940s-1970s cooling that is seen in the land measurements. However, some blog commentaries have gone completely overboard on the implications of this study in ways that are very revealing of their underlying biases.
The best commentary came from John Nielsen-Gammon's new blog where he described very clearly how the uncertainties in data - both the known unknowns and unknown unknowns - get handled in practice (read that and then come back). Stoat, quite sensibly, suggested that it's a bit early to be expressing an opinion on what it all means. But patience is not one of the blogosphere's virtues and so there was no shortage of people extrapolating wildly to support their pet hobbyhorses. This in itself is not so unusual; despite much advice to the contrary, people (the media and bloggers) tend to weight new individual papers that make the news far more highly than the balance of evidence that really underlies assessments like the IPCC. But in this case, the addition of a little knowledge made the usual extravagances a little more scientific-looking and has given it some extra steam.
Global warming
More PR related confusion
Filed under:
Reporting on climate
Climate modelling
Greenhouse gases
Climate Science— gavin @ 9:58 AM
It's a familiar story: An interesting paper gets published, there is a careless throwaway line in the press release, and a whole series of misleading headlines ensues.
This week, it's a paper on bromine- and iodine-mediated ozone loss in marine boundary layer environments (see a good commentary here). This is important for the light that it shines on tropospheric ozone chemistry ("bad ozone") which is a contributing factor to global warming (albeit one which is about only about 20% as important as CO2). So far so good. The paper contains some calculations indicating that chemical transport models without these halogen effects overestimate ozone near the Cape Verde region by about 15% - a difference that certainly could be of some importance if it can be extrapolated across the oceans.
However, the press release contains the line
Large amounts of ozone – around 50% more than predicted by the world’s state-of-the-art climate models – are being destroyed in the lower atmosphere over the tropical Atlantic Ocean.
(my highlights). Which led directly to the headlines like Study highlights need to adjust climate models.
Why is this confusing? Because the term 'climate models' is interpreted very differently in the public sphere than it is in the field. For most of the public, it is 'climate models' that are used to project global warming into the future, or to estimate the planet's sensitivity to CO2. Thus a statement like the one above, and the headline that came from it are interpreted to mean that the estimates of sensitivity or of future warming are now in question. Yet this is completely misleading since neither climate sensitivity nor CO2 driven future warming will be at all affected by any revisions in ozone chemistry - mainly for the reason that most climate models don't consider ozone chemistry at all. Precisely zero of the IPCC AR4 model simulations (discussed here for instance) used an interactive ozone module in doing the projections into the future.
What the paper is discussing, and what was glossed over in the release, is that it is the next generation of models, often called "Earth System Models" (ESMs), that are starting to include atmospheric chemistry, aerosols, ozone and the like. These models may well be significantly affected by increases in marine boundary layer ozone loss, but since they have only just started to be used to simulate 20th and early 21st Century changes, it is very unclear what difference it will make at the large scale. These models are significantly more complicated than standard climate models (having dozens of extra tracers to move around, and a lot of extra coding to work through), are slower to run, and have been used much less extensively.
Climate models today are extremely flexible and configurable tools that can include all these Earth System modules (including those mentioned above, but also full carbon cycles and dynamic vegetation), but depending on the application, often don't need to. Thus while in theory, a revision in ozone chemistry, or soil respiration or aerosol properties might impact the full ESM, it won't affect the more basic stuff (like the sensitivity to CO2). But it seems that the "climate models will have to be adjusted" meme is just too good not to use - regardless of the context.
Filed under:
Reporting on climate
Climate modelling
Greenhouse gases
Climate Science— gavin @ 9:58 AM
It's a familiar story: An interesting paper gets published, there is a careless throwaway line in the press release, and a whole series of misleading headlines ensues.
This week, it's a paper on bromine- and iodine-mediated ozone loss in marine boundary layer environments (see a good commentary here). This is important for the light that it shines on tropospheric ozone chemistry ("bad ozone") which is a contributing factor to global warming (albeit one which is about only about 20% as important as CO2). So far so good. The paper contains some calculations indicating that chemical transport models without these halogen effects overestimate ozone near the Cape Verde region by about 15% - a difference that certainly could be of some importance if it can be extrapolated across the oceans.
However, the press release contains the line
Large amounts of ozone – around 50% more than predicted by the world’s state-of-the-art climate models – are being destroyed in the lower atmosphere over the tropical Atlantic Ocean.
(my highlights). Which led directly to the headlines like Study highlights need to adjust climate models.
Why is this confusing? Because the term 'climate models' is interpreted very differently in the public sphere than it is in the field. For most of the public, it is 'climate models' that are used to project global warming into the future, or to estimate the planet's sensitivity to CO2. Thus a statement like the one above, and the headline that came from it are interpreted to mean that the estimates of sensitivity or of future warming are now in question. Yet this is completely misleading since neither climate sensitivity nor CO2 driven future warming will be at all affected by any revisions in ozone chemistry - mainly for the reason that most climate models don't consider ozone chemistry at all. Precisely zero of the IPCC AR4 model simulations (discussed here for instance) used an interactive ozone module in doing the projections into the future.
What the paper is discussing, and what was glossed over in the release, is that it is the next generation of models, often called "Earth System Models" (ESMs), that are starting to include atmospheric chemistry, aerosols, ozone and the like. These models may well be significantly affected by increases in marine boundary layer ozone loss, but since they have only just started to be used to simulate 20th and early 21st Century changes, it is very unclear what difference it will make at the large scale. These models are significantly more complicated than standard climate models (having dozens of extra tracers to move around, and a lot of extra coding to work through), are slower to run, and have been used much less extensively.
Climate models today are extremely flexible and configurable tools that can include all these Earth System modules (including those mentioned above, but also full carbon cycles and dynamic vegetation), but depending on the application, often don't need to. Thus while in theory, a revision in ozone chemistry, or soil respiration or aerosol properties might impact the full ESM, it won't affect the more basic stuff (like the sensitivity to CO2). But it seems that the "climate models will have to be adjusted" meme is just too good not to use - regardless of the context.
Windows mobile development
Creating Managed Today Screen Items
Today I thought I would demonstrate a proof of concept that may enable you to create today screen items in managed languages such as C# or VB.NET. In part this early preview was brought about by a recent request for advice on how to create managed Input Methods for the SIP keyboard, something that I think could be achieved using a similar approach. This is still a work in progress to see what is possible…. at the moment I have not fully evaluated the technique to be valid and/or tidied the code to my usual standard for release. I would love your feedback on this project.
Problem Definition
The Windows Mobile OS has a Today Screen API that enables custom items to be displayed on the main screen of the device. This API is highly geared towards native (C or C++) developers, and it is not possible for managed (VB.NET or C#) developers to implement the API directly.
Jim Wilson previously demonstrated in an MSDN article titled “Creating a Pocket PC Today Screen Plug-in with the .NET Compact Framework” a technique were a C++ based today screen item was developed to display HTML based content that was generated by a C# application. Although this is suitable for some applications it doesn’t lend itself to highly interactive or graphic intensive animated displays.
What we ideally want to do is to implement a minimal amount of native code that satisifies the requirements of the Today Screen API and have this native stub delegate all the GUI functionality off to a managed application.
It would also be extremely handy if the native part of this solution could be written once and reutilised among multiple managed today screen items. In part because this would open up today screen item development to those developers who currently don’t have experience in developing native code.
Solution Architecture
My solution utilises a native today screen item written in C++. This today screen item is implemented in a DLL called ManagedTodayScreenItem.dll. The OS is configured to load this item into the today screen process. However unlike other today screen items this one looks up additional configuration data stored in the registry to determine the name of a managed (i.e. VB.NET or C#) executable that should be launched when it is first displayed.
The managed executable starts up as normal and displays it’s main form. However once displayed the managed process then proceeds to establish an inter-process communication (IPC) channel back to the native today screen item. Once this channel is established the managed application informs the native today screen item of it’s window handle. The native today screen item then reparents the managed form to be a child of the today screen item and resizes it to fit the space allocated to the today screen item.
From this point on the illusion of a managed today screen item has been made. Whenever the managed form needs to act like a today screen item (such as painting the today screen watermark on it’s background) it can communicate with the native today screen item stub, and conversely whenever the native stub detects a change in it’s size or location it can communicate this change back to the managed part of the item.
Creating a new today screen item
Creating a new today screen item with this framework is relatively easy. Perhaps the easiest way is to modify the SampleTodayScreenItem example within the sample application mentioned below.
If you are creating a today screen item from scratch you need to follow these steps:
Create a new Smart Device Application (win forms project).
Change the FormBorderStyle property of the main form to None. As discussed previously this enables us to make the form non fullscreen.
Add a reference to the Christec.WindowsMobile.TodayScreen.dll assembly found in the sample project below.
Change the main form to derive from the TodayScreenPluginForm base class.
The last step is very important. The TodayScreenPluginForm class itself derives from Form but overrides a couple of methods (such as OnPaint) to ensure the form has the look and feel of a today screen item. This base class also behind the scenes sets up the inter-process communication channel which allows the managed part of the solution to communicate with the native part.
Your form source code should look something like the following after these changes:
using Christec.WindowsMobile.TodayScreen;
public Form1 : TodayScreenPluginForm
{
public Form1()
: base(4567)
{
InitializeComponent();
}
}
A key thing to point out here is the call to the TodayScreenPluginForm constructor that accepts an integer parameter. This integer is an id that is a unique value that identifies this particular today screen plugin. This is the part of the framework that enables the one native today screen item to be reutilised multiple times by different managed plugins (since each managed plugin should be given a different id value to differentiate itself).
Once the managed executable has been created as described above and compiled all that is required is a couple of registry settings to be added to make the operating system aware of the new today screen item. These registry settings are as follows:
Underneath HKLM\Software\Microsoft\Today\Items\
DLL = “\Windows\ManagedTodayScreenItem.dll”
Flags = 4567
Name = “A name for the item”
Options = 0
Type = 4
within the registry key above should be replaced with the name you want to be visible to the user within the Today Screen control panel applet. All these registry values should be identical for each managed today screen plugin you develop. The only difference should be the value you use for the Flags setting. This should match up with the value you passed into the TodayScreenPluginForm constructor within the source code of the managed part of your today screen item.
The native ManagedTodayScreenItem.dll today screen item utilises this “flags” value to lookup another set of item specific registry keys to determine which managed executable needs to be executed as outlined below:
Underneath HKLM\Software\ChrisTec\ManagedTodayScreenPlugins\
(default) = “\path\to\managed\executable.exe”
Height = height of today screen item in pixels.
within the registry key above should be replaced with the unique id value (4567 in the example) for your managed today screen item. At present it is not possible to dynamically change the height of the today screen item at runtime. This would be something that is reasonably easy to implement but is one of the features I have not implemented yet as it wasn’t required in order to prove the validity of the concept.
Sample Applicaton
[Download managedtodayscreenitem.zip - 37.1KB]
The sample project that is available for download contains two CAB files within a subdirectory called “bin”. These are as follows:
ChrisTec.WindowsMobile.TodayScreen-Framework.cab - installs the native part of the today screen item framework. This part can be shared among multiple managed today screen items and only needs to be installed once per device. It can be thought of as being similar to the .NET CF or SQL Server CE CAB files that install a framework for other applications to utilise. This cab file can also be utilised by managed developers who are not comfortable rebuilding the C++ source code.
SampleTodayScreenItem.cab - An example today screen item written in C#. It simply consists of three buttons with each button displaying a simple message box once clicked.
If both of these CAB files are installed on a Pocket PC device and the device is then soft reset you should see the new today screen item appear.
If you would like to have a go at creating your own managed today screen item you should also find a pre-compiled copy of the Christec.WindowsMobile.TodayScreen assembly that you will need to reference within this directory.
Within the other subdirectory (called “src”) you should be able to find solution files that will enable you to rebuild the two CAB files mentioned above.
Outstanding Tasks
As I stated in the introduction, this project is an early proof of concept that I have decided to share early on in the hope that it helps a few people and perhaps gets a couple interested in contributing. Since the code is not fully released there are a number of known issues and outstanding tasks.
Some of these are as follows:
Slight compatibility issues on Pocket PC 2003 devices after a soft reset.
Does not handle the managed application crashing in the most robust manor.
The Visual Studio IDE experience could be improved with project item templates etc.
Having multiple managed today screen items share the single native dll probably doesn’t work (needs a little more work).
The Christec.WindowsMobile.TodayScreeen assembly should be placed into the Global Assembly Cache (GAC).
It would be great if less registry configuration is required.
Summary
Hopefully this blog entry will cause some interest, as I know developing custom today screen items in managed code is a frequent question on online developer help forums. Although this solution isn’t fully complete and isn’t the most straight forward to configure (at present at-least) the results I have managed to get so far are encouraging.
If this proof of concept can validate the technique I am using to host .NET Compact Framework based forms within native processes I can see no reason why it would not work in other situations such as custom SIP based keyboards. The only difference would be the native component that would need to wrap up the native API provided by the operating system.
I would be really keen to hear your feedback and thoughts on this prototype. Especially if you are able to give me a hand to further validate and develop the concept.
Share This
This entry was posted on Sunday, February 17th, 2008 at 10:48 pm and is filed under Native Interop. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
15 Responses to “Creating Managed Today Screen Items”
Peter Nowak Says: February 18th, 2008 at 6:39 pm
Hi Chris,
as you post, an Identifier has to be created from type int. Is it possible for future versions to use GUIDs instead of ints? Makes this more robust and more handy for code generation. What do you think?
Cheers, Peter Nowak
Peter Nowak Says: February 18th, 2008 at 7:01 pm
Hi,
2 more possible enhancements:Is it possible to create a property, which is defined in an Interface. The property would describe the ID you need for the plugin. Therefore you wouldn’t need to create another constructor and the Designer could go on working as usual. Otherwise a set of Attributes would be the other possibility, which could help at this point.A short look at your assembly by using Reflector seems, that these possibilities coud be a possible solution.
Christopher Fairbairn Says: February 18th, 2008 at 7:33 pm
Thanks for your feedback Peter. They are both great ideas, and exactly the kind of feedback that I had hoped for when I decided to release this early rather than later.
The reason the existing code uses integer id’s is because it enables the native part (that interacts with the OS provided today screen API) to store the id in the “flags” field of one of the today screen API datastructures.
I also would like to see this change to using GUIDs if possible, as they would be much more easier to manage and avoid clashes in a distributed manor.
I also like the idea of moving the plugin id into an C# Attribute. This would allow the ID to be extracted from a managed executable via System.Reflection functionality which may help in my desire to simplify the installation process (i.e. avoid needing to set all the registry keys up manually and instead use reflection to obtain the values and configure them automatically via some kind of installer helper utility).
It’s these kinds of finer points that I would like to resolve before worrying about fleshing out the features of the today screen item, such as supporting dynamically sized items, or configuration dialogs etc.
Christopher Fairbairn Says: February 18th, 2008 at 10:51 pm
I had a little bit of time to spend on this tonight. With a little tweaking I have managed to utilise GUIDs instead of integers for the identifiers and tidy up the required code modifications to the managed app to be as minimal as possible, as demonstrated below:
[TodayScreenItem("{C218E62F-8824-46D6-91D0-73F6399616B3}")]
public class MainForm : TodayScreenItem
{
... standard form code ...
}
The attribute provides the GUID based identifier that uniquely identifies this today screen item, while the TodayScreenItem base class implements all the magic of communicating to the native part of the solution.
In the next few days I’ll try to upload the latest source code to a project hosting service, so that other interested developers can download the latest code snapshots and play with it themselves.
Today I thought I would demonstrate a proof of concept that may enable you to create today screen items in managed languages such as C# or VB.NET. In part this early preview was brought about by a recent request for advice on how to create managed Input Methods for the SIP keyboard, something that I think could be achieved using a similar approach. This is still a work in progress to see what is possible…. at the moment I have not fully evaluated the technique to be valid and/or tidied the code to my usual standard for release. I would love your feedback on this project.
Problem Definition
The Windows Mobile OS has a Today Screen API that enables custom items to be displayed on the main screen of the device. This API is highly geared towards native (C or C++) developers, and it is not possible for managed (VB.NET or C#) developers to implement the API directly.
Jim Wilson previously demonstrated in an MSDN article titled “Creating a Pocket PC Today Screen Plug-in with the .NET Compact Framework” a technique were a C++ based today screen item was developed to display HTML based content that was generated by a C# application. Although this is suitable for some applications it doesn’t lend itself to highly interactive or graphic intensive animated displays.
What we ideally want to do is to implement a minimal amount of native code that satisifies the requirements of the Today Screen API and have this native stub delegate all the GUI functionality off to a managed application.
It would also be extremely handy if the native part of this solution could be written once and reutilised among multiple managed today screen items. In part because this would open up today screen item development to those developers who currently don’t have experience in developing native code.
Solution Architecture
My solution utilises a native today screen item written in C++. This today screen item is implemented in a DLL called ManagedTodayScreenItem.dll. The OS is configured to load this item into the today screen process. However unlike other today screen items this one looks up additional configuration data stored in the registry to determine the name of a managed (i.e. VB.NET or C#) executable that should be launched when it is first displayed.
The managed executable starts up as normal and displays it’s main form. However once displayed the managed process then proceeds to establish an inter-process communication (IPC) channel back to the native today screen item. Once this channel is established the managed application informs the native today screen item of it’s window handle. The native today screen item then reparents the managed form to be a child of the today screen item and resizes it to fit the space allocated to the today screen item.
From this point on the illusion of a managed today screen item has been made. Whenever the managed form needs to act like a today screen item (such as painting the today screen watermark on it’s background) it can communicate with the native today screen item stub, and conversely whenever the native stub detects a change in it’s size or location it can communicate this change back to the managed part of the item.
Creating a new today screen item
Creating a new today screen item with this framework is relatively easy. Perhaps the easiest way is to modify the SampleTodayScreenItem example within the sample application mentioned below.
If you are creating a today screen item from scratch you need to follow these steps:
Create a new Smart Device Application (win forms project).
Change the FormBorderStyle property of the main form to None. As discussed previously this enables us to make the form non fullscreen.
Add a reference to the Christec.WindowsMobile.TodayScreen.dll assembly found in the sample project below.
Change the main form to derive from the TodayScreenPluginForm base class.
The last step is very important. The TodayScreenPluginForm class itself derives from Form but overrides a couple of methods (such as OnPaint) to ensure the form has the look and feel of a today screen item. This base class also behind the scenes sets up the inter-process communication channel which allows the managed part of the solution to communicate with the native part.
Your form source code should look something like the following after these changes:
using Christec.WindowsMobile.TodayScreen;
public Form1 : TodayScreenPluginForm
{
public Form1()
: base(4567)
{
InitializeComponent();
}
}
A key thing to point out here is the call to the TodayScreenPluginForm constructor that accepts an integer parameter. This integer is an id that is a unique value that identifies this particular today screen plugin. This is the part of the framework that enables the one native today screen item to be reutilised multiple times by different managed plugins (since each managed plugin should be given a different id value to differentiate itself).
Once the managed executable has been created as described above and compiled all that is required is a couple of registry settings to be added to make the operating system aware of the new today screen item. These registry settings are as follows:
Underneath HKLM\Software\Microsoft\Today\Items\
DLL = “\Windows\ManagedTodayScreenItem.dll”
Flags = 4567
Name = “A name for the item”
Options = 0
Type = 4
The native ManagedTodayScreenItem.dll today screen item utilises this “flags” value to lookup another set of item specific registry keys to determine which managed executable needs to be executed as outlined below:
Underneath HKLM\Software\ChrisTec\ManagedTodayScreenPlugins\
(default) = “\path\to\managed\executable.exe”
Height = height of today screen item in pixels.
Sample Applicaton
[Download managedtodayscreenitem.zip - 37.1KB]
The sample project that is available for download contains two CAB files within a subdirectory called “bin”. These are as follows:
ChrisTec.WindowsMobile.TodayScreen-Framework.cab - installs the native part of the today screen item framework. This part can be shared among multiple managed today screen items and only needs to be installed once per device. It can be thought of as being similar to the .NET CF or SQL Server CE CAB files that install a framework for other applications to utilise. This cab file can also be utilised by managed developers who are not comfortable rebuilding the C++ source code.
SampleTodayScreenItem.cab - An example today screen item written in C#. It simply consists of three buttons with each button displaying a simple message box once clicked.
If both of these CAB files are installed on a Pocket PC device and the device is then soft reset you should see the new today screen item appear.
If you would like to have a go at creating your own managed today screen item you should also find a pre-compiled copy of the Christec.WindowsMobile.TodayScreen assembly that you will need to reference within this directory.
Within the other subdirectory (called “src”) you should be able to find solution files that will enable you to rebuild the two CAB files mentioned above.
Outstanding Tasks
As I stated in the introduction, this project is an early proof of concept that I have decided to share early on in the hope that it helps a few people and perhaps gets a couple interested in contributing. Since the code is not fully released there are a number of known issues and outstanding tasks.
Some of these are as follows:
Slight compatibility issues on Pocket PC 2003 devices after a soft reset.
Does not handle the managed application crashing in the most robust manor.
The Visual Studio IDE experience could be improved with project item templates etc.
Having multiple managed today screen items share the single native dll probably doesn’t work (needs a little more work).
The Christec.WindowsMobile.TodayScreeen assembly should be placed into the Global Assembly Cache (GAC).
It would be great if less registry configuration is required.
Summary
Hopefully this blog entry will cause some interest, as I know developing custom today screen items in managed code is a frequent question on online developer help forums. Although this solution isn’t fully complete and isn’t the most straight forward to configure (at present at-least) the results I have managed to get so far are encouraging.
If this proof of concept can validate the technique I am using to host .NET Compact Framework based forms within native processes I can see no reason why it would not work in other situations such as custom SIP based keyboards. The only difference would be the native component that would need to wrap up the native API provided by the operating system.
I would be really keen to hear your feedback and thoughts on this prototype. Especially if you are able to give me a hand to further validate and develop the concept.
Share This
This entry was posted on Sunday, February 17th, 2008 at 10:48 pm and is filed under Native Interop. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
15 Responses to “Creating Managed Today Screen Items”
Peter Nowak Says: February 18th, 2008 at 6:39 pm
Hi Chris,
as you post, an Identifier has to be created from type int. Is it possible for future versions to use GUIDs instead of ints? Makes this more robust and more handy for code generation. What do you think?
Cheers, Peter Nowak
Peter Nowak Says: February 18th, 2008 at 7:01 pm
Hi,
2 more possible enhancements:Is it possible to create a property, which is defined in an Interface. The property would describe the ID you need for the plugin. Therefore you wouldn’t need to create another constructor and the Designer could go on working as usual. Otherwise a set of Attributes would be the other possibility, which could help at this point.A short look at your assembly by using Reflector seems, that these possibilities coud be a possible solution.
Christopher Fairbairn Says: February 18th, 2008 at 7:33 pm
Thanks for your feedback Peter. They are both great ideas, and exactly the kind of feedback that I had hoped for when I decided to release this early rather than later.
The reason the existing code uses integer id’s is because it enables the native part (that interacts with the OS provided today screen API) to store the id in the “flags” field of one of the today screen API datastructures.
I also would like to see this change to using GUIDs if possible, as they would be much more easier to manage and avoid clashes in a distributed manor.
I also like the idea of moving the plugin id into an C# Attribute. This would allow the ID to be extracted from a managed executable via System.Reflection functionality which may help in my desire to simplify the installation process (i.e. avoid needing to set all the registry keys up manually and instead use reflection to obtain the values and configure them automatically via some kind of installer helper utility).
It’s these kinds of finer points that I would like to resolve before worrying about fleshing out the features of the today screen item, such as supporting dynamically sized items, or configuration dialogs etc.
Christopher Fairbairn Says: February 18th, 2008 at 10:51 pm
I had a little bit of time to spend on this tonight. With a little tweaking I have managed to utilise GUIDs instead of integers for the identifiers and tidy up the required code modifications to the managed app to be as minimal as possible, as demonstrated below:
[TodayScreenItem("{C218E62F-8824-46D6-91D0-73F6399616B3}")]
public class MainForm : TodayScreenItem
{
... standard form code ...
}
The attribute provides the GUID based identifier that uniquely identifies this today screen item, while the TodayScreenItem base class implements all the magic of communicating to the native part of the solution.
In the next few days I’ll try to upload the latest source code to a project hosting service, so that other interested developers can download the latest code snapshots and play with it themselves.
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