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China solar greenhouses, built on south facing slopes, are an underdocumented innovation. A recent study looks at their history and suggests additional ways to improve them.  (Source: Energy Bulletin)
Chinese innovation starting to show itself on the world scene

One perpetual criticism of China, the world’s second largest economic super-power, is that its lacks the innovation found in the U.S., Japan, or European Union.  Perhaps that is a bit of an exaggeration, however.

A great deal of innovation in China has not been absent, but has merely gone undocumented until late.

Take China's advanced solar green houses, which were designed more than 20 years ago.  In a new peer-review study [abstract] published in the journal ASHS (American Society for Horticultural Science) HortTech, researchers at the China Agricultural University in Beijing have detailed how the Chinese innovation -- built on slopes -- offer great savings in power costs and emissions.

It's not surprising that China might know a thing or two about efficient growing.  It has to feed the world's largest population -- over 1.3 billion people, today.  That's no easy task.  To sustain the population, China had to figure out how to grow crops cheaply and effectively in the winter.  To do that it created the slope greenhouse design.

The greenhouses studied lie in regions north of Huai River and the Beijing area.  Like any greenhouses, their feasibility as winter growing sites relies on the temperature at the site and the amount of sunlight during the winter.

What is unique about the Chinese design is that they use the slope to provide a degree of natural insulation, while optimizing solar absorbance.  The back wall is situated directly into the slope and side walls jut out of the slope on a flattened plot of land.  On top, a thin roof is built.  This gives way to the sloping transparent curved roof/front wall, the first thing you see when looking at the greenhouse from outside.

The greenhouses are constructed using simple materials.  A frame made of bamboo, metal, or a combination of both supports the curved glass wall.  The transparent wall is formed of an insulating sheet and plastic film.

While the greenhouses have numerous advantages -- "energy savings, reduced pollution, and improved economic development" -- they also have disadvantages, which the authors note.  Namely, weather conditions can limit sunlight, causing growing problems.  The greenhouses are heavily reliant on sun and weather conditions.

Still their cheap, efficient, easy to construct design has been an alluring innovation for other nations, situated between the applicable 32°N and 43°N latitudes.  Among the countries implementing them are Japan, Korea, and Russia.  The greenhouses are used to grow warm-weather crops like tomatoes and cucumbers.

The report author, Zhen-Xian Zhang, speculates on how to improve upon the tried-and-true design, stating [press release], "Innovation and optimization of the greenhouse structure needs to continue. More work needs to be done on gutter-connected, double-arched, and semi-underground greenhouses. New wall insulation materials need to be developed to reduce the thickness of the wall while improving its insulation efficiency and expanding space utilization. The solar greenhouse has a very bright future, especially given the amount of concern over the global energy crisis and climate change. Additionally, significant energy savings can be realized from switching to solar greenhouses. We hope this technology can be applied to regions of similar climate to help reduce energy consumption and CO2 emissions."

Professor Zhang also suggested breeding special hybrid crops optimized for growth in the occasionally adverse conditions of the winter greenhouse.  Such crops might resist brief chills and add already more utility to this tested design.

                                                                                       



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solar greenhouses ehh?
By Bubbacub on 3/21/2011 5:59:39 AM , Rating: 2
ever heard of a non solar greenhouse?




RE: solar greenhouses ehh?
By JediJeb on 3/21/2011 4:13:06 PM , Rating: 2
Non-solar greenhouses are used all the time growing marijuana in basements and attics.


RE: solar greenhouses ehh?
By Natfly on 3/21/2011 4:58:07 PM , Rating: 2
I think by definition greenhouses use sunlight for convection. If you are growing indoors you don't need the additional heat and in most cases try to get rid of the heat that lamps output.


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