Various studies show
that in northern climatic zones more und more fresh fruits and vegetables are being consumed in winter as well. These fresh agricultural products are coming from countries of the south where the greenhouses are in
extensive use. This consumption pattern causes a considerable use of energy through the massive transport of agricultural products. For example a study in Connecticut, USA, showed that it takes 1kg. food 2000km to drive
up to the dinner table!An answer to this waste of the valuable resources could be raising the fresh products in greenhouses directly at the place of consumption. But it is a dilemma because the greenhouse itself is a
big consumer of energy. It is not unusual that a traditional art of Greenhouse in 40-41° north consumes annually 150-300kWh/m² energy for the heating. Therefore it is most of the time interesting only for the florists
to have a greenhouse at this zone.
A solar greenhouse on the other hand can reduce the energy consumption drastically!
What is a solar greenhouse?
The solar greenhouse uses the energy
of the sun with passive and active means, to be able to provide and guarantee the necessary working temperature and the desired internal conditions such as irrigation-humidity relationship, PH worth of the earth,
lighting-shadowing relationship, CO2 content of the air, etc.
How does it work?
To begin with: it is important that the greenhouse has the right direction to the sun, that is,
the long axis of it should lie in the east-west direction. To be able to use the direct and indirect rays of the sun, the greenhouse should have a transparent covering to it. For this purpose materials like glass and
plastic folly are used.
The greenhouse is closed to the north with a good isolated wall, to be able to reduce the
loss of energy. Moreover, to be able to keep the heat inside the greenhouse, the covering should have double layers, i.e. double-glazing.
The passive use of the solar energy is made
possible through deployment of storage masses in the greenhouse. Here comes water in to consideration as the best natural storage material. Water in containers or sun-hosepipes, which are placed intelligently
in the greenhouse, stores the warmth at the daytime, to give it off at nights.
A more effective method is to use PCM-storage.
stores the excess of the solar energy in the greenhouse in form of latent heat.
One can use the PCM here as a passive storage means or can charge the storage medium actively with the appropriate facilities, to be able to have the stored energy at service for several days.
An additional installation in a Greenhouse is the compost-processor. Composting (especially of the horse dung) produces, first of all, heat. A second valuable product is CO2, which is the necessary
condition for the growth of the plants. Moreover you can revaluate the compost as manure on the fields. It is a relatively cheap technology to produce heat, CO2, and manure through this process of
composting and store them to put in to use at the desired time.
Solar greenhouse as an additional residential quality in urban areas
Looked from the point of view of urban planning and architecture, solar greenhouse is also an important means to increase the quality of living. Think for a moment that you come home on a cold
and wet winter evening and relax in your greenhouse and then prepare for yourself a fresh salad with self-grown products -- perhaps a fish from your own pond as well! The solar greenhouse can also be applied
to clean and acclimatize the air inside your home. There are other advantages of the urban/suburban solar greenhouse like recycling of the residential wastes and supplying of energy.
