Solar greenhouses capture the light energy of the sun and convert it into heat energy and store it. This heat is used to keep warm-weather plants from suffering during the intense cold of winter nights. Many out of season plants too are grown in a greenhouse during the winter months.
The glass or plastic in a greenhouse’s walls and roof let in the short waves of the solar light. This is then absorbed by the earth and plants in a greenhouse and converted into heat energy. This energy cannot escape through the glass or plastic because the heat waves are longer than the light waves.
The heated floor then warms the air immediately above it. This makes the air lighter and it rises, being replaced by cooler air from the top. Through this convection method, the entire greenhouse is heated.
Working of Solar Greenhouse
In a solar greenhouse you apply the same principle, except that the greenhouse is aligned to the sun. The south and west of the greenhouse have large glass windows to the south and east. The north side has black painted stone blocks to help absorb and retain the heat. Any surface that does not have to retain heat is painted white to reflect the heat. In other words, solar greenhouses have oriented glazing to get the maximum benefit from the sun’s energy. It is designed to minimize heat loss in winter and uses natural ventilation to reduce heat in summer.
Besides this a greenhouse that is full of plants is warmer than one without plants. This is because plants give out carbon dioxide, which heats up the air inside the greenhouse. Composts too give out carbon dioxide and help keep the atmosphere of a greenhouse warm in the night time.
Both glass and clear plastic can be used to build greenhouses. Plastic is less expensive, but will not last as long as a glass greenhouse. So, you need to choose a material in conjunction with your long-term plans.
In winter you can use an inexpensive exhaust fan to blow in heat from the greenhouse into your home. This will be less expensive than heating up your living room by conventional methods.
In addition, greenhouse glass can have a low-E glazing applied to it. This is a thin, semi-transparent layer of metal that reflects harmful ultra violet and infrared rays back to the atmosphere. This will help protect seedlings and tender plants from damage. With the proper kind of ventilation, low-E glass can help prevent a greenhouse from getting over heated, especially in the summer.
A solar greenhouse requires less artificial heating than a normal greenhouse in the harsh winter months. The amount of additional heating required will depend on the location of the greenhouse and the climate prevailing in your area.
All greenhouses, solar or not, use the sun’s energy to warm up the atmosphere for plants to thrive in even in the harsh winter months. The basic principle is the same for both solar greenhouses and normal ones. The sun’s light energy is converted into heat energy and used to warm up the air in the greenhouse.
However, there are a few differences as well. In a solar greenhouse, the building is aligned to capture as much as possible of the sun’s heat. This is done by having large glass or plastic windows to the south and east. The north wall is made of heat absorbing material such as concrete and also has ventilation to let out excess heat in the summer months.
Both types of greenhouses use plants and compost to add to the heat inside. This is because both plants and compost produce carbon dioxide.