- Wed Jul 12, 2006 6:02 am
The problem in such a scheme is to design for the total thermal mass involved added to the dynamic heat loss from the house. Though a good absorber of IR, black pvc pipe is a thermal insulator and will not heat the water inside it easily.
Depending on the latitude, the angle of the sun will be low in the winter months and can be easily blocked by even low buildings or trees around except for a short time in the middle of the day.
The pipe assembly should be oriented nearly normal to the rays of the sun, which will have an impact on the design of the green house itself. Since the pipe panel will not track the sun one can expect only about 40% average collector efficiency over the peak efficiency obtained with the sun perpendicular to the panel.
Please look at the following options:
1. A 10 foot x 10 foot pvc pipe panel will hold about 30 gallons of water. Assuming that this much will be heated through about 55 deg F (30 Deg C), which is feasible, you will get about 3.5 KWhr energy.
2. A passive wall of dark coloured or matte black painted boulders (100 numbers one foot dia, about 110 lbs weight each, arranged to form a 10 foot x 10 foot collector) housed inside a green house (this requires some design to optimise solar interception) will collect about five KWHr of energy in a day. A fan ciculates air drawn from the house around the stones to pick up the warmth. A thermostat can regulate the operation.
3. The best will be a 10 foot x 10 foot solatr collector attached to a 200 gallon water tank to store the heat. This can collect as much as 8 KWHr/ day. In India such a collector will cost about US$2000. Associated pumps etc may cost another US$1000. You can expect to save 250 KWhr/month.
Alternative energy is free. Collection is expensive.