How Can We Use Sol r Energy to Heat Houses and Water?
Buildings and water can be heated by solar energy using two methods: passive and active (Figure 6-12). A passive solar heating system absorbs and stores heatfrom the sun directly within a structure (Figure 6-12, left). Energy-efficient windows and attached greenhouses face the sun to collect solar energy by direct gain. Walls and floors of concrete, adobe, brick, stone, salt-treated timber, and water in metal or plastic containers store much of the collected solar energy as heat and release it slowly throughout the day and night. A small backup heating system such as a vented natural gas or propane heater may be used but is not necessary in many climates. On a life cycle cost basis, good passive solar and superinsulated design is the cheapest way to heat a home or small building in regions where ample sunlight is available during daytime. Such a system usually adds 5-10% to the construction cost, but the life cycle cost of operating such a house is 30-40% lower. The typical payback tim
