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Solar energy is a renewable resource that is environmentally friendly. Unlike fossil fuels, solar energy is available just about everywhere on earth. And this source of energy is free, immune to rising energy prices. Solar energy can be used in many ways - to provide heat, lighting, mechanical power and electricity.
Active solar systems use solar collectors and additional electricity to power pumps or fans to distribute the sun's energy. The heart of a solar collector is a black absorber which converts the sun's energy into heat. The heat is then transferred to another location for immediate heating or for storage for use later. The heat is transferred by circulating water, antifreeze or sometimes air. Applications for active solar energy include heating swimming pools, domestic hot water use, ventilation and industrial process air and water for commercial facilities such as laundries, car washes and fitness centres.
The most common form of space heating is passive solar heating described in more detail in the passive solar brochure. However, there are several options for using active solar techniques for space heating. The most common method is to used glazed collectors to heat a heat transfer liquid held in a storage tank similar to the domestic hot water systems described below. Heat from the tank is transferred to a radiant floor heating system, a baseboard radiant heating system or through a fan coil unit to a forced air system.
Another technique is to directly preheat fresh air drawn into the building. This is being used more in commercial and industrial applications. A typical system of this type uses a darkly colored, perforated aluminum sheet mounted on a south-facing wall. As the sun heats the sheet, a fan draws solar heated air through the perforations, warming the air. This preheating can significantly reduce energy use by conventional heaters to bring fresh air up to room temperature.
Another common way to use the sun's heat is with the use of a solar domestic hot water system. Depending on how the system is used, a typical system will provide 50 to 75 per cent of a family's hot water needs. With water heating accounting for about 20 per cent of home energy use, a solar DHW system is an attractive method of reducing a home's fossil fuel consumption.
A solar water heater typically uses glazed collectors mounted on a roof and connected to a storage tank. Fluid is pumped to the collectors where it is warmed by the sun, then returned to a heat exchanger where it heats the water in a storage tank. Year-round residences often will have a additional backup water heater. Modern solar water heaters are relatively easy to maintain and can pay for themselves with energy savings over their lifetime. Large, commercial systems can dramatically cut heating costs, making them ideal for businesses that use a great deal of hot water, such as restaurants, car washes, laundries and fitness centres.
The water temperature in swimming pools can be regulated using active solar heating systems, extending the swimming pool season. From mid-spring to mid-fall there is a great deal of solar energy that can be collected. For outdoor pools, a properly sized solar water heater can replace a conventional heater Ñ saving a tremendous amount on fuel bills and extending the swimming season. Indoor pools that are used year round generally will have a conventional heater as backup. Using a pool blanket is highly recommended, regardless of how the pool is heated. Heating a pool without a blanket is like heating a house without a roof on it; heat loss is instantaneous. Further, pool blankets reduce the loss of expensive pool chemicals through evaporation.
In a typical solar pool heating system, solar collectors are mounted on a nearby roof and connected to the existing filter pump. Most solar pool heaters use cost effective unglazed collectors. When the pool needs heating, water is diverted to the collectors where it is warmed and returned to the pool. Generally speaking, a pool will need a collector area equal to 50 to 75 per cent of the pool surface area.
For more information on renewable energy sources, active solar energy, passive solar energy, and photovoltaic solar energy, please contact:
Solar Energy Society of Canada Inc. Tel: (613) 234-4151 Email: sesci@sympatico.ca Canadian Solar Industries Association Tel: (613) 736-9077 Email: cansia@magmacom.com Kortright Centre for Conservation Energy Theme Co-ordinator Tel: (905) 832-2289 Email: kcc@interlog.com Natural Resources Canada Tel: (613) 996-6220 Email: rudy.lubin@nrcan.gc.ca Ontario Hydro, Environment and Sustainable Development Division Jackie Hennessy Tel: (416) 592-8487 Email: jackie.hennessy@hydro.on.ca Ontario Ministry of Environment and Energy Tel: 1 (416) 325-4000
E-mail:
sesci@sympatico.ca
25 November 1997 URL: http://www.newenergy.org/newenergy/sesci/publications/pamphlets/active.html