Solar Thermal - Water Heating
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Solar Domestic Hot Water systems (SDHW) are a mature technology that was first commercialized over 100 years ago. Through the years, the technology was improved and is now considered market ready and governed by technical standards. Globally, over 125 million square meters of solar collectors have been installed accounting for 88 Gigawatts Thermal (GWth). Although SDHW technology is mainly used for heating water for domestic or process applications, a variant can also be used for space heating through radiant floor heating systems. Larger solar water heating systems have been proven to be cost effective applications for industrial, commercial and farming applications too. Several hundred systems are installed annually in Canada for diverse applications ranging from fish farming to conventional milk producing farms as well as in restaurants, commercial laundries and other.
Solar Hot Water collectors can be mounted on roofs, walls or the ground. The collectors absorb heat energy from the sun and transfer that heat to a storage tank, usually with a heat exchanger. Two SDHW systems appropriate for climates that experience freezing are Closed Loop Drain Back systems or Closed Loop Anti-Freeze liquid (usually propylene glycol) systems with heat exchanger systems.
The most common type of solar collectors for domestic use is a Glazed Flat Plate collector. Another type available for SDHW systems are Vacuum Tube collectors. Appropriate sites for SDHW systems have a clear southern exposure on the roof or close to the house or building free from shading from about 10 AM to 3 PM or longer. The size of the collectors and storage tank will depend on factors such as the climate, solar exposure and amount of hot water required. In addition to the collectors, SDHW systems include additional components such as storage tank, circulation pump, and thermostatic controls.
Solar thermal collectors can be a good investment for domestic hot water heating. With a good southern exposure and adequate space for a solar storage tank, a solar water heater will pay for itself in energy savings in 5 to 15 years under average energy costs. It will provide 75 to 100% of summer hot water needs and 10 to 20% of your residential hot water demand in winter (40-60% over all). Usually systems are installed with a supplementary or backup heat supply such as gas, electric or wood. For other hot water uses such as barns and outbuildings, needs and economics will vary depending on the agricultural uses of the structure.
A single 4 x 8' (approx 3m2) glazed solar thermal collector will capture between 1,500 and 3,000 kWh of energy per year (depending on consumption and climate). At current electricity rates, that energy is worth $150 to $300 a year. In most residential homes, water heating is the second largest energy consumer next to space heating, costing anywhere from $180 to $480 per year (www.cansia.ca).
Solar Hot water is the most direct, efficient and cost effective way to convert the sun’s energy in to useable energy for homes, businesses and industries. Natural Resources Canada's (NRCan's) ecoENERGY Retrofit program provides financial support to homeowners, small and medium-sized businesses, industrial facilities and public institutions to help them implement energy saving projects that reduce energy-related greenhouse gases (GHGs) and air pollution, thereby contributing to a cleaner environment for all Canadians.
For more information, go to: http://www.ecoaction.gc.ca/
Modified: 06-24-2008
