Years before solar photovoltaic panels started appearing on residential roofs to generate electricity, a rooftop collector box for an active solar thermal water heating system was not an uncommon sight. Heating water is one of the oldest uses of solar power, and it can still save money. And because all solar water heating designs incorporate gas-fired or electric backup heaters, you’ll never be without hot water, even on cloudy days. Basically, the solar technology consists of a rooftop solar collector and an insulated storage tank to hold water at temperature. Passive systems utilize a syphoning effect to move water through the collector and into the tank. An active solar thermal water heating system uses a pump and a control system for circulation at preset temperatures.
Active systems utilize one of two collectors:
- Flat plate: The most common method, flat plate systems consists of a low profile, glass-covered box containing black solar-absorbent material and a grid of metallic flow tubes that absorb heat. Flat plate collectors usually do not heat water above 180 degrees.
- Evacuated tube: This method heats metal conductors inside rows of glass tubes. Each tube consists of an outer tube and an inner tube. Air is removed from the space between the tubes to form an insulating vacuum. Metal conductors heated in the vacuum transmit heat to a fluid circulated by a pump. Evacuated tube systems can produce water temperatures from 170 to 350 degrees and are most commonly used in commercial applications.
In direct active solar water heaters, the pump moves fresh water through the rooftop collector and into the storage tank for direct use in the home. In indirect active systems, the pump circulates heat transfer fluid through the collector and into a heat exchanger unit incorporated in the backup tank, which then heats household water. Because the heat transfer fluid contains anti-freeze, indirect active systems are favored for climates where temperatures drop below freezing.
Geisel Heating, Air Conditioning & Plumbing has a 77-year track record of serving Cleveland-area homeowners. Call us today about the benefits of installing an active solar thermal water heating system in your northeast Ohio home.
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