Open-loop direct system
How does an Open-loop
direct system work?
Used in tropical settings where freezing never occurs, this is the
simplest of the active systems. A standard, 52-gallon (200 l) electric
tank can be used, teamed with a 40-square-foot (3.7 m2) solar thermal
collector. Normally the electric element is not hooked up, so this tank
becomes a storage tank only, for preheated water feeding an existing
backup water heater.
Latest Technologies
An air vent, automatic or manual, is installed at the high point of the solar thermal collector to initially purge air. The pump, a small circulator pump using as little as 10 watts, can be powered directly by a 10-watt PV module, or a thermostatically controlled AC pump can be used. A snap-switch sensor can be installed to limit the temperature the solar tank reaches. Standard snap-switch sensors are available for 160°F or 180°F (71 or 82°C).
Quality Standards
Solar Rating and Certification Corporation
The Solar Rating and Certification corporation currently administers a certification, rating, and labeling program for solar collectors and a similar program for complete solar water heating systems. Collector testing apparatus SRCC’s certification program operating guidelines, test methods and minimum standards, and rating methodologies require the performance of nationally accepted equipment tests on solar equipment by independent laboratories which are accredited by SRCC. The test results and product data are evaluated by SRCC to determine the product’s compliance with the minimum standards for certification and to calculate the performance ratings. Equipment which has been certified and rated by SRCC is required to bear the SRCC certification label which shows the performance rating for that product. In addition, each certified product is published by SRCC in a directory. Each product’s directory listing contains information on the product’s material and specifications as well as the certified thermal performance.
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