Solar Hot Water Systems

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A solar water heater can operate together with your current electric or fossil-fuel water heater to supply a portion of the home's total hot water heating requirement. This will reduce greenhouse gas emissions, air pollutants and the cost of your water heating.

Energy Collection

Roof-mounted panels (solar and photovoltaic where required) facing south at an angle equal to the location's geographic latitude are the best type of solar collectors. There are many configurations for a solar collector although the most common are flat plate and evacuated tube collectors.

Opinions differ about the best solar collector, but it really depends on their application.  You may compare various factors such as efficiency, absorber coatings, construction materials and the like but the bottom line is system performance and ROI.

Potential purchasers should check out the Solar Rating and Certification Corporation’s (SRCC) website ( www.solar-rating.org) for a review of solar collectors. This non-profit organization offers third-party, unbiased evaluations of solar thermal water heating products. There is rating documentation for every registered product to allow comparisons between the models.

A table of Collector Thermal Performance Ratings shows how much thermal energy a collector generates on different types of day, such as clear, cloudy, or partly cloudy, in metric (MegaJoules per panel/day) and imperial units (BTU per panel/day). You only need to choose your area’s weather pattern and the category, usually C or D. In the category column, the temperature lists the difference between atmospheric air temperature and the water temperature coming into the solar collector. This is the delta-T (ΔT) temperature difference. In general, a larger delta-T will give you better solar collector efficiency. All collectors tend to function with similar efficiencies in "normal" weather conditions (as in categories C and D), but give greater variance outside these limits.

If certain factors are kept constant, such as the installation quality and warranty, the best solar collector will be the one giving the highest energy at the lowest cost.

No matter which solar collector is chosen, it should receive sunlight without obstruction from 9 a.m. to 3 p.m. the whole year through: make sure that your building site is positioned for such exposure. Collectors should also be angle-mounted from the horizontal to your latitude while facing as close as possible to solar south. There is a phenomenon called magnetic declination that must be considered when you use a compass to align your positions. Use magnetic declination maps to correct your compass readings to locate the north and solar south correctly.