Using the Sun: Solar Hot Water
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Domestic Hot Water
There are two ways to move hot water between solar collectors and the storage tank. In active distribution, a mechanical pump does the work. Passive systems rely on the hot water's natural buoyancy to lift it into an elevated storage tank. These systems include so-called breadbox heaters and thermosiphon heaters. They are described in more detail in chapter 10 (Hot Water).
Which is better—an active or a passive system? A lot depends on the climate. If the temperature goes below freezing in your area, choose an active system. But the simplicity and reliability of a passive system make it the better choice if the storage tank can be left outdoors without getting too cold, and if freeze protection isn't necessary.
In passive solar systems, the water is transported without any pumps, using city water pressure and the principle that hot water rises. Passive systems must be carefully designed, but they have no moving parts. Active solar systems allow more flexibility in design and installation, and they're easier to protect against freezing. However, active systems do have moving parts, so they tend to need more maintenance.
Solar-heated domestic hot water systems must be designed against freezing, overheating, corrosion, and leakage, and rooftop installation must be sensitive to the integrity of the roof. In all installations, the collector and storage tank must be correctly sized. In most metropolitan areas, there are professionals who have years of experience with these systems. Be sure to shop around. Utility programs sometimes provide referrals to solar contractors or give rebates for solar systems.
Pools and Spas
Pools and spas can be the biggest energy guzzlers in the house. If life after remodeling includes a heated pool or spa, you should seriously consider heating it with solar energy. Unless your electric or gas rates are very low, installing solar collectors will save you money within a few years.
Excerpted with permission from No-Regrets Remodeling by Home Energy (1997)