Systems and Heat Exchangers

Natural circulation solar hot water systems — thermosyphon systems, to use the more technical term —' have a lot of appeal for households that don't need very much hot water. We've touched on these a bit already. The real beauty of a free-circulating system is that it operates with no fuel or power costs — although it needs a back-up system, like any other sunpowered heater, to come on whenever the weather's bad. Thermosyphoning solar hot water heaters are generally not as effective as forced circulators in providing a large and dependable hot water supply, but here are some of the very good reasons why people put them in:

• Fluid circulation through the system occurs naturally, without help from a pump, and is completely self-regulating. As long as the collectors can pick up usable solar heat, the heater will keep operating.

• At night, or whenever there's no sun, the circulation stops automatically. This means that no electro-mechanical controls are needed to shut the pump off when the panels can't collect heat any longer.

• Because a pump and thermostatic controls are not necessary, a free-circulating solar water heater is at least $200 less expensive to build than a forced circulator type. (A simple, direct thermosyphon system — including 50 square feet of collector, a 40- to 80-gallon storage tank and plumbing — should cost no more than $500 if you do the installation work yourself.) Operation costs are all but eliminated, too, because no electricity is used. And only rarely is maintenance necessary.

» In a natural circulation system the storage tank must be located above the top of the collector panels. For a lot of people this means the tank doesn't have to be placed, as some have said, in the "cold, damp basement," but in the "warm, dry house where it should be anyway." This reduces heat loss from the tank itself — and from the plumbing — and can save extra dollars in insulation costs.

Assuming that there is room for a storage tank inside the house, the only considerations in many cases are, "Where do we put the collector panels?" and "Do we have a floor or rafter structure strong enough to support a heavy water tank?"

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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