PRACTICAL PHOTOVOLTAICS

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A HYBRID SYSTEM—THE ULTIMATE MARRIAGE?

"That's all very interesting," you may be saying, "but won't it still cost me an arm and a leg to get started in photovoltaics?" The answer is that it might well do so, save for the fact that solar electricity has one further remarkable property: It is perfectly compatible with, and can supplement, another generation package.

Let's say, for instance, that you have a 500-watt wind charger, and the system hasn't quite been able to meet all your needs. Replacing it with a larger, more powerful generator would likely require a new tower plus the new windplant. In such a case, it's quite probable that solar electricity could supply the needed extra energy at a substantial saving. The panels can be made to match the wind generator's voltage by linking the solar units in series. And if your wind charger happens to be a 36-volt model, the addition of three panels in series will almost double your power!

Now that claim might sound a bit far fetched. Bear in mind, though, that windplants are designed to stall in periods of relatively calm breezes—such as often occur in the middle of the day—during which time you must rely on stored power. But it just so happens that solar cells are at their peak at noon, so the panels can "fill in" for the idle wind machine. And the reverse is frequently true under adverse light conditions: During a storm the sun doesn't shine much, but the wind sure does blow.

What's more, when you're augmenting a wind system with photovoltaics, the wiring is not at all complicated. If you anticipate problems with overcharging, by all means include a photovoltaic charge regulator along with any other regulating unit that may already be in the system. Fig. 7 will show you what might be done.

COMMONSENSE REMINDERS

It should go without saying that you'll want to place your panels in unshaded areas. But if you can't quite catch every bit of the early or late sun, don't worry too much . . . the most productive hours are between 10 a.m. and 4 p.m. (If you set up your system so it can track the sun, you can increase its power output by about 40%.)

Locate your storage batteries in a sheltered area that's well ventilated (explosive gases are given off by active batteries) and protected from extremes of temperature. The storage site—as well as the panels—should also be as close to your house as possible . . . to limit the line losses that occur when electricity travels through wire. It's a good idea to check the charge in the batteries regularly with a hydrometer . . . and don't forget to add water as needed.

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