Category SOLAR WATER HEATER BUILD YOUR OWN

Afterthoughts

Everyone seems to be thinking, reading, writing and talking about solar energy these days. That’s good. Mews about solar technology — like sex — pops up regularly in almost every newspaper and magazine in the country. It looks as though both sex and the sun are here to stay. And we can be thankful for both.

But just about everything we pick up starts out

the same way: "We have too many people ____

We have this terrible energy crisis…. We’ve been in an ‘our-energy-will-last-forever’ frame of mind for too long, and so we’re running out of fossil fuels…. We’ve got to find ways to use al­ternative energy sources or we’re all going to die (or at very least, drastically change our style of living)…. The sun’s the answer to all our woes."

That’s the bad-news approach — scare tactics followed...

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How Does a Solar Pool Heater Work?

In a fairly sophisticated solar pool system, water is pumped out of the pool, through the strainer, and through the filter. Alter the filter it passes through a check valve. This check valve is more than just an option. Its purpose is to keep water that’s draining out of the panels from back-washing the filter (Figure 99).

Once it has passed through the one-way check, the pool water reaches a critical tee. This tee separates the upper panel loop from the ordi­nary circulation loop. When the pool temperature is sufficiently warm — or when there’s no sun to heat the panels — water circulates only through the filter loop. A gate valve in this lower loop, immediately after the tee, determines which way the water will flow (Figure 100).

Whenever this gate valve is closed, water is forced u...

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How Are Solar Pool. Heaters Set Up?

The roof of a pool house or cabana makes an ideal location for solar heating panels — espe­cially if the roof faces south. If there’s a flat roof, or if you decide to mount panels on the ground, they will have to be tilted a few degrees to give you reasonable heating efficiency. You may want to build a rack that raises the tops of the panels so they face the sun at a better angle for your latitude — even though finding the exact angle is not critical. Any structure that supports the panels should be super-strong and anchored to the roof or ground so the wind can’t budge it There should be no need to insulate either the water lines or the backs of the panels, but any nails, screws, bolts or lags that fasten the panels should be caulked to keep the roof from leaking...

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Can Pool Water be Heated with Solar Collector Panels?

For some reason, cheaper solar collectors de­signed specifically for swimming pools are called "heating panels" rather than "collectors" — even though they work on the same principle. Regular collectors — the type we’ve been discussing throughout this book — can be used. But it’s a little like taking a Ferrari to pick up a load of 2 x 4’s at the lumber yard.

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Figure 95. Using a little imagination, designers at Parallax in Hinesburg, Vermont, have built a concrete pool deck that doubles as a flat plate collector. There are several features you should notice:

1. The concrete slab sits on at least a foot of well – compacted gravel or sand.

2. The slab is "floating," which means that it’s not firmly anchored to the ground anywhere...

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How Much Do Swimming. Pool Covers Help?

An opaque or transparent swimming pool cover

— which will transmit solar radiation to the water

— can give your pool another 10 degrees of natural storage capacity. This means that if a free-floating cover with pockets of trapped air is stretched over the pool at night (and whenever no one is swimming), we can expect the water temperature to stay at up to 20 degrees above the surrounding air (Figure 94).

Insulating "pool blankets," as they’re called, pass about 85 percent of the light that hits them through to the water. Some are even mounted on convenient reels, which let them be stretched out and rolled up again without a lot of hassle...

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Solar-Heated. Swimming Pools

We’ve saved our discussion of solar-heated swimming pools for last — not because it’s least {or most) important, but because it’s different. On one hand, swimming pools are still consid­ered luxury items, even in the minds of most affluent Americans. Domestic hot water, on the other hand, is something we take for granted in most homes in the United States. To put it another way, we see hot showers as one of life’s necessities, but heated swimming pools as ex­pensive frills.

As we get more and more strapped by our dwindling supply of traditional energy sources, the public will disapprove more and more of burning precious fuels to heat pool water. Already legislatures in California, New York and Illinois lean quite specifically on pools that have gas – powered heaters...

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How is All of This. Controlled?

You are the master controller because you set the temperatures and determine the pump speed (start #3, Figure 86). But when you’re not around to oversee things — which is most of the time — a small electrical box with a differential thermo­stat takes charge. Out of this box run 4 electrical lines. Line A plugs into a regular wall socket. line leads to a sensor in the collector’s ab­sorber plate. Line C goes to a sensor against the side of the solar hot water tank, and Line D leads to the pump.

Electricity runs through the differential ther­mostat to the wire leading to the thermistor sen­sor on the absorber plate...

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Forced-Circulation Systems

Подпись: Now let's talk about forced-circulation systems, specifically, in detail. Actually, we've been discussing them all along, since much of what's been said so far leads up to the design in Figure 86. But remember that Figure 86 represents only a suggested system. It may be more elaborate (and costly) than you want, and it may not suit your house — either old or new — exactly. It's safe to say that you probably will have to make some minor modifications. For instance, you may decide, after reading the last chapter, that you don't need a circulation pump at all, in which case your system will not be "forced." Even if you decide that a thermosyphon system will work for you, you may choose to include some of the controls and other gadgets mentioned here. In many ways Figure 86 represents all of the best elements of sound solar water heating technology at the present time. At first glance it looks complicated and confusing, but it's not — once you break it down and understand what's going on. Each of the component parts — with the ex-ception of the absorber plate and the special solar storage tank — is a standard, time-tested plumbing element that should be sitting on a shelf in your local plumbing supply outlet. There's no more need to lose sleep over the possibility of your system's failing than there's need to worry about a breakdown in your regular household plumbing. That's because basically a forced-circulation solar hot water heater is regular household plumbing.
Подпись: What's in the Collector Loop Besides a Pump? The whole collector loop (start #1, Figure 86) should consist of 3/4-inch Type L soft copper or Type M rigid copper. You'll also need standard 3/4-inch sweat-type fittings, valves, threaded nipples, and other fixtures throughout. These should be joined together with high-grade 95-5 solder which withstands heat better than regular 50-50 solder. Any threads should be coated with Teflon pipe dope normally used in refrigerator tubing. Standard plumbing compound will dis-solve in propylene gycol, and threaded joints will quickly leak. The lowest point in your system no doubt will be where the cold water tap leaves the solar storage tank. Here there should be a short section of tubing and, of course, a boiler drain which can be used to empty the collector loop quickly. This is also where you will most likely fill the system with fluid for the first time, so use a drain cock with hose-connecting threads. Somewhere in the lower part of the loop — either before or after the pump — there should be a poppet-type pressure relief valve (like the Watts model #174A), set to "pop" at 30 psi (Figure 87). If this should blow for some reason, it will dump antifreeze fluid on the cellar floor, so it might not be a bad idea to keep a bucket under that valve so you can save any fluid that's released.

To keep things simple, we’ll divide the heater into its three major parts: (1) the collector loop, (2) the hot water loop, and (3) the thermostatic controls. Then, we’ll trace the flow of antifreeze fluid from the storage tank (beginning at the very base of the collector loop), to the collectors and back through the heat-exchanger coil. Next, we’ll follow the path of the water, beginning at the cold water supply, as it goes through the solar storage tank and existing hot water tank, to the house it­self. Finally, we’ll explain how the control system operates.

Подпись:
This pressure relief valve shouldn’t cost more than $8...

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