Thursday, March 7, 2013

Solar hot water

So we decided to install a solar hot water system. And here it is! We used Apex Solar, located in Glens Falls. They did a very nice and professional job. They happily worked with us on system design - both size and placement - and took our concerns about looks just as seriously as our performance requirements.

I'm going to attempt to explain how it works, but keep in mind that I'm an accountant - not an engineer. Or plumber.

Roof brackets
We needed three sections of tubes to support our household needs (some folks need four).
Had to straddle the chimney

The vacuum tubes are two layers of glass with a copper tube in the center. The copper tube is filled with "magic gas" with converts from a liquid to gaseous state thus creating heat. This heat transfers to the water that is flowing through the top pipe (the one that runs up through the roof, across the top, and then back down through the roof, moving left to right in the picture below). Since the only water in the system is in that one pipe (remember the tubes hold a gas, not water), the system is amazingly light weight. Each tube is independent so if one tube gets broken for some reason (a tree limb, a baseball), it doesn't shut down the whole system.

Installing individual tubes
The water that flows through the roof-mounted pipe never enters the domestic water system. It is only in the small upper tank that is connected to the control unit / heat exchanger. If the weather is freezing and dark (for instance, February at night) then the water cycles back into the small tank in the house and cannot freeze. When the roof temperature climbs because of sunshine, the water cycles back up and gets heated.

The heat is transferred to the domestic hot water tank until the two tanks reach the same temperatures. Yesterday, a mildly sunny day, the water reached 140 degrees by mid-morning. If the DHW tank temperature cools too much, the system starts up again and rewarms it. Before anyone freaks out about how hot the tank water is, there is a mixing valve that adds cold water before it is used in the household. This is a required anti-scalding measure.

The control unit with heat exchanger  hidden inside

Close up of the tubes
The whole thing is surprisingly subtle up there. You can't even see it unless you're in the Southeast section of the yard. Pretty cool
Normal view

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