Monday, March 15, 2010

Solar Sundays- Part I

My interest in solar projects has been growing for a few years, and I've been researching solar water heating hoping to someday install our own system here at Green Gate. While the government tax rebates for solar projects sounded attractive, we found they would only cover a small system- basically enough for domestic hot water heating, but not for winter space heating. Purchasing a multi-panel solar thermal system would be cost prohibitive. So once again, I came to realize if you want to get something done, you have to learn to do it yourself! Having spent many a night perusing websites and solar forums all winter, I thought it was time to dive in and actually build something myself. With an enthusiastic 'okay' from my wonderful wife, I decided to start dedicating a day every week towards getting a 'prototype' system online and tested. Here is our first solar collector, inspired by designs on the Build it Solar website (one of my favorite resources for a variety of sustainability projects, by the way). Basically, I started by making a 4X8 'box of 2x6 lumber and a plywood bottom.
Then I added 1.5" of polyiso insulation over the plywood.
Next, I soldered together the copper piping that will carry water through the collector- basically 1/2" 'risers' connected to 3/4" manifolds, with an inlet on one end and outlet in the opposite corner. This copper is the expensive part of the project, but I managed to get a pile of tubing for less than scrap prices off Craigslist about a month ago! The photo shows the copper assembly as I was pressure testing it prior to the next step.
To make the 'fins', I took my leftover aluminum heat transfer plates (these are the ones I was using for the in-wall hydronic system installed in the bedrooms recently) and expanded them to 7/8" dia using a pipe, a simple wooden jig, and several blows from a sledgehammer. Good exercise. The fins were then clamped around the tubing using some special vice grip clamps made by a friend of ours for this project. With the clamps forcing the aluminum fins tightly around the copper, I put in several screws through to the plywood base to hold everything in place. This system seemed to work very well once I got the hang of it. Here's a close-up of the fins installed over the tubing.
Then I gave the assembly a coat of black paint.
and finally cut a piece of twinwall polycarbonate for glazing (this is the same stuff I used for our raised bed garden covers). Other than trim pieces over the glazing, it is basically weekend I'll work on the pump and controls.....

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