IWillTry.org

Last fall I had the roof on my home replaced. My friend Steve did most of the work. As part of the project I decided to install some transparent polycarbonate panels (rather than shingles) over a south facing section of my attic, effectively turning my attic into a greenhouse. See complete details of that project in the IWillTry.org Wiki. My intent is to experiment with some different solar thermal collector designs under the panels. This arrangement is nice since I can experiment in the relative comfort of my attic rather than having to venture out onto the roof. It’s also less expensive since the panels offset some of the roofing cost and the solar thermal collectors need not be designed as robustly as if they were to be mounted externally.

There is hardly any direct sunlight here (Vancouver, BC) over the winter but I hope to extract some heat in the spring and fall for home heating and much more heat in the summer to heat a hot tub. I’ll likely have far too much heat in the summer so I will be installing silvered mylar under many of the panels to reflect most of the sunlight (unless I can dream up some other use for all that hot water).

Anyway, a couple weeks ago I worked up the curiosity to measure the temperature of my solar attic. I measured at 3 hour intervals over a 24 hour period using a digital weather station with logging capabilities. I measured once on a cloudy day and once on a sunny day for comparison. The following plots show the results.

Impressive though this data may seem (about 40°C peak with outside temperature around 10°C), it’s not particularly useful. It only indicates the maximum stasis temperature of the attic (with no solar thermal collectors in place and no heat being extracted into my home). It gives little indication of how much useful energy I may expect to extract. So what good is it? Well… it was easy to measure and rewarding to see. Sometimes you need a little boost to the morale when tackling large projects like this.Originally posted at www.IWillTry.org.