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Solar Shed -- Performance and Economics

This is preliminary performance of the system -- I'll add more performance data, and the cost/savings results in a couple months.

Performance

At the time I am writing this, the system has only been operating for 3 days, so this is first cut performance.

I intend to install sufficient instrumentation to log the system performance, and some other items.

The weather for these three days has be clear, but VERY cold. Night lows have been -20F, and day highs have been barely over zero.

I have been letting the system heat the 500 gallon storage tank water during the day without using the radiant heat in the house during the collection period. This way I can get an idea how much energy the collectors are producing by how much the tank temperature goes up. After the sun is off the collectors, I turn on the house radiant floor circulation system and use the stored heat overnight -- this brings the tank temperature back down to about 85F by the next morning.

Each day, the 500 gallon tank has started at around 85F, and ended the day at about 125F. So, the stored heat by per day is:

Heat Stored = (500 gal)(8.3 lb/gal)(124F - 85F) (1 BTU/lb-F) = 162,000 BTU

This is equivalent to 2.1 gallons of propane burned in an 85% furnace.

I think that its encouraging that the collectors do well in spite of the very cold temperatures (which result in greater heat loss from the collectors). I expect to do better once temperatures get up to our normal winter highs of about 30F.

Update 2/8/07:

The system has been up since early January, and is doing fine.

I will provide some more in depth performance numbers in a month or two.

As I am looking our the window writing this on March 8, it is snowing hard.

But, we are still on solar from the heat stored in the thermal storage tank yesterday. Yesterday, the collectors both heated the house, and got the storage tank up to 155F -- this should be enough to carry us through the rest of the day. I'm feeling a bit smug :)

Here is some simulation work that was done before the system was built:

Simulations

Gary 1/15/07