100% Solar Thermal, Charleston, WV
Jim Richards decreased his energy use more than 30% with a Sunbank system.
Jim is proud to be 100% solar thermal this summer. As an experiment, he has disconnected any electricity backup and is running his Sunbank with a thermal sensor to keep track of the temperature. Jim has a 50-gallon unit on his roof in the South Hills neighborhood of Charleston, and so far has had plenty of hot water for his three-person household. Jim installed a tempering valve with his system and it has come in handy as the hot water in the Sunbank has regularly reached scalding temperatures of 160 degrees. Way too hot for a shower, the tempering valve allows him to use less hot water and therefore maintain a higher temperature in the tank.
Jim installed the unit himself in stages and before he plumbed it, he had it mounted and full of water on the roof. He was surprised to come out of the house one day and see steam billowing out of the hole where the pressure valve would soon be inserted. The Sunbank was boiling 50 gallons of water on his roof! That is a good indicator of how powerful the heat pipe collectors really are.
When the Fall comes, Jim plans to hook up his backup electrical element to supplement the solar supply.
Late Spring Performance
Keeping track of the temperature, Jim has sent along data points with which we have made this graph:
Below is part of the second page of Jim’s utility bill. It reveals some very good results:
First, it is important to note that we used the air conditioning very little in June of 2010 and in June of 2011, even though it was hotter in 2010. So, with that and all else held more or less constant, we can deduce the following:
June 2010 electricity rate $2.88/34kwh = $0.084/kwh
June 2011 electricity rate $2.28/22kwh = $0.102/kwh
From June 2010 to June 2011 = 19% electricity rate increase
June 2010 usage = 1,013kwh
June 2011 usage = 667kwh
From June 2010 to June 2011 = 34% decrease in energy usage
The Sunbank saved $35.85 in June 2011
$35.85 x 12 months = $430.20 x 75% (average annual energy savings) = $322.65/yr. $1,499/$322.65 = 4.645 years payback (which is slightly better than the calculator’s estimate)