In February 2004 we added a solar hot water and space heating system. This system provides domestic hot water and during some times of the year helps with space heating as well.
The system was installed by John Wakeman of SUR Energy and I helped out a lot as an apprentice.
There are several types of solar hot water systems; ours is called a drainback system. The flat plate collectors we used were originally installed on what was the Climax Molybenum building on the corner of Huron Parkway and Plymouth Road; now the building is part of the Pfizer campus. Interestingly, the homeowner worked in that building when it was being leased by Philips Display Components.
Anyway, the Yazaki SCX-1020 "Blue Panels" that were in use on that building in the early 1980's were discarded and I found them for sale on the side of the road in Whitmore Lake in 1999. I ended up with six of them which I completely restored.
Yazaki SCX-1020 Blue Panels during installation
The system works by circulating water through the collectors when the sun is shining strongly enough to provide useful heat. There are two circulation loops: a collector loop and a tank loop.
The collector loop has about 15 gallons of unpressurized water in a small "drainback" tank in the basement. When there is enough heat in the collectors, a sensor turns the system on and the water is pumped up through the collectors to gain heat and then it returns to the drainback tank.
The tank loop has two 105 gallon storage tanks (actually Marathon water heaters) that contain pressurized water that is circulated through a heat exchanger in the bottom of the drainback tank, where it picks up heat from the water coming back from the collectors. In this way the entire 210 gallons of water is heated up and then used throughout the house.
Two 105 Gallon Storage Tanks
Since the six collectors provide more than enough hot water during most of the year, we installed a thermosiphon loop so that some of the hot water can be used to heat the house during cooler months. This was done by placing an eight foot finned radiator element in the furnace return air duct system and allowing the hot water in the storage tanks to circulate through the radiator, giving off heat that is then supplied to the house through the return air duct system. This works well since we have a heat recovery ventilator (HRV) that is blowing cool air into the return air duct, and that air is warmed by the radiator.
Finned Radiator in Return Air Duct
How does it all work? In winter months, there is not much sun in Michigan; nevertheless the system gave about 15% reduction in total natural gas use in February and March, and starting in early April we were able to turn our boiler off as the system was capable of providing 100% of our hot water needs. In the summer months the storage tanks are regularly at 170F when the system shuts off for the day.