Solar hot water - advice?
Posted: Sun Aug 15, 2010 5:49 pm
I want to install a solar hot water system in our house. I thought about a commercially-installed system with antifreeze in the pipes and a heat exchanger beside the electric water heater. However, my roof gets no sun at all in winter, due to surrounding tall trees, so installing a frost-proof system seems a waste. It will be a summer-only system anyway due to the trees. Given that a Rolls-Royce system is pointless, I am leaning towards a Volkswagen system.
What I have in mind is about 80 feet of 2-inch black pipe on the roof. There will of course, be bleed, drain and bypass valves to empty it in winter. The question is how to connect it to the water heater. I can think of two ways. I am interested in any thoughts anyone might have on them.
1. I could connect in in-line ahead of the electric heater. Cold water would flow through the roof pipe before entering the heater. Pro: Easy, low-tech plumbing job. Con: Collected heat is only used when water actually flows as I draw hot water. When water is not flowing, heat is wasted and could damage plumbing through over-heating.
2. I could connect it in a loop to and from the water heater. This would require a pump, probably solar-powered, to circulate the water, since the heater/tank is in the basement and therefore can't thermo-siphon. The pump would draw water from the bottom of the tank, circulate it up to the roof collector, then back into the top of the tank. Pro: Energy collection is continuous while the sun shines. More energy collected. Less chance of overheating. Con: More elaborate plumbing. Requires differential thermostat (or maybe not?) and pump with solar panel.
Any thoughts? Has anyone tried one of these schemes?
What I have in mind is about 80 feet of 2-inch black pipe on the roof. There will of course, be bleed, drain and bypass valves to empty it in winter. The question is how to connect it to the water heater. I can think of two ways. I am interested in any thoughts anyone might have on them.
1. I could connect in in-line ahead of the electric heater. Cold water would flow through the roof pipe before entering the heater. Pro: Easy, low-tech plumbing job. Con: Collected heat is only used when water actually flows as I draw hot water. When water is not flowing, heat is wasted and could damage plumbing through over-heating.
2. I could connect it in a loop to and from the water heater. This would require a pump, probably solar-powered, to circulate the water, since the heater/tank is in the basement and therefore can't thermo-siphon. The pump would draw water from the bottom of the tank, circulate it up to the roof collector, then back into the top of the tank. Pro: Energy collection is continuous while the sun shines. More energy collected. Less chance of overheating. Con: More elaborate plumbing. Requires differential thermostat (or maybe not?) and pump with solar panel.
Any thoughts? Has anyone tried one of these schemes?