EcoRenovator - View Single Post - Questions about starting small

stevehull · 01-13-15, 06:01 AM

I agree with Mike on using other ways for heating.

I have used PVwatts for calculations and being slightly off due south is only a 5% loss. But the BIG loss is your tilt with your almost flat roof. And the sun has a low angle in the winter so you would need to tilt them up.

All that said, using electricity for winter heating is very inefficient as you can use those construction $ to buy/build a geothermal heat pump (GTHP). That would be where I would concentrate rather than PV to run electric resistance heaters.

A GTHP can extract 4-5 times the amount of heat from the ground with one unit of electricity. In other words, you run the GTHP to leverage FAR more heat out of the ground so it is 400-500% efficient. Or another way to look at it is that your annual heating costs are 1/4 to 1/5 with GTHP compared to resistance heat. Not 20 to 25% less but 75 to 80% less.

That is what I would do with your money rather than use PV panels to make electricity that is very inefficiently used as a resistance heater.

Or get a propane heater and use the PV panels to decreasing your electricity consumption for lights, etc. A four panel system (1 kW) would do a LOT!

Steve

Steve

01-13-15, 06:01 AM	#7
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	I agree with Mike on using other ways for heating. I have used PVwatts for calculations and being slightly off due south is only a 5% loss. But the BIG loss is your tilt with your almost flat roof. And the sun has a low angle in the winter so you would need to tilt them up. All that said, using electricity for winter heating is very inefficient as you can use those construction $ to buy/build a geothermal heat pump (GTHP). That would be where I would concentrate rather than PV to run electric resistance heaters. A GTHP can extract 4-5 times the amount of heat from the ground with one unit of electricity. In other words, you run the GTHP to leverage FAR more heat out of the ground so it is 400-500% efficient. Or another way to look at it is that your annual heating costs are 1/4 to 1/5 with GTHP compared to resistance heat. Not 20 to 25% less but 75 to 80% less. That is what I would do with your money rather than use PV panels to make electricity that is very inefficiently used as a resistance heater. Or get a propane heater and use the PV panels to decreasing your electricity consumption for lights, etc. A four panel system (1 kW) would do a LOT! Steve Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990 Last edited by stevehull; 01-13-15 at 06:06 AM..