Posted by SJC on November 1, 2006, 4:17 am
Robert, I agree. I think operating solar thermal collectors at lower temperatures
raises the efficiency quite a bit. When the water store gets down in temperature
the heat pump can still provide good consistent house heat. When morning comes
and the water store is cool, the solar thermal collectors can operate at a very
efficient part of their curve and really take in the BTUs.
Posted by News on November 1, 2006, 9:39 am
That is in ideal conditions. In a cloudy cold climate you may get sweet
nothing, while the earth is warm.
But a large store of water at 5C still has a lot of heat in it and the COP
may be quite high as the heat pump extracts heat from the water store.
What you are saying is have a combination of solar and heat from the earth.
Fine if you have the space and the finance to built the two.
A major point is keeping the COP of the heat pump high while extracting heat
from the earth. The water thermal store can do this.
Posted by SJC on November 1, 2006, 3:26 pm
I am in Southern California, where we import 80% of our natural gas.
I calculate that if people heat the average 3 bedroom 2 bath home using solar
thermal, they can save enough NG to run their car.
Posted by News on November 1, 2006, 8:53 pm
I don't doubt that at all. However keeping the COP as high as possible on
the operation of a heat pump is also applicable to Californian and beyond.
Posted by SJC on November 2, 2006, 3:14 am
I have yet to see any fluid source heat pump COP curves that show it runs
so much more efficiently with warmer input temperatures. For example,
40F input water produces a COP of 3, while 60F input produces a COP of 4.