Replacing Solar thermal and natural gas with Solar PV and electric pool heater

[California Newbie]

Hi all - Newbie question here:

Where can I find a thread on calculators, past experiences, best practices, etc for replacing a 24-year old rooftop Solar thermal and natural gas heater combo with a rooftop Solar Photovoltaic and electric pool heater combo? I believe my pool and attached spa is about 20,000 gallons.

Thanks!

[Watermom]

Not sure what to tell you other than to use the search link in my signature below (better than the forum software's search feature). Hopefully you'll be able to find something to help. Once your registration is complete and your post is moved out into the classified areas of the forum, you'll get more views and maybe somebody will have some information for you.

[BigDave]

CalNew,
I don't recall reading anywhere about replacing thermal solar pool heating with PV. My first impression is that it would be very expensive and far less efficient than direct Solar Thermal. But, there are, apparently, watercooled PV panels that increase the efficiency of the PV and provide thermal energy to the cooling water. That coupled with efficient heat pump and circulation pump could be worthwhile over the lifetime of such a system.
If you do work up the lifetime cost and output of such a system, I'd love to see it. Please post back here with what you find.

[California Newbie]

Thanks for the replies. Some more background - we're looking at rooftop photovoltaic to funded by rebates/refunds and a significant offset of utility power. Placing the PV on the roof would involve removing existing solar thermal. It's 24 years old (installed by prior owner) and I want to include pool heating into my cost-benefit analysis. It seems that if I am considering going PV anyways, I should factor in sizing it x% larger to replace my 24-year old supplemental gas pool heater with an electric pool heater.

I'll let you know what I come up with.

California Newbie

[BigDave]

See if you can find out about the hybrid watercooled PV - it sounds pretty cool.

[mas985]

PV only makes sense if you are using it to offset current electrical usage and even with that, payback is usually over 10 years.

Also, the combined efficiency of PV with a heat pump, is about the same as the heat transfer efficiency (BTU/sqft) of passive solar so you will need a PV solar panel about the same size as your current pool solar panel to get the same amount of heat. Therefore, you would not be gaining anything using PV to heat the pool and given the up front cost, it would be costing you a lot of money. For those days where you do not need to heat the pool, you would offset some house usage but that will may not be enough to justify the cost.

The water cooled PV might be a better option but I suspect that the heat transfer to the water is a lot less than passive solar.