Why don't they integrate solar water heaters with photovoltaic panels?

[CarlWohlforth]

It's a question that's been bothering me. Yup, that is the kind of thing I think about when trying to get to sleep at night. And I haven't been sleeping well lately!

Photovoltaic panels are getting installed all over the place here in California. They take up prime roof space. They are aimed right at the sun to maximize electricity production. Fine, that is what they are supposed to do.

The fact remains photovoltaic panels produce more power when they are cooler. Most people who pay for solar electric care about the environment and saving money on power costs. So why not transfer that excess heat from where it isn't wanted to a place where it is? You could add a simple 12 volt circulation pump (or whatever voltage the panels produce) and pump a water/anti freeze solution behind the panels through small copper tubes to transfer the heat from there to a 100 or 200 gallon (or larger) tank near your existing water heater. You could then put a 10 gallon tank inside the 300 gallon storage tank and run your water through that before it gets to your hot water heater.

Pre-heating your water will save half or more on your water heating bills. Therefore it will save that much fuel too. Getting solar hot water this way will also increase the efficiency of your solar panels, maybe by enough to make up for the electricity used in the circulation pump.

The solar collectors (the photovoltaic panels) are already provided because you bought a PV system.

The controls are simple. The sun shines, electricity is produced. When electricity is produced water gets pumped. That's it!

Of course you could get fancier with a larger storage tank. If I had a large hot water storage tank I'd pump hot water through the tiles in my bathroom floor the 9 months of the year that my feet are cold. Man it would be nice to get out of the shower and step on a warm floor. Or to walk barefoot over to the bathroom in the middle of the night. I might not want to go back to bed!



If you do know of a PV module that integrates PV and Solar hot water please reply to this post, PM me, send me an email or write me a letter. Contact me.

[cullenbryant]

There's an easier way to go about the goal of getting free hot water, i think, without the incorporation of the panels.     Your water line is a pressurized system starting at your holding tank.    So what you can do is take a worn out, used up hot water heater and place it outside in the sun, build a box around it, usually using 2x4 framing, insulation with glass covering to further enhance the suns impact.   This can be done elaboretely or on the cheap depending on the aestetics of the neighborhood, but in the end you want it all painted black.    Hook your lines back up and everything is still inside the pressurized line.
Hot water?   your main concern at this point is it getting so hot it causes the water heater to explode.

"batch" solar hot water heater.
 
I am going to build this system at some point in the future, however we have the kind of winters that would force me to toggle back to electric about 4 months out of the year.    I have built dehydrators and cookers that are very simple in design using these principles.     

[cullenbryant]

or maybe i didn't understand the question   

[CarlWohlforth]

If you are handy and your goal is to get hot water you have an excellent idea! I've seen many buildings in tropical areas with large, black, water tanks that provide the only hot water available to the building. I'd love to see photos of your project as you build it! Your thinking and efforts can go a long way to making the US energy independent.

I was just thinking of all the PV panels being installed around me. No need to build or buy a separate solar collector when you have just installed panels over a large area of your roof. These are almost always installed by contractors. If the panels supported hot water collection it would be cheaper for people to add solar hot water systems. They also would not need a box or tank or anything in addition to the PV panels.

[CarlWohlforth]

Oh, and a big WELCOME to you cullenbryant!

[cullenbryant]

thanks carl.   yours is an interesting concept and makes sense.   
i've always wondered about taking a
magnifyer and putting the beam onto a copper coil.   think back to the science fair days of burning newspaper with a magnifyer and the suns rays.    imagine how hot that coil would get if aimed properly and how small of a contraption it could potentially be.     harnessed that heat and it could convert to massive amounts of electric.
anyway,   if your over at the refuge you can see
pics of my low budget solar dehydrator in the food and home remedies forum.

i think before it's all said and done each house will be it's own grid.   going to take some
time though.   those of you in california are much further down the road than the rest of us.