Featured Toyota testing new solar powered Prius

possibly a good thing if teraforming mars. All these new technologies and some old one too, could be a big advantage if they are applied timely to specific circumstances.

 

Hot tub

 

Got rid of it ~10 years ago.

But even if that was an option...I'd want to warm my normal household hot water and the hot tub.
Need two different water systems since the hot tub would be chlorinated. Or have to have a costly heat exchanger system, etc.

But this does sound like a good idea for apartment complexes and hotels.

Mike

 

Exactly...the real estate to locate all that stuff is the expensive part

Mike

 

works for a run-of-the-mill home, too - & at last count, i find 3 companies doing this.
CoolPV™ Solar Energy Perfected
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I've got a kind of head slap when I see this stuff proposed.

The market speak - up to 10% more solar electricity. Spec sheet - panel 295 Watts per solar panel. Spec sheet of my affordable LG panel 330 Watts per solar panel -0.37%/ degree C degradation over STP (25 degrees C) tested. That means at 52 degrees C (126 degrees Fahrenheit) The LG panel will drop to 297 watts just a little bit more efficient than the CoolPV panel used at 25 degrees. The more expensive sun power X 345 watt panel only drops 0.3% which means you need to go to 58 degrees C to drop 10%.

CoolPV may work well to heat rich peoples swimming pools in california, but it doesn't make much sense if you aren't heating a pool full of water. For most people for hot water just using an efficient natural gas heater. My local gas utility does have a $750 rebate for installing a gas backed up solar water heater, perhaps big rebates make solar water heaters make more sense in california. For those that want to heat their water with solar a electric hybrid water heater (uses a heat pump for most of the energy) for and more solar panels make sense.

China and Israel seem to be the big markets for solar water heat. China because of its need to increase energy per capita is likely to push the technology forward. Prices and Paybacks of Residential Solar Water Heaters A hybrid water heater claims to use only 25% of the electricity as an inexpensive water heater.

 

This article describes what I experienced, namely efficiency dropping much much more.

How Hot Do Solar Panels Get? PV Temperature Explained | EnergySage
Putting a heat gun on my panels last August, they were at 170°f .
Back of napkin .... >50°c rise above nominal - would mean a 25% efficiency loss? (Not even accounting for lower asmuth in August)
Then back to cool months .... I know it's not popular except in some new construction, but liquid radiant floor heating is another way to dump Heat off of panels - besides the jacuzzi and pool. Yes natural gas is cheap and plentiful, right now. Then again it is a non-renewable.

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That is much hotter than I thought, but let's use real numbers, as I did in picking panels for a hot climate. Do you have a proper air gap on your rack and thermal conductive base to the panels? Let's use the 170 F, which is 77 C or 52 C above 25C. If the temp outside is 100F or 38C then somehow the panels are 39 C above air temperature, which is much higher than the 20 degrees I thought was the rule of thumb. My LG 330W panels would be down 19% to 267 W. The Sunpower X 345 W panels would be down 15% to 293W (rounding errors not carried forward. Let's say the cool PV somehow are magic and they can get lowered to ambient (that takes a lot of water, and no one wants to turn a pool into a hot tub, a solar hot water heater won't cool it much) that would be 285 W panels down to 271W. The specs say not to run it except for short periods in the heat of the day on the coolPV or the pool water will get too hot. Now my LG panels will out perform the cool pv system in all realistic scenarios. SO the question is how much water do you have to heat and how much more cool pv costs up front and in maintenance. To me in a area of lots of hail damage, I feel much more comfortable with hail resistant PV racked on my roof than a heavier system with fluid running through it. Those sunpower panels will outperform in electricity in all conditions but are more expensive than the LG, they likely are a lot less expensive than cool pv unless you are heating a pool.

Yikes if you are trying to not use fuel perhaps you will be more like me and not buy the jacuzzi and pool. Solar doesn't work here to heat either outside the summer, and no one heats their pools in summer here. For hot water heaters I have an efficient gas one. My gas connection is most of the cost. I use about $6/month of fuel for cooking and hot water heating and drying cloths. If you really are worried about that tiny quantity of gas then add more solar panels and a hybrid electric (heat pump + resistive heating) water heater. Yes solar hot water makes sense in china where they don't have cheap natural gas and it is cheaoer than hybrid electric water heaters (different building standards and climate). It made sense in isreal because of the climate and expensive energy, but they started to produce a lot of natural gas 5 years ago (drastic reduction in carbon emissions with it as they switched away from imported coal), but they are installed in most places. This hybrid water solar doesn't make much sense to me with today's prices.

On heating the floor with solar thermal, that would require new construction. Why not use a geothermal heat pump driven by solar PV instead. It costs less and is more efficient. That's what they build around here. It reduces energy for both heat and air conditioning.

Now how much weight and energy will a solar panel cooling system take on a car? It doesn't sound like a viable option, but those cells on sun powers X panels as used in a prototype bev with large solar area and partial solar charging makes some sense.

 

These have been in the works closer to two decades, according to this chart. I was salivating over them for a project proposal back before I retired, though the the 3-junction devices available then had only 2 junctions that worked down here at the surface, the third needed the UV that is obstructed by the atmosphere.

Back then the 4- and 6-junction devices were merely proposals, but I see that they are working now. The quantum dots and perovskites, promising new ideas then, have really taken off now. But the then-promising dye-sensitized families, of which I received actual samples, seemed to have died off.

(If this image is too small, click on it for the linked full-size PDF.)

 

Sorry, I'm not one to ask for best or cheapest or even current home solar choices. My professional acquaintance on this topic was weighted towards small scale indoor (low light) energy harvest, where PV collector cost was a less important factor. Though the space-grade triple-junction cells available at that time were far far out of budget.

While it wasn't directly on topic, what I learned from that exercise was still extremely helpful when deciding to design and install my own home solar system while reroofing a few years later. But the information from that project is now outdated, prices have fallen, vendors and products offerings have nearly all changed, and I haven't kept up.

I also wasn't aiming for lowest cost. Rather, I wanted true energy-net-zero capacity in an installation with significant tree shading impairment, which argued for a specific architecture over some lower cost alternatives. And entering senior citizenhood, I wanted better reliability to minimize the need to get up on the roof to replace failed components when I turn old, weaker, and more fragile. That meant paying a bit extra for equipment with a better track record. This house is being set up with the intention of never needing to move until it is time to go to a nursing home.