For some, solar panels are a status symbol; that's why so many people put them on their homes instead of fixing air leaks or changing light bulbs. The Onion made fun of it a couple of years ago:
Others prefer quiet money, believing the old dictum that "if you've got it, don't flaunt it." For example, real slate roofs are about the most expensive you can buy, but they last almost forever and they are really beautiful. The last thing you are going to want to do is cover them up with photoelectric or solar thermal panels. Solar energy is one thing, but an elegant roof is another thing altogether.
That's why the Thermoslate system from Spanish slate company Cupa Pizarras is so interesting. Being dark, a slate roof absorbs a lot of heat; being stone, it has good thermal mass and holds it for a while.
In the Thermoslate system, slate roof tiles are integrated with thermal cells that are ganged into solar thermal "batteries". These then supply hot water that can be used for domestic purposes or the inevitable swimming pool. It also might keep the interior of the space a bit cooler, taking heat away from the roof and moving it to the pool.
As demonstrated in this lovely french farmhouse renovation by Atome Architectes, the panels are invisible, integrated right into the roof. This system could be particularly useful for historic renovations where you just don't want to see the panels.
One issue that we have talked about often is open building, where designers recognize that different components of a house age at different rates. Slate roofs last a lot longer than plumbing connections, and I wonder how hard it is to maintain a system like this. I suspect that with slate installed with hooks rather than nails (one of the two options shown on the website) that one can slide them out.
Another concern is that raised by Martin Holladay of Green Building Advisor, who suggests that solar hot water doesn't make much sense anymore. However this system was designed in sunny Spain where it still does.
I have no idea what a system like this would cost, but it is probably one of those things that if you have to ask, you can't afford it. I suspect that it might pay for itself in energy savings in about a thousand years. On the other hand, it will reduce the carbon footprint in a year by the same amount as if you rode a bike for ten weeks instead of driving. (the average American car emits 4.7 tons of CO2 per year). So in terms of value it might not give the best bang for the buck, but in terms of elegance, it can't be beat. More at Thermoslate