I just read about a new type of solar based water heaters for households, that are already on the market. The setup is pretty much the same as with normal solar water heaters. There are panels for absorbing solar heat, a pump and a an indoor tank for accumulation. But with this type, there is no water circulating. Instead the system uses gas that will boil at a temperature about 0 degrees. The gas will then be transported inside to a compressor and this will create a temperature at about 100 degrees. The pump and compressor uses a minimum of electricity – far less than the popular ground- air- or lake heating system.
The amazing thing about this setup is that:

• You can color your panels any way you like
• You can harvest up to 50 degrees water while the outdoor temperature is about 0 degrees
• At all time you will gain nearly 7 times more energy that the system consumes
• The panels are flat, really flat – like a flat screen TV
• A panel at 200×0,80 cm is only 8 kg !

The psychical dimensions and features of the system allows for far better architectural integration. It should also be mentioned that the price is about the same as a traditional solar heating system. I would definently check this out if I were to install or reinstall solarpanels.

Read more about this at Termotek here (Website is only in Danish): Link

More details about the technology can be found in this pdf: Link