A solar thermal heating system by Swedish company SolTech looks a lot like the curved clay or concrete tiles that might normally adorn a roof. The tiles are made of ordinary transparent glass, allowing the sun to shine through onto the absorbing surface underneath
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Links:
[1] http://www.earthtechling.com/2012/09/soltechs-ice-like-solar-roof-tiles-keep-your-home-toasty-warm/