Very interesting---thanks IV.
I do have to say as I read that link "I think we have been here before". Not with this new material but the direct heating of water (and other materials) with solar radiation. It is common in many areas of the world where they enjoy moderate temperatures and high levels of sunny days to see domestic water tank/heaters on the roof of houses.
Back in the 80's I designed a passive solar addition to our house--a popular concept at the time. Does it work--to a degree (no pun intended), but at a cost that will never be recovered by me. One small draw back is that thermal sinks, as they are called, work two ways. Once hot they liberate heat (at night for instance), but once cold, after a number of cloudy days---they don't want to warm up again. The good news about my "experiment"---I knew going in that the cost was "stranded"---and I was willing to do that to "play" with the technology.
I have to say, that sitting in that space with a cup of coffee and watching the snow fall all around you while warm and cozy has tremendous intrinsic value for the soul
I should add that the highest heat gain days are those with snow cover---there is a significant multiplier derived by the reflection of the sun light from the snow.
"A pessimist sees the difficulty in every opportunity, an optimist sees the opportunity in every difficulty” ---Sir Winston Churchill
"Political extremism involves two prime ingredients: an excessively simple diagnosis of the world's ills, and a conviction that there are identifiable villains back of it all." ---John W. Gardner
“You can’t go back and change the beginning, but you can start where you are and change the ending.” ---C. S. Lewis