Ford Man-thanks for the link. Such a heater would have been fantastic in the old place,but since my RV in Newport NC runs dual Electric and Propane, it's no longer the issue that it was...still an awesome piece of tech though!
In my former house, my front yard was North, so my neighbors couldn't see my dual Solar Thermal units (not that they would have cared, they were cool that way). The units(old windowpane, plywood box, soupcan 'tubes' made with power drill, high temp gasket sealer and black BBQ paint, the usual) ran the heat through high temp hoses through blocks of SIP board (plywood w/ closed cell foam) acting as window blocks. The ends of the hoses turned up, and leather 'caps' riveted into place on one end, made a one-way valve to prevent heat loss at night.
If I had kept the house, my next step would have been to build a plywood-box 'shelf' running 8" wide, as tall as the windowsill in order to blend with the decor, and the length of the kitchen (Unit A) and the Office (Unit B) and decorated to match the walls. The windows would have been unblocked and closed, permanent mounting points would have been made through the wall and into the boxes, and the hoses lengthened and filled with tiny holes.Each box would have a length of hose, 6" of sand and another fold of hose until the box was full-then covered.From then on the Thermal boxes would leak hot air into the sand for a slower, steadier heat and a longer retention of same for those cold nights. In the summer, the units would disconnect, caps would be fitted and the sand would simply be additional insulation-which would assist the AC.
Alas, I sold the place and purchased the RV a few weeks ago...since the new owners liked the Thermal Units so much, I left them installed, showed them where the Food Dehydrator/Solar Slow Cooker unit was(powered by the Units in Summer when disconnected) and left them my blueprints for the Sand Walls...so who knows, maybe the new owners will create them, if not for their new house perhaps for a Greenhouse they were thinking about.
Back to Hat_man's project though...I keep hearing about the development of IR Photvoltaic panels which can continue to generate power(albeit at a reduced rate) at night-but for some reason the availability seems to remain 'just around the corner' and has been so for about two years now
If anybody could get ahold of these-even at greater cost-we would be looking at a real game-changer here...constant power generation (full by day and partial at night) would reduced battery anxiety for any installation and reduce the need for secondary power sources as the IR function would keep PV from being useless on cloudy days.
Also-have any other Forum members installed battery-only circuits in a pre-wired, On-the-grid house? If so, i'd like to hear your results.