Deciding if I should build this solar heater

Author	Message
rogerdw Guru Joined: 22/10/2019 Location: Australia Posts: 955	Posted: 11:04am 11 Apr 2021         Murphy's friend said   That rocks in a drum as thermal mass for hot air does not work. I have seen a house here, many years ago now, where somebody built the house around a massive (2m diameter & about 8m tall) concrete column (made from culvert sections) which was filled with rocks. This required a *very* powerful fan to draw air through and the power used by the fan was way in excess of the heating power stored in the rocks. The conclusion was that using fan motivated hot air to heat a storage medium was too lossy to be worth while. Now, using water as a heat storage medium is *very* worthwhile. The university I worked for built a gigantic insulated tank that stored one million liters of water. In Summer that was chilled, using off peak power back then (I'll assume its solar power now) and this made a  big saving in the campus air conditioning costs, I remember payback being somewhere around ten years. The storage was reversed to hot water in winter to be also used for air conditioning. Very useful information to read, thanks Murph. All this info helps in building a picture of what's been tried and what might possibly be adapted to work with this project.