We finally insulated the 1000-litre tank this morning with 100mm mineral wool plus a tarpaulin cover. Before this, the tank was un-insulated, which benefited us as it cooled overnight and allowed us to perform repetitive tests. It will be interesting to see how well the tank performs, and heat accumulates.
The tank is a 1 cubic metre IBC. It’s outside, at the bottom of a scaffold tower with two test panels at the top.