Corrugated roofing metal and sand turned into a solar water heater, How I’ve assembled it.

part 4 I have now assembled the solar water heater fins, made from corrugated roofing metal, filled with sand and heating pipes. this will form the daytime heating of a 2 part heating system for my greenhouse, the next system to be added to it will be a compost water heating system for day and night heating, how much heating this will provide, I’m not sure, but i have high hopes. The frost has arrived and the day and night is now cold. i miss my summer crops.