Climate batteries for commercial greenhouses are expensive and involve lots of earth moving! You can get nice results from small scale changes in a hobby greenhouse. No earthmoving necessary! This simple system uses the heat from the greenhouse air to warm the soil in the greenhouse. Hot air in the greenhouse can damage plants but luckily, soil has about 1000 times the heat capacity by volume. This means you can easily cool the greenhouse air by 5 C or 10 C by circulating that hot air to warm the soil by a tiny fraction of a degree! The heat you put into the soil in the day, is slowly released at night, keeping the greenhouse a bit warmer. Some specs! The computer fan is old, and ran in a computer for about 8 years but in its day, it was rated at 32 cubic ft per minute. In metric, that is 15 liters per second. (54 cubic meters per hour). And this means that (when new) it was capable of about 2 air changes per hour in my 10 sq meter greenhouse.