One way to collect heat in a greenhouse is to trap it in water.
A hoop house is an arched greenhouse that resembles a half-circle. Hoop houses are used both by amateur gardeners for backyard production as well as on farms for large-scale commercial crop production. Hoop houses may be made using materials commercially available from any hardware store. The greenhouses are heated during the day by solar radiation trapped beneath the greenhouse membrane. At night, hoop houses lose heat rapidly due to lack of insulation; an alternate form of heating, which uses the sun's energy, can help replenish some of this heat. Does this Spark an idea?
Instructions
1. Obtain a 60-gallon plastic rain barrel from a garden center or hardware store, or make your own using a food-grade storage barrel. Such barrels are typically available for purchase from factories where food is processed.
2. Paint the barrels black using spray paint. Black-colored items absorb the most heat through solar radiation.
3. Fill each barrel with water using a garden hose. Position the barrels throughout the greenhouse so that they are in sunlight for the longest period of time and release heat to the most plants. The barrels absorb heat as long as sunlight touches them. This will heat the water inside the barrels to create a thermal mass. As the air cools, the warm water releases heat into the air to keep nearby plants warm.
Tags: greenhouse that, hardware store, Hoop houses, solar radiation