The Climate Battery Greenhouse - What is it?
A conventional battery stores energy in the form of electricity while a climate battery stores energy in the form of heat that your greenhouse can use.
A climate battery greenhouse utilizes the thermal mass of the earth to heat and (to a lesser degree) cool your greenhouse, much the same as a conventional geothermal system. Unlike common geothermal systems, the climate battery greenhouse simply uses fans to move heated air through corrugated piping, not complicated and expensive heat pumps.
So how does a climate battery work?
Collect the Sun’s Energy
Over the course of a sunny day, a greenhouse usually generates significantly more heat than it can use, venting the hot air outside to avoid damaging your plants. A climate battery allows you to store some of that heat for later use.
Store as Heat
Underneath your greenhouse there is a lot “thermal mass"; an abundance of soil that can store heat, similar to how a battery stores electricity. With simple fans, you can pump the excess heat in your greenhouse through underground tubing and cause soil to warm up while returning the cooled air back into the greenhouse.
Draw when Needed
All that heat stored in the soil can be put to good use. When the temperature drops at night and the greenhouse needs to be heated, the same fans that stored heat can retrieve it by circulating the air through the underground network of pipes. The air absorbs the heat from the soil and returns it back into the greenhouse in a warmer state.
Spotlight: Threefold Farm’s Climate Battery
So why does this matter?
Heating a greenhouse with fossil fuels is very expensive while operating a climate battery is not.
60-80% reduction in heating costs*
In our experience, climate battery greenhouses cost on the order of 60-80% less to operate versus a conventional propane heat source and provide secondary benefits.
A greenhouse is a lossy structure, meaning it lacks much of the insulation that typical houses have. As a result, it uses a lot of energy for heating, usually in the form of natural gas or propane. Since a climate battery just uses fans to move heat around, it costs far less money to generate a similar amount of heat.
*60-80% reduction figure is based off a electric utility rate of $0.12/kWh and a propane price of $1.70/gallon. Based on our calculations for our existing climate batteries, the climate battery greenhouse utilizes approximately 1.8kWh for a hourly cost of $0.22 and produces in the range of 60,000 to 110,000 BTUs/hour based on the 20F temperature differential it creates. By contrast, 60,000 and 110,000 BTU heaters cost $1.07 and $2.12 per hour to operate, respectively, when considering propane cost and the accompanying blower fan electricity. This difference alone is significant. However it must be noted that the climate battery must first run to store the heat, so in essence its operation cost is nearly doubled.