To control the temperature in our GeoDome greenhouse, we used a Water Tank for passive temperature regulation and also an old car radiator for active heat exchange. To use a gas or electric heater can be costly. This used car radiator did the trick for us. No, it’s not really a beautiful piece in the greenhouse, but the functionality outweighs that by far.
Note: Here we share the idea, it is not a complete how-to. The idea is for tinkerers :). If you are one, you will appreciate this post, if you are not, just note that there is this possibility.
How does the Car Radiator Heating and Cooling work
A greenhouse can get very warm, even hot during the day. There are many ways to cool it: openings, ventilators, shade cloths – just to name a few.
Our climate’s uniqueness are the cool nights. It is not unusual to have just 8°C = 46°F at night in the middle of summer and even cooler as the season progresses, which is too cold for heat-loving plants. The radiator heating and cooling system’s simple heat exchanger absorbs the heat energy from the air during the day and gives that heat back to the air at night. To put it this way, whenever the water is cooler than the air it cools and when it’s warmer it heats.
Materials Needed for a Radiator Heating and Cooling System
- 1/4 HP submersible utility pump
- Car radiator (cleaned)
- Electric wiring with a switch
Installing the Radiator Heating and Cooling System
Since we already had a water tank as thermal mass and a pump to filter the water, all that was needed was to connect the radiator in sequence after the filter. So the water would be pumped through the radiator after being filtered and then flow back into the tank. The radiator worked in a very simple but effective way.
Car radiator heating and cooling system in action
Here is a video update on our second dome on a cool spring morning. In the second GeoDome, I placed the radiator in the middle of the dome to provide better air circulation.
If you can’t see the video go here.
Questions and Answers:
Q. With the radiator in there, can you continue to keep the frost out during the winter?
A. It totally depends on how cold it gets in your area in the winter. The radiator does not produce any heat in itself, it is just the water that stores the heat. It works very well in a plastic covered greenhouse till outside night temperatures drop to about -10C (14F), if it gets lower than that there is a danger of water freezing in the tank and potentially damaging the system.
Q. Will this work during a cold and overcast period?
A. This active heat exchange only works in combination with solar energy. On cloudy days there might be not enough heat to hold through a freezing night. A supplemental heater will be needed.
Q. Could you use solar panels or a solar heater to heat the water during the day?
A. You could heat the water in the winter with some kind of aquarium heater using solar energy or even a solar heater to heat water during the day. Except there might not be enough daylight in the winter.
If you want to build a Geodesic Dome too, we share a step by step How to build a GeoDome Greenhouse.
A Geodesic Greenhouse Book: Building and Using a Solar-Heated Geodesic Greenhouse.