Top 5 Greenhouse Climate Batteries giving Free Heat in the Winter!

Top 5 climate battery greenhouses on reviewed, showing 5 examples of Youtubers who built earth battery geo thermal energy storage devices in the ground used to heat a greenhouse in the evening and through the winter.

The magic of phase change from liquid to vapor and back again drives the Climate Battery™, or Subterranean Heating and Cooling System (SHCS).  The system functions like a simple refrigeration system, moving heat from one place to another. But a typical 1200 square foot greenhouse needs only the equivalent equipment and running costs of a single large household refrigerator!  

Learn more: Rechargeable Earth Battery

By slowly circulating all of the hot, moist daytime air of the greenhouse down underground where it is always cooler than the greenhouse air, the Climate Battery forces the vapor to condense.  By doing so, the solar heat as well as the chemical heat from the plant photosynthesis that was required to evaporate the moisture in the first place is forced into the soil.  The "miracle" is that by inducing temperature change over the phase change barrier we have the potential to harness 5 times the energy normally the case if we simply tried to solar heat objects cluttering up your precious greenhouse floor space.  And by inducing this "dewpoint" condition in the soil of the greenhouse, the plant roots are always being bathed in warm, moist conditions - the perfect balance for plants and solar greenhouses.  The space is heated by the massive amount of radiating solar heat stored in the soil under the greenhouse, and with fans to circulate cooler nighttime greenhouse air through the tubing network, adding warmth and moisture back to the greenhouse.

Here are some basic parameters we use for designing a climate battery:

1:  Calculate the volume of space in your greenhouse (cubic feet or meters);

2:  Select a fan (or series of fans) to push all of the greenhouse air volume through the climate battery at least 5 times per hour for slow heating, and up to 20 times per hour for cooling, with a fan speed controller for seasonal adjustments;

3:  Calculate the number of tubes you will need to bury, such that a calculation of the air speed in the tubes is no more than 5 feet (1.5 meters) per second  for heating stages, and no more than 10 feet (3 meters) per second for cooling;

4:  Lay out your tubing so that the tube lengths are at least 25' long (7.5m) and no more than 35' long (10.5m), so that the warm air is traveling in the heat-exchange tubes for at least 3 seconds before exiting the tubes and transiting to the exhaust port.

5:  Bury your tubes so that at least 12 inches (30 cm) of soil is covering the top layer, and so that from the bottom of one tubing layer to the bottom of the next layer, you have a minimum of 2 x the tubing diameter, so a 4" diameter tube will have a minimum of 4" of cover, before the next layer is placed (more is better).

6:  We use buried manifolds to connect all the tubes together at either end, and connect these to vertical risers as a means of laying everything out efficiently, though for a smaller greenhouse, you could gather all the ends of the tubing together in a fan box or barrel, and lay them out evenly across the greenhouse footprint.  If you are using ADS corrugated culvert pipe for manifolds, as shown above, you will locate the holes for heat exchange tubing centered on the top of a rib as shown above, and space them apart at intervals of 3 - 4 ribs, and stagger these holes in different layers.

7:  If your climate battery has vertical risers for the intake and exhaust sides of the battery, like you see in the above photos, you can install a copper coil inside the exhaust riser, which you could heat with a wood-fired boiler or a hot water solar panel.  If this is installed with sufficient air flow around the pipe, the climate battery exhaust air temp will be heated significantly as it re-enters the greenhouse space.  For example, the greenhouse may go down to 40°F when the outdoor temp drops into the teens or lower, and pumping air at this temp through soil that is at 60°, we will soon chill that soil below 50°.  Adding a hot water coil into the exhaust port would add another 10° or so to the exhaust, providing a level of backup heat that may be all you need.  A similar method may be used for backup cooling in summer.  If you have a dry climate (RH = 50% or lower), you can install a misting system into the exhaust port, which will deliver evaporative cooling into the greenhouse.  This works less well with a high humidity level of around 75%+, because you can't add more humidity to air that is already saturated.  Otherwise, if you have a cold water source, such as running your outside irrigation water through the coil before it goes out to the garden, you may be able to chill your summer greenhouse a bit further.

8: For those growing in a Zone 8+, you may benefit from using raised beds with independent "bed batteries" and "row covers", to make a sort of "greenhouse within a greenhouse" to help with insulation against cold nights.

Related: Earth Battery DIY Pipe

You can see examples of these principles at work in the photos above.  The corrugated nature of the heat-exchange tubing we use helps to cause turbulence, so if you must use smooth-surfaced tubing in the ground, it is best to introduce some turbulence by curving, or introducing waves into the tubing layout, to get the air to release more of its heat and humidity into the soil.  The tubing must be perforated as frequently as possible to maximize the exchange of heat and humidity, so you should select tubing with maximum density of perforations.

These are the simple principles behind the battery.  In our experience, every climate battery is different, because we use it in combination with other energy storage features in any greenhouse, and there are many other principles at work, such as proper orientation on site, insulation of all the non solar harvesting surfaces, insulating curtains, etc.  The performance of each greenhouse is dependent on all these factors and more.  It's not like another product you can buy in the marketplace, like a car from which you will expect precise performance as promised by the manufacturer, because the performance of a climate battery greenhouse is dependent on the climate characteristics of its site and the experience level of its manager.