It’s great to hear about all the advantages of Geothermal heating for greenhouses, but what good is it if you’ve already got one - or dozens - of greenhouses using expensive electric heat or unreliable solar options? While most resources out there will tell you how to build one from scratch, we’ll help you out with some guidelines for converting your existing greenhouse(s) to use free, renewable energy even in cold climates!
Where Do I Find the Extra Space?
One of your primary challenges, to start with, will be locating land for burying pipe loops or digging ground wells. Depending on your climate, large greenhouses may need 3 acres or more of open ground to install horizontal pipes. You could opt instead for vertical loops, but there’s a limit to how deep you can go and still achieve proper air exchange, and vertical wells like these are substantially more expensive to drill than for horizontal layouts.
One possibility may be to take down some existing structures and clear out room for excavating and laying pipes. Once those are installed, the structure can be replaced, allowing for access in case repairs are needed in the future.
Can I use Water?
Tapping into a natural source of hot water and running through your greenhouse like an endless free radiator is a dream solution, but it takes a bit of luck to hit that kind of geothermal jackpot. Natural hot springs are relatively rare, but if you’re open-minded and creative, you may actually be able to take advantage of some man-made sources of pre-heated water. So, check with your neighbors! Some industries produce wastewater over 300 degrees F that must be cooled before it can be processed or released. Passing that water through a *tightly closed* loop in your greenhouse can transfer heat out, providing a toasty climate in your greenhouse(s) and making your industrial neighbor happy! This really isn’t geothermal heating, but it is absolutely part of the reduce/reuse/recycle philosophy of sustainable production.
Tighten up the Ship
Since Geothermal systems don’t rely on combustion to produce heat, they don’t emit dangerous gases that must be exhausted for safety. While most greenhouses have some gaps built in to provide venting for this kind of hazard, geothermal greenhouses don’t need it. It’s better to have a tightly sealed greenhouse that doesn’t pour out precious heat on cold nights. Make sure your greenhouse cover is in perfect shape. In fact, you may want to recover it just as a matter of course, since this will eliminate the need to go over the existing film to locate and patch every hole, crack or tear that’s popped up over the years. A new cover will give your improved greenhouses a new lease on life and allow them to take the best advantage of the new heating system.
Greenhouse covers need to be durable, lightweight, easy to repair, and affordable. They must be highly resistant to UV exposure, without weakening or yellowing. They must be able to tolerate temperature variations and resist deformation from snow loads. High light transmittance is an absolute must.
BTL’s ArmorClear is a strong, extremely durable greenhouse film fabricated with flexible layers of LDPE sandwiching a reinforcing layer of woven HDPE. An additional anti-condensate coating is available on some products so that accumulated condensation does not interfere with light distribution. ArmorClear products offer high light transmittance as well as high UV-resistance. It’s flexible, easy to install, and can be custom fabricated for easy installation with minimal waste. Give us a call at (541) 447-0712 for a free evaluation and estimate with our friendly experts.
Gone With the Wind
It doesn’t make sense to try to drop active greenhouses a few feet in the ground, but if you’re in an area with high winds, it’s worth taking a few steps to ensure that your free heat isn’t carried away, especially at night and on cloudy days. Consider adding windbreaks outside the greenhouses - build some berms and add shrubs and small trees, or consider constructing barriers of brick that can serve double duty - blocking the wind while absorbing solar heat during the day and releasing it during the night for a little extra boost.
Divide and Conquer
If you’re growing different kinds of crops in your greenhouse, consider where their needs differ. You may find that it’s worthwhile to separate the more tender types that need steady warmth even during the night from others that actually need to chill in order to produce a good crop. Rather than cheating yourself by maintaining an (un)comfortable average, consider dividing your greenhouse with some retractable thermal curtains. Keep the tender plants closer to the warm air outlet and let the others cool off beyond the thermal curtain - most likely near the cold air intake. Reducing the area that needs extra heat will reduce the load on your system and may even permit you to keep blowers off during the night, reducing your power consumption to zero!
Similar to the concept of windbreaks, if you’re converting a relatively small greenhouse complex, consider investing in some thermal covers to further reduce nighttime heat loss. These covers could be as simple as woven mats to lightweight space-age looking silver blankets. Just remember to put them up at twilight and remove them at dawn so that the plants can enjoy a full day of sun.
