I'm posting up a project that may be of interest to those that have been participating in the Greenhouse Heating discussions.
I recently began construction on a Climate Battery Design to heat a greenhouse that will be used mostly for propagation, but if all works well to help overwinter a collection of tender bulbs as well. You can read a lot more about the project and see pictures of the project underway at the blog: illahe climate battery greenhouse construction
I'll summarize the design here, often called 'Poor Mans Geothermal' the concept relies on buried pipes to move air into the relatively stable soil temperatures underneath the greenhouse. Then to recirculate the air into the greenhouse to either cool or heat it depending on the ambient air temperature. These designs have been widely researched and implemented in the American mid-west where they are often used to grow vegetables year around despite often frigid winter temperatures. I can't find much on the construction or use in the Pacific Northwest, but if anyone on here has any first hand experience I would love to hear it, I may be breaking new ground (no pun intended).
The initial cost is in the cost of the pipe and the installation equipment involving a lot of digging, but the yearly operating costs are just the electricity to run the fans and thermostats that recirculate the air. I have seen some equations relating this cost of operation to that of the yearly cost to operate a household refrigerator. With the rising costs of gas heating for winter and the water scarcity issues that plague the often used evaporative cooling for summer, climate batteries may provide an eco-friendly and cost effective solution.
In the initial digging phase of this project, the original design was to place the lateral pipes (4" perforated ADS running between 12" ADS manifolds with riser pipes at either end of the greenhouse) down about 4' but we ran into groundwater so had to raise them up to just above it at around 3.5' deep. Measurements showed the soil temperature to be 51 degrees at that depth despite the air temps in the high 20's to low 30's. Some research showed that in Western Oregon, the soil temps usually lag about 3 months behind the air temps. So the soil temps of late December are reflective of the warmer temps of Autumn. Pumping this 20 degree temperature difference through the greenhouse has the potential to raise the temperature significantly. Most of the bulbs I grow are quite hardy and the goal is not to grow vegetables year around but maintain a greenhouse just above freezing if possible with as little energy inputs as possible. The benefit in the summer is the cooler soil temperatures can then be used to cool the greenhouse and since I grow a lot of alpine plants as well as bulbs I'm hoping this offset to be particularly useful.
Climate batteries are probably not the easiest design to retrofit into an existing greenhouse, but if you are building a new one it's a design to consider if your soil/conditions allow for it. I'm also doing a lot of research into the new modern phase change liquids and tiles that are coming onto the market, Hoping to implement these in addition to the climate battery design. PCM tiles allow the ability to store massive amounts of a days heat in the greenhouse and then release it back slowly into the greenhouse as temperatures cool at night. You can read about those here: Phase Change tiles for greenhouse heating/cooling
Attached are a couple of pics, but in addition to the blog mentioned above where you can follow this project, i'm also posting updates on the instagram at illahe_rare_plants.
Mark
I recently began construction on a Climate Battery Design to heat a greenhouse that will be used mostly for propagation, but if all works well to help overwinter a collection of tender bulbs as well. You can read a lot more about the project and see pictures of the project underway at the blog: illahe climate battery greenhouse construction
I'll summarize the design here, often called 'Poor Mans Geothermal' the concept relies on buried pipes to move air into the relatively stable soil temperatures underneath the greenhouse. Then to recirculate the air into the greenhouse to either cool or heat it depending on the ambient air temperature. These designs have been widely researched and implemented in the American mid-west where they are often used to grow vegetables year around despite often frigid winter temperatures. I can't find much on the construction or use in the Pacific Northwest, but if anyone on here has any first hand experience I would love to hear it, I may be breaking new ground (no pun intended).
The initial cost is in the cost of the pipe and the installation equipment involving a lot of digging, but the yearly operating costs are just the electricity to run the fans and thermostats that recirculate the air. I have seen some equations relating this cost of operation to that of the yearly cost to operate a household refrigerator. With the rising costs of gas heating for winter and the water scarcity issues that plague the often used evaporative cooling for summer, climate batteries may provide an eco-friendly and cost effective solution.
In the initial digging phase of this project, the original design was to place the lateral pipes (4" perforated ADS running between 12" ADS manifolds with riser pipes at either end of the greenhouse) down about 4' but we ran into groundwater so had to raise them up to just above it at around 3.5' deep. Measurements showed the soil temperature to be 51 degrees at that depth despite the air temps in the high 20's to low 30's. Some research showed that in Western Oregon, the soil temps usually lag about 3 months behind the air temps. So the soil temps of late December are reflective of the warmer temps of Autumn. Pumping this 20 degree temperature difference through the greenhouse has the potential to raise the temperature significantly. Most of the bulbs I grow are quite hardy and the goal is not to grow vegetables year around but maintain a greenhouse just above freezing if possible with as little energy inputs as possible. The benefit in the summer is the cooler soil temperatures can then be used to cool the greenhouse and since I grow a lot of alpine plants as well as bulbs I'm hoping this offset to be particularly useful.
Climate batteries are probably not the easiest design to retrofit into an existing greenhouse, but if you are building a new one it's a design to consider if your soil/conditions allow for it. I'm also doing a lot of research into the new modern phase change liquids and tiles that are coming onto the market, Hoping to implement these in addition to the climate battery design. PCM tiles allow the ability to store massive amounts of a days heat in the greenhouse and then release it back slowly into the greenhouse as temperatures cool at night. You can read about those here: Phase Change tiles for greenhouse heating/cooling
Attached are a couple of pics, but in addition to the blog mentioned above where you can follow this project, i'm also posting updates on the instagram at illahe_rare_plants.
Mark