Winters Work
“It was one of those winter days that suddenly dream of spring, when the sky is blue and soft and clear, and the wind has dropped its voice and whispers instead of screaming, and the sun is out and the trees look surprised, and over everything there is the faintest, palest tint of green.” Shirley Jackson
The incessant rain followed by a perpetual cold fog that has marked this winters weather more than those of the past finally broke this week. The sunshine was a welcome sight and it brought with it some cold chilly nights and a few good hard frosts again. While the geothermal system has churned out some impressive buffering to those cold temps I have been planning for a backup system to provide heat should we see something like we did with the great ice storm of 2021 where I was out of power for over a week during February’s cold. Last years dip into the single digit cold temperatures after a super mild start to winter reminded me that we should always expect the unexpected.
Since I produce mostly very hardy plants, many from high mountain environments, the heating system in the greenhouse really only needs to provide the very minimal amount of heat, in fact I really want to keep things just at or barely above freezing so as not to cause unwanted growth through the mostly dormant months. My goal with the design of the geothermal system and the backup heat system was to be able to have a frost free greenhouse in the winter, a cooler greenhouse in the summer and to do it as efficiently and environmentally sustainable as possible.
Natural gas isn’t available in my rural location, so that leaves propane as a gas option which would need to be delivered and a tank rented to power a greenhouse unit heater, which need electricity to power the fans and the pilot light making them not a great choice for resiliency and off grid independence. I thought about a wood stove, the romanticism of those old stove houses of the victorian era and the age of exploration has always been something I geeked out on. This is timber country and coming across cord wood isn’t hard. But I wanted to try something more efficient, less polluting and if possible even easier to run through a power outage to keep the plants alive during an arctic outbreak.
A sure sign that spring is on the way. But we do have more winter to go for sure.
Some research into pellet stoves showed a great possible solution, carbon-neutral pellets, are a sustainable byproduct of the timber industry that is a major economic driver in this “Emerald Empire'“ of towering douglas fir trees where I live. Pellet stoves are considered very efficient, with efficiency ratings typically ranging between 70% and 83%, an improvement over wood stoves by a decent margin. Pellets are widely available here and cheaper than propane and natural gas on a BTU basis, a few bags of pellets are easier to store than cord wood and when burning the, more complete combustion produces less carbon dioxide and particulate matter than wood stoves as well. The European Union's 2020 climate and energy program classifies wood pellets as a carbon-neutral form of renewable energy, and European companies have invested billions to convert coal plants to plants that can burn wood pellets. The ability to fill the hopper and not have to get up in the middle of the night to stoke the fire also seemed like a benefit.
So I found a cool design that operates without any electricity I knew this was what I wanted to complete the greenhouse heating system as a backup to the Geothermal. The wiseway pellet stove design has a relatively compact footprint so i’m not losing production space, It can burn for up to 30 hours on a bag of pellets making it super cheap to run. Coupled with the super cool Phase Change Material tiles that I sandwiched into the north wall, to make an eco radiator, this system would provide the perfect amount of controlled, efficient heat, with another benefit being the balancing effect of the dryer wood heat to counteract the moist, humidity raising effect of the geothermal system.Warm, moist air can be the bane of any alpine grower in a wet winter climate where molds and fungi love to run rampant under such conditions, so the choice between the wood heat which helps dry it out a bit and the moisture creating effects of propane combustion was another key in the design.
So we spent a sunny weekend, building the Phase Change heater/battery wall and installing an off grid pellet stove to the greenhouse to create a novel system of eco-friendly, carbon-neutral heating for the winter protection of plants. Check out the gallery to see how we did it:
I love science and to a reasonable extent technology (that which makes our life easier does not always make it more simple), the easy button would be to have just installed the standard propane unit heater, paid the money for the ongoing rental of the tank and then hope fingers crossed that the necessary delivery for propane wouldn’t coincide with one of our legendary ice storms that shuts everything down for sometimes days on end. But I like to do things different and I love experimentation, since someone has to be doing the research for a better future. I think this setup of the insulated north wall with Phase Change Material tiles has real promise. The wax like substance in the tiles starts to slowly melt as temperatures rise, this change from a solid, crystal like matter to a liquid results in a storage of energy and the latent heat is then stored to be given back as it changes back to a crystal upon solidifying as the temperatures drop. So the wall behind the stove has essentially become a giant radiator, an even cooler thing is that in the summer when the temps are really heating up the PCM tiles absorb that extra heat, helping to keep the greenhouse cooler. Check out the link for some really cool research on this stuff : Phase Change Material seems like they should become common place in building insulation materials for passive heating and cooling in the future. I use some under the heat mats in my propagation chamber and it’s cut down on the electricity use for those since the phase change buffers the on and off effect of the heating mats.
I will be continuing to run some more tests on the geothermal and how it works in conjunction with the back up heat now that we have it installed throughout this winter and hopefully I don’t really need it but it is there if I do!
Post thought:
So much I could write about today being the day that it is, but I’m happy to have sat here for a bit and penned my thoughts on this fun little experiment in designing the lowest environmental impact greenhouse that I could design. It will be some great science to see how it works and the long game is really in the efficiency and the ability to prove that concepts like Phase Change Material tiles and Geothermal systems have a place in lessening our impacts on the environment, it seems like that is more common sense to me.
Much more common sense than watching the richest man in the world, who coincidently owns the largest electric car company in the world, buy an election and then clap and cheer for the man saying they will do away with the incentives to buy electric cars. Common sense doesn’t seem to play into it anymore.