When emergencies strike, there’s so many directions they can come from. From a simple storm to a pandemic, from a week without outside power to a year, there’s such a wide spread of circumstances to consider and prepare for. Without outside food, or with limited access to food, a greenhouse becomes more essential than ever. But how do you keep a greenhouse functioning on its own? In the event of an emergency, without access to outside supplies or power, a greenhouse needs to be as self-sustaining as possible. This includes power, heating, water, seeds, fertilizer, soil. How can you make a greenhouse that can withstand even a complete societal cut-off?
Passive Power, Passive Heat
One of the most essential ways to take your greenhouse off the grid is through sourcing or generating your own power. Power is used for a variety of things within a greenhouse, lights, irrigation systems, timers, heaters, fans, etc. Without an electrical hook-up, greenhouses need to get this power from somewhere. Solar panels are an excellent and affordable way to easily capture and reutilize energy from the sun’s rays. These can be set-up without a terribly large initial investment and offer powerful returns in a relatively short time span. But what about generating heat? While small electric heaters may be able to run off a few solar panels, they probably won’t be able to run all night, when they’re most needed. Thankfully, there are lots of options for passively keeping your greenhouse warm and safe, even in the coldest conditions.
Deep underneath the earth’s surface is a molten core. From there, great amounts of energy and heat radiate out towards the earth’s surface, warming the soil, the oceans, etc. Even in the middle of winter, that heat can be accessed only a few feet beneath the crust of the earth. Somewhere between 6 and 8 feet underneath the ground, the soil maintains a temperature in the range of 55 to 65 degrees year-round. Geothermal heating harnesses this thermal energy in order to heat a building, like a greenhouse. When using a geothermal heat pump, air is pumped from the greenhouse into pipes found underneath the ground. As air moves past the soil, it rises or cools in temperature to match the ambient temperature of the ground. It’s then pushed back up into the greenhouse in order to raise or lower the temperature within.
Alternatively, sunken or greenhouses with earthen walls are also put into direct contact with the earth’s warmth. This can be done by placing the foundation of the greenhouse a few feet underground, or by excavating a small hill in order to nestle the greenhouse inside. There, warmth from the earth naturally warms the air in the greenhouse. Geothermal heat is especially useful in the winter, where freezing temperatures can have disastrous effects on vulnerable or young plants. In an emergency, geothermal heating keeps working, regardless of outside factors or unrest. This works best with a well-insulated greenhouse in order to keep trapped heat inside. Make sure that seals, vents, and framework are well-sealed and securely fitted. Use dual covers when covering your greenhouse, or even thick blankets in the nighttime or winter. This, traps heat inside, keeping it from escaping out into the cooler air.
Heat, of course, is in great supply when it comes to sunlight. The sun’s rays fuel a greenhouse’s power, but how can we conserve and trap that energy, to use when the sun isn’t there? Thermal batteries are an excellent solution for this. Made out of dark materials, that quickly absorb a lot of sunlight and heat, thermal batteries store that thermal energy until the ambient temperature drops. As the temperature drops in the nighttime, heat is transferred from the batteries into the cooler air, heating up the greenhouse. Dark-colored, dense, absorbent materials work best for this.
Heat sinks combine geothermal heat and the sun’s energy. A part of the ground is excavated, and dense materials are placed inside. Often bricks, masonry, or gravel. These are then heated both by the sun, and through thermal energy transferring from the soil into the material. This then works as a thermal battery, releasing heat as the air in the greenhouse cools down.
