There’s a million and one ways to make your greenhouse as efficient as possible. The more your greenhouse can sustain itself, and lower your energy costs, the more money you will save, and the better it will be for the planet.
Heat
There are numerous renewable and freely accessible sources of energy all around us. There are some obvious answers, like the installation of a solar panel. However, there are even cheaper ways to begin sourcing your own natural energy and warmth.
Sunlight
The sun’s rays are a powerful transmitter of warmth, something everyone who’s spent too long on the beach knows well. Any material allowed to sit underneath extended periods of sunlight will gradually absorb thermal energy in the form of heat.
Bricks, black barrels of water, bags of water, wood, or any other kind of dense material that can absorb and store heat can be harnessed as a thermal battery. Water stores four times as much heat as soil does, and even twice that of concrete and stone. Materials painted black absorb more than a third more heat than light-color objects and surfaces.
Sometimes, heat sinks are installed within greenhouses for additional media that can absorb the sun’s heat. An excavated pit, usually in the center of the area to be warmed, is filled with dense materials. This can be slabs of concrete, dark mulch, brick, or other materials that are good at absorbing and storing heat. Stone and concrete absorb twice as much thermal energy as soil.
Once the sun goes down, and the ambient temperature within the greenhouse drops -- the natural heating system is activated. Thermal batteries and heat sinks release their stored heat into the cooling air, preventing the temperatures inside from dropping too low.
Geothermal Heat
Beneath the first few feet of the Earth’s surface, the soil maintains a steady temperature somewhere between 50 and 75 degrees Fahrenheit. Even when cold nights can drop below freezing, deep enough beneath the ground is a temperate environment. This can be harnessed in a few different ways.
Since the earliest greenhouses, exposed and excavated earth has been used to help insulate and regulate temperature within the growing structure. This can be done by excavating a hillside and nestling the greenhouse within. Or, by digging a few feet into the ground before constructing your foundation, sinking your greenhouse’s structure. This is powered by the same law of conduction and thermal storage as heat batteries.
There are more advanced ways of using geothermal energy. A heat pump is a buried series of pipes that pump cool air from the greenhouse into the ground, where the temperature is higher. The air travels a winding path in order to collect enough heat before being pumped back into the greenhouse.
Water
Rainy Days
Rainwater is, of course, an openly available source of water (in most cases, check your local ordinances on water-use). Usually, it’s also better for your plants than standard tap water. Our drinking water is treated with several chemicals, like chlorine, that can really upset a sensitive plant. A rainwater collection and irrigation system may take some elbow grease to install, but it can have massive benefits both for your plants and your water bill.
You can collect rainwater either directly in rain barrels, or through a gutter and ridge system. A gutter system catches water dripping off the greenhouse roof and directs it into storage containers. A common design involves two rain barrels on each side of the greenhouse so that no water is wasted during times of precipitation. Make sure that the materials you use to transport and contain your water are plant-safe and won’t leach chemicals into the water over time.
Minimize Your Water Waste
Run-off can be a major source of excess water, especially in overhead and sprinkler irrigation systems. Standing water on your greenhouse floor isn’t only a missed opportunity, it’s also a huge attractor for pests, diseases, and algae alike. An exorbitant amount of runoff can be avoided by changing your irrigation methods, like utilizing drip tape or irrigation trays. Alternatively, instead of letting that water go to waste, run-off collection methods can be used to collect and return that water into your next cycle of irrigation. However, it’s important to monitor and treat the water you intend to reuse. The level of salts, chemicals, nutrients, and the overall acidity of the water are all essential qualities to healthy, plant-safe water.
Lighting
Throughout most of the year, sunlight will provide most of the light you need. However, if you’re planning to grow throughout the winter, or extend your daylight hours, we’ll need to find something other than just the sun. LEDs are the most efficient option when it comes to artificial lighting. They can use up to 70% less energy than that of standard light bulbs, and last ten times as long. While they require a moderate initial investment, the cost-savings over the long term are substantial.
