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Science

Geothermal Energy, Heat Pumps and Cannabis Cultivation

Whether in an indoor crop or in a greenhouse crop, energy consumption is an important expense and a determining factor for the profitability of a business. Each location has its own challenges in the form of temperature, humidity, growing season, the need for additional lights, availability of electricity, gas and operating range. Geothermal energy, in its various forms, can offer a solution to heating or even cooling. Some areas, such as Iceland and other hotspots, can also use overheated water to supply electricity.

 

The earth has a temperature range from the extremely hot core to the icy vacuum of space. The thermal insulation properties of magma, various types of rocks, water and atmosphere act as a lid to keep this heat trapped. In the upper subsoil high thermal inertia (resistance to heat or power release tendency) tends towards average annual temperatures in a given area. In temperate regions, while the outside temperature may be 2⁰C, when we reach 2.5 meters depth the temperature is warmer, at 15C. When we reach 25 meters the temperature starts to remain at 22C and is resistant to any fluctuations in atmospheric temperature. At the same location, the summer temperature under the ground remains 12-14C while the outside temperature can reach 35C. This temperature difference can be used to carry out work and provide energy in the form of heating and cooling.

 

There is a variety of high and low technology means to take advantage of temperature differences in order to achieve our ultimate goal: to offer an ideal environment for our growing spaces throughout the year. We can also add additional devices to increase the productivity of the systems.

 

Heat Pumps – Heat pumps move energy by absorbing energy from a colder room to a warmer one. As this is contrary to normal heat flow rules, a small amount of energy must be used to achieve this goal. Heat pumps require a refrigerant (liquid/gas) and four main components: a compressor, a condenser, a relief valve and an evaporator. Your refrigerator and air conditioners are heat pumps, but using the reverse setting they can provide heating and ventilation as well. Heat pumps can use reversal valves to provide heat or cooling as needed. In general, heat pumps for heating are 3-4 times more efficient than electrical resistance heating devices. The source of heat in heat pumps, can be air or water. Water has higher thermal inertia and can carry more heat per unit of volume than air, while it can be more applicable to larger plants. Almost constant water temperatures under the ground, from 2.5 to 25 meters, allow a large thermal drop or heat source, depending on the application and the season of operation. In addition, one can use other means of heating water used in heat pumps, such as boilers, solar reflectors or cooling motors with encapsulated pipes. If cool water is needed, cooling towers or other means of cooling can be added to the system.

 

How it works:

 

The refrigerant is compressed on one side of the alternator to make it warmer, while the pressure is released on the other side where the heat is absorbed (resulting in cooling). The hot and compressed liquid is cooled in a heat exchanger (the condenser), to slightly reduce the pressure and the temperature a lot. This concentrated liquid then passes through a device, to significantly reduce the pressure (expansion valve) and then enters another heat exchanger, where it absorbs more heat and boils. This boiling gas is then recycled into the condenser, where the cycle is repeated. Work, cooling or heating can be provided, depending on the setting of where each side of the appliances is located (think of the hot air emitted by your air conditioner, this warm air is the heat absorbed by the rooms you want to cool!)

 

For large-scale greenhouse structures, the geothermal heat pump uses the almost constant underground temperatures (10C-16C) and a circular system of underground water pipes for cooling or heating supply, depending on the time of year. In combination with other sources of heating or cooling (including heat pumps), this combined system significantly expands the ability to heat or cool your unit efficiently. While these systems have higher costs in advance, energy savings can pay off the initial investment in a few to several years, while the life of the installation can be 3-4 times longer than the repayment period.

 

Due to the various yields and settings, geothermal heat pumps can help you save money, thanks to lower consumption of electricity or gas, a stable environment, which allows your crops to mature with fewer problems and the stability and long-lasting nature of the system, due to its relative simplicity.

 

While the goals for growing medicinal-grade cannabis are the same, there are many paths to get there. Spending time and money, with a competent engineer and professional HVAC companies, to explore the set of systems that provide energy, cost savings, and an optimal environment, is key. Before you install the default system, discover the length of operation you expect and all the available alternatives to make your installation outperform the others.

 

By Damon Lippert

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