Sustainable Energy from Underground

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With the world shifting its focus to solving the earth’s climate challenges, renewable energy has quickly become the focal point for many designers, developers and contractors. As a means of protecting the earth and its future generations, we are learning to harvest the earth’s renewable natural resources—such as sunlight, wind, and rain—and turn them into clean, renewable energy. And while those sustainable sources of energy have become the most common, there is another that is becoming more prevalent but is less discussed—geothermal energy. Exactly as it sounds, geothermal energy in its most basic form is heat from the earth. It can be found as shallow as the first ten feet of the earth’s surface, where temperatures are consistently maintained between 50 and 60 degrees Fahrenheit. A few miles deeper underground you will find hot water and rock, with the extremely high temperatures of the earth’s magma deeper than that. A clean and sustainable resource, geothermal energy has been commonly used for thousands of years in some countries for cooking and heating.

Traditionally harvested from sources such as volcanoes, geysers and hot springs, geothermal energy is currently produced in over 20 countries, with the United States being the world’s largest producer. Geothermal energy requires limited burning of fossil fuels for its extraction, and geothermal fields only produce about one-sixth of the carbon dioxide when compared to a clean, natural gas-fueled power plant. Also, unlike solar and wind energy, geothermal energy is available 365 days a year, and typical costs from direct use are approximately 80 percent less than using fossil fuels. To date, most of the country’s geothermal energy production occurs in the West, which offers more compatible geographic resources than the rest of the country. While the northeast lacks the aforementioned traditional geothermal energy sources, the earth’s ability to absorb 50 percent of the sun’s energy allows for geothermal heat pumps to become more commonly used across the region. Our region’s humid continental climate, with stark temperature contrasts in the summer and winter months, makes geothermal heat pumps particularly advantageous. They utilize the energy-absorbing capacity of the earth to heat indoor air during cold winters and cool indoor air during warm summers.

As it stands, there are three main types of geothermal heat pump systems: closed loop, open loop and standing column. On Long Island, because of the aquifer, open loop systems are typically the most popular and cost-effective. These systems utilize groundwater or surface water, which is pumped from the earth for the purpose of heat exchange, and then discharged to the surface or underground. Closed loop systems exchange heat by recirculating a fluid, which is typically a chemical compound, through closed piping from underground to a building and back underground. Standing column systems pump groundwater through a central pipe, use the water once for heat exchange, and then discharge it into the upper casing of the well from where it was derived.

Along with the environmental benefits that are intrinsic to geothermal systems, there are specific financial benefits for those who invest in geothermal heat pump systems. These systems require little upkeep, which lowers maintenance costs, and their efficiency reduces heating and cooling bills. While the technology for geothermal heat pumps is still relatively expensive, purchasers typically see a quick return on investment because of the monetary savings the systems offer. As far as renewable resources are concerned, geothermal energy may eventually become the most sustainable and commonplace energy source. Because geothermal heat pump systems can be used in both new and existing buildings, and due to the infinite availability of the earth’s heat, these systems have the potential to pay dividends for generations with minimal environmental impact.Joe Manzella, P.E., LEED AP BD+C is H2M’s Mechanical Engineering Department Manager and Chief Mechanical Engineer. You can reach Joe at mail