Geothermal
MEP Proven Geothermal Design Performance
There is great potential to benefit from the earth’s vast storehouse of geothermal energy. Identified by the Environmental Protection Agency as among the most efficient and comfortable heating and cooling technologies currently available for homes and other buildings, geothermal heat pump technology offers convenient access to a portion of this free, reliable, and clean energy homegrown just beneath our feet.1
Having over 25 years of design experience, MEP Associates has specialized in geothermal design for commercial and industrial application. We have proven designs with energy usage as low as 42,000 BTU per square foot per year. Average buildings are in the range of 80,000 BTU/SF/year. We have designed geothermal systems utilizing ponds, and we have designed geothermal designs using ice storage for using off peak electric rates to cool during peak rates.
Why Geothermal?
According to the U.S. Environmental Protection Agency, geothermal heat pumps are the most energy-efficient, environmentally clean, and cost-effective systems for temperature control.1
Geothermal heat pumps are less costly to implement than other renewable energy technologies, such as power generation from solar, wind, geothermal, and biomass. In addition to saving 25 to 50% in utility costs, the 2008 Federal Economic Stimulus Bill provides a 30% tax credit to residences and a 10% tax credit to businesses that install geothermal heat pump systems. A growing number of states and utilities also offer tax credits and/or incentives.
With a proven installed base of 600,000 geothermal heat pumps nationwide, approximately 60,000 new units are shipped each year. Homegrown energy means less dependence on volatile foreign markets, and reliability that extends beyond proven performance.
Incorporating geothermal heat pump technology into all buildings by 2030 could potentially avoid 91 to 105 Gigawatts of electrical generation construction, or 42 to 48% of the nation’s projected net electricity generation capacity additions. The annual reduction of solid ash wastes and greenhouse gases from the elimination of coal-fired equipment would be huge, representing billions of pounds of carbon dioxide pollution alone.
Geothermal Solution
Like a conventional air-source heat pump, a ground-source heat pump captures heat from a cool area and transfers it to a warm area, against the natural direction of flow. Acting like a refrigerator that is able to reverse itself, it rejects heat to the ground loop during the summer for cooling and pulls heat from the ground loop during the winter for heating. At its core is a loop of refrigerant pumped through a classic vapor-compression refrigeration cycle. Because they move heat instead of generate heat, conventional air-source heat pumps can move up to 2.5 units of heat for every unit of electricity, resulting in a practical equivalence of 175 to 250% efficiency, while the most efficient fuel-burning heater can only reach an efficiency of 95%.
Unlike an air-source heat pump, a geothermal heat pump exchanges heat with the ground loop instead of the outside air. Instead of utilizing a conventional air-cooled condenser or cooling tower, it pumps heat to or from the ground loop below the surface, using it as either a heat source in the winter, or a heat sink, or coolant, in the summer. The ground temperature is warmer than the outside air in the winter and cooler than the outside air in the summer. Therefore, the heat pump doesn’t have to work as hard against the natural direction of flow. This increases the efficiency over a conventional air source heat pump, which has to rely on hostile outside air temperatures, by as much as 44%, enabling it to reach an efficiency of 300 to 600% on the coldest of winter nights.2 This will create a 25-50% reduction in total electrical utility costs over conventional heating and cooling systems.1
Of the four basic types of geothermal pump systems, the closed loop, vertical-bore ground source heat pumps are by far the most common, especially in commercial buildings. This design incorporates two loops that exchange heat inside the appliance cabinet. The primary loop, which contains refrigerant, goes through the standard vapor-compression refrigeration cycle. The secondary loop, which contains a water and ethylene glycol, or antifreeze, mixture, is routed through a series of buried u-shaped pipes before it is returned to the heat exchanger. These u-shaped pipes are housed in boreholes similar to those drilled for water wells, typically 4 inches in diameter, 20 feet apart, and 75 to 400 feet deep.
Market Status, Barriers to Adoption, and Actions to Overcome Barriers.
The report estimates a geothermal heat pump energy savings potential at 2.5 to 3 quadrillion Btu annually by 2030 if fully deployed into the existing building stock. Incorporating anticipated new construction between now and 2030, this figure rises to 3.4 to 3.9 quadrillion Btu in the United States alone. These figures represent 7 to 8% of the total projected building energy consumption in 2030, and 35 to 40% of the growth of the nation’s projected building energy consumption from now until 2030.1
1 U.S. Department of Energy’s Office of Energy and Renewable Energy, http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm?mytopic=12640
2 Oak Ridge National Laboratory. 2008. Geothermal (Ground-Source) Heat Pumps