What is geothermal energy?
Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, heating buildings, and generating electricity. Geothermal energy is old technology. Ask any early caveman who lived in a cave. Geothermal energy is contained in the rocks and fluids beneath the earth’s crust and can be found as far down as the earth’s hot molten rock, magma.
How do we use it?
We’ve laid the ground loops for the geothermal heat exchange pipes at Burnside Boardwalk, our 31unit net-zero affordable housing development on E. Burnside. A ground loop is a series of pipes buried underground at a depth where temperatures stay consistent year-round. It serves as the critical link allowing geothermal heat pumps to use the earth as a heat source or heat sink, to assist in both heating and cooling the entire building.
How does a ground loop work?
Just a few feet below the ground’s surface, the earth maintains a steady temperature of 50 to 55 degrees, no matter what the outside air temperature is. This difference allows the earth to act as a heat source in winter and a heat sink in summer.
A geothermal heat pump (located inside the Building) captures this energy by circulating thermally conductive regular water through the buried pipes in the ground loop. In winter, the water absorbs heat from the warmer earth and the heat pump carries it into the building, where it enters a heat exchanging system and is used to warm your home. In summer, the same process is used to capture heat from the building and release it into the cooler ground, leaving every unit comfortably cooler.
Horizontal Ground Loop
A horizontal ground loop is installed over a wide area of ground and requires enough space to dig trenches hundreds of feet long and 6-10 feet deep. Horizontal ground loops can only be used when adequate yard space is available and trenches are easy to dig. We have installed 500 feet of pipe in 16 loops, 8 loops buried at 14 feet deep, and 8 loops buried at 7 feet deep. When we start to backfill around the foundation we will bury an additional 6 loops at an average of 6 feet deep. This will give us a total of 11,000 feet or a little more than 900 feet of pipe per ton.
To install a horizontal system, workers utilize trenchers or backhoes to dig trenches 5-10 feet below ground and then install a series of plastic pipes that comprise the geothermal heat exchanger. They will then backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. A common practice is to coil the pipe into a slinky shape to fit the loop field in a smaller area. While doing this reduces the amount of land area needed, it will require the installation of more pipe. We have used a combination of straight pipe and a modified slinky approach.
Is it actually energy efficient?
The U.S Environmental Protection Agency (EPA) has called ground source heat pumps the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available. Its source is the almost unlimited amount of heat generated by the Earth’s core. Even in geothermal areas dependent on a reservoir of hot water, the volume taken out can be reinjected, making it a sustainable energy source.
Experts say geothermal energy is cleaner, more efficient, and more cost-effective than burning fossil fuels, and it can reduce our dependence on foreign oil. Geothermal power plants emit 97% less acid rain-causing sulfur compounds and about 99% less carbon dioxide than fossil fuel power plants of similar size. (IEA) Other forms of heat production are more carbon-intensive, more energy-intensive, and less efficient.