This is Part 8 of a paper written about the projected US Energy profile in the year 2050. In this chapter, we take a look at some less significant energy sources, including geothermal energy, hydropower, and tidal energy.
The greatest potential for geothermal energy is in the use of heat pumps in residences or commercial buildings. A geothermal heat pump works like an electric heat pump except the heat comes from the ground. In an open loop cycle, water from an underground well circulates through the pump and back into the well, into a separate well, or through surface discharge. A closed loop cycle circulates water into horizontal or vertical pipes, where the water exchanges heat with the ground. Once back to ground temperature (around 55 degrees Fahrenheit), the water is cycled back through.
Because of tax incentives in the Energy Improvement and Extension Act of 2008, consumption of geothermal energy is four times higher than it was five years ago. Like all other renewable technologies, geothermal has high fixed costs and low maintenance costs. Geothermal power currently makes up 5% of our renewable energy profile, more than wind and solar combined. The EIA 2010 Energy Outlook predicts that 2.25 million residences will have geothermal heat pumps in 2030. However, this would still account for only 2.2% of residential heating. The U.S. consumes the most energy from geothermal sources of nations worldwide, although several countries in the Far East, such as the Philippines, consume a much larger percentage of geothermal energy out of their total energy consumption.
Geothermal power plants use steam from several miles below the earth’s surface to generate electricity. Most power plants still use fossil fuels, which, though not as expensive, is worse for the environment and less efficient. The three types of geothermal plants are dry steam, flash steam, and binary cycle. Binary power plants are the most common because they only require low-temperature reservoirs.
Hydroelectric dams supplied 2.4% of U.S. energy consumed in 2008, (EIA AEO 2010). The U.S. has fully harnessed its hydroelectric power, so the amount of energy supplied from dams is likely to remain constant over the next forty years.
We do not foresee wave, tidal, and ocean current technologies playing a part in the near term future. In addition to lack of economically viable technologies, the potential environmental harm to already fragile marine eco-systems is too great. Perhaps ocean energy will be harnessed successfully in the far future. Wave energy has the most potential and the possibility of providing one-fourth of world energy consumption with advancements in technologies.