Geothermal Education and Training Key Terms

Grasp key terms associated with geothermal energy education and training

Around-the-clock energy that uses little or no outside fuel to keep running may sound like a fantasy, unless you consider geothermal energy. Below-ground heat acting on reservoirs produces enough steam to run generators or heat buildings directly. You can even apply the concept of using the ground to regulate temperature to control a building’s temperature year-round. If you’re looking for more geothermal education and training, get to know key terms covering three areas: geothermal electric generation, direct-use geothermal heating; and geothermal heat pumps.

 

Dry steam

Magma closer to the earth's surface can heat water ho high it produces dry steam, with no condensed water at all. The first geothermal plants were dry steam plants, drilling into "vapor-dominated" reservoir systems where dry steam controls the pressure.
Try: University of California–Davis’ California Geothermal Energy Collaborative explains dry steam plants, first utilized in 1962 in The Geysers geothermal field in northern California.

Flash steam

The most common of the three types of geothermal electric plants, flash steam plants, drill deeper wells to draw high-pressure hot water into tanks; the suddenly lowered pressure lets the water expand into "flashed" steam that drives turbines.
Try: The Idaho National Laboratory describes flash steam generation, with an accompanying diagram.

Binary-cycle

Sometimes the water isn't at boiling point, but still too hot to handle. So, a binary-cycle plant employs a two-stage system where the water runs through a heat exchanger to pass the heat energy to a liquid that has a lower boiling point. This secondary fluid "flashes" into vapor to drive the turbines.
Try: Bassfeld Technology Transfer hosts a video produced by CNN about a binary-cycle plant in Utah.

Direct use

At even lower temperatures, geothermally heated water can be used directly to regulate the temperature of a building or in the case of "district heating" a series of buildings fed from a central field. The applications venture beyond just warming a room: industrial cleaning, aquaculture and greenhouses all use direct use geothermal energy.
Try: The State of Utah hosts a number of PowerPoint presentations showcasing direct use geothermal heat in a variety of applications.

Heat pump

You don't have to use a geothermal field to take advantage of "earth heat." Ground temperature below the frost line remains relatively constant. Employ a heat pump to transfer heat between a building and the ground, either to cool the space by dissipating it into the earth, or to heat the space by extracting heat from the ground.
Try: The SMU Geothermal Lab links to a Heat Pump page with several sources and links for more education on heat pumps.

Enhanced or engineered geothermal systems

Rather than looking for naturally-occurring geothermal fields, where water reservoirs already exist, energy producers now engineer the geothermal system by selecting sites of heated rock formations to inject water, so the rock heats the engineered reservoir to produce steam.
Try: Stanford University’s Department of Energy Resources Engineering has a video that gives a good overview of geothermal energy, including describing enhanced geothermal systems.

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