U.S. Department of Energy - Energy Efficiency and Renewable Energy

Geothermal Technologies Office

EGS – Enhanced Geothermal Systems (Text Version)

Below is the text version for the EGS - Enhanced Geothermal Systems animation.

This animation is a Calpine Corporation and Lawrence Berkeley National Laboratory collaborative project co-funded by the U.S. Department of Energy.

Geothermal wells are traditionally drilled in locations where hot rock is located near the surface of the earth , and permeable rock make it easy for underground liquid to heat up.

Some hot rock formations have the potential to produce energy, but lack either the necessary permeable rock or underground water to produce steam.

EGS makes it possible to create fissures in the rock and inject water underground. This process can transform many potential sites into working geothermal wells.

Step 1: Identify a Site

After geologic, geochemical, and geophysical surveys are performed, exploratory wells are drilled to determine if a site will work for EGS.

It is important to determine if there are heat, fractures and underground water present.

Step 2: Create a Reservoir

An injection well is drilled.

Injection of water will result in the stimulation of existing fractures by causing them to slip and open.

New fractures are also created, expanding the amount of permeable rock.

Production wells are drilled.

Water is heated underground by the hot rock and the production wells move the hot water to the surface. This completes the water circulation loop.

Step 3: Power Plant Operation and Reservoir Maintenance

In a binary power plant system the hot water from a production well passes through a heat exchanger, where it heats a working fluid that then boils. The vapor from the working fluid then passes through a turbine generator to create electricity.

The working fluid is then cooled by a condenser and reused again. The water that was used to heat the working fluid is recycled into the reservoir through the injection well.

EGS can be expanded by adding additional production and injection wells. There is no loss of steam pressure when adding new wells.

Adding wells increases power generation capabilities.

Benefits of EGS Development

  • Increases domestic energy production by tapping new resources
  • Produces renewable energy around the clock
  • Creates environmentally friendly green jobs