Enhance Geothermal Systems (EGS) Fact Sheet

What is geothermal energy? Geothermal energy relies on the Earth’s natural heat to generate steam which can drive a power plant and generate electricity. Naturally occurring geothermal energy is stored in hot rocks below the surface of the Earth. Water moving through fractures in the rocks becomes steam that can be delivered via geothermal wells to the surface. Once at the surface, steam moves through pipes into the power plant and drives a turbine and generator system. Electricity moves from the power plant out into the grid system, and cooled steam is re-injected back into the hot rock to be reheated, continuing the cycle.

The world’s first commercial geothermal power plant was built in 1911 in Larderello, Italy and is still producing power today. Today, the US leads the world in geothermal electricity generation with more than 3,000 MW installed. Many other countries also produce geothermal power- Indonesia, The Philippines, Iceland, New Zealand, Kenya, Mexico, El Salvador and others.

Why geothermal? Most electricity generated in the world today is produced from non-renewable fossil fuel resources which damage and pollute the environment. Geothermal is a clean, safe and renewable energy source that has minimal ecological impact and can be sustainably produced over long timescales. Geothermal power plants have the least down-time of any source of power including coal, gas, oil, hydro, solar, wind or nuclear. Geothermal plants produce only a tiny fraction of the emissions that fossil fuel power plants do, and there is a seemingly endless amount of heat near the Earth’s surface that remains untapped for power production.

What is EGS? Enhanced Geothermal System (EGS) projects produce electricity by using heat extracted with engineered fluid flow paths in hot rocks. These pathways are developed by injecting pressurized cold water into hot rock at depth in a process called ‘stimulation’. Thermal contraction of the rock opens pre-existing fracture networks, allowing cold water to flow through the reservoir. The heated water and steam moves through the reservoir and returns thermal energy from the rocks back to the surface through geothermal wells.

In the EGS power generation cycle, water is continuously pumped down injection wells into the EGS reservoir. As water moves through the reservoir from injection well to production well, it absorbs heat from the surrounding rock. Hot water and steam is pumped out of the reservoir through production wells. At the surface, the hot fluid is piped through the power plant where it drives a turbine and generates electricity before being re-injected into the reservoir.

Why is EGS so important? Enhanced Geothermal System (EGS) offer an environmentally sustainable, politically independent and economically viable source of energy. This technology has the potential to provide up to 10 percent of US energy needs within a generation- and to do so using not only domestic natural resources, but domestic technology as well. This green energy technology can be used to improve existing geothermal reservoirs, significantly increasing the life of existing power plants. In hot dry rock areas where no known steam resource exists, EGS technology can be used to create a geothermal reservoir for development.

What does AltaRock do differently? Traditional means of improving geothermal wells include drilling and mechanical stimulation techniques- both of which are high-cost, high-risk. AltaRock has developed and uses a variety of proprietary techniques which are the subject of our patent portfolio. Our EGS technologies allow us to improve reservoir production at existing power plants, and to develop EGS reservoirs in hot dry rock systems with little or no known fluid resource. Well stimulations using AltaRock’s Thermally-degradable Zonal Isolation Materials (TZIMs) make multiple-zone stimulation a reality without the use of mechanical packers or explosives, significantly reducing risk and cost associated with well field improvement. For more information on TZIMs, click here.

What are the benefits of geothermal power? Geothermal energy provides clean, safe and reliable electricity generation. It is an environmentally sustainable, politically independent and economically viable source of energy. In addition, development of this technology requires only a small surface footprint, produces few to no greenhouse gas emissions and generates baseload (24/7) power.

Is this the same as the fracking that has been getting so much negative press lately? No, it is not. Hydraulic fracturing, or fracking, is a method for extracting oil or natural gas in which water and chemicals are injected at pressures up to 10,000 psi at the surface, into an oil or gas well. The water pressure causes the rocks to fracture or crack open, and then propping agents, carried by gels, are injected to keep the hydrofracture open so that oil and gas can be collected and piped to the surface. Some of the chemical additives used in fracking and the recovered hydrocarbons can be toxic.

The hydroshearing process used in geothermal stimulations uses lower pressure than hydraulic fracturing. Hydroshearing takes place below the fracture point of the rock, and no fracking chemicals or propents are used.  As was discussed earlier, there is also no danger from earthquakes.

Is EGS safe? Yes. Some induced microseismicity is inevitable and expected with EGS, however, it is far below the threshold of what can be felt by a person let alone cause any surface damage.  AltaRock uses state-of-the-art microseismic monitoring systems to control induced seismicity during well stimulation activities, and has developed a seismic mitigation protocol that insures that all induced seismicity stays far below the level that could be felt on the surface. Our highly trained staff are industry experts with decades of experience, and do extensive work to ensure environmental and human safety at geothermal project sites. We are subject to and comply with Federal, state and local regulation, and work in conjunction with many outside scientific research groups to ensure proper monitoring of microseismicity, groundwater and other environmental factors over the lifetime of our projects.