Most Texans already know that the state’s fortunes were and are fueled by oil and natural gas. What many don’t realize, however, is just how much the future of the Lone Star State will be powered by renewable energy. With the Green Energy in Texas series, we will explore various aspects of the green energy industry and keep you informed on how those changes and innovations might affect your Texas electricity bill.
Is Texas’ Energy Future Geothermal?
Back in February, 1,369 thousand mWh of electricity in the US were generated by geothermal energy. While Texas boasts a possible capacity of up to 10,000 MW, according to EIA’s statistics, not a single Texas kilowatt added to those standings. Almost all of that electricity was made in California.
According to the EIA, the unique geothermal sources deep below the Texas turf are largely untapped. For decades, both oil and natural gas drillers have tapped subterranean pools of hot water. It’s thought as much as 12 billion barrels heated to nearly 400°F — well above the boiling point to make steam — may be available. Research has identified 17,000 wells in Texas with bottom temperature ranges above 212 °F. Southern Methodist University’s Geothermal Laboratory and the University of Texas at Permian Basin have estimated Texas could have 2,000 to 10,000 MW in geothermal generating capacity. The hottest well, located east of Victoria, was recorded at 510°F!
Texas has three types of geothermal resources:
- Hydrothermal (hot water)—A geothermal power plant would use steam or heat directly from below ground to drive turbines. Generation capacity could be up to 250 MW and have ZERO fuel costs.
- Hot dry rock (HDR) — Heated formations of rock without water. There are more of these than hydrothermal wells in Texas. The difficulty lies in efficiently and reliably capturing the heat and bringing it to the surface. HDR reservoirs deep below ground surface can be prone to causing mild earthquakes.
- Geopressured — This is hot brine water saturated with natural gas under high pressure. Steam energy can be used to drive turbines plus the natural gas can be captured to drive a gas turbine, further augmenting generation.
Raising Some Steam
The energy technology was tested in the late 1970s when the Department of Energy built the Pleasant Bayou #2 geothermal pilot plant in Brazoria County. The plant generated 905 kW: 541 kW from water, 650 kW from gas, and and a parasitic load of -286 kW (used to run pumps, etc.) During 121 days of operation, the plant produced 3,445 MWh of electricity for what was then Houston Power and Light.
Though a success when compared to coal and natural gas geothermal, it was still too expensive to interest serious capital investment. But as the new millennium began with spiraling energy prices and renewed interest in green energy, geothermal energy developers began visiting Texas. In 2005, 9 leases were granted for wells on state land. The Federal government got interested, too, with the DOE authorizing a $5 million grant for the El Paso County Geothermal Project at Fort Bliss (the initial study concluded in February, 2016). While enthusiasm in the state’s geothermal potential persisted for years, the natural gas glut unleashed by fracking ultimately drowned it out.
All the same, while geothermal’s fans have kept interest simmering, no geothermal-powered electricity is contributing to the Texas grid. But, that might change.
Will Geothermal Go Supercritical?
This past February, newly-formed Raven Petroleum announced plans to build a new refinery and power it with geothermal power. Texas-based Thermal Energy Partners is designing the $500 million refinery project in South Texas to use geothermal energy to generate electricity.
It’s also going to employ an evolving type of turbine system that uses CO2 as a fluid instead of water. The plan is to capture the refinery’s carbon dioxide emissions and pump them into a deep well where pressure and heat will make the CO2 supercritical. Water used for steam turbines becomes supercritical steam at 705°F and 3199.5 psi (pounds per square inch). Supercritical CO2, meanwhile, uses much less energy—forming at 87.8°F and 1072.8 psi. The benefit is increased efficiency, increased power output, less water used, CO2 emissions reduced, and lower fuel costs.
Supercritical CO2 is a fluid state of CO2 where temperature and pressure impart it with properties of both a gas and liquid. Not only is it a valuable commercial substance, Supercritical CO2 is also being developed to drive power generation turbines instead of using steam. Called sCo2 turbines, they are 50% more efficient and 10 times smaller than steam turbines.
Will sCO2 technology finally unearth geothermal as an energy source that is more efficient and affordable than fossil fuels? Time will tell and there are still problems to work out. But it’s clear that Texas will need to find more generation for the future —or it will just find itself in hot water.