Clean Energy is Buried at the Bottom of Abandoned Oil Wells

A solar developer has the plan to turn oil wells into energy storage

A surprising source of untapped power

Geothermal energy works on a simple premise: The Earth’s core is hot, and by drilling even just a few miles underground, we can tap into that practically unlimited heat source to generate energy for our homes and businesses without creating nearly as many of the greenhouse gas emissions that come from burning fossil fuels. However, drilling doesn’t come cheap — it accounts for half the cost of most geothermal energy projects — and requires specialized labor to map the subsurface, drill into the ground, and install the infrastructure needed to bring energy to the surface.

But the US, in the wake of an oil and gas boom, just so happens to have millions of oil and gas wells sitting abandoned across the country. And oil and gas wells, it turns out, happen to share many of the same characteristics as geothermal wells — namely that they are deep holes in the ground, with pipes that can bring fluids up to the surface. So, the US Department of Energy (DOE) asks, why not repurpose them?

“The idea here is basically that you produce oil and gas resources for a couple of decades, and at the end of the production of oil and gas, you don’t completely retire the assets — you turn them toward heat production,” said Saeed Salehi, associate professor of petroleum engineering at the University of Oklahoma and the leader of one of the four groups receiving funding from the DOE. Oil and gas wells have a limited lifespan of a few decades, Salehi explained, after which they become depleted. Geothermal energy, if managed correctly, doesn’t have that problem. “The beauty is that this is a constant source of energy which is not going to change. It’s probably going to be [there] forever, as long as your well is functioning,” Salehi told Recode.

Salehi and his team at the University of Oklahoma want to use four wells owned by Blue Cedar Energy, a local company, for a concept called “direct use” — using hot water to heat nearby buildings. The water can either be extracted from existing underground reservoirs or, as the University of Oklahoma team is doing, pumped into the ground and brought back to the surface. Salehi and his team expect the water they pump into the wells to heat up to temperatures around 150 degrees Fahrenheit, after which it can be used to provide heating and cooling for an elementary and middle school located about a mile away from the wells, in the town of Tuttle.

Some European countries already rely on the direct use of geothermal energy on a large scale; Iceland, which is famously volcanically active (remember Eyjafjallajökull, which shut down European air travel for a few days in 2010?), uses its vast reserves of geothermal energy to heat 90 percent of its homes. But there are some drawbacks to direct use. Heat is quickly lost in transit unless pipes are well-insulated, explained Patrick Fulton, assistant professor of earth and atmospheric sciences at Cornell, so geothermal wells being tapped for direct use have to be near the buildings they’re going to service — usually within a few miles.

That distance limitation is why the three other projects receiving funding from this year’s DOE award are focusing on turning geothermal energy into electricity, which can travel much farther than heat. While wells located close to towns and cities may be better used for supplying heat through direct use, wells in remote areas might be better suited for generating electricity.

A California developer of concentrated solar power (CSP) systems has announced an innovation that it says combines the company’s technologies to turn existing oil wells into energy storage sites that can provide clean energy.

Hyperlight Energy said it was launching Tectonic Sun, an electricity generation technology that when paired with the company’s Hylux solar thermal solution can provide “zero-carbon electricity” from oil wells “while reducing emissions during the extraction process at enhanced oil recovery [EOR] sites.” Hyperlight said the new system “is capable of providing emissions-free power with 80% capacity factor for use at any time of day or night throughout the year.”

The company has a technology demonstration project, Tectonic Sun Alpha, at a Hathaway oil drilling site in Bakersfield, California. Hathaway is an independent, Bakersfield-based drilling company that operates six oil and gas fields in Kern County, California.

Renewable Energy 101: How Does Geothermal Energy Work?

Hyperlight said the application of CSP thermal energy for power generation and emissions reduction “is an industry first,” adding that the company “estimates the statewide potential [energy] storage capacity of its technology” would exceed the combined generation from California’s natural gas-fired power plants. Hyperlight said the Bakersfield demonstration “builds on groundbreaking analysis work on geological thermal energy storage (GeoTES) performed by Hyperlight partner, the National Renewable Energy Laboratory.”

Jefferson Tester, a professor of sustainable energy systems at Cornell University said, Americans need to start thinking about our energy needs as interconnected systems with multiple parts to the solution. Instead of relying on one power source for everything, we should use solar and wind energy to power our appliances and electric vehicles, for example, while relying on geothermal energy to heat and cool many of our homes.

That’s going to require a shift in how we think about our energy sources, Tester said. In most of the country, the oil and gas extracted from a well can go toward heating and cooling homes, running appliances, and powering our cars; for a decarbonized future, that will have to change. “I don’t think we’ve gotten into a state yet of thinking of these things as systems,” Tester said. “I think that’s what we have to weave into the American mindset. It’s going to be a game, I think, for everybody to get all the renewables working together.”

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