NASA Engineers Want to Save the World with Geothermal Electricity
Tom Lombardo posted on August 27, 2017 |

There's a supervolcano lying under Yellowstone National Park in Wyoming. Geological evidence suggests that this particular supervolcano erupts every 600,000 years or so, and its most recent occurrence was 640,000 years ago. In other words, we're due, at least on a geologic time scale. When it happens, the eruption's debris could blanket much of the US in ash and dust, pollute water supplies, and make farmland infertile - a taste of nuclear winter, minus the bombs.

Potential ash covering as a result of a Yellowstone supervolcano eruption. (Image: USGS)
Potential ash covering as a result of a Yellowstone supervolcano eruption. (Image: USGS)

To prevent Earth from blowing its top, so to speak, NASA engineers have a strategy: have the planet let off a little steam … literally. They're proposing a plan to drill geothermal wells into the supervolcano in order to release some of the pressure that's building up under the surface. Doing so wouldn't be cheap - we're talking about $3.5 billion - but it would provide a source of renewable energy: geothermal electricity.

Image by Joe Lombardo
Image by Joe Lombardo

How Much Energy?

Through its geysers, Yellowstone vents about six gigawatts of heat into the atmosphere - two-thirds of the thermal energy that's produced by the underground magma. The remaining heat continues to build, creating enough pressure to eventually cause an eruption.   

Geothermal electric plants could tap into that pent up heat, use it to generate clean power, and cool the underground chamber in the process. Harvesting a fraction of that energy and taking conversion efficiency into account, it's conceivable that geothermal wells on one supervolcano could generate a billion kilowatt-hours of electricity every year - enough to power more than 150,000 US homes. Selling the electricity at $0.10/kWh, utilities would see about a thirty year unsubsidized payback period.

A geothermal electricity plant in California (Image: NREL)
A geothermal electricity plant in California (Image: NREL)

It's an Insurance Policy...

I've paid more money in insurance premiums - health, auto, and home - than I've received in benefits. (I've been lucky - no major illnesses and no catastrophic accidents.) That's the nature of insurance: everyone buys a ticket to a lottery that we hope we don't win. The difference here is that we know the supervolcano will eventually blow, but it may not happen for thousands of years, so we might ask, "Why worry about it now?" My answer is twofold. First, I would turn the question around and ask, "Why pass the problem to the next generation?" Second, unlike insurance, where you don't get a monetary return on investment unless you file a claim, this expenditure would provide clean electricity generation, so even if the supervolcano doesn't erupt for thousands of years, humanity will have benefitted from that power in the meantime.

… And an Engineering Feat

Drilling holes to release pressure sounds simple in principle, but it's not so easy to implement. For one thing, these wells would be a whopping 10 km (6.2 miles) deep - not quite record-breaking, but deeper than the average geothermal well, which rarely goes beyond three kilometers. Past that level, temperatures rapidly increase, making it difficult to keep the drill operational. On the other hand, the water at that depth is considerably hotter, which makes it more desireable for geothermal electricity production, since the amount of energy available is dependent on the temperature difference. But even that silver lining has some grey: geothermal electric generators are designed to handle steam temperatures up to 200C (392F), but these wells would tap into steam that's hotter than 350C (662F).

We'll need some heftier equipment and more than a touch of ingenuity, but the engineering community can rise to the challenge. The only question is whether those in power are willing to fund it. With twenty known supervolcanoes around the world, let's hope the decision-making body can keep a cool head.

To see how electricity is generated by geothermal wells, check out this video and NREL's geothermal page.


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