Energy

Big oil invests in Eavor's "holy grail" pump-free geothermal loops

Big oil invests in Eavor's "ho...
Eavor's low-enthalpy geothermal generators make use of the thermo-siphon effect to circulate fluid without any energy losses in pumping
Eavor's low-enthalpy geothermal generators make use of the thermo-siphon effect to circulate fluid without any energy losses in pumping
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Eavor's low-enthalpy geothermal generators make use of the thermo-siphon effect to circulate fluid without any energy losses in pumping
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Eavor's low-enthalpy geothermal generators make use of the thermo-siphon effect to circulate fluid without any energy losses in pumping
A two-station implementation with send and return loops
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A two-station implementation with send and return loops
The Eavor-Lite prototype station has been up and running for more than a year in Alberta, Canada
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The Eavor-Lite prototype station has been up and running for more than a year in Alberta, Canada
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BP and Chevron have led a US$40 million investment round for a Canadian startup that claims to have developed a unique way to extract energy from geothermal heat on demand, using an unpowered looping fluid design that's already prototyped in Alberta.

Solar and wind are scalable renewable resources, but only produce energy when the sun and wind are up, not when the grid needs it. Hydro can respond well to demand, but it's not really scalable; the geometry of your dam dictates the size of your operation. Regular geothermal needs volcanic levels of heat, which restricts it to certain locations, the same way hydro needs mountain reservoirs.

There are lower-temperature, low-enthalpy geothermal projects out there that can generate energy from hot rock in a flexible, scalable, on-demand fashion, but according to Eavor CEO John Redfern, these haven't taken off because they lose between 50-80 percent of the power they generate in the task of pumping the water up and down.

Which makes this Eavor-Loop technology a bit of a unicorn. Essentially it's a low-enthalpy geothermal station that sends fluid through a sealed loop in a way that self-perpetuates without adding any extra energy at all once it's running.

The idea is devilishly simple: hot water wants to rise, cool water wants to fall. So the Eavor-Loop tunnels way down, miles deep into the Earth where the rock is hot, then runs a series of parallel tunnels out horizontally through the rock, where the water can get nice and hot. These tunnels themselves run for several miles deep beneath the surface, then join back together and rise up vertically again.

A two-station implementation with send and return loops
A two-station implementation with send and return loops

The heat is harvested at the surface, and used either directly as commercial heating or by using a traditional heat engine to convert it into electricity. This cools the water, after which it gets sent back down underground into another similar set of underground radiator tunnels that heat it back up and send the hot water back up to the surface at the original site, where the heat can be harvested again.

The fact that this all happens in a sealed loop, says Eavor, means that once the fluid is in motion, the higher density of cooler water will push it downward, and the lower density of the hot water will make it easier to push upwards. Kick-start the loop with a pump, and the water will begin to circulate itself, with no energy losses.

It can run in a number of configurations, not all of which require multiple spaced-out ground stations. You can scale it as much as the Earth allows by adding extra loops to your facility. Eavor says a single loop can generate "industrial-scale electricity or produce enough heat for the equivalent of 16,000 homes with a single installation." The target cost of energy production is $50 per megawatt-hour.

The company has a full-scale prototype running at a site near Rocky Mountain House in Alberta. The Eavor-Lite site started construction in August 2019, and was up and running circulating fluid by early December. A simpler design than the one described above, it burrows some 2.4 km (1.5 mi) deep into the crust, runs along 2 km (1.2 miles) laterally, rises back up and then returns to the original site via a pipe along the ground, completing the loop that way instead of going back under.

The Eavor-Lite prototype station has been up and running for more than a year in Alberta, Canada
The Eavor-Lite prototype station has been up and running for more than a year in Alberta, Canada

The prototype was built to prove that the "thermo-siphon" effect can keep fluid circulating by itself, as well as testing the process of drilling intersecting wellbores way underground and prove that Eavor's RockPipe designs can maintain the necessary pressure levels to keep things running with a negligible leak rate.

The company says the fluid has been circulating by itself for more than a year now. It's not harvesting heat; indeed it's basically venting it skyward in an aerial cooler at the surface. But the company's happy that the prototype has proven the technology and the premise, and it's now bringing more investors on board as it moves to commercialize. Yesterday, Eavor announced the closing of a $40 million funding round led by BP Ventures and Chevron Technology Ventures, among others.

The first commercial-scale project is likely to be built in Germany at a site in Geretstried owned by Enex Power Company, which was attempting to create its own geothermal energy project, but found there wasn't enough heat for the type of installation it was planning.

There is, however, enough heat to run an Eavor-Loop. And the geothermal permits are already in place, as well as a deal with the German government to buy the power produced for about $270 per megawatt-hour. And there's a couple of wells already drilled. An ideal first project.

Eavor CEO John Redfern told Recharge News this first project is likely to start out as a 10-MW station, with construction starting next January if it gets the green light. But there's ample space at the site to ramp it up to 200 MW simply by adding more underground loops. Scaling up to this degree would cost around $2.9 billion.

But then you'd have a highly reliable, completely green energy source with which to augment your solar and wind and hydro projects. Eavor is looking to BP and Chevron not just as investors, but as partners who can run these kinds of giant projects effectively. So if the initial German project goes ahead, the relationships are being put in place to see this tech rolled out globally across many markets.

Check out a short video below.

How Eavor Works (Full)

Source: Eavor

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18 comments
paul314
Thermosiphon for hot-water solar panels has been around for decades, so it seems plausible it would work here. The main potential obstacle is that you typically don't get water flowing as fast as a pump could drive it, so gross heat output is lower. But if your drilling costs are low enough the total capital cost works out, I guess...
Worzel
Whoopee! ''They've just reinvented the wheel!''
The earliest water based central heating systems used gravity/thermal feed, in exactly the same way this system works.
They were generally abandoned, for pumped systems, using small bore pipework, due to the much higher cost of the large bore pipes required for the gravity system to operate effectively,
Also, I've been saying for years, to anyone who would listen, that the only sustainable long term power source, is geothermal. Some ''off grid'' adherents are also experimenting with similar systems, but obviously, in a much smaller capacity.
buzzclick
This is significant. I have friends whose home has a geo-thermal setup, but it's true, the heat is not sufficient to produce better thermal energy. Using convection for circulation is brilliantly simple, but how do they drill large bores laterally for such long lengths that are so deep?
And how much heat is hot enough? Shouldn't they be using this method near hot springs or places with volcanic activity? Or at the base of mountains where drilling lateral bores deep enough would be helped by the mass that's already there?
Anyways, this is the way to go. Solar, wind, tidal and hydro could pale in comparison to the energy that's down below.
riczero-b
I wonder if the underground radiator network is difficult to engineer and maintain . If the circulation system has momentum, maybe sporadic pumping powered by renewables on a simpler loop would be cheaper and sturdier.
guzmanchinky
What a cool concept!
FB36
Geothermal power plants known to trigger earthquakes, just like fracking, because they keep pumping so much water into all rocks around!

Would not this design also keep leaking water into bedrock beneath?

IMHO, geothermal power plants need to be designed so that they never leak/pump water into the bedrock all around!

So, how about just 2 very deep pipes, side by side, connected at the bottom, to circulate the water?
Jerome Morley Larson Sr eAIA
Perhaps a cool way to unfreeze those wind farms in Texas?
Username
How much heat is extracted? How much heat would be extracted yearly if this became the planet's primary energy supplier? Way back when some short sighted people thought we would never run out of oil. There was so much. People though we couldn't possibly pollute the oceans , they are so big. Like all our earth bound ressources the core's heat is finite. How much accelerated cooling can it sustain before a catastrophic tipping point is reached?
ChairmanLMAO
Dinosaurs trying to justify their existence? Looks to me like free energy until they get invested in it.
buzzclick
@FB36...this is a closed loop system, so no water gets pumped into the bedrock, like in fracking operations.

But now I have another issue. If water is circulated into the loop, that would mean that the heat is limited by the boiling point. If an antifreeze is used it could run hotter. If an oil is used, even hotter. So what exactly are the heat levels at a few miles deep? To generate electricity you need the hot stuff.