A typical geothermal power plant works by drilling down into a naturally occurring underground reservoir of hot water, normally in volcanic regions. This hot water is pumped to the surface and turns into steam when it returns to atmospheric pressure, driving an electricity-generating turbine. The steam is then cooled and the cold water is pumped back into the underground reservoir to be reheated.

A so-called low-enthalpy geothermal energy (LEGE) plant has similar principles but does not utilise underground hot-water reservoirs — it simply pumps water down to a depth of 1-5km and uses the hot rock to heat the water, which is then pumped back to the surface to power an organic rankine cycle (ORC) electricity-generating system. But according to Redfern, LEGE has never taken off because the amount of energy needed to pump the heated water to the surface and later reinject it equates to 50% or more of the electricity the plant generates.

The idea for Eavor-Loop came from the company’s co-founder and now chief business development officer, Paul Cairns, during a chat with Redfern in 2017 about how suspended oil wells in Alberta could be re-used for profit — a conversation which then turned to LEGE.

“Luckily for us, my co-founder wasn’t an engineer, he wasn’t a scientist, he was a finance guy, but a creative one, and so unencumbered by geoengineering knowledge. He said, ‘why doesn’t low-enthalpy geothermal energy work?’ And I said, ‘because of the parasitic pump load that uses about 50-80% of the power produced, so little energy is produced’.

“He says, ‘well, to get around that, why don’t we just drill down two wells and connect them horizontally [below ground] and we’ll connect them on the surface and make this big loop — wouldn’t that flow better?’

“And I thought it was the dumbest idea I’d ever heard in my life… incredibly inefficient [and] capital intensive.”

But engineers such as Matt Toews, who is now the company’s chief technical officer, pointed that such a configuration would not only eliminate the parasitic pump load but would in fact pump itself due to the thermosiphon effect. This is because cold water is denser than warm water, so the cold essentially pushes the warm water towards the surface.

“And that got us excited…. This is something where we can actually make a difference. This is the Holy Grail.”

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