Busting Geothermal Myths: The Promise & Limits of Deep Closed Loop & Enhanced Techniques

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Lately, I had the chance to take a seat down Simon Todd, PhD geologist, founding father of Causeway Energies, and skilled on geothermal. That is the transcript of the second half of our dialog, frivolously edited.

Michael Barnard [MB]: Hello, welcome again to Redefining Vitality — Tech. This episode is powered by TFIE Technique, guiding buyers towards climate-smart bets that can win in the true world and the market. I’m your host, Michael Barnard, and my visitor right this moment is Simon Todd, Managing Director of Causeway Energies, a Ph.D. in geology and an skilled in geothermal vitality. That is the second half of our dialog, spanning the very helpful, the extra speculative, and the extra science fiction features of the house.

There are two or three issues I’d like to drag out of that as a result of they’ll change into vital in about 10 minutes. That’s a bunch of electronics on a drill head underground, and that’s a drill face working towards shale, which has a sure hardness. If the drill bit bumped into an igneous extrusion, what would occur to the effectiveness of the ahead motion of the drill bit, in your skilled opinion as a geologist?

Simon Todd [ST]: That’s one of many different advances from oil and gasoline drilling that’s now being transferred to geothermal. PDC bits, that are usually utilized in drilling, have been tailored. Modified mud mixtures, mud weights, weight on bit—all of these parameters from the shale trade have been speedily and incrementally utilized to extend the speed of penetration. Horizontal wells that might have taken weeks again in 2005 now take only a handful of days due to steady adaptation and enchancment. I believe we’re seeing the identical factor taking place, in bits and items—pardon the pun—in geothermal and EGS.

From my perspective, Fervo are the leaders on this. They’ve been very systematic between Challenge Purple and the Cape mission, incrementally studying, properly by properly, the best way to drill by means of granite—which is a special proposition from shale. A few of my drilling mates truly say that, in some instances, homogeneous, constant rock like granite is simpler to cope with than layered, heterogeneous, or inconsistent rocks. It’s actually attention-grabbing to see these learnings being transferred, and Fervo, particularly, has been publishing and demonstrating that they’re creating studying curves for drilling that look loads like what we’ve seen over the previous 20 years within the shale trade.

MB: Let’s truly ask the actually nerdy, actually primary query: why are we drilling by means of granite as a substitute of by means of shale for geothermal?

ST: For geothermal, you want two issues: temperature and a few sort of warmth switch mechanism that can be just right for you. Sometimes, it’s permeability somewhat than conduction that individuals are counting on. The temperature features are sometimes a consequence of the geological evolution of the realm you’re . The Basin and Vary space within the western United States—Nevada and Utah—has had a geological historical past over the previous 70 to 80 million years involving continental collision, intrusion of volcanics, intrusion of granites, after which a return to extension, creating the literal Basin and Vary sample you possibly can see on topographic maps.

The crust that was beforehand compressed is now being pulled aside, and that thinner crust elevates the warmth flux, bringing the warmer materials nearer to the floor. That shallower, hotter warmth sits within the bedrocks that kind the area—granite, metamorphic rocks, and a few superficial sedimentary rocks as properly. It’s the geological convergence that causes the play to be in granite or volcanic rocks. In Iceland, after all, it’s largely basalts—volcanic rocks they should drill by means of—as a result of that’s how the island was fashioned.

Does that make sense? 

MB: It does, in all probability as a result of I’ve spent manner an excessive amount of time limestone and shale over the previous 4 years. Additionally, to a sure extent, limestone substitutes—like basalt—have come up, with folks claiming they’re going to make use of basalt as a substitute, regardless of its totally different traits, like 6 to eight% quicklime in comparison with 65% in limestone. It’s not a terrific supply. I’m not going to call names, however $300 million of U.S. cash has gone to a agency whose whole goal is to exchange limestone with basalt in cement. To simplify it, limestone—the stuff we make marble counter tops and cement out of—is rather more appropriate.

The stuff in southern Florida is sedimentary rock that comes from outdated seas, the place seashells and carbonates filtered out of the ocean over hundreds of thousands of years, compressed underneath gravity, and had been then uplifted to the place we are able to entry them. Shale comes from outdated swamps and inland seas with excessive biomass that settled to the underside, compressed into layers, and over geological time fashioned hydrocarbons from that biomass, then had been uplifted to the place we are able to now drill into them. However these rocks haven’t gone by means of the metamorphic strategy of being uncovered to huge warmth, in order that they’re softer. They’re simpler to mine, which is why we like mining limestone and use it for cement.

However after we get to rocks which can be heat-bearing, they’re both metamorphic—become more durable rocks—or molten rocks which have solidified. In each instances, granites and metamorphics are typically in locations the place there’s sufficient warmth nearer to the floor. When you’ve got a giant limestone or shale mattress, it means it hasn’t gone by means of that course of, so the warmth is deeper down.

ST: Yeah, cheap assertion—form of 50/50, Michael. I believe it’s in all probability price speaking about totally different geological settings for deep geothermal. Within the UK and Eire, for instance, we might in all probability discuss two essential geological settings. One is what we name scorching sedimentary aquifers, or HSA. That is the place a sedimentary basin continues to be considerably intact, and you’ve got rocks—shales, limestones, sandstones—buried to variable depths. With the geothermal gradient rising with depth, by the point you get to round 3 kilometers within the UK and Eire, you is perhaps anticipating to get near 100 levels Celsius.

MB: However that’s testing by means of sedimentaries, that are simpler to drill, align with fracking drilling methods and applied sciences, and are aquifer-based—which by definition have a terrific Darcy outlook, regardless of the particular Darcy numbers are.

ST: The numbers will deteriorate with depth as a result of what occurs to these rocks is that they get compressed. Those with porosity have these little pores crammed up with what we name diagenetic cement. With out synthetic fracturing, you find yourself with a lot much less permeability. The following a part of the method geologically is that the rock will get buried by a mountain and undergoes metamorphosis. The opposite sort we’ve got within the UK are radiogenic granites. These are granites of variable age and variable warmth move, the place the extra warmth move comes from radiogenic warmth in addition to the overall warmth flux.

One of many earlier EGS initiatives on this planet is in Cornwall, the place Geothermal Engineering Ltd. has drilled right into a pure fault system within the granite. They’ve drilled two boreholes—one deep down to five kilometers, which is the depth wanted to achieve significant temperatures for the generators—and a water injector properly that’s a little bit shallower, round 3 kilometers. They’re enhancing pure fractures in that fault zone. They did a wonderful job managing societal expectations round induced seismicity and associated considerations. They’re about to return on-line with an influence era plant, however the entire thing will solely be about 5 megawatts of electrical energy. Scaling that up stretches my creativeness. It’s an actual mission within the UK, however I don’t suppose it’s going to ever be a giant factor—not less than not in my lifetime.

When you concentrate on the Basin and Vary techniques or drilling on the flanks of lively volcanoes in Indonesia, New Zealand, or Iceland, we’re actually speaking a few third sort of system: volcanic lively magmatic zones. In these areas, the rocks aren’t significantly porous however are usually naturally fractured, and you’ve got scorching, usually brackish to saline fluids transferring by means of them by convection. This results in a distinction between two sorts of techniques. One is known as conductive, the place the system is of course dry and warmth motion occurs primarily by means of warmth flux conduction, with little or no water within the fractures.

The opposite one folks are actually referring to is convective techniques, the place there’s a pure convection course of with faults and fractures, and highly regarded water circulating due to the excessive geothermal gradients. That’s usually the place standard geothermal energy vegetation have been situated, which is the place we began this dialog. I hope that helps draw some distinctions.

MB: So now we’re moving into the just about science fiction–sort geothermal stuff. Thus far, we’ve been speaking about tapping warmth that’s available at excessive temperatures—collections of volcanoes which can be quickly inactive, like in Iceland and New Zealand. We’ve been speaking about aquifer-based techniques a number of hundred meters underground. We’ve talked about shallow geothermal at round 100 meters. Then we talked about deeper aquifers, the place it’s nonetheless comparatively straightforward rock however you begin shedding Darcy, and with that, you begin shedding the curiosity of people that aren’t nerds like us—and of the individuals who truly need to become profitable off geothermal—as a result of it turns into an financial problem.

Now we get into among the extra science fiction–sort concepts. Let’s discuss it. There’s a little bit of an alphabet soup: there’s superior geothermal, enhanced geothermal, deep geothermal, Eavor’s closed-loop geothermal—which is totally different from the closed-loop geothermal you had been speaking about earlier. Why don’t we begin by briefly characterizing Eavor’s closed loop versus regular closed loop, and what the important thing variations are?

ST: Yeah, so Eavor is closed loop. What they’re doing goes deep for warmth with the purpose of mixed warmth and energy, or energy era from that warmth. Their mannequin is a closed loop that’s successfully a giant U-tube within the subsurface. Their authentic pilot mission in Canada had two horizontal wells drilled from factors 2 kilometers aside, the place they steered within the subsurface—at about 2 kilometers depth—for the toes of every horizontal properly to satisfy, just like the Channel Tunnel. Once more, one other directional drilling know-how from oil and gasoline has proved very helpful in geothermal. Their huge declare is that as a substitute of utilizing commonplace metal casing to maintain the borehole open, they’re utilizing a chemical compound, one thing like a liquid casing.

They’re circulating water round that huge, kilometer-scale U-tube. That’s what they’re doing in Germany proper now, although we’re not listening to a variety of information about precisely what’s taking place or what progress is being made. In that German mission, they’re making a bunch of these U-tubes underground from single mother or father wells drilled from the floor, successfully constructing a subsurface radiator of U-tubes. We studied the fundamental idea of deep closed loop ourselves and had been fairly enthusiastic about it after we obtained began. The essential downside, once more, is conduction. If you inject a cooler-than-formation-temperature medium—whether or not it’s CO₂, which they generally discuss, or water—into that huge U-tube, the quick impact is that the rocks close to the closed loop borehole begin to chill.

As a result of conduction is sluggish, what occurs is a cooler thermal halo or bubble expands out from the borehole. Within the exiting temperature profile, you see a really speedy decline from the unique bottom-hole temperature—typically as a lot as 75%—within the first few hours, days, or handful of weeks. Then that curve asymptotes to what I discussed earlier: a pseudosteady-state decline at a temperature that, underneath good situations, is about half of what you began with. Beneath poor situations, it’s even much less. That slowness of conductivity in rocks just isn’t a pal to closed loop techniques.

What we present in our financial modeling is that you just want a gazillion mild kilometers of borehole to reap sufficient warmth, and the temperature of the formation needs to be considerably above the temperature you want for the turbine with a purpose to be helpful. You’re nonetheless having to drill rather more than you’ll in the event you had been simply drawing warmth out of water. I’m nonetheless sort of fascinated by deeper closed loop, however I see extra alternative within the comparatively shallower subsurface—lower than a kilometer deep—the place I can get a little bit extra temperature and a greater delta T on my supply warmth, which helps the warmth pump system considerably. However I don’t should lay our a fortune placing in kilometers and kilometers of deep borehole.

I truly did some math two or three years in the past and discovered that, for a megawatt, we may do the identical job with, say, 100- to 200-meter-deep closed-loop boreholes in comparison with a one-kilometer-deep borehole. We may do the identical job. The drilling prices shift enormously as you go deeper, so it makes financial sense to remain shallow. If you too can optimize the warmth pump effectivity—even to the purpose the place it could actually deal with 15 levels Celsius warmth and elevate it to 120 levels, like we did at Southwest Analysis Institute—then the economics begin to look actually attention-grabbing.

MB: There are two or three issues about that. First, the longer you drill underground, the extra the dangers accumulate. That’s the primary level. Horizontal drilling has achieved superb issues, however each further kilometer provides dangers to the drill, provides length, and provides prices.

Their German mission is 60 megawatts of warmth and solely 8 megawatts of electrical energy as a result of, as soon as once more, with the natural Rankine cycle, they’re working off a lower-quality warmth supply that’s truly going to degrade over time, as you level out, geologically. They’re utilizing totally different refrigerants to extract much less environment friendly quantities of labor from it, and that’s simply the character of the beast. I don’t personally charge their probabilities for fulfillment. I believe it’s very attention-grabbing, I’m glad they’re making an attempt it, and I’m amazed we are able to have drill heads meet two kilometers underground—that’s insanely exact and superb. So full props to the drillers. Okay, in order that’s closed loop—deep closed loop—Eavor.

Then there’s enhanced geothermal, and Fervo is sort of the front-runner in that. You’ve alluded to it a number of instances, and also you’re extra optimistic about Fervo than I’m, however you’re additionally a lot nearer to it. If anybody needs an opinion, they could take yours somewhat than mine. So inform us about enhanced geothermal—and why is it EGS as a substitute of simply EG?

ST: It’s an enhanced geothermal system. The terminology will get a bit like spaghetti soup right here. As for Fervo, I agree—I truly suppose that if this turns into an actual factor, they’re the leaders. I like the way in which they’ve systematically labored by means of the technical challenges of transferring shale horizontal drilling and fracking methods over to geothermal. They’ve additionally thought actually rigorously—or as rigorously as they will—in regards to the offtaker and the best way to construct a worth proposition round it. The jury’s nonetheless out on whether or not it’s going to occur, proper? I agree. What they’re doing is these conductive and convective conditions within the Basin and Vary Province, licensing tracts of acreage in granitic and volcanic terrains.

They’re drilling vertically all the way down to 4 or 5 kilometers, then going horizontal with the target of becoming a member of up as many pure fractures as doable. They’re utilizing hydraulic stimulation to open up these pure fractures, make them extra permeable than they’d be naturally, and likewise to generate new propagated fractures. As you talked about earlier, they’re conserving them open with little grains of sand or quartz proppant. They’re throwing the shale playbook and kitchen sink at it. It’s actually spectacular how they’re making use of directional drilling, the drilling studying curves we talked about earlier, and, for stimulation, utilizing stage stimulation know-how—a more moderen growth within the oil patch—to maximise the impact of every fracture stimulation alongside every part of the horizontal properly.

They’re matching up a producing horizontal properly with an injecting horizontal properly, making a convection-advection system underground in a layer of rock that’s a number of hundred meters thick and a number of other hundred meters vast. They’re even utilizing terminology from the shale patch, calling these “benches” the place they place every doublet or pair of horizontal wells. They inject into the injector and summary from the producer. The early outcomes are good. They’re getting move charges from the producer with cheap calculations on energy era effectivity that counsel precise megawatts of electrical energy—not simply thermal vitality—from a person borehole pair.

Secondly, they’ve now obtained a few years—possibly getting on three years—of information from their first mission alongside the federal government’s FORGE mission, which they name Challenge Purple. The temperature and move charge have stayed fairly regular. One fear would have been a speedy thermal decline, such as you see with a shale properly, however not less than over three years of information, that’s not the case.

MB: It’s going to last more than a shale properly, not less than.

ST: It seems that manner. All proper, there’s loads to love about what Fervo is doing from a technical perspective, and that’s why I’m a little bit extra optimistic than you’re.

MB: However what in regards to the financial perspective? 

ST: For me, there are possibly three issues to speak about right here. The primary is a technical one: will that two-year efficiency flip into 25-year efficiency? Is the move charge and the temperature sustainable?

MB: That’s as a result of they’re nonetheless taking warmth out of a quantity of rock with low flux for the quantity of rock. 

ST: Proper. They’re at present saying, sure, it’s going to, and that they may drill one other bench to exchange it in the end. They’re speaking about 10 or 15 years out, not subsequent week like in shale. That’s huge query primary for Fervo. The second query is sustainability. And the third is the industrialization query that you just raised in your article.

MB: By the way in which, the Fervo CEO left a remark suggesting I didn’t know what I used to be speaking about and dismissed every thing I’ve ever written on the topic. He was in search of a motive to. 

ST: I believed he was fairly well mannered truly in comparison with among the different feedback that you just obtained. 

MB: I didn’t say it was rude, however he was in search of a motive. To be clear, I’ll be clear: my analysis didn’t point out that they had been in a position to do multi-well per pad deep drilling. Seems Fervo cracked that one—I obtained that unsuitable.

ST: That’s proper. 

MB: I believe that’s going to introduce different issues. However let’s check two issues: what’s the common depth of a shale oil properly or a stimulated gasoline properly?

ST: Just like barely shallower and complete size is identical. 

MB: However then there’s the rock.

ST: There’s the rock, after which there’s all of the infrastructure, and so forth.

MB: As a result of the rock—igneous and metamorphic rock—is more durable to drill by means of than shale, I perceive.

ST: I’d say the speed of penetration that Fervo is attaining is now turning into equal to shale drilling. Within the circumstances they’re working in, that problem has basically evaporated. The rationale for that’s the methodical, systematic studying of the best way to pace up drilling—properly size by properly size, properly by properly, mission by mission—which is an artwork kind the oil and gasoline trade is aware of very properly. There are nonetheless technical features that Fervo is studying about. On the extra industrial facet, I believe there are huge query marks. Lots of people within the geothermal trade nonetheless discuss baseload, however you and I do know that’s probably not the difficulty anymore. A whole lot of others within the trade, together with Fervo, are beginning to acknowledge that dispatchability is the true prize.

MB: And suppleness. 

ST: Flexibility and dispatchability. I’ve to say, I heard geothermal of us speaking about this 5 years in the past at an early convention. One man from Ormat, one of many main standard geothermal companies, spoke on a enterprise mannequin panel and mentioned the competitors is battery plus wind, battery plus photo voltaic. That also is smart to me. It’s probably not about baseload. I believe it’s about flexibility and dispatchability.

MB: One factor right here is, if they may get beneath $10 or underneath $100 per megawatt-hour at a coal plant web site, and substitute the coal plant with this, that might be higher. However it nonetheless requires a selected sort of subterranean geology, appropriate?

ST: Your useful resource for energy era is distant from the demand, so there’s an infrastructure problem. Inside that, there’s a simultaneous equation to resolve round dispatchability and suppleness. How would geothermal match into that? Right here’s the underside line for me: possibly I’m an excessive amount of of a geo-optimist, however I can’t utterly get to Michael Barnard’s place that it’s a rounding error. Nonetheless, I don’t suppose it’s going to be massively important or materials. I actually shudder after I hear among the current hype about filling knowledge heart demand with materials quantities of geothermal by the early 2030s. That annoys me as a result of I believe it displays badly on the true alternatives in different geothermal purposes.

The way in which I fear about it, huge image, is vitality return on vitality invested. In case you assume for a minute that we may do EGS for roughly the identical prices as shale oil drilling, the subsequent huge downside is that the vitality density—and due to this fact the financial worth of the product—is not less than 15 to 25% of what you get from shale. And with shale, you’re getting most of it within the first hundred days.

MB: Proper now, we’re at 2 to 4 EROEI—vitality return on vitality invested. The EROEI of shale proper now’s 2 to 4. Wind and photo voltaic are at 12 to 18. If geothermal—particularly enhanced geothermal—is getting a decrease vitality density end result, it may find yourself with a unfavorable EROEI. It may take extra vitality to drill and energy the system than it produces, relying on the length of the useful resource. The shale oil useful resource comes out quickly. It takes a variety of vitality to get it, however you get two to 4 barrels of oil for each barrel’s price of vitality you expend. If the useful resource lasts for 10 years, then the equation…

It’ll be attention-grabbing to see the way it works out. However proper now, even the very best, most optimistic projections are saying $150 to $250 per megawatt-hour, which is manner out of competitiveness. It’s nowhere close to aggressive.

ST: I did some math this morning, Michael, simply to consider this. I took a shale properly producing 5 million barrels over 10 years. By the way in which, Google says it’s about 1,700 kilowatt-hours per barrel of oil—an equivalency that can drive you mad. To even the enjoying discipline with geothermal, I stretched it to twenty years for the shale properly. My thermal capability got here out to 48 megawatts for that. Fervo is saying they’ll get 12 megawatts electrical over a 25-year mission time period. Once I ran the numbers, I gave $70 a barrel to the oil guys and $0.07 per kilowatt-hour to the geothermal guys.

The numbers are greater than twice the worth proposition. If that’s proper—2 to 4 EROEI for shale wells in comparison with 12 for photo voltaic—and assuming you’ve constructed the total infrastructure and intermittency prices into that quantity, as a result of typically I fear they aren’t, then even when they’re comparable, the massive image for geothermal is wanting difficult.

MB: The factor I say about enhanced geothermal is that the capital prices are so excessive, they should run at 90% capability elements to make the economics work. They want a knowledge heart load and that sort of fixed demand. In order that’s EGS—we’ve talked about EGS. Let’s spend a few minutes on actually deep geothermal. 

ST: Let’s solely spend 30 seconds. Proper? 

MB: Come on, speak Quaise.

ST: I’m a little bit of an spectator with that stuff. I’ve to admit, I’ve taken a somewhat agricultural view of it: if it had been doable, it will have already got been accomplished by the oil and gasoline trade.

MB: Let’s speak in regards to the depths. Let’s begin with the depths and the temperatures. 

ST: The large concept is to go deep sufficient that you just’re reaching supercritical temperature and stress situations, the place the vitality proposition is gigantic in comparison with the depths that Fervo and others are concentrating on. The thought is that you just drill one among these wells and also you’ve obtained sufficient vitality to substitute for a coal-fired energy station proper underneath your ft. You can do that anyplace on this planet as a result of the know-how would will let you drill deep sufficient—regardless of the geothermal gradient—to achieve the super-hot rocks. The know-how challenges are miles and miles of drilling by means of more durable, higher-temperature rock. Strain isn’t as a lot of a problem, however temperature undoubtedly is. After which, after all, there’s the query: what do you do when you get there?

How do you get the warmth out? What are the techniques which can be going to have the ability to harvest supercritical warmth and produce it to the floor? That half actually does look like an episode from Star Trek the place the blob melted its manner by means of the wall, proper?

MB: My favourite level on that is in regards to the electronics on the directional drill heads. All of the know-how simply doesn’t work at these temperatures. All of the electronics have to get replaced, all of the drill bits have to get replaced, and the traits of the rock change into extra plastic. Every thing that has been working properly—what Fervo managed to pivot from shale to granite, from oil and gasoline to electrical energy—stops working. They should invent new stuff. Now we’ve obtained microwaves and…

ST: For the lasers and the electronics, and among the different temperature-dependent gear, there’s a tempering remark I’d prefer to make. The temperature of the circulating fluid across the drill bit, the motor, and the measurement-while-drilling gear is considerably totally different from the formation temperature. Mud acts as a lubricant for the drilling course of, offers weight inhibition to stop undesirable fluid influx, and, in these circumstances, may also function a cooling support. So the temperature problem for electronics is unquestionably actual, however a cooling mud system affords a chance to make that specific problem extra manageable.

MB: Closed loop and EGS each have black swans on their very own and capital prices that make electrical energy unviable, although for various causes. However deep geothermal is a flock of black swans—they usually’ve obtained lasers strapped to their fricking heads. It’s science fiction.

ST: That’s sufficient now. That was three minutes not less than. 

MB: Let’s shut off with what Causeway does and what your candy spot is on this house. In my analysis, I described it as reasonable geothermal uplifting with industrial warmth pumps. Industrial warmth accounts for about 10% to 25% of all world emissions, and about 50% of that’s within the candy spot for this strategy. Inform us about that and about Causeway.

ST: We began out with the dream of energy. Inside a yr, we pivoted to warmth, however we didn’t surrender on larger temperature warmth. Most industrial warmth demand is definitely beneath 80 levels Celsius. It’s solely whenever you get into processes like drying and pasteurization that you just transfer into the 150 levels Celsius vary, and it’s actually solely cement, metals, and a few chemical processes the place you want lots of and even 1000’s of levels Celsius. In the present day’s industrial warmth pumps are greater than able to delivering sub-steam temperatures very simply with excessive COPs. They’re additionally able to producing low-grade steam—round 120 levels Celsius at 5 bars. There are actually machines that may ship as much as 150 levels Celsius. Certainly one of our skilled advisors, Professor Neil Hewitt at Ulster College, is fairly assured about reaching even larger temperatures.

Industrial warmth pumps are already a actuality, significantly in Europe. What they’re usually doing there’s utilizing undesirable waste warmth from fossil gas heating techniques and upcycling it so it may be used usefully as low-grade steam or highly regarded water. In our work with industrial warmth pumps, we noticed that the way in which the know-how is progressing, we are able to now use decrease and decrease temperature warmth—not simply waste warmth from fossil combustion—and nonetheless ship the identical outcomes. This opens up massive demand purposes like water and house heating for hospitals, huge buildings, and networks. We’re beginning to consider low-grade steam, and we’ve been doing a little work with a distillery on that. The warmth pump know-how is already there for that. The following frontier is attending to even hotter temperatures.

With the subsurface, the massive aha for us was realizing that, given the effectivity of warmth pumps to realize temperature lifts of 60, 70, 80, even 90 levels Celsius whereas nonetheless sustaining excessive or sufficiently excessive COPs, we don’t essentially must drill that deep for our warmth. Twenty levels would possibly do. Thirty levels would in all probability do very properly. Sixty levels could be even higher. After we ran the numbers and in contrast the variations in COP relative to temperature improve with depth towards the rising drilling prices and dangers with depth, we noticed a Goldilocks zone—or candy spot—emerge. It’s between 500 and 1,500 meters. You can go deeper than 1,500 meters in UK and Irish circumstances, however as I mentioned earlier, at that time you in all probability want to maneuver to geothermal techniques to extract the warmth, as a result of the pure permeability would should be clarified.

MB: Again to aquifer geothermal.

ST: In deeper aquifers—yeah. I discussed earlier the instance in Liverpool, the place the deeper aquifer is simply about 500 meters deep, however that further 6 levels Celsius in comparison with the shallow aquifer makes all of the distinction to warmth pump effectivity and the delta T on the supply—how a lot you possibly can extract from that larger temperature. We’ve accomplished a variety of feasibility research that help the idea. The following step is transferring towards a industrial pilot, and we’ve got two or three clients within the UK who’re . 

We additionally had a brewery mission in Nigeria, owned by a really well-known drinks producer, the place we superior to testing the boreholes. Sadly, that drinks producer bought the brewery and the mission to a 3rd get together late final yr. That mission is sadly at present in abeyance. Hopefully the brand new proprietor will come round. That one was about six or seven megawatts of brewing and in-place cleansing of the brewing gear, equipped by an unusually scorching aquifer at solely 650 meters deep, with 70 levels Celsius beneath Lagos. There are a selection of alternatives to progress towards one thing related. We’re additionally actually within the thermal vitality storage mannequin. If you get that proper, the economics are actually attention-grabbing—and so is the impression.

MB: Individuals haven’t been speaking about warmth as a result of it’s too boring. We’ve lastly obtained folks enthusiastic about warmth pumps, however now we have to get them enthusiastic about this low-risk, broadly accessible possibility. Let me ask you one query: aren’t you going to be interfering with consuming water from these underground aquifers?

ST: For shallow open loop, the allowing and regulation are rather more rigorous when the water is of consuming water high quality. It often boils all the way down to having to re-inject the water so there’s zero internet abstraction of the useful resource. In some nations the place regulation is extra superior, you additionally should show that you just gained’t intrude with the chemistry or biology of the water, and that you just gained’t have your “milkshake sucked by any individual else’s straw.” It’s important to run numerical simulation fashions to point out how thermal plumes will evolve. It’s all doable—it simply takes longer than allowing and regulation for closed loop, as a result of closed loop doesn’t work together with the groundwater in any respect.

MB: Then for reasonable depth like the five hundred to 1500 meter?

ST: That is the place it turns into actually attention-grabbing. In most elements of the world I’ve checked out, as a result of the temperature and residence time of the water are larger within the rocks we’re speaking about, the water interacts with the formation rocks and the chemistry, turning into brackish after which saline with depth. There’s a variety of knowledge collected within the US and the UK exhibiting that salinity will increase with depth. By about 500 meters, the water is already brackish and never of consuming water high quality. In precept, which means you aren’t uncovered to the identical regulatory constraints—not less than when you get by means of the primary couple of hurdles, as a result of the environmental authorities will initially ask you to clarify and show it. That sample of accelerating salinity continues with depth.

Certainly one of our rising deep geothermal warmth pump initiatives, which I’m hoping to safe the primary part of engineering for at a hospital in Northern Eire within the subsequent few weeks, entails an aquifer we anticipate to be someplace between 650 and 1,000 meters deep. If we attain 1,000 meters, the salinity can be a few instances larger, which introduces some further points—however all of them are manageable as a result of we all know the best way to deal with scaling and related challenges. It’s not tremendous corrosive like among the hotter geothermal brines, so we anticipate it to be simpler to make the most of that aquifer useful resource. 

MB: The final query about this, how prevalent are these reasonable depth aquifers? 

ST: They’re not in all places. For the UK and Eire, we’re saying let’s begin with those we all know finest. Sarcastically, we learn about them due to oil and gasoline exploration.

MB: In fact. 

ST: There was a little bit little bit of geothermal exploration within the UK within the early 80s—the final time folks nervous significantly about vitality safety. We now have legacy seismic data, different geophysics, and boreholes that had been usually drilled for deeper oil and gasoline targets. Our goal geothermal aquifers are shallower, so the boreholes have drilled by means of them. Within the UK and Eire, we actually like 4 or 5 explicit areas. That doesn’t imply it’s going to work in all places, however they’re actually good locations to begin. There’s an outdated oil discipline adage: if you wish to discover oil, drill the place oil has already been discovered.

I believe it’s the identical for this kind of geothermal utilization: we begin the place the subsurface danger is already lowered by legacy knowledge and expertise, sarcastically from oil and gasoline. For the tougher rocks, I haven’t given up on closed loop. We’ve additionally simply completed and submitted a report right this moment to the Division for the Economic system in Northern Eire, the place we’ve checked out a hybrid system known as a standing column properly. You possibly can consider it as a hybrid between open loop and closed loop. It’s been used modestly in the US over the previous three a long time. It circulates water round an open borehole that’s not cased off, so that you’re getting warmth from conduction in addition to from advection.

The enjoyment of it’s that it really works in modestly productive aquifers that solely have fracture move. These aquifers characterize a lot of the northeastern United States, the place the know-how originated, but additionally the UK and Eire. We’re fairly enthusiastic about this. The benefit is that, due to the extra advection in addition to conduction—and we’ve confirmed this now with some discipline testing, proving it for Irish rocks—they’re three, 4, possibly 5 instances thermally extra highly effective than the equal closed loop system. The place you possibly can’t do closed loop due to house, and you’ll’t do pure open loop as a result of the aquifer isn’t productive sufficient, there’s this intermediate resolution that appears actually thrilling. It reduces the variety of boreholes and capital expenditure, which improves the economics. We’re actually enthusiastic about that software as properly.

We’re engaged on three or 4 purposes. We need to be a developer and construct an funding thesis round it. We’re placing mission finance into it to show it right into a enterprise mannequin—every thing from capital financing to the shopper, by means of to a thermal buy settlement, or it might be utterly off steadiness sheet for the shopper. These are the sorts of enterprise fashions we’re interested by. There’s know-how within the pipeline, however we’re actually centered on making the practically confirmed and confirmed applied sciences work in these mixtures first, earlier than going again to the blue-sky drafting board and doing issues like supercritical CO₂ once more. That’s what we’re about. Proper now, we’re coping with the chicken-and-egg downside of demonstrating the know-how to clients, stakeholders, and policymakers.

We’d like first of a form initiatives to try this. So as to do this we’d like some assist. 

MB: However that’s first of a form initiatives in Eire, not first of a form initiatives. It’s being accomplished elsewhere. 

ST: It’s been accomplished a number of instances. You discovered a few examples in your analysis. There’s one other one nearly to return on-line in Denmark. We discovered one two or three years in the past—I’d get this unsuitable—I believe it was in Slovakia, the place they had been utilizing a heritage geothermal properly for heating tomato greenhouses. When the properly declined, they put a warmth pump on it. These had been unstoried pioneers, but it surely’s nonetheless only a few and much between so far as I can inform, Michael. First-of-a-kind initiatives in Eire or the UK are nonetheless a good subject. 

One other factor I’ve discovered and relearned is that for lots of the applied sciences we’re speaking about, know-how innovation and diffusion are nonetheless geographically restricted, which amazes me given the digital world we dwell in. Time and time once more, we discover that for purchasers, shoppers, and buyers, we are able to level all day at Sweden—the European chief for geothermal, with 16 or 17 terawatt-hours of geothermal warmth harnessed by warmth pumps every year. We are able to level all day on the Danish instance or the Slovakian instance. It doesn’t imply something to them till it’s within the neighbor’s yard or within the neighbor’s facility.

MB: That parochialism is an issue. We now have to look all over the world, discover the examples, the spots of the longer term, and undertake them domestically rather more quickly. We’re at two hours, which has been a terrific dialog. I’d like to shut it off. I all the time like to complete by leaving you an open-ended alternative to say something you suppose is related out of your journey, out of your expertise with warmth—one thing we might have missed within the dialog.

ST: I might simply return to the why—each the strategic why and the non-public why. The strategic why is that roughly 50% of vitality emissions are related to warmth. We’ve made some good progress on electrical energy and energy era, and a few good progress on mobility and transport—although there’s nonetheless tons extra to do—however little or no on warmth. I believe that’s a giant, highly effective why. And it’s amplified for me as a result of it’s not nearly emissions and sustainability; it’s additionally about safety and vitality resilience. For instance, in Northern Eire, there aren’t any fossil fuels, and within the UK, fossil gas availability is declining. There’s solely a single gasoline discipline off the west coast of Eire. So dependency on imported fossil fuels is a extremely severe matter.

And the variety of unhealthy actors that maintain these fossil fuels is rising, not lowering, for everyone else. So the notion of inexpensive, indigenous, and due to this fact safe and sustainable warmth is, I believe, an exquisite prospect. As for the non-public why—I’m not out to make a giant fortune from this. My profession with BP set my spouse Fiona and me up fairly properly for the rest of our lives. This has change into a form of final part of the profession, a legacy factor for me: simply to make a distinction, use the talents of extraction, study some new issues, and hopefully make a distinction within the dwelling nations and elsewhere.

MB: That’s nice. I’m your host, Michael Barnard. This has been Redefining Vitality-Tech. My visitor right this moment has been Simon Todd, Managing Director of Causeway Energies, Ph.D. in geology, and skilled, as we’ve found over the previous two hours, in geothermal vitality. Todd, thanks a lot for becoming a member of me.

ST: You’re very welcome, Michael. Thanks for the invitation.