From Guest Blogger Gary Tulie: Geothermal Anywhere
Imagine it was both possible and affordable to drill down anywhere to a sufficient depth to find rock hot enough to generate high pressure steam!
This is the target of a Slovak company called Geothermal Anywhere.
Geothermal Anywhere uses a Spallation technique using a combination of high pressure water jet and plasma discharge from a plasma torch (artificial lightning) to break off small chips of rock without contact using equipment designed to operate at extreme temperatures and pressures found at depths up to 10 km.
In conventional drilling, cost tends to rise exponentially with depth beyond around 3 km depth as friction increases with consequent rises in energy consumption and wear. In addition, the drill bit spends more and more time being raised and lowered for maintenance so increasing the time related costs of drilling. This places an economic cap on drilling depth – so that drill depth is decided by the intersection of resource temperature which affects yield and drilling cost. (Drilling is generally responsible for around 60 to 80% of the capital cost of geothermal power.)
Where Geothermal Anywhere has an theoretical advantage (yet to be proved with a full size rig) is that drilling is expected to be both quicker and less costly than conventional techniques with cost broadly linear with depth. This means that for the first time, there is the prospect of drilling pretty much anywhere to a depth which gives optimal resource temperature, so vastly increasing viable geothermal reserves – a renewable resource which is available 24/7 unlike most sources of renewable energy and so can provide reliable base load electricity.
Why is linear drilling cost significant?
Both electrical generation efficiency and the amount of heat available increases with temperature, so that doubling the borehole depth is likely to yield substantially more than twice the electricity per borehole. This combined with reduced balance of system cost per MW due to higher temperature more powerful wells can give substantially reduced levelised cost of electricity so achieving a step change in geothermal power viability.
If this, or other advanced drilling techniques pan out, no other technology I know of offers such large scale and geographically diverse potential for clean base load power generation at costs comparable with fossil fuels.
For a long time, Geothermal power has been something of a poor relation with minimal investment in improving Geothermal technology. In the light of the work of Geothermal Anywhere and other groups such as Potter Drilling which appears to use broadly similar principles (Thanks to Tim Kingston for alerting me to them), there would appear to be a very strong case for more fundamental research into further reducing Geothermal power costs.
Geothermal is a very promising source of renewable energy but it has to overcome several challenges that have not been addressed in this news release about spallation drilling.
The steam produced from geothermal wells is highly corrosive due to the extreme mineralization of the water. The clogging of heat exchangers needs to be addressed.
Also, the delivery of power to the drill head has not yet been developed for multi Km depth holes. A powerful tool on the benchtop does not readily translate into a lean mean boring machine at 10 Km down under.
But, keep up the good work. Someday it will all come together and the electricity will be “too cheap to meter”. Tha is an inside joke for those of us old enough to remember the beginning of the nuclear power age which hasn’t quite arrived yet!
Although it would be unwise to attempt to predict how this will pan out, it would be exceedingly unwise not to pursue it further. There are potential problems, such as the possibility of setting off earthquakes and corrosion caused by dissolved salts. But who knows? It might turn out to be an inexpensive source of huge amounts of power.
Craig,
I have done a good bit of “drilling down” into the costs of enhanced geothermal… The idea of linear drilling costs past 3km is truly a major breakthrough if it works out (of course, it is also a major breakthrough for the petrochemical industry, as they are pursuing ever-deeper reserves). But as I understand it, it’s not just the drilling costs, but also the well stimulation costs that increase geometrically with greater depth. So this solves half of the cost issues with ultra-deep geothermal… and that’s a huge breakthrough! But there’s more cost issues to come.
An analysis that I did several years ago showed we could have cost competitive geothermal with current drilling cost assumptions if we used two seperate input sources – one shallow well (4 km) and one deep well (6 km) that both powered a dual-source heat engine (our novel “DORC”) using low-cost high efficiency recuperation (our novel “CRLI”).
The idea is that if you use a shallow well to provide the lower-temperature heat, and only use the deeper well to provide final heating, you can do most of the heating at low cost, making the overall system costs reasonable. The calculated LCOE of the system in question was ~$45/MWh. If you were to take the same idea using a linear cost deep drilling, it might be less than that.
The big unanswered question here: At what depth does this “spallation” technique become more cost effective than traditional drilling. It’s assumed that while the cost increases linearly, the base coefficient is higher, so for the first X km of drilling it is still cheaper to do it the old fashioned way. I’m curious as to what depth this breakeven occurs.
Thanks Glenn for your comments.
The idea of dual heat source to reduce the demands on the deeper well is very interesting.
I suppose that the second source of heat could come from industrial heat recovery at temperatures usually considered too low for economic electricity generation, or from low cost solar thermal fields. This may in some cases lower the overall cost, and in the case of solar thermal introduce a degree of load following.
The other possibility is to incorporate the low temperature heat remaining after electricity generation into district heating networks. Such networks are very common in Scandinavia, Germany, and the former Eastern bloc nations.
Gary,
There’s been a lot of development of combined heat-and-power systems in the last decade… but at heart is the issue of scale: we have an infrastructure that can easily distribute electricity… but the distribution of thermal heat is far more expensive and less developed… and most places you would want to put a large geothermal operation are remote, making the distribution of heat that much more difficult.
The best way to use the Earth for residential and commercial heating is a geothermal heat pump – which is just using a few thousand cubic feet of shallow earth as a thermal storage, where you dump excess heat in the summer and draw the stored heat during the winter. Otherwise, if we can generate electricity competitively, that’s a pretty good thing.
🙂
Glen,
In New York City, centralized heating plants have for well over 50 years distributed heat to numerous buildings which don’t have their own heating systems. When I grew up in Manitowoc, Wisconsin, the local power company sent heat to the Rahr Malting Company which was perhaps half a mile away. Thus, there is nothing new about distributing thermal heat here in the U.S.
The main investment cost of geothermal heating and cooling systems is digging and installing the ground coils or thermal wells. In some areas that investment cost can be greatly reduced if there are bodies of water nearby, such as a river or lake, which can be used instead of ground coils or wells.
In northern climates, it is possible, without heat pumps, to use air to produce ice in the winter time and, in the summer, use that ice for cooling. Whether that would be economical I don’t know; the ice storage tanks would have to be quite large.
Frank,
Ground temperature in northern U.S. (continental states) is typically ~50 F. Running a heat exchange fluid through that ground would allow you to blow 50 degree air into your home with no excess power. The amount of power required to heat or cool using a heat pump is proportional to the difference in temperature from the base heat… So in the winter you would be heating the base heat by ~15 degrees F (rather than heating the outside temperature ~65 F), and cooling the ground below 50 F (maybe as low as 49)… In the summer you’d be directly blowing the 50 degree air into your house, using no excess energy, and you’d be heating the ground (perhaps as much as 51 degrees). This is quite efficient.
Using seasonal ice storage doesn’t make any logistical sense. My house has a 1.8 ton unit, which means that over every hour the heat pump is working at max, it is providing cooling equivalent to melting ~150 lbs of ice.
During any given day when the AC must be on 12 hours, that yields half-a-ton. Over a 180 day cooling period, assuming an average cooling need of 12 hours per day, that would be 90 tons, or >90 m3 of ice. That’s not small. My home is only ~1700 ft2 with 8′ ceilings. The ice storage would have to be more than a quarter the size of my house…
Energy would have to be spent during the winter, in most places, to freeze that much water. There simply wouldn’t be enough cold days to have a concentrated amount of water freeze naturally like that – it would be analogous to having a lake freeze 8 or more feet deep. Maybe a few places in Wisconsin Minnesota, and North Dakota, but in most cases it just doesn’t get that cold in the winter… and then you have cases like this winter…
Gary,
I am very familiar with heat pump technology, including air conditioning. I’ve had two years of physics at the college level and did considerable research while my new house was in the design stage. I’m also familiar with the Carnot system which, unfortunately, cannot be built.
When my new house was in the design stage in 2008, I considered a ground source heat pump. However, I found that the interest on the increased cost would exceed the savings thereby making the investment unsound, mainly because of ground coil cost. Since then air source heat pumps have become available that could make sense, but it’s somewhat too late. However, it could make sense at a later date especially considering that using a heat pump for heating would integrate very well with my radiant floor heating which requires a relatively low water temperature. In this climate, the normal high during January is 45F, at which temperature an air source heat pump would be effective. The normal low is 25F so even with a low RH, the effectiveness of an air source heat pump at night would be a bit questionable.
Using ground coils to cool a house without a heat pump could work very well if you had HUGE ground coils, but I suspect that the extreme size of the ground coils would often make that approach impractical, especially with city-size lots. If one had a house on a lake, it is possible that the water temperature at the bottom of the lake would remain cold enough, but the percentage of people with lake homes is very low.
There are air conditioning systems available that do not circulate air. One is the chilled ceiling system using chilled water coils in the ceiling; it’s been used in Europe for many years. Obviously it can handle only sensible heat and not latent heat since we would not want water condensing on the ceiling. The latent heat would have to be handled separately, perhaps with a very small conventional air conditioning system or a valance cooling system. The system is more efficient than conventional systems because 1) the cold side operates at a higher temperature, 2) because the ceiling re-radiates less heat, the occupants are comfortable at a higher temperature, and 3) it requires less power to circulate water than to circulate air. It would also require a well-insulated house else the available cooling would not be adequate. The cooling available is a bit less than 25 BTU per hour per square foot with a ceiling temperature slightly lower than 60F.
A valance air conditioning system uses (housed) finned coils on the ceiling adjacent to outside walls; chilled water is circulated through them. It is marketed for both heating and cooling but my experience with injecting heat at the ceiling level has not been favorable; it results in annoying temperature stratification. But for cooling, the system could work well. Unfortunately, when my house was in the design stage, valance air conditioning was available only for commercial installations. I would have found it attractive because it would be silent and draft-free and perhaps more energy efficient. It can be more efficient because, again, circulating water requires less power than circulating air. However, if the fin area were too small, then a lower water temperature would be required thereby reducing efficiency.
Regarding making ice during the winter for summer cooling, the ice could be produced with ZERO energy consumption! A refrigerant could be used to transfer heat from the underground tanks to heat exchangers on the roof with the heat exchangers being similar to classic radiators. Natural convection, often augmented by the wind, would transfer heat from the heat exchangers to the outside air. Ammonia would perhaps be a suitable refrigerant to transfer the heat; it would boil in the tubes in the ice tanks and condense in the roof-top heat exchangers. Also, NH3 is environmentally friendly. Of course the system would have to be carefully designed so that a leak would not be hazardous.
True, a large, easily computed, amount of ice would be required and the tanks would have to be shaped in such a way as not to be damaged by freezing. And, as you say, it would be practical only where winters are really cold, such is in northern Minnesota, Wisconsin, North Dakota, Montana, and Ontario. Those areas also have a short cooling season, definitely far less than 180 days. A well-insulated house would require less ice. On the other hand, the short cooling season would reduce the importance of the energy saving.
There are a number of very large district heating networks in Europe, such as that of the Copenhagen region which has 1,500km of district heating mains. This network extends to communities as much as 40 km from Copenhagen.
It would appear that geothermal district heating is under serious consideration in Denmark, with geothermal gradients at around 25 to 30C per km and reasonable porous rock down to 2.5 km, however it is less certain that there would be a good financial case for electricity generation with present technology. (this could well change with advances in drilling and enhanced geothermal systems.)
Turkey is another possibility with excellent geothermal resources, and close to 500MWt of existing geothermal district heating, and nearly as much geothermal heating of greenhouse crops.
it would be practical only where winters are really cold, such is in northern Minnesota, Wisconsin, North Dakota, Montana, and Ontario. Those areas also have a short cooling season, definitely far less than 180 days. A well-insulated house would require less ice. On the other hand, the short cooling
Regarding ice cooling..
While the northern climes are definitely more suited to ice cooling that the southern states, I am wondering if a simpler green approach to cooling in these short summer locations is to just design a passive cooling system instead of going to the expense of rigging a large scale plumber’s delight.
Earth sheltered homes do not need to be more expensive than conventional construction and they take care of the heating and cooling for a few dollars of firewood in the winter and a few dollars of electricity for a fan in the summer.
I have a walk-out basement in Wisconsin that is essentially a earth sheltered house with a house on top of it. I keep telling my wife that we are going to move into the basement if the economy and our financial system collapses.
Of course in many areas, the water table would prevent such construction unless a lot of dirt was imported for mound construction.
Earth sheltered homes can work well in some places, especially where they can be built into hillsides. However, I question their practicality in large cities with small lot sizes. Also, many of us would not be happy with very little window area.
My new house, completed 3.5 year ago, was constructed to be energy efficient, with the exception of a rather large glass area for the living room and the master bedroom. The main living area is on the second floor to take advantage of the wonderful view of the mountains and the wonderful view required a large glass area. I’m sure that some people would be happy with a very small glass area, but that would be almost certain to reduce resale value which should always be a consideration. Probably there is room for improvement in window efficiency. Having outside shutters which could be operated conveniently would probably help, at least in the winter time, because they could be closed at night. It’s interesting that glass block windows are less energy efficient than good double-glazed windows; that’s not what one would expect.
Also, there are restrictions on burning firewood because of air quality considerations. Then too, firewood is not automatically delivered. Many of us want to be able to set a thermostat and have the HVAC system totally automatic.
When getting insurance, insurance companies always want to know what kind of heating system a house has and whether it has a fireplace or wood-burning heating device. My not having even a fireplace does result in lower insurance costs.
Here in NM, evaporative cooling is common, mainly in older houses. It requires far less power than a vapor compression system, but there is concern about the water usage. Also, when air pollution is high, the polluted air is blown into the house. Better evaporative systems could be designed so that far less water would be used and a heat exchanger system would permit recirculating the air to avoid drawing in polluted air, such as smoky air resulting from wildfires.
Yes, green energy of any type is suitable for nitche markets. I can envision an earth sheltered city carved out of the soft volcanic ash in Turkey but nothing like that would be possible in NY or Chicago.
I also live on top of a hill and my closest neighbor is nearly a 1/2 mile away. Heating with wood is not objectionable to anyone when those chimneys are widely dispursed. In many cases the solution to pollution is still dilution. The CO2 emitted was once absorbed by my own trees and the system in microscale is in a steady-state balance. Vail olorado on the other hand has had to severely limit the burning of wood in the chalets to prevent suffocating air pollution.
The problem of claustrophobia in an earth sheltered home canbe prevented by a modified envelope system that doubles as a porch and greenhouse. The envelope is a double glass wall with enough space inbetween to be usseful. It needs a window covering in the summer to keep out unwanted heat.