Episode 69      33 min 41 sec
Geothermal Energy from Uranium Deposits

Geothermal energy is most frequently associated with volcanic activity. However, new research suggests the possibility of producing commercially viable geothermal energy from uranium deposits. Prof Mike Sandiford and Dr Sandra McLaren discuss the science behind this endeavor to produce clean energy. With host Dr Shane Huntington.

"We have a large amount of resource in a very, very enriched source. We’re ideally placed to be the world leaders really in exploitation of this technology." - Dr Sandra McLaren




           



Prof Mike Sandiford
Prof Mike Sandiford

Professor Mike Sandiford is Professorial Fellow at the School of Earth Sciences, and Director of the Melbourne Energy Institute.

Mike's research has focused on the geodynamic evolution of the continents with his main contributions in the fields of thermal evolution of metamorphic terranes, mechanics of orogenic systems, nature of stress fields and deformation in continental interiors.

His research on the long-term evolution of the continents has provided new insights into the way in which tectonic processes modify the geochemical structure of the lithosphere and, in particular, the distribution of heat producing elements, leading to the notion of “tectonic feedback”.

Dr Sandra McLaren
Dr Sandra McLaren

Dr Sandra McLaren is a geologist with research interests in a wide range of earth science fields. She is currently a Lecturer in the School of Earth Sciences at the University of Melbourne. Sandra's main research interest is in understanding the long term evolution of the Australian continent. Her main teaching responsibilities are in the field of Structural Geology and Tectonics.

Sandra is a member of the Geological Society of Australia, and the Women in Science and Enquiry Network (WISENet).

Credits

Host: Dr Shane Huntington
Producers: Kelvin Param, Miles Brown and Dr Shane Huntington
Series Creators: Eric van Bemmel and Kelvin Param
Audio Engineer: Miles Brown
Theme Music performed by Sergio Ercole. Mr Ercole is represented by the Musicians' Agency, Faculty of Music

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Geothermal Energy from Uranium Deposits

VOICEOVER
Welcome to Melbourne University Up Close, a fortnightly podcast of research, personalities and cultural offerings of the University of Melbourne, Australia.  Up Close is available on the web at upclose.unimelb.edu.au.  That’s upclose.unimelb.edu.au.

SHANE HUNTINGTON
Hello, and welcome to Up Close, coming to you from Melbourne University, Australia.  I’m Dr Shane Huntington.  Just a few decades ago, the idea that our desire for our energy would catastrophically change our environment received little attention.  Today realities of climatic change are starting to present themselves, and we are urgently in need of new energy solutions.  It is imperative that we break our addiction to coal and oil.  To achieve this we need to utilise a combination of technologies to meet our future energy needs.  We have already started harnessing the energy of the sun, although the contribution overall is small.  In a similar way, wind power is gaining popularity, but like solar it cannot provide base load power 24 hours a day.  It is easy to forget the vast energy reserves that actually exist beneath our feet.  The heat that has been stored inside our earth waiting to be accessed could supply the world’s energy needs for an estimated 30,000 years.
Today on Up Close we are joined by two of our local leaders in geothermal energy.  Professor Mike Sandiford, Director of the Melbourne Energy Institute, and from the School of Earth Sciences, University of Melbourne, Australia, and Dr Sandra McLaren, also from the School of Earth Sciences, University of Melbourne, Australia.  Welcome to Up Close, Mike and Sandra.

MIKE SANDIFORD
Pleasure to be here.

SANDRA McLAREN
Thank you, Shane.   It’s a pleasure to talk to you.

SHANE HUNTINGTON
Okay.  Mike, let’s actually go through the earth and talk about the various positions, because I think it’s good to put things in context about where some of this energy is coming from.  If we start at its centre and move out, what do we expect to see?

MIKE SANDIFORD
The very centre of the earth is solid nickel iron alloy, the inner core, surrounded by a liquid metallic region, still an iron nickel alloy, and it’s that region which gives us our magnetic field.  Beyond that we have a dense silicate mantle made of the minerals such as pyroxene and olivine which, although solid, on geological time scales are flowing and convecting, and they carry the tectonic plates of the outer hundred kilometres, the so-called lithosphere which is made of the rigid cold material which is capable of breaking and generating earthquakes.  The very outer part of that, the outer 30 or so kilometres, is the earth’s crust and that is, of course, the material of which the continents are made.

SHANE HUNTINGTON
Sandra, if we go through the same process but instead of talking about material we talk about temperature, what sort of temperatures do we see as we move from the core out towards the crust of our planet?

SANDRA McLAREN
Well, Shane, we see a very strong gradient in temperature from the centre of the earth right to the earth’s surface, but it varies quite considerably within each of those layers that Mike mentioned.  The temperature right in the very centre of the earth is about 6000 degrees.  As we get to the core mantle boundary, it’s about 3000 degrees, and as we get to the base of the lithosphere it’s about 1500 degrees.  In parts of the crust, Mike was mentioning the very outer 30 or 40 kilometres of the earth, we tend to expect temperatures of about 500 degrees or less.  Obviously less and less, the temperature gets cooler as we get out towards the earth’s surface.

SHANE HUNTINGTON
I suppose everyone listening would be aware that on occasions we see scenarios where some of that deep material is actually breaching the surface:  volcanoes, along some of the oceanic ridges and so forth.  Why does this occur?

SANDRA McLAREN
Well, this is one of the manifestations of the actual movement of the earth’s tectonic plates which is in itself a response to the need for the earth to actually lose its heat.  So many parts of the earth in the middle of the mid ocean ridges through the Atlantic, for example, we actually have plates moving apart and the mantle material that Mike mentioned, the silicate material, comes up to the surface so quickly that it actually melts.  So that material is brought out at the surface at extremely hot temperatures of about 1500 or so degrees on average, or a bit less by the time it comes out on the surface.

SHANE HUNTINGTON
My understanding, reading some of your work, is that this isn’t the only reason we get higher temperatures as we look down.  There is also a nuclear element.

SANDRA McLAREN
Yes, that’s right, Shane.  There are two components that determine the way in which temperature varies within the outer part of the earth.  It’s that heat that’s supplied from the mantle which convects, but there’s also the heat that’s being produced within the outer layer of the earth itself, and that’s being produced by the decay of naturally occurring radioactive isotopes, most particularly uranium, thorium and potassium.

SHANE HUNTINGTON
These were isotopes that presumably were created in exploding stars from long long before our planet was formed.

SANDRA McLAREN
Yes, that’s right, and they’ve made their way by processes that we’re beginning to understand as geologists to be much more concentrated in the outer part of the earth than in some other layers inside the earth.  So they’re sitting there and they’re producing heat by natural radioactive decay on geological timescales.

SHANE HUNTINGTON
What sort of temperatures are we talking about producing?

SANDRA McLAREN
Well, it depends on the concentrations of these elements that you have in your particular part of the crust.  We tend to find more of these elements in certain rock types than we do in others.  So, for example, there is significantly more in the rocks that make up the continents than there are within the rocks that make up the oceans themselves.

SHANE HUNTINGTON
Now, in terms of the location of these being close to the surface of the earth, why is it that this material is making it to where we can get at it?  Why isn’t it evenly distributed throughout the planet?

SANDRA McLAREN
Uranium, thorium and potassium, which are those three elements that produce most of the heat on the timescales that we’re interest in, they’re what we call incompatible elements geologically.  So they don’t like to be deep within the earth.  They like to be in melts, and those melts are produced and move up closer to the earth’s surface.  So most commonly most people are familiar with the rock type granite, which is one of the biggest container, if you like, of uranium, thorium and potassium.  The way the earth is formed, the way the crust is formed, those granites are produced and the melt migrates upwards into the crust.  So that’s why we tend to find them in the top 10 or 15 kilometres of the crust, generally speaking.

SHANE HUNTINGTON
I know Australia has an abundance of this material, but just how much of this sort of material do we have on earth?

SANDRA McLAREN
That’s something that we’re not 100 per cent certain of yet, as geologists, exactly what the volumetric total amount would be.  It’s certainly very true that Australia has an extraordinary amount compared to other parts of the continental crust, for reasons that we’re still not entirely sure about.

SHANE HUNTINGTON
Mike, how do we go about finding this material?  It’s obviously valued, by the sounds of things, not just from the point of use in nuclear reactors and the like, but also in just its potential as a heat source under the ground.  How do we isolate this material?

MIKE SANDIFORD
We have a number of approaches to trying to isolate these hot rocks that Sandra has mentioned, the granites which have an abundance of potassium, uranium and thorium, the heat producing elements.  One way is to drill shallow holes into the earth’s crust, one or two kilometres deep, or even a few hundred metres, and measure the rate at which heat is flowing out.  The heat flowing out is a combination of  the amount of heat supplied from deep within the earth that results from the very early formation of earth;  it’s still trying to get out;  plus the heat produced by an enrichment of uranium, potassium and thorium.  
We have quite a good idea of how much heat to expect from the long term heat loss of the earth, so anything additional we attribute to the natural abundance of uranium, potassium and thorium.  So in the continents we measure the amount of heat flowing out typically to be around 65 milliwatt per square metre.  That’s about one thousandth of the amount of heat we get from the sun on the surface of the earth, so it’s a very small heat flow.  In parts of South Australia particularly, we can find areas which have almost twice that amount of heat flowing out, which we ascribe to having extra abundance of uranium potassium and thorium, and in fact as part of Sandra’s PhD she set out to find out just how much uranium potassium and thorium there were in the rocks that made up South Australia, Northern Territory, parts of Queensland, and showed that they have three or four times, in many cases, more than we would anticipate, even for granitic rocks.  So again, that’s a reason Australia seems unusually hot.  In fact Sandra, in one of her papers, called Australia the hot southern continent.

SHANE HUNTINGTON
You’re listening to Melbourne University Up Close.  I’m Dr Shane Huntington, and we’re speaking with Mike Sandiford and Sandra McLaren about geothermal ene rgy.
We’ve established that there is clearly a huge resource of energy beneath our feet.  I think that’s a given, both from the original motion and formation of the planet, and also from this leftover nuclear material from exploded stars in the long distant past.  The promise of geothermal power plants is to actually harness this energy in some way.  Mike, in other sorts of power plants, like nuclear and coal, how do you go about producing electricity from those materials?

MIKE SANDIFORD
The prime way of generating stationary energy is to generate heat and transfer it to a medium which is capable of great expansion.  So we boil water, essentially, at extremely high temperatures and generate power by converting that boiling water to a gas phase, condensing it again – sorry, we generate large temperatures, either in a nuclear reactor or in a coal combustion furnace, transferring it to water, turning it to steam, driving turbines, recovering that water.

SHANE HUNTINGTON
I’m assuming, in geothermal, the goal is the same again – to heat the water.  What sort of temperatures are desirable in this case to actually get a turbine to run?

MIKE SANDIFORD
The way in which we can generate electrical power from geothermal sources really depends on the temperatures at which we try and extract the heat from the earth.  Conventional geothermal, which doesn’t apply to Australia, it’s really restricted to those tectonically active plate boundaries with active volcanoes, steam is naturally venting from the earth through natural processes, and what we do is trap that steam when it’s still in a liquid phase deep in the earth, and bring it to the surface and allow it to expand to a gas, driving turbines that way, and that can come out at well over 200 degrees, even approaching 300 degrees, and the expansion of the gas there is sufficient to generate quite large capacity efficient power stations.
In the sort of geothermal that we’re looking at in Australia, what we’re trying to do is emulate those natural geothermal systems by enhancing the deep heat reservoirs three or four kilometres underneath the surface of the earth by injecting fluids in them.  To try and understand the sorts of temperatures we’re after, we need to understand the typical temperature gradient in the continent is about 25 degrees per kilometre.  So if we go down four kilometres, we’re looking at temperatures a bit over 100 degrees typically.  That’s not hot enough to generate very much electrical power by the time we bring those fluids back to the surface.
Really what we’re after is trying to find areas such as there are in the Cooper basin in northern South Australia, where temperature gradients are around 50 degrees per kilometre.  So at four kilometres depth, we find temperatures of around about 200 degrees.  We inject fluids into those, transfer the heat to the fluids, and bring those fluids back to the surface, they come back at 200 degrees as steam, capable of driving turbines.  Of course, we can use other methods at slightly lower temperatures, down to around about 150 degrees.  We can bring the fluids back and transfer their heat to other compounds, other fluids, in o-cycle electrical power binary plants.  Generate rather lower efficiency, but still meaningful quantities of electrical power.

SHANE HUNTINGTON
So, Mike, let me get this straight.  In Australia, where we don’t have parts of the crust kind of bursting open at the seams, producing vast quantities of energy, we essentially are drilling a hole and then pumping water down to heat that water.  Where does it go?  What happens at the bottom of the hole?  What are we actually doing, and what’s the mechanism to get the water back up in a heated form?

MIKE SANDIFORD
Okay.  That’s a very good question.  If we just had the hole and poured water down, nothing very much would happen, because down at four kilometres depth under tremendous pressure the natural permeability, the way in which holes exist within the rocks, is very low.  Fluids wouldn’t naturally flow through those rocks unless we could open cracks in those rocks and force the fluid through it.  The way we do that is by pressurising the fluid as we pump it down, pressurising it enough to open up cracks.  So in some ways we’re providing the energy to break the earth open, generating tiny little earthquakes as we do that, to pass the fluid through it.  So we have to be able, in an enchanced geothermal system to recover more energy than it takes to pump the fluids through in the first place, and that’s one of the challenges.

SHANE HUNTINGTON
What prevents the water from all being lost?  I understand you have an entry point and you have an exit point where the water comes back up.  But what’s to prevent the water from just leaking out in those layers, or is it a completely closed system?

MIKE SANDIFORD
Well, that’s again a very good point.  The essential physics is that fluids will flow down pressure gradients.  So what we do is have at least two wells, an injection well under high pressure and a recovery well under low pressure, so that the fluids naturally find their way from the injection well to the recovery well.  There are, of course, challenges.  We have to open the fractures between those two, and we don’t want to open just one fracture.  We want to open a network of fracture which allows the fluid to pass out through a volume of rock, extract its heat, mine its heat, if you like, from that volume, and come back to the injection well.
There’s only been a few places in the world where this has been demonstrated to happen.  The results are encouraging and we’ll hear a little bit more about that later from Roy Baria, but there is the potential – and it is a risk for Australian geothermal – that we will lose significant fluid to the surrounding rock, that it will open fractures and disappear into the rock mass.  Of course, that’s a risk for Australia, especially in Central Australia where the water resource is scarce and we have to conserve it.

SHANE HUNTINGTON
Sandra, let me ask you for a moment about the aspect of actually making these holes.  I mean, drilling these holes presumably is a very difficult task.  We’re not talking about 100 metre hole here.  We’re talking about three to five kilometres in a controlled way.  How do we go about drilling holes that size?

SANDRA McLAREN
Well, holes that deep certainly are an unusual thing for humans to try and do to the earth, but what has happened over the dependence we’ve had on petroleum is that we’ve actually become very good at drilling quite deep holes.  There are certain problems associated with doing that, most certainly, but the technology is there to do that, and many of the places in Australia where we’re interested in trying to develop geothermal energy are places which have already been exploited in the past, and continue to be exploited, for petroleum resources, like Cooper basin in the central parts of Australia where drilling of three to four kilometre wells, although it’s expensive and although there are risks involved, it’s not as unusual and it’s not as difficult as might first seem.

SHANE HUNTINGTON
Now, Mike, you mentioned there was an issue around potential water loss, but I guess the bigger question for many people with regards to this energy is what the impact is in terms of greenhouse gases.

MIKE SANDIFORD
One of the drivers, of course, and you mentioned it earlier, Shane, is that geothermal has the potential of providing base load power.  Because we use a fluid as a medium to derive the energy, water, or even potentially CO2, if we have access to CO2, but we conserve that fluid through a cycle of extracting, mining the heat, producing energy in the surface engineering plant, and re-injecting it, there should be very little waste production in the whole system.  So it’s one of the few base load power options we have which has minimal waste generation.

SHANE HUNTINGTON
Sandra, the first example of the use of geothermal as a power source was in 1908, I understand, in Italy.  Why are we sitting 100 years down the track and this technology is still relatively under-utilised?

SANDRA McLAREN
Well, certainly conventional geothermal energy is not under-utilised.  It’s very well utilised in places like New Zealand and Iceland, and having been to Iceland and enjoyed their spectacular geothermal baths, it certainly does very well there, and being able to have bananas all year round growing in greenhouses.  It’s fantastic.  But certainly this enhanced geothermal system has proven very difficult to exploit over the last 100 years, as you say.
I think many of the problems have in the past related to identifying good sources, the rocks that are most enriched in the uranium, thorium and potassium;  the hottest parts of the earth, and currently in times when we have good geophysical methods and good drilling, more of a problem is this issue of understanding the engineering in moving the water around in the best way to actually make the system most efficient.  Those are things that people are still working on.  Exploration for targets:  there are a lot of targets identified in Australia at the moment, but it’s the engineering issue of actually extracting the heat and moving the water around that seems to be where we’re at at the moment.

SHANE HUNTINGTON
Mike, in some of these cases of geothermal plants, and it sounds like, partly in Australia, but more so in the ones that are using the non-enhanced version of things, what are the potential negative effects of trying to extract this type of energy from the earth?

MIKE SANDIFORD
In the natural geothermal systems, the way in which fluid moves occurs under natural pressures and exploding the geothermal reservoir by sucking the natural fluids out of the earth’s crust actually changes the pressure distributions.  So those systems can collapse and that may have feedback on how the geology of those systems works.  It may change the way in which earthquakes are generated or the way in which volcanoes even work in those areas.  Our understanding of that is not well advanced.  
We come to the engineered or enhanced geothermal systems that we would hope to apply in Australia and use for generating power into the future.  One of the things that has to be understood is that in making the fracture networks deep inside the earth, four kilometres down, we’re in effect making mini earthquakes.  Each time a fracture opens it generates an earthquake.  Precisely the way in which we make the engineering of these systems work is creating a risk in itself, because those earthquakes, those induced earthquakes, can get quite large.
One of the largest earthquakes in Victoria occurred when we filled Thomson Dam.  We generated an earthquake in the mid 80s, a magnitude 5 earthquake, just by filling that dam.  Every time we start to play around with the distribution of pressure and stress inside the earth, we generate earthquakes.  There was a recent attempt at generating enhanced geothermal systems under the town of Basel in Switzerland which generated a close to magnitude 4 earthquake which was enough to cause the people of Basel to say, we don’t want this.  There was history there, of course, because in the middle ages Basel had an unusually large earthquake for its geological setting and so the city is a bit nervous about earthquakes.

SHANE HUNTINGTON
You’re listening to Melbourne University Up Close.  I’m Dr Shane Huntington and today we’re speaking with Professor Mike Sandiford and Dr Sandra McLaren about geothermal energy.
We are now joined by Roy Baria, a specialist in enhanced geothermal energy, and formerly with HDR Soultz, part of the European Deep Geothermal Energy program.

ROY BARIA
Hello.

SHANE HUNTINGTON
Now, Roy, this project has been ongoing since 1987.  It’s an enhanced geothermal system.  Can you give us an overview of the various phases that have been completed to date?

ROY BARIA
Why, certainly.  The reason the project started because there were too many small European projects.  There was a UK one, there was in Germany, and others.  So a gentleman called John Garnish persuaded all the governments to give up their projects and concentrate on one single project, and this is why it became successful, because sufficient funds were directed towards to it to solve some of the problems needed.  So it started in ’87 but the first bore hole was built to two kilometres.   Again, because that particular area has an oil industry background, they had lots of shallow bore holes up to say 8[00], 900 [metres].  This showed the temperature gradient of about 100 degrees per kilometre, and this was misunderstood, so when they drilled up to two kilometres they were expecting 180 degrees, and it turned out to be at about 140 [degrees].
So my work was done initially on the first well but the negotiation between countries decided that need to go at least to 175 degrees.  So when further money was available from Brussels, and we drilled up to 3.6 kilometres deep, but even then we only found 160 [degrees].  A number of simulations were done at that depth:  one at the bottom, one in the middle and one at the top, and then we targeted a second bore hole called GPK2, again about 3.6 [kilometres]. And in 1997 we were able to circulate between the two bore holes, and these bore holes were about 450 metres apart.  That was the largest separation ever achieved.  We were able to get break through time using tracers at about 2.2 days, and we were able to circulate for nearly four months.  The experiment also demonstrated that you can have relatively lower impedance, so that you do not use parasitic power.  Various other techniques were tried and that showed that if you look at the economic table that the technology is possible.
From that we were going to continue that for a number of years because we were only circulating 25 litres per second, but then industry came in like Shell, NL and others, and they said 145 degrees was not really their target, that we should go for 200 degrees.  So we had to deepen the existing bore hole to five kilometres deep, and we found about 202 degrees, and then we stimulated that one by injecting fluid under high pressure, and we drilled a second bore hole called GPK3 into it.  Again we stimulated and circulated, but this time instead of being 450 metres apart, we went to 650 metres.  Again, it was a significantly bigger separation than anybody had achieved before.
Again we had impedance, manageable impedance, of .29 megapascal per litres per second, and again we were able to circulate something like 25 litres per second.

SHANE HUNTINGTON
Roy, can I ask you how long did it take to go from two kilometres to five kilometres?

ROY BARIA
Two kilometres to five kilometres, the drilling doesn’t take very long.  It’s about 60 days or 50 days.  The problem was because it was EC funded, the funding was every three years.  So if you used up your funds, you had to wait until the next lot of money became available.  That is the reason why Soultz appears to have taken so long.  It’s not the technical.  It’s the financial.

SHANE HUNTINGTON
When you talk about originally there 25 litres per second that you were pumping down, how much of that do you manage to get back?

ROY BARIA
Almost all of it.  Virtually all of it.

SHANE HUNTINGTON
Roy, my understanding now is that you’ve actually connected the system up to the grid and you’re producing about 1.5 megawatts of power.  Is that correct?

ROY BARIA
Yes.  That is unfortunate because the original plan was 5 megawatts.  This is difficult to put across but some of the industrial partners lost their interest and Brussell is not going to support, I understand that they are not going to support any more.  So the third well was put in called GPK4, and it was not connected to the existing system properly, so now all we’re doing is circulating – well, I’m not there at present – but all they’re doing is they’re circulating the two deep wells, two and three, but the four is not really playing a part.  But in principle, we should have been producing 5 megawatt electric.

SHANE HUNTINGTON
What’s the next step?  I mean, it’s clearly impressive that you guys have managed to demonstrate a closed system here.  You’ve managed to show that the water loss is minimal and you are actually producing 1.5 megawatts.  It’s not significant.  It’s still something that’s quite impressive given the difficulties involved in the technology.  It sounds very exciting.  Thank you very much for your comments today on Up Close.   I wish you luck with your future work in geothermal energy, and hopefully we’ll make this a viable technology sooner rather than later.

ROY BARIA
All right.  Thank you.  Bye bye.

SHANE HUNTINGTON
Now, I know that Australia has some of the largest accessible deposits of nuclear material.  Sandra, tell me, does this put us in a very unique position for a geothermal energy industry to be established?

SANDRA McLAREN
It certainly does, Shane.  Many of the rocks which are most enriched in those heat producing elements, uranium thorium and potassium, are found in the central parts of Australia.  So all the way through the Northern Territory down into South Australia.  They’re in rocks that are about one and a half billion years old.  So this material has been sitting in the crust since that time.  Compared to other rocks of the same age around the world, even if you average the concentrations of uranium thorium and potassium over the entire central part of Australia, which is over half a million square kilometres, you get an average that’s more than twice as much as there is anywhere else in the world.  Over such a large area, it’s an extremely significant potential resource.
There are certainly some other rocks around the world which are enriched to the levels that we see here in Australia but they’re very - much smaller volume features in the crust.  So we have a large amount of resource in a very, very enriched source, more than twice what we would normally get.  So, yes, in terms of our actual heat source, we’re ideally placed to be the world leaders really in exploitation of this technology.

SHANE HUNTINGTON
Mike, my understanding is that the very coal deposits we have which are in many regards causing the problems with the climate that we are seeing by burning of coal may actually be potentially very advantageous for geothermal energy production.

MIKE SANDIFORD
Yes, absolutely right, and there’s a certain irony in this.  Most of the emphasis, or press, on geothermal energy is focussed on the heat production side, and that comes from unusual enrichments in uranium, and just as uranium taken out of the crust can fuel nuclear reactors, what the geothermal industry says is if it sits in the crust it can produce a natural geothermal source.  But we also need that natural radioactivity of elements like uranium to be trapped inside the heat, and it’s best where it’s trapped under tremendously insulating sedimentary rocks.  
That’s precisely what happens in the Cooper basin, in north and south Australia.  We have these very enriched rocks sitting under relatively insulating sedimentary rocks, sedimentary rocks which are rich in carbon.  They have coals, they have oil and gas fields, and as a consequence of that carbon they are quite insulating.  Of all the rocks we know, coal is by far the most insulating.  It turns out to be about 10 times more insulating than the very hot rocks which produce the heat in South Australia.
So if we have thick sequences of coal, we actually don’t need very much extra heat production.  Thick sequence of coal can trap sufficient heat beneath them without extraordinary amounts of heat being produced beneath them.  The problem is we rarely get thick sequences of coal.  Coal usually occurs in thin layers a few metres thick, and that’s not thick enough to trap much heat.  We need about 200 metres of coal to trap the same quantity of heat as is produced by a hot rock in South Australia.  One of the few places in the world we get that is in the Latrobe Valley in Victoria where the coal sequences get up to 400 metres thick.  It’s probably the most thermally resistive bit of geology on the planet and therefore one of the most exciting geothermal prospects.

SHANE HUNTINGTON
Of course, that comes with the caveat that we need to not dig it up and use it all, I suppose.

MIKE SANDIFORD
That’s certainly partly true, Shane.  The coal sequences where they’re shallow are mined, but when they’re deep, 500 metres buried inside the earth, they’re not particularly accessible and they will still perform their heat trapping capability, and in fact our own work, work done by my students as part of their Honours research last year, showed that the deeply buried ones more efficiently trap heat than the shallow ones.  So these coals by their very existence in the earth provide the natural heating, you’re right, and if we mined them all away we would lose it.  Of course, it takes a long time to lose the heat from four kilometres inside the earth, and it would take probably several million years, in fact, to get rid of that heat.  So it’s not a particular issue at this stage.

SHANE HUNTINGTON
It’s more of an indicator of where to go looking.

MIKE SANDIFORD
Absolutely, and we’re learning how to target that, and as we are presented with the geothermal challenge, one of our big issues is targeting the best resources because this is, at this stage, essentially an unproven technology, and identifying temperature differences of a few, 10 degrees, at four or five kilometres in the crust could be the difference between making the technology a feasible, viable source of base load power, or an economically unviable source of base load power.  In Victoria we have a particular challenge of seeing beneath the coals, and that’s one of the issues which has hampered our own exploration here, so far.  Coals have a tremendous ability to absorb the energy produced by earthquakes, or seismic energy we call it, and we use seismic energy to probe deep inside the earth.  It’s the way oil explorers use to find oil and gas.
Because the coals absorb that energy, we can’t actually see beneath them, and we won’t know what’s down there until we drill.  The problem is it costs $10 million to drill to five kilometres depth, and no one has at this stage been prepared to risk drilling blind beneath the coals.

SHANE HUNTINGTON
So, Mike, in terms of the Cooper basin, when we bore down into this area, where do we get the water that we need to pump in to that particular environment to create the exchange of heat?

MIKE SANDIFORD
The Cooper basin is out in the deserts in north eastern South Australia and there is very little surface water, except of course when it floods in Queensland and the rivers flow into Lake Eyre as they’re doing at the moment.  However, underneath the surface there are vast aquifers of the artesian basin.  The great artesian basin gets its water from rain in the eastern highlands of Australia stretching up to Queensland, that flow through aquifers that eventually discharge in the salt pans around Lake Eyre itself.  These carry significant volumes of water, and that water can be accessed from aquifers only a few hundred metres to almost a kilometre depth beneath the surface.  In fact, the drilling for the geothermal targets drills through these aquifers itself.  

SHANE HUNTINGTON
Mike, in addition to your role in the School of Earth Sciences, you are also the director of the Melbourne Energy Institute here at the University of Melbourne.  I understand there is a new project, soon to be initiated in 2009, regarding the next steps for this particular industry in Victoria in particular, and I guess in a broader sense for Australia.  What’s happening there?

MIKE SANDIFORD
The new research institutes that are being formed at Melbourne University including the Energy Institute are mandated with tackling broad multidisciplinary research projects that tackle some of the big issues of our time.  Geothermal energy is an example of that.  Making geothermal energy work in Australia is going to require new ways of understanding the science:  how to predict temperatures at depth.  New engineering:  how to engineer the reservoirs at depth.  Economics:  how to understand the risk and finance the operations so that they become feasible into the future.  
It’s a great opportunity to join the strengths of the university that exist within faculties, within departments, to meet challenges of creating a more sustainable, more secure but potentially base load provider of power into the future.

SHANE HUNTINGTON
Mike and Sandra, it’s certainly an extraordinarily interesting area, and one that I’m sure everyone listening hopes that you have some success in.  Congratulations on your work so far, and we look forward to good news in the future on geothermal energy.  Thanks for being our guests on Up Close today.

MIKE SANDIFORD
Thank you, Shane.

SANDRA McLAREN
Thank you, Shane.

SHANE HUNTINGTON
Relevant links, a full transcript and more info on this episode can be found on our website at upclose.unimelb.edu.au.  We also invite you to leave your comments or feedback on this or any episode of Up Close.  Simply click on the ‘Add New Comment’ link at the bottom of the episode page.  Melbourne University Up Close is brought to you by the Marketing and Communications Division in association with Asia Institute of the University of Melbourne, Australia.  Our producers for this episode were Kelvin Param and Miles Brown.  Audio engineering by Miles Brown.  Theme music performed by Sergio Ercole.  Melbourne University Up Close is created by Eric van Bemmel and Kelvin Param.  I’m Dr Shane Huntington.  Until next time, goodbye.

VOICEOVER
You’ve been listening to Melbourne University Up Close, a fortnightly podcast of research, personalities and cultural offerings of the University of Melbourne, Australia.  Up Close is available on the web at upclose.unimelb.edu.au.  That’s upclose.unimelb.edu.au.  Copyright 2009, University of Melbourne.


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