Geothermal Power Generation - The sleeping giant?

CR4 can take these problems one -a-time and try to find optimum solutions .

May be moderated/piloted by our dear Sparkstation.

The whole must be kept intact and must go forward -worldwide.

We hear Kamchatka is the place where the action is:

It seems that the circuit was an open one but there is possible to work with double closed circuit so that most of what you mention can be avoided. Of course the investment is more important at start but cost of energy is nil. A ROI should be analysed.

Correct

All the new plants in the US are closed loop - also waste is reinjected into the resevoir. In fact waste water from cities are now being used to boost the resevoir.

Result is resevoir stays powered and minimum release of any CO2 and til toxics.

I agree whole-heartedly. The problems with geothermal energy can be overcome by careful, thoughtful engineering, good maintenance programs and the use of reasonable investments. It baffles me that so many technical and non-technical people look to low efficiency heat sources (such as solar and wind power) and turn their backs on major known sources of energy.

"Measures have been taken to re-inject the used water/steam, back into heated strata below, but that lowers the plant efficiency."

I wonder if they have tried re-injecting it upstream far enough in the water table flow. Then the efficiency should increase. On the way to the re-input point, the steam will condense back to water. Possibly, run it through a long concrete tube. Just some things that you probably though of, but just in case...

Dear all,

Let me counter the reinjecitn thought of waste water into the water table. All we are discussing for the eco-friendly energy and in the way we are contaminating the water table itself which is supposed to be the purest of all water source. Let us not repeat the same (pollution) through other way.

Dear Rajdarbhangi,

You are right with the stated necessity to preserve the integrity of the ground water table.

But this aquifer is very distant from any place where thermal energy can be recovered and used water be re-injected.

If the source of geo-energy is near the surface then any water with a good (drinking) quality will leach very quickly the volcanic material that is or was transporting this heat. The minerals that get into solution will quickly make the water highly poisonous. This is very different to flow through cool ordinary rock when often good mineral-water is resulting. The bad examples (containing some cadmium and arsenic at worst) are rejected or the poisonous minerals selectively extracted.

Any water used in the primary loop of geothermal energy will be highly laden with minerals. So any use for household use or irrigation cannot be considered.

But if re-injected to the area where the thermal energy is heating up this water there will be established a stable situation of recirculation. Any water flow from adjacent areas will be blocked by the re-injection.

This is the best situation we can get from thermal energy recovery.

RHABE

Los Alamos National Lab in New Mexico USA has been researching this for going on 30 years, and have dealt with the same issues that Sparky brought up.

I still wonder about the assumptions of these sorts of things. The assumption in burning coal, oil, and natural gas was originally that the combustion by products would be harmless as they would be diluted in the atmosphere. (The solution to pollution is dilution!) Now the science suggests that combustion by products are altering the environment.

So what assumptions are being made in geothermal, or even wind? What non obvious problems might we cause with these technologies?

You answered your own question. Sleeping Giants (that wake up). If all the untapped resources were convenient to get to and exploit, the capital would be likewise convenient. Actually there's probably much more geothermal exploitation that many people realize...and more coming on line as well.

As chem engineer, I tell you that Geothermal power plants are not as ecological as you think.

Sparkstation (?) clearly describes, -the logic reazons- to not promote this power generations. Forgget ilogic scientific propposals.

Could you unveil your reasons ?

It is very interesting to know why you consider them not "ecological".

As previously described, there are downsides with large-scale GT power generation, especially open loop.

But isn't this the case with any method that tries to wring every last kilowatt out of a power generation facility? They construct a huge hydroelectric dam (clean, renewable, right?) in China, for example, and we read about the subsequent environmental damage as a result.

The problem is the mentality of bigger = better = maximum ROI.

I can sink a few wells on my property, run water through closed loops in and out of those wells and heat my home with a heat exchanger, saving power. I can run a couple of pipes 3 feet underground to a shady spot at the treeline, and draw cool air into my house, using a convection chimney on the roof, for air conditioning.

Both of these small scale, benign systems are "geothermal". They can also be scaled up to commercial building size, possibly with no ill effects.

But when you go mega-scale, or when everyone and their friggin' neighbor's dog is doing it, the odds of encountering problems rise dramatically.

Duh.

you wrote: "Why is there so limited capital employed to exploit this resource...."

The only reason I can think of is sheer stupidity.

As an active volcanic country Chile is known for it's vast GT sources. Just as one example. In northern Chile up in the Andes mountain chain there is a place called El Tatio. Back in the early 60ties a team of geologists funded by the UN has made an extensive study of that field. It was concluded that there is over 100MW of continues power to be exploited at a very minimal cost as the source is almost at ground level. A preliminary design was made by an Israeli company (Ormat Turbines), taking into account most of Sparkstation et-al arguments, and was based on the use of heat exchangers, with some specially and advanced design of the GT water re-injection system, and the best part is, It would cost nothing to the Chilean government, as the builder will charge for the energy produced by injecting it into the existing grid. This source is still pouring it's 100MW daily (for almost 50 years!) without anyone using it simply because the Chilean authorities couldn't decide who is the legal owner of this energy, a question which is still open today involving labor unions and government controlled agencies.

I can only quote Napoleon: "It is far worse than a crime, it is stupidity."

Wangito.

P:D: a quick math will show you that during the last 50 years the power station at Tocopilla, the nearest coal burning generator, by generating these 100MW also produced over one and a half million tonnes of solid ash dispersing it into the already contaminated air of northern Chile. (and the world).

If you make a quote it is better to check if it is right.

In fact not Napoleon said it, it was said ABOUT a crime ordered by him: the execution of the duke of Enghien.

OK OK my appology....

But whatever happened in El-Tatio and whoever said it, it is still worse than a crime.... it is , (you know the continuation...)

Wangito.

I've looked into commercial gt, in a known area, and the first drawback is the risk capital up front to prove the resource. For an exploratory well, you're starting at $1 million. Ormat is the best pure gt company out there, but also check out Chena Hot Springs making power out of some of Carrier compressors using 160 degree water.

I would like to add some comments to my last.

Temperature grows with about 3...4 °C/100m of depth. A 1.000 m it will be around 40°C. This under "normal" conditions. If magma comes nearer to the surface the temperature will be higher. We can the make a simple computation: we can reach temperatures around 100°C only at depth of ≈ 3000m. Only in limited areas we can reach really high temperatures good for power generation. But even the low temperatures of 60 to 80°C can be used for heating either houses or water or for refrigeration/conditioning with a huge energy economy of electrical power or fossil fuels. So that even if we cannot get "power" every where we can "save power" and this is also important.

Emphatic yes to all was said before.

Let us add some more data to the ideas outlined before. The number I recall as the whole Earth average heatflow is in the neighborhood of 130 Watts / square meter up from the magma below. That is enough to keep ground temperature in the temperate zone in 3 meters depth stable at around 14 Celsius (58 Fahrenheit). It is plenty for a building heatpump, which basically act as a concentrator of that heat. Its efficiency can be 10 times that of a heat generator. The smaller the temperature it has to bridge, the higher the efficiency calculated this particular way, tending to a teorethical infinity as the temperature difference to be bridged trend to zero. Known and widely used technology, with payback period under 15 years at 2005 energy prices. Now and in the future, shorter. Too bad, it does not lend itself readily to retrofit, rather than as designed-in.

Going back to large scale Geothermal Power Generation. Obviously, 130 W/m2 is measly, so the focus should be on places where the hot magma is quite close to the surface: hot spots, dormant supervolcanoes, midoceanic ridge. And the heatflow should be 10 times or even better. So, picking 3 kW/m2 raw heat source and 33% overall efficiency (quite optimistic, but what the heck, this is a paper exercise now) we get 1kW/m2 electric output 24/7/365. A 1000MW plant have to tap into 10^6 m2 = 1 km2 (square kilometer, about 0.4 square mile) for heat transfer into pumped liquid. That is huge area for huge power, as Gigawatt power generation stations are the largest. At 100MW, the area is 100m*1000m, much more manageable. Here now I stick my neck out into pure guesstimate land: You could space a number of them every few kilometers until running out of space or water to replenish.

Siting such a generating plant can get quite interesting, as such places are usually national parks. But, at least the magma dome under the supervolcanoes is very large, and lateral drilling widely used for oil extraction can get to it from outside the park.

The liquid coming up is a mostly concentrated witches brew of ions. Some of will inevitably precipitate, as steam generation extract heat. What remains, can be pumped back down with sweet water added for the next cycle. It will diminish precipitation in the boreholes. By the way, unlined boreholes in solid rock are the best imho, as I for one cannot recall a single metal able to withstand the corrosive effect of that witches brew.

Hello leveles

<".....can be pumped back down with sweet water added for the next cycle....">

And pray tell, where this huge quantity of drinking water quality "Sweet water" is to be obtained?

Believe me, this has become a major problem in New Zealand and elsewhere.

If all water is re-injected, then there is less ground slumping, I grant you that, but nevertheless, the ground still slumps over vast areas, due to the heat extraction, causing major topological changes above, along with extreme disturbance to people, animals, forests and so on.

The Toxic "witches brew" of dissolved and deposited chemicals corrodes everything it touches, after all, it has been dissolving all kinds of minerals and rocks for centuries.

You refer to Supervolcanoes of which the NZ major Central Volcanic area is one, only being prevented from exploding today by Lake Taupo which fills the crater, and that water cools somewhat the top rock layer under the lake.

Note that on a Winter's morning, one can see steam rising in line with the outlet fault/source of the Waikato River, and that rising steam extends for almost a mile acoss the surface of the lake itself.

Yellowstone (Plenty more links re this are available), in the US is also a Supervolcano area, long overdue for a major blowout, which will destroy much of the US and Canada when it happens, there is no way to stop these events, and of course the almost "nuclear winter" for the rest of the planet earth for a few years into the bargain.

There is at the present time, no ecologically sound way for long-term extraction of heat from geothermal area bores, for power generation.

Perhaps if we survive that long, in some future time, the extensive and expensive difficulties maybe overcome.

Kind Regards....

Dear Sparkstation,

there is no need to pump down sweet-water as this will be laden with minerals very soon.

I did see 2 geothermal plants that operate since longtime: Lardarello in Italy and on SaoMiguel, one of the Azores islands belonging to Portugal.

As both are not really modern may be a modern powerplant will have many more difficulties with higher temperature and pressure necessary today to extract more energy.

You are absolutely right about the likely devastating impact of any super-volcano eruption.

Is there any knowledge how often the volcano below lake Taupo will burst? Yellowstone seems to come to life "regularly" in intervals of 600- to 700-thousand years.

Is there any knowledge about damage done from the last big eruption of Taupo volcano? There must be some biological-fossilised information also from early human inhabitants.

I am not sure about your statement that we cannot prevent these super-eruptions.

The energy that drives the eruptions is stored in supercritical? or superheated water depending on pressure and location. As this will expand a lot at pressure relief this is driving the high yield of ash and other ejecta.

So if we start to drain?

Some 100 to 500 cubic kilometers to accumulate in 25thousand years is not too much per year: below 200,000 cubic meters per year.

I estimate that in the volumes that are stated in the reports the mass is much lower as in lapilli the density may be near 1.

So I am sure that less than 200,000 m³ superheated water is needed to blow to ash and fragments this amount of 200,000 m³ resulting material.

200,000m³ per year is around 600m³ per day, not at all enough to power a big power-plant.

So we shall puncture the storage reservoir where magma is mixed with water at a location above where there is more water than magma in the mixture and try some pressure relief.

May be simple drilling will do, may be we need a big nuclear explosion.

Nobody will do this as the fear of a catastrophic event will be overwhelming.

But if we wait until the pressure buildup starts the natural cycle every action will come too late.

So let us start to learn how to drill down to a really hot place (550°C was reached at an experimental drilling of a volcano in Japan).

Then to learn where to drill to extract not only energy but also water.

This water shall not be fed back as we want to lower the explosivity a lot.

This should be an international project, any "owner" of a super-volcano should be interested.

Shall we try a start?

RHABE