Sunday, 19 August 2012

Geothermal Energy: What is it? How does it work?



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There has been quite a lot in the media lately about GEOTHERMAL ENERGY. The US government has a programme that allocates hundreds of millions of dollars for the development of Geothermal Energy. The BBC recently has aired articles about the development of Geothermal Energy in the UK explaining that there is enough geothermal energy available in the UK to replace all coal, gas, wind and nuclear that are currently used to power all the UK's Electrical Generating Stations. Also there have been several news reports about the development of Geothermal Energy in Australia and in several other countries.

Knowing that I have been following the development of Geothermal Energy for some time, I was asked to give a talk on the subject to residents and guests on The World. Based on that talk, attached is a paper in the 'As I See It…….' series,

As usual, comments and brickbats welcome!




GEOTHERMAL ENERGY
What is it?     How does it work?


What does the word 'Geothermal' in 'Geothermal Energy' mean? Its origin is Greek: 'Geo' means 'The Earth' and 'Thermal' means 'Heat'. 'Geothermal Energy' means 'Heat from the Earth'.

OUR PLANET HAS A VERY HOT CENTRE.

Our planet has a very hot centre. The temperature at the core is 6,000ºC (11,000ºF). Compare the temperature at which rock melts: 1,000ºC (1,800ºC). Iron melts at 1,500ºC (2,700ºF).


How do we know that the centre of the Earth is very hot? In some parts of the world molten rock breaks through the crust, the planet's outer layer, and forms a Volcano where some of the magma (as molten rock is named) spills out as lava.






We are all familiar with the existence of Hot Springs found at various places round the world. A natural Hot Spring occurs when rain water percolates down from the surface and comes in contact with hot rocks below the surface and then emerges at a spring as warm or hot water. The Romans made good use of Hot Springs and constructed many Roman Baths. Probably the most famous of these is in the city of Bath in England.

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Many of the Health Spas of today are built over natural Hot Springs.

Iceland is fortunate enough to have many Hot Springs: 87% of Iceland's houses are heated by piped natural hot water.

Another manifestation of subterranean heat is a Geyser. A geyser occurs where surface water has percolated deep down to some 2,000m (6,000 ft) below the surface where, at that depth, the rocks are much hotter than the temperature at which water boils. As the pressure builds up boiling water and steam gush up to the surface as a spray that can be many feet high.

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A geyser at Yellowstone Park, USA

GEOTHERMAL ENERGY POWER PLANT

In the 20th century, demand for electricity led to the use of geothermal energy as a heat source to generate electricity.

But first, how is electricity generated? Here is a diagram of a standard Electrical Power Plant.


Water in a boiler is heated to produce high pressure steam. The Steam drives a Steam Turbine that in turn drives an Electricity Generator; the electricity generated flows out on the Grid. The fuel used to heat the water is normally coal, oil, gas or nuclear. The spent steam is condensed back to water and returned to the boiler.

In certain places in the world there are subterranean reservoirs, formed many millions of years ago, containing very hot water. If a well is sunk into such a reservoir, superheated steam will emerge. In a Geothermal Energy Power Plant that steam is piped directly to the turbine, thus eliminating the need for the boiler and its heat source. The spent steam is condensed to water an injected back down to the reservoir.

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Prince Piero Ginori Conti tested the first geothermal power generator in 1904 in Larderello, Italy. Later, in 1911, the world's first commercial Geothermal Power plant was built there. In 1958, New Zealand became the second major industrial producer of geothermally generated electricity. 1960 saw the launching of the first successful geothermal electric power plant in the United States, at The Geysers in California. Today 24 countries operate Geothermal Energy Power Plants.

A modern Geothermal Power Plant looks like this:

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                    New Zealand                       

                              
               Iceland

AS A SOURCE OF ENERGY, HOW DOES GEOTHERMAL ENERGY RATE?

Here is a list of the qualities that, ideally, a source of energy should have and how Geothermal Energy scores.
  • CONTINUOUS OUTPUT         
  • VARIABLE OUTPUT           √
  • RENEWABLE/SUSTAINABLE     √
  • NO CO2                    √
  • NO OTHER EMISSIONS        
  • NO HAZARDOUS WASTE        
  • LOW RUNNING COST          √
  • SAFETY                    √
  • SMALL LAND AREA           √
  • ENVIRONMENTALLY FRIENDLY  √
AVAILABILITY - VERY LIMITED

As a source of energy, as desirable as Geothermal Energy may be, the amount of energy currently produced by Geothermal Energy is only about a tiny 1% of the world's total energy consumption.

GLOBAL FUTURE ENERGY NEEDS 

I would now like to turn our attention to the world's future energy picture.

Energy is now vital to our civilization. We need energy for 1) electricity, 2) road transport, aircraft and ships, 3) heating and cooling

The world uses more energy every year. Over the last 50 years the increase in energy consumption has been about 2% a year. There is no reason to suppose that, assuming energy will be available at or near the same price as it is now, the annual increase will not continue at 2% a year. It must be remembered that some 25% of the world's population is living in poverty and without electricity. Also that the global population is increasing at over 1% a year. It is simple arithmetic that an increase of 2% a year means doubling the consumption in just 33 years, that is by the year 2045.


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Where will energy come from? Let us look at where energy comes from now.

  • OIL            36% )
  • COAL           27% ) 86%
  • NATURAL GAS    23% )
  • HYDROELECTRIC   6%
  • NUCLEAR         6%
  •    GEOTHERMAL)
  •    WIND      )
  •    SOLAR     )
  •    BIOMASS   ) 2%
  •               100%

What is the world's potential for not only continuing to generate energy at the present level but over the next few decades of doubling it?

Currently the fossil fuels, oil, coal and natural gas, generate 86% of the total consumption.  We know that the remaining stocks of these three sources of energy are diminishing, and that what remains is getting more difficult and more expensive to extract. Moreover their use releases CO2 and other gasses into the atmosphere that many believe is causing climate change that is going to have disastrous consequences for mankind. Clearly for the future we need to wean ourselves off fossil fuels and switch to another source of energy.

Hydroelectric (dams), now produces 6% of the total. Most of the sites where hydroelectric power is practical have already been developed. Replacing fossil fuel with hydroelectric is out of the question.

Nuclear, now accounting for 6% of the total, could, in theory, be extended to replace fossil fuel. However, nuclear has several very serious disadvantages: popular protest (Japan 2011); toxic waste disposal; high cost of construction; would need over 7,000 to replace fossil fuel; decommissioning after 25-50 years; need for imported uranium, to mention but a few.

With energy consumption increasing, fossil fuel supply reducing, and with nuclear being unacceptable
the human race is facing a major problem.


WHAT IS THE SOLUTION? IS THERE A SOLUTION?

I think there is a solution -- Engineered Geothermal System or EGS

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An Engineered Geothermal System is similar to a normal Geothermal Energy system except that the source of the steam is a subterranean hot water reservoir that has been artificially created. How can that be achieved? As explained earlier in this paper, at any point on the planet, the temperature of the rock in the crust increases with the depth from the surface. If a well (an Injection well) is bored deep into the earth to a depth where the rock is very hot, and water is pumped down that well at very high pressure, the rock surrounding the end of that well will fracture allowing water to penetrate into the fractures. That water will take up the temperature of the hot rocks through which it is percolating. If then other wells (Production wells) are bored to the same depth the very hot water will rise up those wells as steam.

This steam is used to power a standard turbine and electric generator. As with a 'natural' Geothermal Energy plant, the spent steam is condensed back to water and pumped down the Injection well, thus forming a looped circuit. The process—pump water down; water heated by hot rock; Heated water emerges at power plant as steam; steam drives the turbine and generator; condensed steam pumped down again—will generate electrical power continuously. Since the heat from the centre of the earth is inexhaustible, the electricity generation by EGS is likewise inexhaustible.

No new technology is involved. The process of drilling geothermal wells is identical to drilling for oil or gas. The process of fracturing subterranean rock is in general use in the oil/gas industry. Many existing oil and gas wells are bored down to the same depth as would be required for EGS wells. The surface plant (turbine, generator, condensers) is the same as for a existing 'natural' Geothermal plants.

In 2006 The US government commissioned the Massachusetts Institute Of Technology (MIT) to research "THE FUTURE OF GEOTHERMAL ENERGY IN THE USA". The findings of that report were:

"We estimate the extractable portion of the geothermal resource to exceed 2,000 times the annual consumption in the United States in 2005. With technological improvements the economically extractable amount of useful energy could increase by a factor of 10 or more, thus making geothermal energy sustainable for centuries".

Professor J.Tester, who headed the MIT report, said, "The numbers (the amountsof geothermal energy that could be harnessed) are staggering. Developing the technology to enable world-wide deployment of EGS could be accomplished for about the price of a new coal-fired power plant...It’s not as if we don’t know how to drill holes and fracture rocks."

THE FACT IS that heat from centre of the earth exists everywhere, in every country.
The Geothermal Energy available is unlimited and inexhaustible.

So, how deep would EGS wells have to be? The temperature of the rock surrounding the artificial reservoir needed to work an EGS system is around 200ºC (400ºF). It is not a question of 'if' rock at 200ºC exists—it does; rock at the critical 200ºC temperature exists below everyplace on Earth. It is only a question of 'how deep' However. The depth at which that temperature is found varies from one part of the world to another but on average that depth is 3-5 miles or 5-8 Km.

Information of the world's subterranean rock temperatures already exists. Here are the charts for the US and for Europe.

SUBTERRANEAN ROCK TEMPERATURES
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WHAT WOULD AN EGS POWER PLANT LOOK LIKE?

What would an EGS Power plant look like? According to Geodynamics Ltd of Australia, an EGS Power Plant would consist of four injection wells surrounded by five Production wells. The output would be 50 MWs. EGS plants would be low and unobtrusive, occupying a relatively small surface areas. They would look something like this.



EGS plants could be sited one kilometre apart, near where their output is required e.g. around cities and industrial areas. However, as has been explained, forming the underground reservoir entails fracturing subterranean rock. This fracturing process can in some cases cause a minor earthquake. For this reason, EGS plants must not be sited within or very close to built-up areas.

Is generation of electrical power by EGS practical—or is it merely a theory? Does an EGS plant exist, and if so does it work? Yes, there is a working EGS plant at Soultz in France. It was constructed as a demonstration plant by the European Union and has been generating electricity continuously for several years. Here is a photo of the Soultz plant

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The Engineered Geothermal System of generating electricity is eminently practical.

WHAT IS THE POTENTIAL OF EGS?

What is the potential of EGS? What if EGS were to be deployed on a world-wide scale? What if EGS were to replace the use of coal, oil and gas? If by the use of EGS we could generate unlimited cheap electricity, we could solve most of the World’s existing problems! We would:

  • END CO2 AND OTHER EMISSIONS
  • END WORLD CONFLICT OVER ACCESS TO OIL AND GAS
  • END WORLD CONFLICT OVER ACCESS TO WATER
  • END WORLD FOOD SHORTAGES
  • END WORLD POVERTY
  • IF THE SEA LEVEL RISES; FACILITATE RELOCATING EFFECTED POPULATIONS

IS EGS PRACTICAL?

To replace oil, gas, coal and nuclear with EGS would be a vast engineering task. Is the concept practical?

Let us consider what engineering feats the world has achieved.

§  In World War 2, Germany, Japan, Russia, the US and the UK built many hundreds of thousands of warplanes, ships, tanks, artillery pieces and trucks. All in the short space of just six years.

§  In the last 50 years 153,000 miles (1,225,000 Kms) of motorway (freeways) have been built—enough to go round the world six times.

§  There are some 800 million cars on the road, most of which have been manufacturews in the last ten years.

§  There are some 3,000 million more people on the Earth today than there were 50 years ago. Housing, work-places and infrastructure have been built to cater for this vast population increase.

§  World-wide there are no less than 880,000 oil and gas wells in daily operation. In addition there are 1 million wells that have been worked out and are abandoned. The great majority of these wells were drilled in the last 50 years.!


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         Mothballed WW2 US warplanes          153,000 miles of motorways         800 million cars on the road

                    
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                      Brasilia built since 1960                                


                         6,000 in the Gulf of Mexico
                              
       World population 3 billion increase in 60 years                         


              1,800,000 wells since 1950

The conversion from coal, oil, gas and nuclear to EGS would be phased over four or five decades. On that time-scale, in my opinion, the change-over is well within the engineering capability of governments and industry.

ROAD VEHICLES, PLANES AND SHIPS

In the change-over from fossil fuels and nuclear to EGS the first priority would be the generation of electricity. As the availability of liquid fuel becomes less and the price per gallon becomes higher, road vehicles will turn to electric propulsion. Either with on-board batteries, or with hydrogen-powered fuel cells or with hydrogen-fuelled internal combustion engines. The hydrogen they will use is manufactured by EGS-generated electricity.

Fuelling airplanes with other than oil-based fuel is still a long way off. Research is currently being conducted with hydrogen-fuelled aero engines. Again, the hydrogen they will use is manufactured by EGS-generated electricity.

Like airplanes, fuelling ships with other than oil-based fuel is a long way off. Probably hydrogen-powered fuel cells and electric motor propulsion is the best solution.

WHAT ARE THE OBSTACLES TO EGS?

The cost of drilling the many thousands of wells that would be necessary is the main obstacle. However, if the establishment of EGS plants was undertaken on a massive scale, the rigs and the drilling process would lend themselves to automation and standardisation, and the costs of drilling would come down dramatically.

The greatest driver will be economic; the cost of fossil fuels and nuclear versus the cost of EGS. As fossil fuels become more difficult to extract and the price increases, market forces may well effect the change.

Traditionally governments have sponsored major power projects such as Hydroelectric dams, the first Nuclear Power plants, Wind Turbines: large Solar installations, etc. Governments would need to encourage the change from fossil fuels and nuclear to EGS by means of legislation, guarantees, grants and penalties.

I believe that the solution to mankind's future energy supply problem is the generation of electrical power by the Engineered Geothermal System.

I believe EGS is the ONLY practical solution.

.......................................................................

Addendum

A recent MIT report "The Future of Geothermal Energy" says the heat that lies in the rock six miles beneath Oregon’s Newberry Volcano alone could provide 2,500 times as much energy as the United States currently uses. 


http://www.energyboom.com/geothermal/mit-study-says-investments-geothermal-will-reap-major-energy-rewards


http://pdfuri.com/altarock-energy-davenport-newberry-newberry-egs-demonstration-


The report says, "Market changes and an investment of $800 million to $1 billion over 15 years could bring more than 100 GW of geothermal energy to the US grid by 2050, according to a study recently released by a multi-disciplinary research group at MIT. That investment is less than the cost of a single “new generation” coal-powered plant, and the amount of energy is equivalent to 200 coal-fired power plants or 100 new nuclear power plants."

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