Iceland drills deep to release geothermal future

Posted: 8 April 2008

Author: Don Hinrichsen

Iceland is in the forefront of global research and development of geothermal energy. Now the country has launched an ambitious programme to tap deeper geothermal fields, up to 5 kilometres below the surface. If all goes well this could open the way to a geothermal future that could provide renewable energy to the whole of Europe, says Don Hinrichsen in this second special report from Iceland.

Hellisheidi geothermal power plant
Hellisheidi geothermal power plant
Hellisheidi geothermal power plant. The pipes on the left channel the hot water from the boreholes into the plant. Photo © Don Hinrichsen
The Hellisheidi region just east of Iceland’s capital city, Reykjavik, looks like something straight out of the Pleistocene era. Ancient lava flows pile on top of even older ones, the ground rumbles as hot steam belches out of faults in the earth’s crust and the valley is wrapped in a fog of water vapour and the all pervading smell of hydrogen sulphide.

Locked away in this primordial-looking valley is Iceland’s newest geothermal plant, producing both hot water for district heating and electricity. Known as the Hellisheidi Power Plant, it has been designed to provide 400 MW of heat (hot water) and 300 MW of electricity for Reykjavik. Currently, three turbines generate 123.5 MW of electricity (one lower pressure turbine and two steam turbines). Hot water production for district heating will begin in 2009.

Like most geothermal plants, this one can be expanded easily to meet future demand by tapping more of the field’s potential. Eventually, the plant will be generating 300 MW of electricity, but that could be exceeded by simply adding on more steam turbines.

“We construct our geothermal plants in such a way that they can be expanded as needed,” points out Hans Benjamínsson, in charge of public relations at the plant, which is operated by Reykjavik Energy, the largest supplier of district heating in the world. “Since these plants don’t require a lot of space, and don’t emit any pollutants, their impact on the environment is also minimal, especially if you compare them to thermal power stations burning fossil fuels such as coal or oil.”

Magma lake

The word geothermal comes from the Greek geo, meaning earth, and therme, meaning heat. “Earth heat is exactly what this energy is,” explains Benjamínsson. “Because Iceland sits atop one of the most active volcanic ridges in the world, there is a lot of hot water and steam beneath the surface. And much of it is near enough to the surface to tap.”

Iceland - Nesjavellir and Hengill mountain
Iceland - Nesjavellir and Hengill mountain
Geothermal activity in the Hengill area east of Reykjavik, in summer.
Basically, Iceland straddles a vast lake of magma and hot rock. And its subterranean environment is in constant turmoil. The high temperature geothermal field in the Hengill area, a few kilometres to the east of Hellisheidi Heath, registered 24,000 earthquakes exceeding 0.5 on the Richter scale in the four years between 1993 and 1997. “That gives you an idea of how active this system is,” says Benjamínsson.

Geothermal energy is a free, renewable resource. As water filters down through the porous volcanic rock, it heats up and sometimes finds it way back to the surface through fissures, taking the form of geysers, boiling mudpots, hot springs, and fumaroles. But much of the water is trapped underground in pockets, where temperatures can reach upwards of 350-500° C. Since Iceland’s rocky soil is highly fractured, there is plenty of groundwater below 50 metres.

The deeper the groundwater in these geothermal fields, the higher the temperatures and the more energy can be extracted. Water stays liquid even at over 200° C because of the tremendous pressures found at depths of more than one kilometre.

Closed system

Iceland - low and high temperature areas
Iceland - low and high temperature areas
Iceland - low and high temperature areas.
Bore holes drilled into geothermal fields tap into these underground cauldrons, bringing the hot water, along with wet steam, to the surface, where it can be harnessed to generate electricity and produce hot water for district heating. The very high pressure steam is dried before being channelled into turbines which drive electric generators. At the same time, the hot water, reaching around 190° C, is passed through several heat exchangers, heating cold surface water to 80-90° C. The heated surface water is then fed into the district heating system, while the briny, mineral-rich hot geothermal water is pumped back into the ground where it can be reused.

“It’s basically a closed system, with very few, if any, by-products,” comments Einar Gunnlaugsson, Manager of Geothermal Research at Reykjavik Energy. “The main thing we need to contend with in using geothermal waters is hydrogen sulphide gas, the rotten egg smell so characteristic of geothermal fields. But except for the smell, it’s harmless.”

Hellisheidi geothermal power plant - turbine room
Hellisheidi geothermal power plant - turbine room
Hellisheidi geothermal power plant - turbine and generator. Photo © Don Hinrichsen
Most of Iceland’s high temperature fields – 26 have been identified – lie at depths of up to 3 kilometres, with temperatures varying between 200° C and 350° C. So far, only five have been developed – most of them producing both hot water and electricity. The country’s total generating capacity is now 480 MW of electricity. Two more fields to be developed over the next decade – both close to the Reykjavik area, which contains 70% of the island’s total population of 300,000 – will push that figure well above 500 MW.

The island is also covered with literally hundreds of low temperature geothermal fields that could be exploited for hot water, especially for heating greenhouses, fish ponds, or other commercial uses. Some of these are being utilized for growing vegetables and raising fish, mostly for export to Europe. But for power production it is more economical to build geothermal stations that can produce electricity along with hot water for district heating.

Cheap energy

This policy has fostered the cheapest rates for heating houses in all the Nordic countries. It costs Icelanders just under 2 kronor per kilowatt hour, compared to 3.5 kronor per KWh for Finland, 5 kronor per KWh for Norway (which is 100% hydroelectric), 5.5 kronor for Sweden and over 8 for Denmark.

“The government took a deliberate decision some years ago that we would develop our natural energy supplies – geothermal and hydropower – as much as possible, so as not to be dependent on imported oil or gas,” explains Ólafur Flóvenz, General Director of Iceland GeoSurvey (ÍSOR). “One result is that Iceland is now a world leader in the development of geothermal energy.”

Another result of the decision to rely on renewable energy is one of the most pristine landscapes in the world. Reykjavik has virtually no pollution at all, except from vehicle exhausts. Reykjavik Energy calculates that the use of geothermal energy for space heating in the capital’s metropolitan area alone has eliminated the need to import 360,000 metric tons of oil a year (or 560,000 metric tons of coal).

Currently, Iceland meets over 80 per cent of its total energy needs from hydropower and geothermal. The only oil imported is for vehicles and to power the country’s large fishing fleet. But by the middle of this century, thanks to a large scale programme to develop hydrogen fuelled vehicles, Iceland may be the first country in the world to divest itself entirely from hydrocarbons, at least as an energy source. (See: report on Iceland's hydrogen power)

Deep drilling

More immediately, Iceland is at the forefront of research and development of new deeper geothermal fields down to 5 kilometres. No country has ever managed to exploit supercritical fluids at such depths. But Iceland is well along in its plans to do so.

By August 2008, the first deep bore well near the Krafla geothermal power plant will be ready for testing under the Iceland Deep Drilling Programme (IDDP). It is expected to reach 4 kilometres below the surface, tapping super heated water and steam at temperatures reaching 450-600° C. IDDP, which is actually a consortium of Icelandic power companies, public organizations and international science foundations, plans to drill at least four bore holes between 3.5 and 5 kilometres in depth over the next few years. By 2010 three should be developed, the deepest reaching 4.5-5 kilometres.

Hellisheidi geothermal power plant - schematic diagram
Hellisheidi geothermal power plant - schematic diagram
Hellisheidi geothermal power plant - schematic diagram. Photo © Don Hinrichsen
“The deeper you go down into geothermal fields, the energy per bore hole increases by a factor of 5-10,” observes Flóvenz. “In other words, there is 5-10 times more energy per mass unit contained in deep wells than in conventional bore holes.”

“The problem,” continues Flóvenz, “is that at such great depths, we don’t know how much of the supercritical fluids and steam is extractable for energy production.” It is also much more expensive to drill deep, but studies conducted by IDDP indicate the power potential per hole is much greater.

High potential

Energy experts agree that geothermal bore holes at depths greater than 3 kilometres have the potential to yield 50 MW of electricity compared to just 5 MW in conventional wells. The reason for the dramatic increase in power is because the pressures are much higher at such depths, between 230 and 260 bar compared to 30 bars for conventional dry steam wells.

The potential generating capacity from known high temperature fields in Iceland is in the order of 25 TWh/year (Terawatt hours per year). “But once you go below 3 kilometres, the new fields we are developing could yield 40-80 TWh per year of electrical production,” says Flóvenz.

However, the full energy potential of the country’s deep geothermal fields could be much higher than current estimates. Some experts think there is enough earth energy under Iceland to power all of Europe, if a way could be found to connect the Icelandic power grid to Europe’s and minimize line losses from an undersea cable.

Whatever the potential, the rest of the world is watching developments in Iceland with great interest. High level delegations have come from the United States, Japan, Europe and some developing countries, such as the Philippines. With the imminent prospect of escalating environmental and economic costs from climate change, largely a result of the use of fossil fuels, continued research and development of geothermal energy, along with other alternatives, is a global imperative.

For the 40 plus countries around the world with geothermal fields, most of them unexploited or under-exploited, reducing dependence on increasingly expensive fossil fuels makes both economic and environmental sense. “Clearly we are at the beginning of a new age in the development of geothermal energy, one that could have significant impacts on future energy supplies,” concludes Flóvenz.

FOOTNOTEExporting know-how

Over the past 30 years, Iceland has trained over 400 scientists, engineers and other specialists from 40 countries in geothermal science and the technology of using geothermal energy resources.

The programme began in 1978, when Iceland’s National Energy Authority entered into a long-term cooperative agreement with the United Nations University (UNU) to train specialists, mostly from developing countries, in a broad range of geothermal energy disciplines. Nine areas of study are available: Geological exploration; borehole geology; borehole geophysics; geophysical exploration; reservoir engineering; environmental studies; chemistry of thermal fluids; geothermal utilization; and drilling technology.

The training courses all last six months and consist of both theoretical and practical work. The training is tailored to the interests of each group and involves individual mentoring.

“We carefully select our trainees, according to their experience, interests, academic degrees, and capacity to actually utilize the knowledge gained when they return to their home countries,” explains Ludvik S. Georgsson, Deputy Director the UNU Geothermal Training Programme. “The costs of the training are borne mainly by Iceland, though some come on scholarships provided by other professional institutions.”

The graduates of the programme come from every corner of the globe, with the largest number from China, Kenya, Philippines, El Salvador, Ethiopia, Poland, Indonesia, Costa Rica and Iran.

“We trained virtually all of the Kenyan experts working on geothermal energy, and most of those working in El Salvador,” points out Georgsson. “But in quite a few developing countries, the state of their geothermal research and development is due in large measure to our graduates.”

Don Hinrichsen is a former editor of Ambio magazine and a Contributing Editor of this website. To read his previous report from Iceland on hydrogen power click here

Related link:

Factfile on geothermal energy