Geothermal Power Plant

Heat from Earth

noreply@blogger.com (Energetic) — Tue, 12 Jun 2012 00:43:00 +0000

Earth's temperature increases gradually. with depth, at the center reaching more than 4,200C (7600F). Some of this heat is a relic of the globe's fiery formation about 4.5 billion years ago, but most has been generated by the decay of radioactive isotopes. As heat naturally moves from hotter to cooler regions, so earth's heat flows along a geothermal gradient from the center to the surface, where an estimated 42 million thermal megawatts are continually radiated into space.

The bulk of this immense heat supply cannot be practically captured, because it arrives at the surface at too low a temperature. Fortunately, the fundamental geologic process know as plate tectonics (responsible for seismic, mountain building, and volcanism) ensures that some of this heat is concentrated at temperatures and depths favorable for its commercial extraction.

The planet's thin lithosphere its rigid shell of crust and outermost mantel has been broken into 12 large and several smaller moving plates by thermally and gravitationally driven convection of the underlying mantle, at rates measured in millimeters per year. The world's geothermal provinces are conspicuously concentrated at the margins of these jostling slabs. Where plates move apart, along globe encircling mid ocean ridges, basaltic magma rises in the fissures to form vast undersea volcanoes. Where two plates collide, one is commonly thrust (subducted) beneath the other, causing formation of a deep ocean trench and occasionally inducing powerful earthquakes.

At great depth just above the down-going plate, temperatures become high enough to melt rock. The resulting magma bodies are less dense than surrounding rocks, and ascend buoyantly through the upper mantle into the crust, where they sometimes give rise to explosive volcanoes, and are always profound shallow pools of heat. Under the right conditions, these near surface heat anomalies can be harnessed for commercial production of geothermal energy.

Installed geothermal electric capacity by country

noreply@blogger.com (Energetic) — Tue, 22 Nov 2011 17:42:00 +0000

The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in online capacity since 2005. IGA projects growth to 18,500 MW by 2015, due to the projects presently under consideration, often in areas previously assumed to have little exploitable resource.

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California. The Philippines is the second highest producer, with 1,904 MW of capacity online. Geothermal power makes up approximately 18% of the country's electricity generation.

**Installed geothermal electric capacity**
Country	Capacity (MW) 2007	Capacity (MW) 2010	Percentage of national production
USA	2687	3086	0.3%
Philippines	1969.7	1904	27%
Indonesia	992	1197	3.7%
Mexico	953	958	3%
Italy	810.5	843	1.5%
New Zealand	471.6	628	10%
Iceland	421.2	575	30%
Japan	535.2	536	0.1%
Iran	250	250
El Salvador	204.2	204	25%
Kenya	128.8	167	11.2%
Costa Rica	162.5	166	14%
Nicaragua	87.4	88	10%
Russia	79	82
Turkey	38	82
Papua-New Guinea	56	56
Guatemala	53	52
Portugal	23	29
China	27.8	24
France	14.7	16
Ethiopia	7.3	7.3
Germany	8.4	6.6
Austria	1.1	1.4
Australia	0.2	1.1
Thailand	0.3	0.3
TOTAL	9,981.9	10,959.7

Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-Forêts, France, while an earlier effort in Basel, Switzerland was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America.

The thermal efficiency of geothermal electric plants is low, around 10-23%, because geothermal fluids do not reach the high temperatures of steam from boilers. The laws of thermodynamics limits the efficiency of heat engines in extracting useful energy. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. System efficiency does not materially affect operational costs as it would for plants that use fuel, but it does affect return on the capital used to build the plant. In order to produce more energy than the pumps consume, electricity generation requires relatively hot fields and specialized heat cycles. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor can be quite large – up to 96% has been demonstrated. The global average was 73% in 2005.

New Geothermal Energy Project in New Zealand

noreply@blogger.com (Energetic) — Sun, 09 Oct 2011 09:31:00 +0000

Tauhara 2 was a key geothermal energy project for Contact and for New Zealand. Six years ago a small Maori trust in the central North Island faced a big decision. Either sit back as passive landlords and collect the rent on the land while a power company tapped its geothermal riches or take a risk and take an equity stake in what is the country's fastest growing electricity source.

Tauhara North No 2 Trust chose what it knew would be the tougher path - but one which it says is already paying dividends. The trust - held by about 800 owners who affiliate to Ngati Tahu - borrowed more than $100 million to take a 25 per cent stake in the $430 million Nga Awa Pura geothermal station, in partnership with state owned enterprise Mighty River Power.

"We were the land owners and knew the resource was there. It was a matter of understanding its true value and wanting to do something ourselves and participate in the venture instead of just leasing the land," said the trust's chief executive, Aroha Campbell.

The station was commissioned early this year and the investment is on track to deliver gross revenue of $20 million a year to the trust, she says.

"The key for the trust is providing a balance between our economic investment which ultimately we want to end up with jobs for our owners and beneficiaries - we want to maintain a balance."

The trust is set to take a further 10 per cent of Nga Awa Purua and has the option of taking an equity stake in an even bigger Mighty River project, Ngatamariki.

"We have been there and we understand what the risks are."

At Mokai a 113MW power station is 75 per cent owned by the Tuaropaki Trust, the rest owned by Mighty River.

Further development is under investigation.

Further north, on the shores of Lake Rotoiti, Maori land owners Taheke 8c Incorporated of Ngati Pikiao have partnered with Contact Energy and exploratory drilling has begun.

Maori have tapped the geothermal resources of the North Island for centuries, first for cooking and warmth, then tourism and now power. And right now energy from the earth is the most cost-effective way of generating it.

From the 1950s to the 1970s it was hydro - massive public works schemes were built on rivers and canals.

Huge dams were built for the ultimate in green energy. For the next two decades, cheap and plentiful Maui shone, providing peaking and then baseload generation for the next two decades before wind became viable around the turn of the century.

For the past 50 years geothermal was chugging in the background and largely under the radar.

But with all the easy hydro sources tapped, gas prices up sharply and the best wind sites built on or consented, the focus over the past five years has been on new geothermal plants exploiting fields and technology New Zealand helped pioneer at Wairakei.

Contact Energy and Mighty River have been at the forefront of the geothermal renaissance.

Mighty River's development general manager Mark Trigg says when the company began its life in 1998 with predominantly hydro assets on the Waikato River, it determined that strategically, it needed to diversify its fuel base and embarked on a programme of geothermal development.

It was not until the 2000s and the realisation that Maui gas was coming to an end if not physically, then contractually, that the playing field was levelled for other fuel sources.

"In the past few years the fossil fuels tax impost has made geothermal even more attractive as is the case for all other renewables. The advantage over other renewables in that geothermal is baseload, much more manageable and easier to quantify and justify economically," Trigg says.

Geothermal projects are clustered around the Taupo area, and in contrast to South Island hydro projects are close to population centres and near the national grid which is being upgraded.

Latest data from the industry group, the Geothermal Association, shows the the most recent capacity additions have lifted the contribution of geothermal electricity from around 6 per cent of generation (in terms of gigawatt-hours) in 2004 to current levels of around 10 per cent.

Projected development curves based on announced projects now suggest geothermal energy could be generating 20 per cent of New Zealand's electricity possibly as early as 2020.

Power stations have been developed on geothermal fields at Wairakei, Kawerau, Ohaaki, Rotokawa, Ngawha and Mokai. Community-owned Ngawha is at the stage of being able to supply 70 per cent of the Far North's electricity demand, the association says. And the geothermal is not limited to electricity generation.

The latest technology is geothermal heat pumps. These are like the air-source heat pumps available from specialists and local hardware stores, but exchange heat with the ground or groundwater rather than air.

Mighty River Power has invested more than $1 billion that it has made over the past five years in geothermal generation. New capacity has resulted in a 400 per cent increase in geothermal output since 2007, was a major contributor and driver of the 22 per cent increase in the company's earnings to $233.6 million for the second half of last year and has underpinned two announcements on a lift in earnings guidance since.

Enthusiasm, expertise and the availability of capital to invest has encouraged the company overseas. Global demand for geothermal is also outstripping the comparatively low demand for electricity in New Zealand.

Mighty River has so far deployed about half of US$250 million capital committed through international partner GeoGlobal Energy (GGE) to projects in California, Chile, and into Bavaria in Germany.

Trigg says the company has a genuine competitive advantage on a global scale; the same couldn't be said for wind, hydro or gas. "Around 0.3 per cent of global generation is fragmented and therefore what we bring is technical expertise and the business development expertise of our partners and, most importantly, the ability to apply risk capital.

"Going offshore provides a very strategic diversification or our growth. From a Mighty River Power business perspective the fact demand growth is only around 2 per cent means it pretty much limits the rate of new generation development that will be able to be achieved domestically and that's on the assumption you just get your market share of growth," he says.

In New Zealand generators face a big variable - the price they receive - but in most other countries there are long-term power price agreements with retailers and, in a carbon conscious world, subsidies and other incentives from governments.

"That eliminates a significant risk you have in New Zealand."

Trigg warns that easy geothermal is almost at an end. Beyond the next "tier one" projects, Contact's Te Mihi and Tauhara and Mighty River's Ngatamariki, developments will be tougher.

"Once you move beyond those you probably get to a stage where it's project by project - there's not a clear fuel source that is superior to all fuel classes. That's about the time when the wind projects that are currently being consented will come into play as the best economically viable."

Contact's general manager of renewable development James Kilty says his company's focus is definitely in New Zealand. "I see five to six years of heavy lifting here in New Zealand and that's where our priorities lie."

"There's a lot of claim-staking around the world on geothermal, but in terms of actual projects a lot of the development has been in our back yard."
A Taupo Maori land trust and Contact Energy have signed an agreement that will allow exploratory geothermal drilling to go ahead within a year. The drilling will be carried out on trust land north of Taupo and 600m from Contact's proposed Tauhara 2 geothermal energy development.

Tauhara Moana Trust chairman Toby Rameka and Contact Energy chief executive Dennis Barnes said strong relationships were essential for responsible development and the agreement marked the beginning of a new phase in the relationship between the trust and Contact.

"Over the time we have spent together advancing Tauhara 2, we have developed a respect for each other. It takes time to get to this place in a relationship and I look forward to strengthening our ties in the years ahead." Rameka said the trust was looking forward to its next phase of development.

"Particularly as it relates to the geothermal resource which our whanau and our leadership have a deep and emotional connection with. "It is far better to be part of a project, be informed and be active partners than be on the outside and in the shadows."

Rameka said the trust and Contact had an interest in sustainable and responsible development that brought benefits to the region and New Zealand. "For Tauhara Moana, any development undertaken on our whenua or that we are involved in has to take into account cultural, environmental, social and commercial issues. If this can be achieved, then making use of your resource for the benefit of your people and your community is an easy decision.

"We know from our longstanding relationship with Contact Energy that these things are important to them too," he said. The trust believed Contact was committed to developing Tauhara in a way that made the best use of the trust's geothermal resources in the long term.

Trustee Topia Rameka said the agreement was unique and was based on a value-sharing arrangement reflecting the risks and certainties of the project. He said the trust had not decided to look at a royalties-only scheme but instead wanted to share the risk and receive more of the benefits of geothermal energy production.

The full commercial details of the agreement were not revealed, both parties asking for confidentiality in the short term. Barnes said Tauhara 2 was a key project for Contact and for New Zealand. "Geothermal energy provides reliable, renewable baseload energy, whereas other renewable resources are intermittent."

Hydro, wind energy and thermal generation faced the cost of offsetting its carbon footprint and gas supplies were uncertain. "Tauhara 2 was consented last year and will be built when market conditions allow."

Geothermal projects commissioned in the past decade or under development:

Mighty River Power: The company is active in three geothermal fields - at Rotokawa, Mokai and Kawerau - and significant potential exists for further development within the Taupo volcanic zone

(source)

Gunung Salak Geothermal Power Plant

noreply@blogger.com (Energetic) — Tue, 14 Dec 2010 11:07:00 +0000

The Gunung Salak Geothermal power plant generates emission free electricity for the Indonesian power grid. Greenhouse gas emission reductions are achieved through updating its capacities, thus avoiding the burning of fossil fuel (coal) for the growing demand in Indonesia.

Gunung Salak Geothermal Power plant uses the natural resource of Indonesia's underground geothermal activity, by turning heat into power.

The project activity comprises of a capacity upgrade of an existing geothermal power plant from 3 x 55 MW to 3 x 60 MW, which generates and supplies electricity to the connected grid, the Jamali regional grid.

The capacity upgrade is established by:

Changing turbine diaphragm of unit 1 and 2
Modifying the gas extraction system or ejector for unit 3

Chena Geothermal Power Plant

noreply@blogger.com (Energetic) — Tue, 14 Dec 2010 11:00:00 +0000

Alaska has more geothermal resources than any other state in the country, and yet none of these resources has been developed for power generation prior to 2006. In 2004, Chena Hot Springs Resort entered into a partnership with United Technologies Corporation (UTC) to demonstrate their moderate temperature geothermal ORC power plant technology at Chena Hot Springs.

Project partners include:

Chena Hot Springs Resort
Chena Power
United Technologies Corp.
Department of Energy
Alaska Energy Authority

The Chena geothermal power plant came online in late July 2006, putting Alaska squarely on the map for new geothermal technologies. Chena Hot Springs is the lowest temperature geothermal resource to be used for commercial power production in the world. We hope this will be the first step toward much greater geothermal development in the state. The cost of power production, even in semi-remote locations such as Chena, will be reduced from 30¢ to less than 7¢ per kWh once the UTC plant is installed and operational.

The challenge for moderate temperature small scale geothermal development has been to bring the cost down to a level where it is economical to develop small geothermal fields. UTC has been working toward that goal. In the past, small geothermal power plants have been built to order using tailor made components, which has greatly increased both the expense and the lead time for such units.

UTC’s Research Center has teamed up with their sister divisions, Carrier and UTC Power, to reverse engineer mass produced Carrier chiller components to dramatically reduce the cost of production, and allow for modular construction. UTC has already proven this technology with the release of their PureCycle 225 power plant in 2003, which is designed to operate off waste heat applications.

How Chen Geothermal Power Plant Works?

Because the geothermal water at Chena Hot Springs never reaches the boiling point of water we cannot use a traditional steam driven turbine. Instead a secondary (hence, "binary") fluid, R-134a, which has a lower boiling point than water passes through a heat exchanger with 165°F water from our geothermal wells. Heat from the geothermal water causes the R-134a to flash to vapor which then drives the turbine. Because this is a closed loop system virtually nothing is emitted to the atmosphere. Moderate temperature is by far the most common geothermal resource and most geothermal power plants in the future will be binary cycle plants. Here are the steps in the cycle:

Hot water enters the evaporator at 165ºF (480gpm). After the hot water runs through the evaporator, it is returned to the geothermal reservoir via our injection pump and injection well system. Some of the water is also used to heat buildings on site before it is reinjected.
The evaporator shell is filled with R-134a, a common refrigerant found in many air conditioning systems. The 165ºF water entering the evaporator is not hot enough to boil water, but it is hot enough to boil the R-134a refrigerant. The evaporator is a giant heat exchanger, with the hot water never actually coming in contact with the refrigerant, but transferring heat energy to it. The R134a begins to boil and vaporize.
On initial system startup, the vapor bypasses the turbine and returns directly to the condenser via a bypass valve. Once there is adequate boiling/evaporation of the refrigerant, the bypass valve closes and the vapor is routed to the turbine.
The vapor is expanded supersonically through the turbine nozzle, causing the turbine blades to turn at 13,500rpm. The turbine is connected to a generator, which it spins at 3600rpm, producing electricity.
Cooling Water enters from our cooling water well which is located 3000ft distant and 33ft higher elevation than the power plant. Cold water (40ºF-45ºF) is siphoned out of this well and supplied to the power plant condenser at a rate of 1500gpm.
The cooling water entering the condenser and recondenses the vapor refrigerant back into a liquid. As in the evaporator, the condenser only allows heat transfer to occur between the refrigerant (in the shell) and the cold water (in the tubes within the condenser). The two liquids never actually come in contact.
The pump pushes the liquid refrigerant back over to the evaporator, so the cycle can start again. By doing so, it also generates the pressure which drives the entire cycle.

Chena Geothermal Resource Overview

The Chena Hot Springs Geothermal Resource, like all interior Alaskan hot springs, is located along the margins of a granite pluton. These plutons are ancient (cooled) magmatic bodies that have pushed up into the surrounding rock at some time in the distance past (at least 80 million years ago). These intrusions cooled below the surface to become huge granite geologic formation, called plutons. Plutons can host geothermal systems in two ways. Granitic rock is very brittle and fractures easily. These deep, often steeply dipping fractures can sometimes act as conduits for water which has circulated deep into the earth's crust (picking up heat along the way) to rapidly short circuit' back to the surface. In the case of the Chena system, this short circuit is probably caused by the intersection of two small faults, the primary one located parallel to Spring Creek and identifiable by the string of natural hot springs and seeps along one section of it.

Granite rock is also frequently high in Uranium and Thorium. When these elements decay, heat is generated which is trapped in the host rock, which in this case is the granite pluton. This radioactive decay generates an abnormally high geothermal gradient in the pluton, which means the water does not need to circulate to extreme depths to pick up heat. In the case of Chena Hot Springs, it appears the water is circulating to a depth of approximately 3000-5000ft and reaching a maximum temperature of 250ºF. Chena is working on an exploration project under the Department of Energy to identify and quantify the deep geothermal resource at Chena Hot Springs. This project will culminate in the drilling and testing of a 4000ft hole sited to intersect the geothermal reservoir at depth. For more information on Chena's GRED III project, click here.

source:http://www.yourownpower.com/Power/

Geothermal Power Plant Ulubelu Operates by 2012

noreply@blogger.com (Energetic) — Wed, 03 Nov 2010 13:27:00 +0000

Geothermal Power Plant Ulubelu in capacity of 2x55 MW will operate in the end of 2012.

The Communication Manager of Pertamina Geothermal Energy (PGE) Adiatma Sardjito said that recently this construction project is in the process of Engineering, Procurement, Construction (EPC). “PLTP Ulubelu will operate in the end of 2012,” he says in Jakarta. Wednesday October 14th, 2010.

He explained that PLN and PGE have dealt about the steam price in US$ 4, 2 cent per kilowatt hour (kwh).

While, Ministry Expert Staff of Communication and Information, MEMR Kardaya Warnika stated that PLTP Ulubelu is one of government’s project in the program of geothermal utilization improvement to encourage renewable energy utilization. “For Ulubelu is in the stage of price evaluation,” he says.

Besides Geothermal Power Plant Ulubelu, he continues, other PLTP projects inserted inside the target of geothermal utilization improvement is PLTP Lahendong (North Sulawesi which is now in the stage of facility working. Finishing PLTP Sarulla (North Sumatera) is in the verification stage by Financial and Development Supervisor Agency (BPKB). PLTP Ulumbu (NTT) in capacity 5 MW is redesigned. (AK)

Poihipi Power Station

noreply@blogger.com (Energetic) — Sun, 03 Oct 2010 19:47:00 +0000

The Poihipi Power Station is a geothermal power station owned and operated by Contact Energy. It is located on Poihipi Road near Taupo in New Zealand.

The plant produces around 200 GWh pa, utilising geothermal steam from the Wairakei field, and is operated as part of the Wairakei geothermal system.

Poihipi Power Station
Location	Waikato
Owner	Contact Energy
Status	Operational
Fuel	Geothermal
Maximum capacity	55 MW
Commissioned	1996

Krafla Geothermal Power

noreply@blogger.com (Energetic) — Tue, 28 Sep 2010 01:56:00 +0000

The Krafla Geothermal Power Station is a geothermal power station located near the Krafla Volcano in Iceland. Since 1999, it produces 60 MW of energy.

From the first exploratory drilling in 1974 to reaching full 60MW capacity in 1999, the Krafla geothermal power plant has had an interesting story.

For a while it was uncertain whether Krafla would ever actually enter operation when, early on, large-scale volcanic eruptions occurred only two kilometers away from the station, posing a serious threat to its existence. Work continued, however, and phase one of the power station went on line early in 1977.

Krafla Geothermal Power Station Timeline:

1974 - The first trial boreholes are drilled
1975 - Beginning of seismic and volcanic impacts threaten continued development of the plant
1975 - Sinking production wells and construction of power plant despite seismic activity
1977 - Power Plant begins operation
1978 - Plant begins power production
1984 - Significant decline in seismic and volcanic impacts
1996 - Installed 2nd steam turbine and beginning of additional drilling
1999 - Producing 60MW (planned capacity)

In total, 33 boreholes were drilled, including 17 high pressure production wells and 5 low-pressure production wells. The plant uses 110kg/second of 7.7 bar saturated high-pressure steam and 36 kg/sec of 2.2 bar saturated low-pressure steam and has been in operation at 60MW since 1999.

Mannvit's involvement in the Krafla geothermal power plant started in 1994 and lasted until 2002 and revolved mainly around the development of the second phase of the project.

Mannvit Services:

Feasibility report
Site lay-out planning
Conceptual design
Detailed mechanical design
Environmental impact study and report
Modeling of groundwater flow and transportation of contaminants
Project management
Overall plant design
Detailed design of HVAC systems
Bid preparation and tender evaluation
Site supervision
Commissioning

Olkaria II Geothermal Power Plant

noreply@blogger.com (Energetic) — Fri, 24 Sep 2010 20:27:00 +0000

The Olkaria II Geothermal Power Plant is one of Kenya's largest geothermal power plant having an installed electric capacity of 70 MW.

Olkaria II Power Station is currently Africa’ s largest Geothermal Power Station. It is currently generating 70 MWe and is the second geothermal plant that is operated by KenGen. The power plant was commissioned in November 2003.

Olkaria II Geothermal Power Plant is located in the North Eastern Sector of the greater Olkaria geothermal field. Wells were drilled between 1986 and 1993 but construction of the power plant was delayed until the year 2000 when funds became available.

The project was co-financed by the World Bank, the European Investment Bank, KfW of Germany and the Kenyan Government. Designed and constructed with an advantage of newer technology, this state-of-the-art plant is highly efficient in steam utilization.

Olkaria II Geothermal Power Plant operates on a single flash plant cycle with a steam consumption of 7.5 tonnes per hour per megawatt generated. The turbines are single flow six-stage condensing with direct contact spray jet condenser. The Power generated is transmitted to the national grid via 220 kV double circuit line to Nairobi. Olkaria II power station is also connected to Olkaria I Power Station by a 132 kV line.

Svartsengi geothermal power plant

noreply@blogger.com (Energetic) — Fri, 17 Sep 2010 11:35:00 +0000

Svartsengi geothermal power plant is a power plant just about 34 years old and is situated on Reykjanes. It is owned by the local communities in the Suðurnes. From Svartsengi the geothermal energy is harnessed for the area. The waste water from the plant work is best known as the Blue lagoon which is definitely one of the most famous tourist attraction in Iceland.

The Svartsengi Geothermal Power Plant is a geothermal power station located in Keflavik, Iceland, near the Keflavík International Airport at the Reykjanes Peninsula. As of December 2007, it produces 76.5 MW of energy, and about 475 litres/second of 90 °C (194 °F) hot water (ca. 80 MW). Surplus mineral rich water from the plant fills up the Blue Lagoon, a tourist bathing resort.

Svartsengi Power Station
The Blue Lagoon with the power station in the background.
Location	Keflavik, Iceland 63°52′44″N 22°25′58″W / 63.87889°N 22.43278°W / 63.87889; -22.43278Coordinates: 63°52′44″N 22°25′58″W / 63.87889°N 22.43278°W / 63.87889; -22.43278
Owner	HS Orka
Status	Completed
Fuel	Geothermal
Installed capacity	76.5 MW
Commissioned	1976

Kawerau Geothermal Power Plant

noreply@blogger.com (Energetic) — Thu, 09 Sep 2010 21:10:00 +0000

The Kawerau Geothermal Power Plant is a 100-megawatt geothermal power plant located just outside the town of Kawerau in the Bay of Plenty region of New Zealand. The power station is situated within the Kawerau geothermal field, which is part of the Taupo Volcanic Zone. Completed in July 2008 by Mighty River Power at a cost NZ$300 million, the plant's capacity proved greater than expected.^[1] The station is the largest single generator geothermal plant in New Zealand.

The Kawerau Geothermal Power Plant boosted the country's geothermal capacity by 25 percent and significantly increased local generation capacity in the Eastern Bay of Plenty. The plant meets approximately one third of residential and industrial demand in the region and provides cost certainty to local industry including Norske Skog Tasman.

The Kawerau Geothermal Power Plant uses a single Fuji turbine and steam from geothermal bores. The two phase fluid is flashed/separated twice to produce high and low pressure steam to feed the turbine.

The Kawerau Geothermal Power Plant field also supplies process steam to the Kawerau pulp and paper mill. This is used for process and power generation. Two small binary power plants use waste hot geothermal water for power generation.

A binary plant is also located west of the main power station. This station uses two phase fluid from one production well, KA24.

Kawerau Power Station

Location	Bay of Plenty
Owner	Mighty River Power
Status	operating
Fuel	geothermal
Maximum capacity	100 MW
Commissioned	2008

Centennial Drive Binary Geothermal Power Plant

noreply@blogger.com (Energetic) — Fri, 03 Sep 2010 22:18:00 +0000

The Centennial Drive Binary Geothermal Power Plant is a 23 MW binary cycle geothermal power station situated near Taupo, New Zealand. The power station is operated by Contact Energy.

In July 2008, Contact Energy announced that the contract for supply and construction of the binary cycle equipment was awarded to Ormat Technologies.

The Centennial Drive Binary Geothermal Power Plant is powered with steam and fluid from the Tauhara steamfield, and all used geothermal fluid is reinjected back into the edge of the steamfield.

The Tauhara One plant was opened in May 2010, three weeks ahead of schedule.

Centennial Drive Binary
Location	Centennial Drive, opposite Rakaunui Road, Taupo, New Zealand
Owner	Contact Energy
Status	operating
Fuel	Geothermal
Maximum capacity	23 MW
Commissioned	2010

Ohaaki Power Station

noreply@blogger.com (Energetic) — Tue, 31 Aug 2010 13:37:00 +0000

The Ohaaki Power Station is a geothermal power plant owned and operated by Contact Energy. A distinctive feature of this power station is the 105 m high natural draft cooling tower, the only one of its kind in New Zealand.

Although initially constructed to generate 104 MW, decline in the steamfield has meant maximum net capacity is about 65 MW with an annual output of around 400 GWh pa.

There are currently three turbines in operation. One smaller turbine runs off high pressure steam which then backfeeds into the main intermediate pressure system that feeds the two main units. Condensers on the back end of the main turbines are fed cooled water from the cooling tower to condense the steam back into water. Additional condensate gained in this process is reinjected back into the ground.

The Ohaaki geothermal power plant is located adjacent to the Ohaaki Marae (Ngāti Tahu) on the banks of the Waikato River in New Zealand. Gradual sinking of the marae has been attributed to draw-off of geothermal fluids by the power station. The area of the marae is sinking approximately 170mm a year. In the 1960s, the marae was moved to its present location because the previous site was flooded when the dam for the Ohakuri Power Station was filled.

Ohaaki Power Station

Location	Waikato
Owner	Contact Energy
Status	Operational
Fuel	Geothermal
Maximum capacity	104 MW
Commissioned	1989

Nesjavellir Geothermal Power Station

noreply@blogger.com (Energetic) — Fri, 27 Aug 2010 13:48:00 +0000

The Nesjavellir Geothermal Power Station is the second largest geothermal power plant in Iceland. The facility is located 177 m (581 ft) above sea level in the southwestern part of the country, near Thingvellir and the Hengill Volcano.

Plans for utilizing the Nesjavellir area for geothermal power and water heating began in 1947, when some boreholes were drilled to evaluate the area's potential for power generation. Research continued from 1965 to 1986. In 1987, the construction of the plant began, and the cornerstone was laid in May 1990. The station produces approximately 120MW of electrical power, and delivers around 1,800 litres (480 US gal) of hot water per second, servicing the hot water needs of the Greater Reykjavík Area.

Nesjavellir Geothermal Power Station
Nesjavellir Geothermal Power Station
Location	Thingvellir, Iceland 64°6′29″N 21°15′23″W / 64.10806°N 21.25639°W / 64.10806; -21.25639Coordinates: 64°6′29″N 21°15′23″W / 64.10806°N 21.25639°W / 64.10806; -21.25639
Status	Completed
Fuel	Geothermal
Installed capacity	120 MW
Commissioned	May 1990

Nga Awa Purua Power Station

noreply@blogger.com (Energetic) — Thu, 26 Aug 2010 16:53:00 +0000

Nga Awa Purua is a geothermal power plant located near Taupo in New Zealand. The project was developed by Mighty River Power. Nga Awa Purua is New Zealand's second largest geothermal power station and the steam turbine is the largest geothermal turbine in the world.

The geothermal power plant is a joint venture between Mighty River Power and the Tauhara North No 2 Trust. The $430 million project first generated electricity on 18 January, and was officially opened by Prime Minister John Key on 15 May 2010.

The Rotokawa Power Station is situated close by.

Nga Awa Purua
Location	Waikato
Owner	Mighty River Power
Status	Operational
Fuel	Geothermal
Turbines	1
Maximum capacity	140 MW
Commissioned	2010

Reykjanes Power Station

noreply@blogger.com (Energetic) — Wed, 25 Aug 2010 15:42:00 +0000

The Reykjanes Power Station is a geothermal power plant located in Reykjanes at the southwestern tip of Iceland. As of 2009, the plant produces 100MW of electricity, with an expansion plan to increase by 50MW in 2010.

The pioneering Reykjanes Geothermal Power Plant in Iceland is now producing 100MWe from two 50MWe turbines. The plant uses steam from a reservoir at 290 to 320°C – the first time that geothermal steam of such high temperature has been used to generate electricity on a large scale.

The new plant is located on the Reykjanes peninsula, in the south-western corner of Iceland. Owned by Sudurnes Regional Heating Corporation, the plant was designed by Enex, a conglomerate from the Icelandic energy sector with wide experience in developing geothermal energy and hydropower. The two turbines started operation in May 2006 after testing and were formally brought on-line in December 2006.

HIGHEST TEMPERATURE YET FOR GEOTHERMAL STEAM

The Reykjanes plant uses steam and geothermal brine extracted from twelve 2,700m-deep wells. After extraction, the brine is piped into a steam separator. From there, the separated steam passes under 19 bars of pressure to a steam dryer and into the two 50MW turbines.

The plant is situated close to the ocean front, so seawater (4,000l/s) at 8°C can be pumped through a condenser for cooling and condensing the brine.

NEARLY 20% OF ICELAND'S ELECTRICITY FROM GEOTHERMAL

Geothermal resources have been used for over 70 years in Iceland. The geothermal area at Reykjanes is located on top of the Mid-Atlantic Ridge, formed by plate tectonics that are moving in separate directions. That gives high geothermal energy, with the Reykjanes area being where the plate boundary of the Reykjanes Ridge comes on land. The area is about 2km2 in size. Energy has been extracted from the area for around 30 years without significantly reducing the geothermal reserves.

Geothermal power plants produce nearly 20% of the country's electricity; geothermal heating also supplies nearly 90% of the country's domestic heating and hot water requirements. Nearly all the rest comes from hydroelectric generation, with less than 0.1% from fossil fuels.

Geothermal brine cannot be used directly for heating because of its high mineral content. On cooling, it releases great quantities of hard deposits (silica) which block pipes and other equipment. The high temperature and salt content of the water therefore demands heat exchangers.

Reykjanes Power Station
Reykjanes Power Station
Location	Reykjanes, Iceland 63°49′35″N 22°40′55″W / 63.82639°N 22.68194°W / 63.82639; -22.68194Coordinates: 63°49′35″N 22°40′55″W / 63.82639°N 22.68194°W / 63.82639; -22.68194
Owner	SRHC
Status	Completed
Fuel	Geothermal
Technology	Steam turbine
Turbines	2
Installed capacity	100 MW
Maximum capacity	150 MW
Commissioned	May 2006

Jermaghbyur Geothermal Power Plant

noreply@blogger.com (Energetic) — Mon, 23 Aug 2010 19:42:00 +0000

The Jermaghbyur Geothermal Power Plant will be Armenia's largest geothermal power plant having an installed electric capacity of 150 MW. It will be situated in Syunik Province of Armenia.

Low-potential sources of geothermal power were founded in Garni, Arzni,Jermuk, Ankavan and Sisian. The geothermal power can be utilizedfor heat-supply, heating of hothouses, residential buildings and industrial enterprises.

"Ameria" CJSC was contracted by World Bank Energy Invest PIU to develop a detailed feasibility study for the construction of "Jermaghbyur" geothermal power plant in Syunik Marz of the Republic of Armenia. The study was carried out in the scope of the process aimed at diversifying energy resources in Armenia and achieving a higher level of independence from the importing energy sources. The document, elaborated by Ameria consultants, proved the strategic importance and effectiveness of utilizing geothermal energy in Armenia, as well as the investment attractiveness of the overall project. Geothermal energy is considered as an effective resource for heat supply and generation of electric power. Today geothermal plants with the total heat production capacity of 12000 MW operate in more than 30 countries. The geothermal plants generate also electric power with the total capacity of 8000 MW. The share of geothermal energy in the world installed capacities is 0.4%.

"Jemaghbyur" station, which commissioned in 2008-2009, is a unique project. It does not have any analogues in the region and will positively differ from the majority of other energy generation capacities, especially in its renewability of resources, independence of importing energy sources, as well as in the minimal environmental impact.

The feasibility study of the project has indicated that the station based on 6 direct wells with the depth of up to 2.5 km each can have a capacity up to 25 MW and generate up to 195 mln KW/hour electric power a year.

Ameria is a group of professional services companies registered in Armenia with the objective to provide a comprehensive package of professional advisory and assurance services. Ameria specializes in four major areas of professional activities: management advisory services; assurance and advisory services; legal advisory services; investment banking. Established in 1998, the company has become a leader in the Armenian market of advisory services bringing an
international reach and local touch to complex issues rising in more than 30 industry sectors.

Wairakei Power Station

noreply@blogger.com (Energetic) — Fri, 20 Aug 2010 09:29:00 +0000

The Wairakei Power Station is a geothermal power station near the Wairakei Geothermal Field in New Zealand. Wairakei lies in the Taupo Volcanic Zone.

The geothermal power plant was built in 1958, the first of its type in the world, and it is now being operated by Contact Energy. A binary cycle power plant was constructed in 2005 to use lower-temperature steam that had already gone through the main plant. This increased the total capacity of the power station to 181MW. The Wairakei power station is due to be phased out from 2011, replaced by the Te Mihi geothermal power station. The Poihipi Power Station was built in 1996 at a nearby site in the same field.

The use of steam from the field has had a number of visible effects on the local environment. Visible geothermal activity has increased (due to changes in the water table / water pressure allowing more steam to be created underground, upsurging at places like Craters of the Moon), while there has also been some land subsidence and reduction in steam volumes from the field after some decades of use. So far, total electrical production has been sustained or increased, with the investment in additional power stations such as the binary plant of 2005 designed for lower-temperature generation. Some power stations in the field are now capped in their extraction capacities and a substantial part of the water / steam is being reinjected after use.

The hot geothermal fluid that is extracted is originally cold rainwater that had percolated downwards and been heated by hot rock; pumping back the warm water that emerges from the exhaust of the generator system thus reduces the heat drawn from the ground. Also, the Waikato river water is already too high in arsenic content to be safe to drink without special treatment, and so reinjection of the facility's water does not exacerbate this problem.

Wairakei Power Station
The Wairakei Power Station, with the main two blocks at the left rear. The binary plant is in front.
Location	New Zealand
Owner	Contact Energy
Fuel	Geothermal
Maximum capacity	181MW
Commissioned	1958
Decommissioned	2011 onwards (planned)

Wayang Windu Geothermal Power Station

noreply@blogger.com (Energetic) — Wed, 18 Aug 2010 22:55:00 +0000

The Wayang Windu Geothermal Power Station is the largest geothermal power plant in Indonesia. The facility utilizes two units, one with 110 MW and the other with 117 MW, totalling the installed capacity to 227 MW. The power station is located in Pangalengan, West Java, in Indonesia. An estimated cost of US$200 million was incurred in constructions and development.

Wayang Windu Geothermal Power Station
Location	Pangalengan Indonesia
Coordinates	07°12′00″S 107°37′30″E / 7.2°S 107.625°E / -7.2; 107.625Coordinates: 07°12′00″S 107°37′30″E / 7.2°S 107.625°E / -7.2; 107.625
Owner	Star Energy
Employees	1,500
Status	Operational
Fuel	Geothermal
Technology	Steam turbine
Turbines	1 × 110MW 1 × 117MW
Installed capacity	227 MW
Commissioned	2000

Construction of Wayang Windu Unit II Geothermal Power Plant Inaugurated

The construction of geothermal power plant (PLTP) Wayang Windu Unit II officially inaugurated by Minister of Energy and Mineral resources, in Pangalengan, Bandung, in Saturday (26/8). The construction of this 110 MW power plant is expected to be completed in 2008 and will improve the security of power supply in the region.

According to Minister Purnomo, the reliability of power supply system in Java-Bali system is now improved following the construction of some new power plants in West Java including the Wayang Windu Unit II as well as the completion of the construction of 500 KV transmission southern line, stretching from Tasikmalaya in West Java to Jakarta. Minister Purnomo also added that the construction of Wayang Windu Unit II will be followed by the Wayang Windu Unit III with the same capacity of 110 MW. “The development of geothermal power plant will improve the security of power supply for West Java region” said Minister Purnomo.

Hellisheidi Power Station

noreply@blogger.com (Energetic) — Thu, 12 Aug 2010 23:56:00 +0000

The Hellisheidi Power Station is the second largest geothermal power plant in the world, and the largest geothermal power plant in Iceland. The facility is located in Hengill, southwest Iceland, 11 km (7 mi) from the Nesjavellir Geothermal Power Station. As of February 2009, the plant produces 213 MW of electricity, with a target capacity of 300 MW of electricity and 400 MW of thermal energy. Once this capacity is reached, it would rank as the largest geothermal power station in the world, in terms of installed capacity.

Electricity production with two 40 MW and 45 MW turbines commenced in 2006. In 2007, an additional steam turbine of 30 MW was added. In 2008, two 40 MW and 45 MW turbines were added with steam from Skarðsmýrarfjall Mountain. The hot water plant will be introduced in 2010.


Country	Iceland
Location	Hengill
Coordinates	64°02′14″N 21°24′03″W / 64.03722°N 21.40083°W / 64.03722; -21.40083Coordinates: 64°02′14″N 21°24′03″W / 64.03722°N 21.40083°W / 64.03722; -21.40083
Owner	Orkuveita Reykjavíkur
Status	Operational
Fuel	Geothermal
Technology	Steam turbine
Turbines	5
Installed capacity	213 MW (February 2009)
Maximum capacity	400 MW
Commissioned	2006

Cerro Prieto Geothermal Power Station

noreply@blogger.com (Energetic) — Mon, 09 Aug 2010 20:33:00 +0000

The Cerro Prieto Geothermal Power Station is the largest geothermal power station in the world, with an installed capacity of 720 MW, with plans for expansion up to 820 MW by 2012. The facility is located in south Mexicali, Baja California, in Mexico, and is built in five individual units, namely CP1, CP2, CP3, CP4 and CP5.

Cerro Prieto I
The CP1 powerhouse has a total installed capacity of 180 MW, generated by four units of 37.5 MW and one unit of 30 MW. Units 1 and 2 of this powerhouse was commissioned between 1973, followed by 3 and 4 in 1981.

Cerro Prieto II
The CP2 powerhouse has a total installed capacity of 220 MW, generated by two 110 MW units which were commissioned in 1982.

Cerro Prieto III
The CP3 powerhouse has a total installed capacity of 220 MW, generated by two identical units as CP2, measuring 110 MW. This powerhouse was commissioned in 1983, a year after the commissioning of CP2.

Cerro Prieto IV
The CP4 station commenced operations in July 2000, and consists of four turbines, each with a capacity of 25 MW.

Cerro Prieto V
The CP5 station is the newest powerhouse of the Cerro Prieto station. It was proposed in July 2009, with the commencement of constructions in September 2009. CP5 will consist of two 50 MW units, increasing the total capacity of the Cerro Prieto Geothermal Power Station by 100 MW.

List of Geothermal Power Plants

noreply@blogger.com (Energetic) — Thu, 05 Aug 2010 20:32:00 +0000

The following page lists all the geothermal fuel power plants that are larger than 50 MW in nameplate capacity which are currently operational or under construction. Those power stations that are smaller than 50 MW, and those that are only at a planning/proposal stage may be found in regional lists, listed at the end of the page.

Station	Country	Capacity (MW)
Cerro Prieto Geothermal Power Station	Mexico	720
Hellisheidi Power Station	Iceland	400
Inyo Power Station	United States	272
Wayang Windu Geothermal Power Station	Indonesia	227
Salton Sea Power Station	United States	185
Wairakei Power Station	New Zealand	181
Calistoga Power Station	United States	176
Jermaghbyur Geothermal Power Plant	Armenia	150
Reykjanes Power Station	Iceland	150
Nga Awa Purua Power Station	New Zealand	132
Nesjavellir Geothermal Power Station	Iceland	120
Ohaaki Power Station	New Zealand	104
Centennial Drive Binary Plant	New Zealand	100
Kawerau Power Station	New Zealand	100
Svartsengi Geothermal Power	Iceland	77
Olkaria II Geothermal Power Plant	Kenya	70
Krafla Geothermal Power Station	Iceland	60
Serrazzano Power Station	Italy	60
Poihipi Power Station	New Zealand	55
Mutnovskaya Power Station	Russia	50

Geothermal Power Plant Technology

noreply@blogger.com (Energetic) — Sat, 05 Jun 2010 15:27:00 +0000

What are Geothermal Power Plants?

There are three geothermal power plant technologies being used to convert hydrothermal fluids to electricity. The conversion technologies are dry steam, flash, and binary cycle. The type of conversion used depends on the state of the fluid (whether steam or water) and its temperature. Dry steam power plants systems were the first type of geothermal power generation plants built. They use the steam from the geothermal reservoir as it comes from wells, and route it directly through turbine/generator units to produce electricity. Flash steam plants are the most common type of geothermal power generation plants in operation today. They use water at temperatures greater than 360°F (182°C) that is pumped under high pressure to the generation equipment at the surface. Binary cycle geothermal power generation plants differ from Dry Steam and Flash Steam systems in that the water or steam from the geothermal reservoir never comes in contact with the turbine/generator units.

Types of Geothermal Power Plants

Dry Steam Power Plants

Dry steam power plants in California.

This is the earliest form of geothermal power plant, which directs steam into turbines to produce electricity. Excess heat from the production well is channeled back into the reservoir via an injection well. This type of generator was first used in 1904, to generate electricity in Lardarello, Italy, where it still stands today, fully operational. The United States have also built dry steam power plants, including those in Northern California geysers.

Steam plants use hydrothermal fluids that are primarily steam. The steam goes directly to a turbine, which drives a generator that produces electricity. The steam eliminates the need to burn fossil fuels to run the turbine. (Also eliminating the need to transport and store fuels!) This is the oldest type of geothermal power plant. It was first used at Lardarello in Italy in 1904, and is still very effective. Steam technology is used today at The Geysers in northern California, the world's largest single source of geothermal power. These plants emit only excess steam and very minor amounts of gases.

Flash Steam Power Plants

Hot springs above 1750ºC may is used to power Flash Steam Power Plants. These hot fluids are channeled to a low pressure flash tank, magnifying its steam formation. This flash steam is then used to power turbines, activating the generator to produce electricity. Excess heat is returned to the reservoir by means of an injector well. One example of a flash steam power plant is the Cal-Energy Navy I, located in Coso Geothermal Field, California.

Hydrothermal fluids above 360°F (182°C) can be used in flash plants to make electricity. Fluid is sprayed into a tank held at a much lower pressure than the fluid, causing some of the fluid to rapidly vaporize, or "flash." The vapor then drives a turbine, which drives a generator. If any liquid remains in the tank, it can be flashed again in a second tank to extract even more energy.

Binary-Cycle Power Plants

This type of power plant use a completely different method compared with the above systems, where the steam from production wells does not directly come into contact with the turbines. Steam is used to heat working fluids in the heat exchanger, which then generates flash steam. This steam is then used to power the turbines and generator to produce electricity. Steam from the heat exchanger is what’s called Binary / Secondary Fluid. This is a closed loop system, where no excess heat is released into the air.

BCPP is able to be operated in low temperatures, between 90-1750ºC. One example of this technology is the Mammoth Pacific Binary Geo-Thermal Power Plants in Casa Diablo geothermal field. This technology is a glimpse of future geothermal technology, one that will be used in the future.

The Agency For the Assessment and Application Technology (BPPT) has built a prototype 2KW binary cycle power plant with hydrocarbon as its primary fluid. BPPT has also planned to develop small scale power plants between 2010-2014 which includes a 1 MW binary cycle power plant (targeted for 2014) through a 2 KW prototype (2008) and 100 KW pilot project (2012), and the development of condensing turbine power plant technology with a capacity of 2-5 MW (2011 and 2013).

Most geothermal areas contain moderate-temperature water (below 400°F). Energy is extracted from these fluids in binary-cycle power plants. Hot geothermal fluid and a secondary (hence, "binary") fluid with a much lower boiling point than water pass through a heat exchanger. Heat from the geothermal fluid causes the secondary fluid to flash to vapor, which then drives the turbines. Because this is a closed-loop system, virtually nothing is emitted to the atmosphere. Moderate-temperature water is by far the more common geothermal resource, and most geothermal power plants in the future will be binary-cycle plants.

The Future of Geothermal Electricity

Steam and hot water reservoirs are just a small part of the geothermal resource. The Earth's magma and hot dry rock will provide cheap, clean, and almost unlimited energy as soon as we develop the technology to use them. In the meantime, because they're so abundant, moderate-temperature sites running binary-cycle power plants will be the most common electricity producers.

Before geothermal electricity can be considered a key element of the U.S. energy infrastructure, it must become cost-competitive with traditional forms of energy. The U.S. Department of Energy is working with the geothermal industry to achieve $0.03 to $0.05 per kilowatt-hour. We believe the result will be about 15,000 megawatts of new capacity within the next decade.

source:http://www.geothermalpowerplant.com/

Resources of Geothermal Power Plant

noreply@blogger.com (Energetic) — Sat, 29 May 2010 02:09:00 +0000

The Earth's internal heat naturally flows to the surface by conduction at a rate of 44.2 terawatts, (TW,) and is replenished by radioactive decay of minerals at a rate of 30 TW. These power rates are more than double humanity’s current energy consumption from all primary sources, but most of it is not recoverable. In addition to heat emanating from deep within the Earth, the top ten meters of the ground accumulates solar energy (warms up) during the summer, and releases that energy (cools down) during the winter.

Beneath the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C per kilometre (km) of depth in most of the world. The conductive heat flux is approximately 0.1 MW/km² on average. These values are much higher near tectonic plate boundaries where the crust is thinner. They may be further augmented by fluid circulation, either through magma conduits, hot springs, hydrothermal circulation or a combination of these.

A geothermal heat pump can extract enough heat from shallow ground anywhere in the world to provide home heating, but industrial applications need the higher temperatures of deep resources. The thermal efficiency and profitability of electricity generation is particularly sensitive to temperature. The more demanding applications receive the greatest benefit from a high natural heat flux, ideally from using a hot spring. If no hot spring is available, the next best option is to drill a well into a hot aquifer. If no adequate aquifer is available, an artificial one may be built by injecting water to hydraulically fracture the bedrock. This last approach is called hot dry rock geothermal energy in Europe, or enhanced geothermal systems in North America. Much greater potential may be available from this approach than from conventional tapping of natural aquifers.

Estimates of the electricity generating potential of geothermal energy/geothermal power plant vary from 35 to 2000 GW depending on the scale of investments. Upper estimates of geothermal power plant resources assume enhanced geothermal wells as deep as 10 kilometres (6 mi), whereas existing geothermal wells are rarely more than 3 kilometres (2 mi) deep. Drilling at this depth is now possible in the petroleum industry, although it is an expensive process. The deepest research well in the world, the Kola superdeep borehole, is 12 kilometres (7 mi) deep. This record has recently been imitated by commercial oil wells, such as Exxon's Z-12 well in the Chayvo field, Sakhalin.

Environmental Impact of Geothermal Power Plant

noreply@blogger.com (Energetic) — Mon, 26 Apr 2010 15:34:00 +0000

Fluids drawn from the deep earth carry a mixture of gases, notably carbon dioxide (CO2), hydrogen sulfide (H2S), methane (CH4) and ammonia (NH3). These pollutants contribute to global warming, acid rain, and noxious smells if released. Existing geothermal electric power plants emit an average of 122 kg of CO2 per megawatt-hour (MW·h) of electricity, a small fraction of the emission intensity of conventional fossil fuel plants. Plants that experience high levels of acids and volatile chemicals are usually equipped with emission-control systems to reduce the exhaust. Geothermal power plants could theoretically inject these gases back into the earth, as a form of carbon capture and storage.

In addition to dissolved gases, hot water from geothermal sources may hold in solution trace amounts of toxic chemicals such as mercury, arsenic, boron, antimony, and salt. These chemicals come out of solution as the water cools, and can cause environmental damage if released. The modern practice of injecting spent geothermal fluids back into the Earth to stimulate production has the side benefit of reducing this environmental risk.

Direct geothermal heating systems will contain pumps and compressors, and the electricity they consume may come from a polluting source. This parasitic load is normally a fraction of the heat output, so it is always less polluting than electric heating. However, if the electricity is produced by burning fuels, then the net pollution of geothermal heating may be comparable to directly burning the fuel for heat. For example, a geothermal heat pump powered by electricity from a combined cycle natural gas plant would produce about as much pollution as a natural gas condensing furnace of the same size. Therefore the environmental value of direct geothermal heating applications is highly dependent on the emissions intensity of the neighboring electric grid.

Plant construction can adversely affect land stability. Subsidence has occurred in the Wairakei field in New Zealand and in Staufen im Breisgau, Germany. Enhanced geothermal systems can trigger earthquakes as part of hydraulic fracturing. The project in Basel, Switzerland was suspended because more than 10,000 seismic events measuring up to 3.4 on the Richter Scale occurred over the first 6 days of water injection.

Geothermal has minimal land and freshwater requirements. Geothermal plants use 3.5 square kilometres per gigawatt of electrical production (not capacity) versus 32 and 12 square kilometres for coal facilities and wind farms respectively. They use 20 litres of freshwater per MW·h versus over 1000 litres per MW·h for nuclear, coal, or oil.