Geothermal Power Plant Technology

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
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/

Read more...

Geothermal Energy : Advantages And Disadvantages

Geothermal energy is the energy obtained from the earth(geo) from the hot rocks present inside the earth. It is produced due to the fission of radioactive materials in the earth’s core and some places inside the earth become very hot. These are called hot spots. They cause water deep inside the earth to form steam. As more steam is formed, it gets compressed at high pressure and comes out in the form of hot springs which produces geothermal power.

To harness this geothermal energy, two holes are dug deep into the earth and cold water is pumped through the first one and steam comes out through the second long pipe which helps in generating electricity. The holes dug for harnessing geothermal energy result in lesser emission of greenhouse gases than due to burning of fossil fuels. Thus if used at a larger scale and more efficiently, it gives a hope to reduce global warming.

Geo-thermal energy is one of the rare forms of energy which is not directly or indirectly from solar energy. In areas where hot springs are found, hot springs baths are very common and enjoyable form of recreation. However, they need to be in a controlled environment since they cannot be accessed without proper supervision. We have earlier seen how it is harnessed, the process involved is a long and expensive one and not feasible in some areas.

Construction of geothermal energy plants can affect the seismic stability to a large extent. Even though there are lesser emissions, digging deep holes causes seismic disturbances which have led to earthquakes.

Now lets discuss advantages and disadvantages of Geothermal Energy.

Advantages of Geothermal Energy
1) It is a renewable source of energy.
2) By far, it is non-polluting and environment friendly.
3) There is no wastage or generation of by-products.
4) Geothermal energy can be used directly. In ancient times, people used this source of energy for heating homes, cooking, etc.
5) Maintenance cost of geothermal power plants is very less.
6) Geothermal power plants don't occupy too much space and thus help in protecting natural environment.
7) Unlike solar energy, it is not dependent on the weather conditions.

Disadvantages of Geothermal Energy
1) Only few sites have the potential of Geothermal Energy.
2) Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed.
3) Total generation potential of this source is too small.
4) There is always a danger of eruption of volcano.
5) Installation cost of steam power plant is very high.
6) There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs.
7) It may release some harmful, poisonous gases that can escape through the holes drilled during construction.

Keep Reading : http://www.ianswer4u.com/

Read more...

Geothermal Energy

Geothermal energy comes from within the earth. It may be the result of the decay of radioactive substances, chemical reactions, friction from the movement of the continents or heat present when the earth formed.

Most of this heat is at depths beyond the reach of current technology. One of the most famous examples of geothermal energy is the geyser Old Faithful in Yellowstone National Park in the United States.

The four basic forms of geothermal energy are dry steam, hot water (or wet steam), hot dry rock and geopressurized systems. Dry steam occurs only in a few places, but it is the only one of the forms that is in commercial use.

Dry steam
The Geysers plant north of San Francisco, California, uses dry steam to run turbine generators, producing more than 500 megawatts of electric power. Operators pipe dry steam from natural underground reservoirs through a conventional steam turbine generator to produce electricity. The system converts the steam to water in a condenser and returns the water to the earth.

Hot water
Hot rock far beneath the earth's surface heats underground water to temperatures up to 2,200 degrees Fahrenheit. Pressure keeps the water in liquid form. The hot water flows to the surface through wells. Deprived of its pressure, it becomes steam to drive a steam turbine directly or to heat another fluid to run a turbine. Hot water geothermal energy provides central heating for all the buildings in Reykjavik, Iceland.

Hot dry rock
Extracting energy from subterranean hot dry rock means introducing a heat exchange fluid (water) to carry the heat from the rock to the power plant. Scientists inject water deep into fractured hot rock. Then they use the heated water as geothermal water for conversion to useful energy.

Geopressurized systems
Reservoirs of hot water mixed with methane gas, trapped underground, offer the energy potentials of both pressure and burnable methane, as well as the heat energy available from any geothermal resource.

Read from : http://www.txucorp.com/

Read more...

What is geothermal energy?

Figure 1: Earth’s Temperatures

Geothermal energy is defined as heat from the Earth. It is a clean, renewable resource that provides energy in the U.S. and around the world in a variety of applications and resources. Although areas with telltale signs like hot springs are more obvious and are often the first places geothermal resources are used, the heat of the earth is available everywhere, and we are learning to use it in a broader diversity of circumstances. It is considered a renewable resource because the heat emanating from the interior of the Earth is essentially limitless. The heat continuously flowing from the Earth’s interior, which travels primarily by conduction, is estimated to be equivalent to 42 million megawatts (MW) of power, and is expected to remain so for billions of years to come, ensuring an inexhaustible supply of energy. (1)

Figure 2: The Formation of a Geothermal Reservoir

A geothermal system requires heat, permeability, and water. The heat from the Earth's core continuously flows outward. Sometimes the heat, as magma, reaches the surface as lava, but it usually remains below the Earth's crust, heating nearby rock and water — sometimes to levels as hot as 700°F. When water is heated by the earth’s heat, hot water or steam can be trapped in permeable and porous rocks under a layer of impermeable rock and a geothermal reservoir can form. This hot geothermal water can manifest itself on the surface as hot springs or geysers, but most of it stays deep underground, trapped in cracks and porous rock. This natural collection of hot water is called a geothermal reservoir.

Figure 3: Typical Direct Use Geothermal Heating System Configuration

1.3. What are the different ways in which geothermal energy can be used?

Geothermal energy can be used for electricity production, for commercial, industrial, and residential direct heating purposes, and for efficient home heating and cooling through geothermal heat pumps. For a video presentation on the different ways to use geothermal energy, visit http://geothermal.marin.org/video/vid_pt5.html.

Geothermal Electricity: To develop electricity from geothermal resources, wells are drilled into a geothermal reservoir. The wells bring the geothermal water to the surface, where its heat energy is converted into electricity at a geothermal power plant (see below for more information about the different types of geothermal electricity production).

Heating Uses: Geothermal heat is used directly, without involving a power plant or a heat pump, for a variety of applications such as space heating and cooling, food preparation, hot spring bathing and spas (balneology), agriculture, aquaculture, greenhouses, and industrial processes. Uses for heating and bathing are traced back to ancient Roman times. (2) Currently, geothermal is used for direct heating purposes at sites across the United States. U.S. installed capacity of direct use systems totals 470 MW or enough to heat 40,000 average-sized houses, according to the GeoHeat Center Web site, http://geoheat.oit.edu/.

The Romans used geothermal water to treat eye and skin disease and, at Pompeii, to heat buildings. Medieval wars were even fought over lands with hot springs. The first known "health spa" was established in 1326 in Belgium at natural hot springs. And for hundreds of years, Tuscany in Central Italy has produced vegetables in the winter from fields heated by natural steam. (See the Geothermal Education Office Web site, http://geothermal.marin.org/).

A few examples of geothermal direct use applications today are at the Idaho Capitol Building in Boise http://idptv.state.id.us/buildingbig/buildings/idcapital.html, Burgett Geothermal Greenhouses in Cotton City, New Mexico http://geoheat.oit.edu/directuse/all/dug0144.htm, and Roosevelt Warm Springs Institute for Rehab in Warm Springs, Georgia http://www.rooseveltrehab.org/index.php

Figure 4: Geothermal Heat Pump Diagram

Geothermal Heat Pumps (GHPs): Geothermal heat pumps take advantage of the Earth’s relatively constant temperature at depths of about 10 ft to 300 ft. GHPs can be used almost everywhere in the world, as they do not share the requirements of fractured rock and water as are needed for a conventional geothermal reservoir. GHPs circulate water or other liquids through pipes buried in a continuous loop, either horizontally or vertically, under a landscaped area, parking lot, or any number of areas around the building. The Environmental Protection Agency considers them to be one of the most efficient heating and cooling systems available.

Animals burrow underground for warmth in the winter and to escape the heat of the summer. The same idea is applied to GHPs, which provide both heating and cooling solutions. To supply heat, the system pulls heat from the Earth through the loop and distributes it through a conventional duct system. For cooling, the process is reversed; the system extracts heat from the building and moves it back into the earth loop. It can also direct the heat to a hot water tank, providing another advantage — free hot water. GHPs reduce electricity use 30–60% compared with traditional heating and cooling systems, because the electricity which powers them is used only to collect, concentrate, and deliver heat, not to produce it.
For more information about GHPs, please visit www.geoexchange.org and http://www.igshpa.okstate.edu.

Figure 5: Flash Power Plant Diagram

1.4. How does a geothermal power plant work?

There are four commercial types of geothermal power plants: a. flash power plants, b. dry steam power plants, c. binary power plants, and d. flash/binary combined power plants.

a. Flash Power Plant: Geothermally heated water under pressure is separated in a surface vessel (called a steam separator) into steam and hot water (called “brine” in the accompanying image). The steam is delivered to the turbine, and the turbine powers a generator. The liquid is injected back into the reservoir.

Figure 6: Dixie Valley, NV, Flash Plant

b. Dry Steam Power Plant: Steam is produced directly from the geothermal reservoir to run the turbines that power the generator, and no separation is necessary because wells only produce steam. The image below is a more simplified version of the process.

Figure 7: The Geysers, CA, Dry Steam Plant

Figure 8: Dry Steam Plant Diagram

c. Binary Power Plant: Recent advances in geothermal technology have made possible the economic production of electricity from geothermal resources lower than 150°C (302°F). Known as binary geothermal plants, the facilities that make this possible reduce geothermal energy’s already low emission rate to zero. Binary plants typically use an Organic Rankine Cycle system. The geothermal water (called “geothermal fluid” in the accompanying image) heats another liquid, such as isobutane or other organic fluids such as pentafluoropropane, which boils at a lower temperature than water. The two liquids are kept completely separate through the use of a heat exchanger, which transfers the heat energy from the geothermal water to the working fluid. The secondary fluid expands into gaseous vapor. The force of the expanding vapor, like steam, turns the turbines that power the generators. All of the produced geothermal water is injected back into the reservoir.

Figure 9: Binary Power Plant

Figure 10: Burdett, NV, Binary Power Plant

d. Flash/Binary Combined Cycle: This type of plant, which uses a combination of flash and binary technology, has been used effectively to take advantage of the benefits of both technologies. In this type of plant, the portion of the geothermal water which “flashes” to steam under reduced pressure is first converted to electricity with a backpressure steam turbine and the low-pressure steam exiting the backpressure turbine is condensed in a binary system.

Figure 11: Flash/Binary Power Plant Diagram

Figure 12: Puna, HI, Flash/Binary

For more information about the above four types of power plants, access GEA’s Environmental Guide or Surface Technology Report.

In addition to different power plant technologies in use today, additional applications and technologies continue to emerge. The following are some commonly discussed as areas of future development:

Enhanced Geothermal Systems (EGS): Although the deeper crust and interior of the Earth is universally hot, it lacks two of the three ingredients required for a naturally occurring geothermal reservoir: water and interconnected open volume for water movement. Producing electricity from this naturally occurring hot, but relatively dry rock requires enhancing the potential reservoir by fracturing, pumping water into and out of the hot rock, and directing the hot water to a geothermal power plant. Research applications of this technology are being pursued in the U.S., France, Australia, and elsewhere. (3) EGS is also sometimes referred to as Hot Dry Rock. See further discussion of EGS in section 3.2.

Mixed Working Fluid/ Kalina System: As of January 2009 the Kalina System was being used at two power plants. The first is a small demonstration power plant operated as part of Iceland's Husavik GeoHeat Project. The second plant to use the Kalina System is in Germany at the Unterhaching Power Station. The Kalina cycle uses an ammonia-water mixed working fluid for high efficiency. The Kalina cycle is only one of the possible mixed working fluid approaches to possibly achieving greater heat transfer efficiency and/or lower temperature production of power. (4)

Figure 13: Kalina Power Plant in Husavik, Iceland

Distributed Generation: Geothermal applications can be sized and constructed at geographically remote sites in order to meet on-site electricity demands. Examples of remote geothermal power systems are at Chena Hot Springs in Alaska and at the Rocky Mountain Oil and Gas Testing Center (RMOTC) in Wyoming. In the first, the unit powers a remote resort, in the second the power supplies electricity to operate an oil field. For more information about the Chena Hot Springs Project, visit http://www.geo-energy.org/plantdetails.aspx?id=46x. For more information about the RMOTC project, visit http://www.rmotc.doe.gov/.

Supercritical Cycles : Supercritical fluids are at a temperature and pressure that can diffuse through solids. A supercritical fluid such as carbon dioxide can be pumped into an underground formation to fracture the rock, thus creating a reservoir for geothermal energy production and heat transport. The supercritical fluid used to form the reservoir can heat up and expand, and is then pumped out of the reservoir to transfer the heat to a surface power plant or other application. An example of work in this area is the Iceland Deep Drilling Project, and for more information on this effort visit http://www.iddp.is.

Source : http://www.geo-energy.org/Basics.aspx

Read more...

How Geothermal Energy Works

Introduction
Heat from the earth can be used as an energy source in many ways, from large and complex power stations to small and relatively simple pumping systems. This heat energy, known as geothermal energy, can be found almost anywhere—as far away as remote deep wells in Indonesia and as close as the dirt in our backyards. Many regions of the world are already tapping geothermal energy as an affordable and sustainable solution to reducing dependence on fossil fuels, and the global warming and public health risks that result from their use. For example, more than 8,900 megawatts (MW) of large, utility-scale geothermal capacity in 24 countries now produce enough electricity to meet the annual needs of nearly 12 million typical U.S. households (GEA 2008a). Geothermal plants produce 25 percent or more of electricity in the Philippines, Iceland, and El Salvador. The United States has more geothermal capacity than any other country, with more than 3,000 megawatts in eight states. Eighty percent of this capacity is in California, where more than 40 geothermal plants provide nearly 5 percent of the state’s electricity.¹ In thousands of homes and buildings across the United States, geothermal heat pumps also use the steady temperatures just underground to heat and cool buildings, cleanly and inexpensively.

The Geothermal Resource
Below the Earth's crust, there is a layer of hot and molten rock called magma. Heat is continually produced there, mostly from the decay of naturally radioactive materials such as uranium and potassium. The amount of heat within 10,000 meters (about 33,000 feet) of Earth's surface contains 50,000 times more energy than all the oil and natural gas resources in the world.

The areas with the highest underground temperatures are in regions with active or geologically young volcanoes. These "hot spots" occur at plate boundaries or at places where the crust is thin enough to let the heat through. The Pacific Rim, often called the Ring of Fire for its many volcanoes, has many hot spots, including some in Alaska, California, and Oregon. Nevada has hundreds of hot spots, covering much of the northern part of the state.

These regions are also seismically active. Earthquakes and magma movement break up the rock covering, allowing water to circulate. As the water rises to the surface, natural hot springs and geysers occur, such as Old Faithful at Yellowstone National Park. The water in these systems can be more than 200°C (430°F).

Seismically active hotspots are not the only places where geothermal energy can be found. There is a steady supply of milder heat—useful for direct heating purposes—at depths of anywhere from 10 to a few hundred feet below the surface virtually in any location on Earth. Even the ground below your own backyard or local school has enough heat to control the climate in your home or other buildings in the community. In addition, there is a vast amount of heat energy available from dry rock formations very deep below the surface (4–10 km). Using a set of emerging technologies known as Enhanced Geothermal Systems (EGS), we may be able to capture this heat for electricity production on a much larger scale than conventional technologies allow.

If these resources can be tapped, they offer enormous potential for electricity production capacity. In its first comprehensive assessment in more than 30 years, the U.S. Geological Survey (USGS) estimated that conventional geothermal sources on private and accessible public lands across 13 western states have the potential capacity to produce 8,000–73,000 MW, with a mean estimate of 33,000 MW.² State and federal policies are likely to spur developers to tap some of this potential in the next few years. The Geothermal Energy Association estimates that 132 projects now under development around the country could provide up to 6,400 megawatts of new capacity.³ As EGS technologies improve and become competitive, even more of the largely untapped geothermal resource could be developed. The USGS study found that hot dry rock resources could provide another 345,100–727,900 MW of capacity, with a mean estimate of 517,800 MW. That means that this resource could one day supply nearly all of today’s U.S. electricity needs.⁴

Not only do geothermal resources in the United States offer great potential, they can also provide continuous baseload electricity. According to the U.S. National Renewable Energy Laboratory, the capacity factors of geothermal plants—a measure of the ratio of the actual electricity generated over time compared to what would be produced if the plant was running nonstop for that period—are comparable with those of coal and nuclear power.⁵ With the combination of both the size of the resource base and its consistency, geothermal can play an indispensable role in a cleaner, more sustainable power system.

How Geothermal Energy Is Captured
Geothermal springs for power plants. The most common current way of capturing the energy from geothermal sources is to tap into naturally occurring "hydrothermal convection" systems where cooler water seeps into Earth's crust, is heated up, and then rises to the surface. When heated water is forced to the surface, it is a relatively simple matter to capture that steam and use it to drive electric generators. Geothermal power plants drill their own holes into the rock to more effectively capture the steam.

There are three designs for geothermal power plants, all of which pull hot water and steam from the ground, use it, and then return it as warm water to prolong the life of the heat source. In the simplest design, the steam goes directly through the turbine, then into a condenser where the steam is condensed into water. In a second approach, very hot water is depressurized or "flashed" into steam which can then be used to drive the turbine.

In the third approach, called a binary system, the hot water is passed through a heat exchanger, where it heats a second liquid—such as isobutane—in a closed loop. The isobutane boils at a lower temperature than water, so it is more easily converted into steam to run the turbine. The three systems are shown in the diagrams below.

The choice of which design to use is determined by the resource. If the water comes out of the well as steam, it can be used directly, as in the first design. If it is hot water of a high enough temperature, a flash system can be used, otherwise it must go through a heat exchanger. Since there are more hot water resources than pure steam or high-temperature water sources, there is more growth potential in the heat exchanger design.

The largest geothermal system now in operation is a steam-driven plant in an area called the Geysers, north of San Francisco, California. Despite the name, there are actually no geysers there, and the heat that is used for energy is all steam, not hot water. Although the area was known for its hot springs as far back as the mid-1800s, the first well for power production was drilled in 1924. Deeper wells were drilled in the 1950s, but real development didn't occur until the 1970s and 1980s. By 1990, 26 power plants had been built, for a capacity of more than 2,000 MW.

Because of the rapid development of the area in the 1980s, and the technology used, the steam resource has been declining since 1988. Today, owned primarily by California- utility Calpine and with a net operating capacity of 725 MW, the Geysers facilities still meets nearly 60 percent of the average electrical demand for California's North Coast region (from the Golden Gate Bridge north to the Oregon border).⁶ The plants at the Geysers use an evaporative water-cooling process to create a vacuum that pulls the steam through the turbine, producing power more efficiently. But this process loses 60 to 80 percent of the steam to the air, without re-injecting it underground. While the steam pressure may be declining, the rocks underground are still hot. To remedy the situation, various stakeholders partnered to create the Santa Rosa Geysers Recharge Project, which involves transporting 11 million gallons per day of treated wastewater from neighboring communities through a 40-mile pipeline and injecting it into the ground to provide more steam. The project came online in 2003, and in 2008 provided enough additional electricity for approximately 100,000 homes. The city of Santa Rosa plans to further expand this program by increasing the amount of wastewater sent to the Geysers to nearly 20 million gallons per day.⁷

One concern with open systems like the Geysers is that they emit some air pollutants. Hydrogen sulfide—a toxic gas with a highly recognizable "rotten egg" odor—along with trace amounts of arsenic and minerals, is released in the steam. In addition, at a power plant at the Salton Sea reservoir in Southern California, a significant amount of salt builds up in the pipes and must be removed. While the plant initially started to put the salts into a landfill, they now re-inject the salt back into a different well. With closed-loop systems, such as the binary system, there are no emissions; everything brought to the surface is returned underground.

Direct use of geothermal heat. Geothermal springs can also be used directly for heating purposes. Hot spring water is used to heat greenhouses, to dry out fish and de-ice roads, for improving oil recovery, and to heat fish farms and spas. In Klamath Falls, Oregon, and Boise, Idaho, geothermal water has been used to heat homes and buildings for more than a century. On the east coast, the town of Warm Springs, Virginia obtains heat directly from spring water as well, using springs to heat one of the local resorts.⁸

In Iceland, virtually every building in the country is heated with hot spring water. In fact, Iceland gets more than 50 percent of its energy from geothermal sources.⁹ In Reykjavik, for example (population 115,000), hot water is piped in from 25 kilometers away, and residents use it for heating and for hot tap water.

Ground-source heat pumps. A much more conventional way to tap geothermal energy is by using geothermal heat pumps to provide heat and cooling to buildings. Also called ground-source heat pumps, they take advantage of the constant year-round temperature of about 50°F that is just a few feet below the ground’s surface. Either air or antifreeze liquid is pumped through pipes that are buried underground, and re-circulated into the building. In the summer, the liquid moves heat from the building into the ground. In the winter, it does the opposite, providing pre-warmed air and water to the heating system of the building.

In the simplest use of ground-source heating and cooling, a tube runs from the outside air, under the ground, and into a house's ventilation system. More complicated, but more effective systems use compressors and pumps—as in electric air conditioning systems—to maximize the heat transfer.

In regions with temperature extremes, such as the northern United States in the winter and the southern United States in the summer, ground-source heat pumps are the most energy-efficient and environmentally clean heating and cooling system available. Far more efficient than electric heating and cooling, these systems can move as much as 3 to 5 times the energy they use in the process. The U.S. Department of Energy found that heat pumps can save a typical home hundreds of dollars in energy costs each year, with the system typically paying for itself in 8 to 12 years. Tax credits and other incentives can reduce the payback period to 5 years or less.¹⁰

More than 600,000 ground-source heat pumps supply climate control in U.S. homes and other buildings, with new installations occurring at a rate of about 60,000 per year.¹¹ While this is significant, it is still only a small fraction of the U.S. heating and cooling market, and several barriers to greater penetration into the market remain. For example, despite their long-term savings, geothermal heat pumps have higher up-front costs. In addition, installing them in existing homes and businesses can be difficult, since it involves digging up areas around a building’s structure. Finally, many heating and cooling installers are just not familiar with the technology.

However, ground-source heat pumps are catching on in some areas. In rural areas without access to natural gas pipelines, homes must use propane or electricity for heating and cooling. Heat pumps are much less expensive to operate, and since buildings are widely spread out, installing underground loops is not an issue. Underground loops can be easily installed during construction of new buildings as well, resulting in savings for the life of the building. Furthermore, recent policy developments are offering strong incentives for homeowners to install these systems. The 2008 economic stimulus bill, Emergency Economic Stabilization Act of 2008, includes an eight year extension (through 2016) of the 30 percent investment tax credit, with no upper limit, to all home installations of EnergyStar certified geothermal heat pumps.¹²

The Future of Geothermal Energy
Geothermal energy has the potential to play a significant role in moving the United States (and other regions of the world) toward a cleaner, more sustainable energy system. It is one of the few renewable energy technologies that—like fossil fuels—can supply continuous, baseload power. The costs for electricity from geothermal facilities are also declining. Some geothermal facilities have realized at least 50 percent reductions in the price of electricity since 1980. A considerable portion of potential geothermal resources will be able produce electricity for as little as 8 cents per kilowatt-hour (including a production tax credit), a cost level competitive with new conventional fossil fuel-fired power plants.¹³ There is also a bright future for the direct use of geothermal resources as a heating source for homes and businesses in any location. However, in order to tap into the full potential of geothermal energy, two emerging technologies require further development: Enhanced Geothermal Systems (EGS) and co-production of geothermal electricity in oil and gas wells.

Enhanced Geothermal Systems. Geothermal heat occurs everywhere under the surface of the earth, but the conditions that make water circulate to the surface are found only in less than 10 percent of Earth's land area. An approach to capturing the heat in dry areas is known as enhanced geothermal systems (EGS) or "hot dry rock". The hot rock reservoirs, typically at greater depths below the earth’s surface than conventional sources, are first broken up by pumping high-pressure water through them. The plants then pump more water through the broken hot rocks, where it heats up, returns to the surface as steam, and powers turbines to generate electricity. Finally, the water is returned to the reservoir through injection wells to complete the circulation loop. Plants that use a closed-loop binary cycle release no fluids or heat-trapping emissions other than water vapor, which may be used for cooling.¹⁴

The Department of Energy, several universities, the geothermal industry, and venture capital firms (including Google) are collaborating on research and demonstration projects to harness the potential of hot dry rock. Australia, France, Germany, and Japan also have R&D programs to make EGS commercially viable. The DOE hopes to have EGS ready for commercial development by 2015 and is currently funding several demonstration projects.


One cause for careful consideration with EGS is the possibility of induced seismic activity that might occur from hot dry rock drilling and development. This risk is similar to that associated with hydraulic fracturing, an increasingly used method of oil and gas drilling, and with carbon dioxide capture and storage in deep saline aquifers. Though a potentially serious concern, the risk of an induced EGS-related seismic event that can be felt by the surrounding population or that might cause significant damage currently appears very low when projects are located an appropriate distance away from major fault lines and properly monitored. Appropriate site selection, assessment and monitoring of rock fracturing and seismic activity during and after construction, and open and transparent communication with local communities are also critical.

Co-production of Geothermal Electricity in Oil and Gas Wells. Oil and gas fields already under production represent another large potential source of geothermal energy. In many existing oil and gas reservoirs, a significant amount of high-temperature water or suitable high-pressure conditions are present, which could allow for the production of electricity and oil or gas at the same time. In some cases, exploiting these resources could even enhance the extraction of the oil and gas itself. An MIT study estimated that the United States has the potential to develop 44,000 MWs of geothermal capacity by 2050 by co-producing electricity, oil, and natural gas at oil and gas fields—primarily in the Southeast and southern Plains states. The study projects that such advanced geothermal systems could supply 10 percent of U.S. baseload electricity by that year, given R&D and deployment over the next 10 years.¹⁵

These exciting new developments in geothermal will be supported by unprecedented levels of federal R&D funding. Under, the American Recovery and Investment Act of 2009, $400 million of new funding was allocated to the DOE’s Geothermal Technologies Program. Of this $90 million is expected to go towards a series of up to 10 demonstration projects to prove the feasibility of EGS technology. Another $50 million will fund up to 20 demonstration projects for other new technologies, including co-production with oil and gas and low temperature geothermal. The remaining funds will go exploration technologies, expanding the deployment of geothermal heat pumps, and other uses. These investments will very likely produce great net benefits in the future.¹⁶

Endnotes:
1. Geothermal Energy Association (GEA) 2009. U.S. Geothermal Power Production and Development Update.
2. Williams, C.F., M.J. Reed, R.H. Mariner, J. DeAngelo, and S.P.Galanis Jr. 2008. Assessment of moderate- and high-temperature geothermal resources of the United States. U.S. Geological Survey fact sheet 2008-3082, 4. Washington, DC: U.S. Department of the Interior
3. See Note 1.
4. See Note 2.
5. National Renewable Energy Laboratory. Energy Technology Cost and Performance Data.
6. Calpine. The Geysers.
7. City of Santa Rosa, CA. Geysers Expansion.
8. Virginia Tech. Hot Springs in the Southeastern United States.
9. National Energy Authority and Iceland Ministry of Industries and Commerce. 2004. Energy In Iceland: Historical Perspective, Present Status, Future Outlook.
10. Department of Energy – Oak Ridge National Laboratory (ORNL). 2008. Geothermal (Ground-Source) Heat Pumps: Market Status, Barriers to Adoption, and Actions to Overcome Barriers. Report ORNL/TM-2008/232.
11. Ibid
12. Energy Star. Federal Tax Credits for Energy Efficiency.
13. California Energy Commission ( CEC) (June 2003). Comparative Cost of California Central Station Electricity Generation Technologies, Final Staff Report.
14. Office of Energy Efficiency and Renewable Energy (EERE). 2008a. An evaluation of enhanced geothermal systems technology. Washington, DC: U.S. Department of Energy.
15. Tester, J. et al. 2006. The Future of Geothermal Energy: Impact of Enhanced Geothermal Systems (EGS) on the United States in the 21st Century. Massachussetts Institute of Technology and Idaho National Laboratory.
16. See Note 1.

Source : http://www.ucsusa.org/clean_energy/technology_and_impacts/energy_technologies/how-geothermal-energy-works.html

Read more...

Geothermal Energy: Intelligent Use Of The Earth’s Heat

Geothermal energy falls under the category of renewable energy source because the water is replenished by rainfall and the heat is continuously produced inside the earth. Geothermal energy is derived from heat within the earth. People can use the steam and hot water created inside the earth to heat buildings or produce electricity. Wondering what makes the water so hot? Geothermal energy is produced in the earth’s core.



People utilize geothermal energy to heat their homes and to produce electricity. This is achieved by digging deep wells and pumping the heated underground water or steam to the surface. But we can also use the stable temperatures near the surface of the earth to heat and cool buildings.

Dr. Ernst Huenges is the head of Geothermal Research at the institute GFZ – German Research Centre for Geosciences. He is of the opinion, “The new methods deliver important decision-support for the selection of sites for future geothermal projects. With this we can considerably reduce the risk of expensive misdrills,”

Geothermal energy is making its presence felt worldwide and Iceland is the best example of the utilization of geothermal power. In fact Iceland leads the world in the development of geothermal utilization. They have doubled their annual power supply capping it up around 500 MW as far as electricity supply is concerned. Germany is also emerging as a major user of geothermal energy. Germany is deriving its 100 MW of heat from geothermal energy. Italy is not far behind. A team of European scientists, in the region of Travale (Italy), is planning to tap the potential of localized geothermal reservoirs. If this project is completed it will produce energy akin to a potential of around 1,000 wind power plants. This is one of the projects discussed at the international final conference of “I-GET” (Integrated Geophysical Exploration Technologies for deep fractured geothermal systems) in Potsdam.

The European Union is also feeling the “heat” of geothermal energy. European nations are waking up to the potential of geothermal energy. This conference aimed at the development of state-of-the art technology with potential geothermal reservoirs. Seven European nations participated in this “I-GET” conference. They want to explore more and more geothermal reservoirs and utilize it for clean and green energy. The project “I-GET” could be a substantial step towards renewable energy source.

The newly developed techniques have been tried at four European geothermal locations. They are combining different geological and thermo¬dynamic conditions. High-temperature reservoirs have been examined in Travale/Italien having metamorphic rocks and in Hengill/Island (volcanic rocks). They are also examining two deposits with medium-temperature in deep sediment rocks in Groß-Schönebeck/Germany and Skierniewice/Poland.

The implications of the results of “I-GET” would be felt worldwide. Geothermal experts from Indonesia, New Zealand, Australia, Japan and the USA also participated in the “I-GET” project. There were 120 scientists and industry representatives from the 20 countries.

“Reliable geothermal technologies are in demand worldwide. Even countries with a long experience in geothermal energy such as Indonesia and New Zealand are interested in the results acquired in I-GET,” says Dr. Ernst Huenges. Therefore, we hope that this “I-GET” will give the necessary push to the geothermal research. GFZ is currently establishing an International Centre for Geothermal Research, which will, focus on carrying out application-oriented large-scale projects on a national and international level.

Source : http://www.alternative-energy-news.info/geothermal-energy-intelligent-use-of-earths-heat/

Read more...

Geothermal Powers New Zealand’s Needs

Ask most Americans what geothermal energy is and you’re likely to get some quizzical looks. But in New Zealand, it would appear, the adoption and installation of geothermal systems is at an all-time high.

This information comes courtesy of New Zealand’s Minister of Energy and Resources, Gerry Brownlee, based on the June 2010 quarter energy data published in the latest edition of the Ministry of Economic Development’s New Zealand Energy Quarterly. The main use of geothermal energy in the country is for electricity generation (according to the Ministry of Economic Development’s Energy Outlook Reference Scenario, geothermal is currently the most economic option for new electricity generation in New Zealand). In 2009, electricity generation from geothermal accounted for over 10% of New Zealand’s total electricity supply, and that number is expected to increase substantially over the next 25 years.

According to the government of New Zealand, the country has easily accessible and large geothermal resources (as do many other countries with a significant landmass situated on the Pacific Rim). Currently, most of New Zealand’s installed geothermal generation capacity (about 600 megawatts) is situated in the Taupo Volcanic Zone, with another 25 MW installed at Ngawha in Northland. These installations utilize either dry steam, flash steam or binary cycle (or a combination of technologies) to create electricity, based on the temperature and conditions of particular geothermal reservoirs.

“Geothermal is a significant source of electricity generation in New Zealand, and made up over 13 per cent of total generation in the June quarter,” said Mr Brownlee, in a statement. “With a number of new geothermal projects in the pipeline, this will continue to grow.” Other highlights from this quarter’s New Zealand Energy Quarterly include the fact that renewable generation currently accounts for 73% of New Zealand’s total electricity generation, and that, in the remaining 27%, gas has now displaced coal–a combination of factors that have caused the country’s greenhouse gas emissions due to electricity generation to drop to their lowest level since 2000.

Source : http://www.tomorrowisgreener.com/geothermal-powers-new-zealand%E2%80%99s-needs/

Read more...