Geothermal Information

"Geothermal" comes from the Greek words geo (earth) and thermal (heat). So, geothermal means earth heat. People around the world use geothermal energy to produce electricity, to heat buildings and greenhouses, and for other purposes.

About Geothermal Energy
About Wind Energy
About Solar Energy
About Waste Heat Recovery

About Geothermal Energy

History of Geothermal

From earliest times, people have used geothermal water that flowed freely from the earth's surface as hot springs. The oldest and most common use was, of course, just relaxing in the comforting warm waters. The Romans used geothermal water to heat buildings in the city of Pompeii.

In North America geothermal energy was used as early as 10,000 years ago. Paleo-Indians used hot springs for cooking and medicine. For centuries the Maoris of New Zealand have cooked "geothermally," and, since the 1960s, France has been heating up to 200,000 homes using geothermal water.

Prince Piero Ginori Conti invented the first geothermal power plant in 1904, at the Larderello dry steam field in Italy.

First geothermal power plant, 1904, Lardarello, Italy.

In 1921, John D. Grant tried to develop geothermal power in the United States at The Geysers steam field in northern California. The project failed because the pipes and turbines of the day could not stand up to the abrasion and corrosion of the particles and impurities that were in the steam. However, the next year at another site across the valley, Grant becomes successful and began producing 250 kilowatts to light up the buildings and streets at a resort.

In 1960, the country's first large-scale geothermal electricity-generating plant begins operation. Pacific Gas and Electric operates the plant, located at The Geysers. The first turbine produces 11 megawatts (MW) of net power and operates successfully for more than 30 years.

Advantages of Geothermal Energy

What Makes a Good Site for Geothermal Electric Development?

The most active geothermal resources are usually found along major plate boundaries where earthquakes and volcanoes are concentrated. Most of the geothermal activity in the world occurs in an area known as the "Ring of Fire." The Ring of Fire rims the Pacific Ocean and is bounded by Japan, the Philippines, the Aleutian Islands, North America, Central America, and South America.

Hydrothermal resources are used for different energy purposes depending on their temperature and how deep they are. These resources can be classified as low temperature (less than 90°C or 194°F), moderate temperature (90°C - 150°C or 194 - 302°F), and high temperature (greater than 150°C or 302°F). The highest temperature resources are generally used only for electric power generation where the low and moderate temperature resources are used for "direct use" and ground-source heat pumps.

In the United States, geothermal heat pumps are used in 45 states to heat and cool homes and buildings. Twenty six states are offering heat pump incentives. Idaho, Oregon, Nevada, and some other states use geothermal energy to heat entire districts. Over 2,800 megawatts of electricity is produced from geothermal power plants.

U.S. Geothermal Resource Map

The geothermal resources map of the United States below shows the estimated subterranean temperatures at a depth of 6 kilometers. To determine the Earth's internal temperature at any depth below the capabilities of normal well drilling, multiple data sets are synthesized. The data used for this figure are: thermal conductivity, thickness of sedimentary rock, geothermal gradient, heat flow, and surface temperature. Also see geothermal resource maps. http://www1.eere.energy.gov/geothermal/maps.html

Source: EERE http://www1.eere.energy.gov/geothermal/geomap.html

For more information on where geothermal resources are located please visit the Geo-Heat Center http://geoheat.oit.edu/colres.htm.

Geothermal Sources of Information

US Department of Energy (US DOE) http://www.energy.gov/energysources/geothermal.htm
US DOE Energy Efficiency & Renewable Energy (EERE) http://www.eere.energy.gov/
Geo-Heat Center http://geoheat.oit.edu/index.htm
Geothermal Education Office http://geothermal.marin.org/
Geothermal Resource Council http://www.geothermal.org/index.html

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About Wind Energy

Winds are created by uneven heating of the atmosphere by the sun, irregularities of the Earth's surface, and the rotation of the Earth. As a result, winds are strongly influenced and modified by local terrain, bodies of water, weather patterns, vegetative cover, and other factors.

History of Wind Use

As far back as 5000 B.C. wind was being harnessed to help propel boats along the Nile River. In 200 B.C., simple windmills in China were pumping water, while vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East. By the 11th century, people began using windmills for food production. In the late 19th century, windmills were being used to pump water for farms and ranches, and later, to generate electricity for homes and industry. Industrialization sparked the development of larger windmills to generate electricity that are commonly called wind turbines. These turbines appeared in Denmark as early as 1890. In 1940, Vermont began operating the largest wind turbine of its time producing 1.25 megawatts in winds about 30 mph.

Present Day

With the lessons learned and continuing R&D, wind-generated electricity is very close in cost to the power from conventional utility generation in some locations.

The U.S. Department of Energy has announced a goal of obtaining 6% of U.S. electricity from wind by 2020--a goal that is consistent with the current rate of growth of wind energy nationwide. As public demand for clean energy grows, and as the cost of producing energy from the wind continues to decline, it is likely that wind energy will provide a growing portion of the nation's energy supply.

One megawatt of wind capacity is enough to supply 240 to 300 average American homes.

About 6,740 megawatts of wind power capacity were installed in the U.S. (as of January 2005), generating over 17 billion kilowatt-hours annually. That is as much electricity as about 1.6 million average American households (with 4.3 million people) use each year.

Advantages of Wind Energy

Classes of Wind Power

The wind flow, or motion of energy when harvested by wind turbines, can be used to generate electricity. Wind-based electricity generating capacity has increased markedly in the United States since 1970, although it remains a small faction of total electric capacity.

Source: DOE Energy Information Administration (EIA)
http://www.eia.doe.gov/cneaf/solar.renewables/page/wind/wind.html

Installed US Wind Capacity

The graph below from American Wind Energy Association provides a chart showing historical cumulative capacity.

Click on link to enlarge http://www.awea.org/faq/instcap.html

For additional maps and websites for information regarding installed and planned wind capacity, please visit: http://www.eere.energy.gov

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How a Wind Turbine Works

A wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity.

The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.

The diagram below shows some of the pieces and parts inside a wind turbine:

Wind turbines have an emergency shut-off if a wind storm or tornado happens. You can see a wind turbine in action at the U.S. Department of Energy Web site: Wind Turbine Animation http://www1.eere.energy.gov/windandhydro/wind_animation.html

Small Wind Turbine Market

Small wind, defined as 100kW capacity or less, has experienced major growth in the past decade. The market for small wind recently grew 35% in a single year and the industry has set ambitious growth targets continuing at 18-21% through 2010. The U.S. is a leading producer of small wind turbines, with one-third of the world market commanded by four U.S. producers. AWEA predicts continued growth in this market that has about 45 MW of installed capacity in small wind turbines domestically, and makes 50% of its sales in foreign markets.

For a List of Wind Energy Resource Atlas of the United States Please Visit http://rredc.nrel.gov/wind/pubs/atlas/maps.html

Wind Energy Sources
US Department of Energy (US DOE) http://www.energy.gov/energysources/wind.htm
UD DOE Energy Information Administration (EIA) http://www.eia.doe.gov/
Alliant Energy http://www.alliantenergykids.com
American Wind Energy Association (AWEA) http://www.awea.org/
Renewable Resource Data Center (RReDC) http://rredc.nrel.gov/

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About Solar Energy

The word solar stems from the Roman word for the god of the sun, Sol. Therefore, the word solar refers to the Sun and "solar power" is power from the Sun. The sun provides us with two major forms of energy, heat and light. Some solar powered systems utilize the heat energy for heating while others transform the light energy into electrical energy (electricity).

History of Solar Thermal Energy

In the 1760's a Swiss inventor, Horace de Saussure captured the sun in a "hot box" made of glass, with two boxes inside. When exposed to the sun, the bottom box heated to 228 degrees F (109 degrees C) or 16 degrees F (9 degrees C) above the boiling point of water. Little did he know that his invention has become the prototype for the solar collectors that have provided sun-heated water to millions since 1892.

In nineteenth century, there were little natural resources for heating water. Wood and coal was being used for heating purposes, but even this proved to be difficult as wood and coal or coal-gas cost a lot and could be difficult to obtain. Farmers and others began using painted black metal water tanks to absorb as much solar energy as possible. This was the first solar water heaters on record. However, this technique took a long time to heat the water (up to a half day) and the water would rapidly cool at night.

In 1891, Baltimore entrepreneur Clarence Kemp became the first man to patent a solar thermal system. Kemp combined the old practice of exposing metal tanks to the sun with the scientific principle of the hot box, thereby increasing the tanks' capability to collect and retain solar heat. Kemp successfully marketed his invention to homes on the east coast. In California and other temperate states with more sunshine, this technology proved to a great asset. In 1897, a third of the homes in Pasadena, CA were heated by the sun.

In 1909, William Bailey patented his solar water heating system that separated the storage tank from an element that collected heat from the sun. Bailey's heating element consisted of pipes attached to a black-painted metal sheet placed in a glass-covered box. Because the water to be heated passed through narrow pipes rather than sat in a large tank, Bailey reduced the volume of water exposed to the sun at any single moment and therefore, the water heated up faster. By 1918, Bailey had sold over 4,000 of his Day and Night Solar Hot Water Heaters.

During the 1920's, the discovery of natural gas in the basin of Las Angeles, California effectively killed the solar thermal industry there. However, as California solar took a hit with the discovery of natural gas, Florida in the 1920's saw a building boom. The high cost of energy, along with the tropical weather made conditions strong for the solar water heaters. By 1941, over half the homes used solar to heat water. After World War II, declining electricity rates put a stop to Florida's solar thermal industry.

Today, the solar energy market is making another comeback due to the rising oil costs, environmental concerns, and shrinking solar thermal costs.

Advantages of Solar Energy

Electrical Generation

The generation of electricity from solar energy can be achieved through two major technology alternatives. One uses the light from the sun to generate electricity directly, (photovoltaic technologies), and the other uses the heat from the sun to increase the temperature of a working fluid which-in turn can be used to generate electricity, (solar thermal technologies). Each of these major alternatives can, in turn, be subdivided into variants of the major technology. Photovoltaic technologies fall into crystalline, multi-crystalline, thin-film or concentrator variants while the solar thermal technologies fall into trough, power tower, dish engine and thermal electric variants.

Photovoltaics

Generally speaking, photovoltaic solar cells use a semiconductor material that is exposed to sunlight. The energy of the incident light displaces electrons from their normal atomic orbits and an electrode grid structure on the surface of the semiconductor collects these electrons and makes them available for use in an external circuit. This is very similar to the way that the chemical reaction and the electrodes in a dry battery cell make electrons available for external use.

The terms crystalline, thin film and concentrator describe the manner in which the semi-conducting material is processed and optimized as a photovoltaic cell. Crystalline cells are fabricated from ingots of the semiconductor material, usually silicon that are cut into relatively thin slices, processed to optimize the electron collection efficiency and laminated into a protective enclosure. Thin film cells are extremely thin layers of semi-conducting material that are evaporated onto a substrate, and concentrating cells use a plastic lens to concentrate sunlight from a large area onto a much smaller area of crystalline semi-conducting material. All types have their merits and problems and are described in detail in the referenced locations.

Solar-thermal

Both the trough and power tower solar thermal technologies use mirrors to concentrate the heat from the sun onto a vessel containing a heat transfer fluid. The fluid is then pumped into a steam generator where the heat is transferred to water turn it into steam. The steam can then be used to spin a conventional steam turbine connected to a generator to make electricity.

In the case of the trough, the mirror is a long parabola with a steel tube containing the heat transfer fluid running along the focal axis of the mirror. The axis of the mirror is usually aligned in a North-South direction and the mirror is rotated from East to West as the day progresses so that the energy from the sun is continually focused onto the steel tube. Rows of mirror/tube assemblies are used to form large multi-acre solar fields from which the heated transfer fluid is collected and used in the generation of steam.

The power tower system is a little different in that all of the transfer fluid heating is achieved in a heat receiver on the top of a tower located in the center of a field of computer controlled mirrors, or heliostats. Cold fluid is pumped up to the top of the tower, the heliostats focus the sun's energy onto the receiver and heat the fluid which is subsequently returned to the ground and used in a steam generator in the same way as the heat transfer fluid in the trough system.

Dish/engine systems are somewhat different in that the heat from the sun is used to heat a working fluid within a heat engine. The rotating shaft of the engine is connected to a generator, which produces electricity without the need to go through a steam generation process. The engine is located at the focal point of a parabolic dish mirror, which is made to track the sun across the sky throughout the day.

Solar Thermal Costs

Solar Map

Solar Energy Sources
California Solar Center http://www.californiasolarcenter.org/history_solarthermal.html
Home Solar Panels http://www.solarhome.org/infoadvantagesofsolarenergy.html
Arizona Solar Center http://www.azsolarcenter.com/technology/electric.html
Renewable Energy Policy Project http://www.crest.org/articles/static/1/994186938_2.html
National Renewable Energy Laboratory http://www.eere.energy.gov/states/alternatives/csp.cfm

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About Waste Heat Recovery

Waste heat is heat generated in a process by way of fuel combustion or chemical reaction and then released (called "exhaust heat") into the environment even though it could still be reused for some useful and economic purpose. The strategy of how to recover this heat depends in part on the temperature of the waste heat gases and the economics involved. Examples of use would be preheating of combustion air, space heating/district space heating, space cooling/district space cooling, pre-heating boiler feed water or process water, dehydration.

Advantages of Waste Heat Recovery

Methods for Heat Recovery

Common methods of heat recovery include direct heat, recuperators, regenerators, and waste heat boilers.

It is necessary to evaluate the selected waste heat recovery system on the basis of financial analysis such as investment, depreciation, payback period, rate of return etc. to determine which recovery technique is right for your operation.

Direct heat recovery to the product

In this system, the higher temperature exhaust gases are brought into contact with a relatively cool incoming load. The energy will be transferred to the incoming load, preheating it and reducing the energy that finally escapes with the exhaust. Often, a transfer takes place such as combustion air to the burner system. This reduces the amount of purchased fuel required to sustain the process. According to the Department of Energy (DOE) this is the most efficient method.

Recuperators

Gas-to-gas heat exchanger placed on the stack of the furnace. These rely on tubes or plates to transfer heat from the outgoing exhaust gas to the incoming combustion air, while keeping the two streams from mixing. According to the Department of Energy (DOE), recuperators are the most widely used heat recovery devices.

Regenerators

An insulated container filled with metal or ceramic shapes capable of absorbing and storing relatively large amounts of thermal energy (basically a rechargeable storage device for heat). During part of the operating cycle, process exhaust gases flow through the regenerator, heating the storage medium. After a while, the medium becomes fully charged, so the exhaust flow is shut off and cold combustion air is admitted to the unit. As it passes through, the air extracts heat from the storage medium, increasing in temperature before it enters the burners. Eventually, the heat stored in the medium is drawn down to the point where it's necessary to recharge the regenerator.

Waste Heat Boilers

They are similar to conventional boilers with one exception-they are heated by the exhaust gas stream from a process furnace instead of their own burners. Waste heat boilers are of most value to process industries that require large amounts of steam in their process. The steam generated from a waste heat stream will not generally replace existing boilers but will supplement the steam that they produce, thereby reducing the energy cost to operate the direct-fired boilers. As the steam from a waste heat stream is available only when the process is running, waste heat boilers are generally designed to operate with existing boilers or with steam generators in a combination system.

Cogeneration

Also known as combined heat and power or CHP. This power is an efficient, clean, and reliable approach to generating power and thermal energy from a single fuel source. These efficient systems recover heat that normally would be wasted in an electricity generator, and save the fuel that would otherwise be used to produce heat or steam in a separate unit. This energy is used to provide cooling or heating for industrial facilities, district energy systems, and commercial buildings. Under common circumstances, CHP systems will achieve efficiencies exceeding 70%. CHP systems achieving efficiencies exceeding 80% are frequent, and some systems have been shown to reach levels in excess of 90%. CHP systems higher efficiencies reduce air emissions of nitrous oxides, sulfur dioxide, mercury, particulate matter, and carbon dioxide, the leading greenhouse gas associated with climate change.

According to the United States Combined Heat & Power Association, present CHP systems:

Trigeneration

Also know as CHCP (combined heating, cooling and power generation). The energy producing scheme recovering "waste" heat to cooling energy is comprised by CHP systems combined with absorption chillers. The absorption chillers utilize the heat from the cogeneration process. The chillers rely on condensation and evaporation to produce cooling.

Industry Plant Managers & Engineers

Below are "20 ways to save energy now" according to the U.S. Department of Energy - Energy Efficiency and Renewable Energy.

All Combustion Systems

1. Operate furnaces and boilers at or close to design capacity
2. Reduce excess air used for combustion
3. Clean heat transfer surfaces
4. Reduce radiation losses from openings
5. Use proper furnace or boiler insulation to reduce wall heat losses
6. Adequately insulate air or water-cooled surfaces exposed to the furnace environment and steam lines leaving the boiler
7. 7. Install air preheat or other heat recovery equipment

Steam Generation Systems

1. Improve water treatment to minimize boiler blowdown
2. Optimize deaerator vent rate
3. Repair steam leaks
4. Minimize vented steam
5. Implement effective steam trap maintenance program
6. Use high-pressure condensate to make low-pressure steam
7. Utilize backpressure turbine instead of pressure-reducing or release valves
8. Optimize condensate recovery

Process Heating Systems

1. Minimize air leakage into the furnace by sealing openings/li>
2. Maintain proper, slightly positive furnace pressure
3. Reduce weight of or eliminate material handling fixtures
4. Modify the furnace system or use a separate heating system to recover furnace exhaust gas heat
5. Recover part of the furnace exhaust heat for use in lower-temperature processes

Waste Heat Sources

Department of Energy - Energy Efficiency & Renewable Energy (EERE):
http://www.eere.energy.gov/industry/bestpractices/energymatters/articles.cfm/article_id=106

The National Certification Examination for Energy Managers and Energy Auditors (NCEEMEA):
http://www.em-ea.org/Guide%20Books/book-2/2.8%20Waste%20Heat%20Recovery.pdf

United States Combined Heat & Power Association
http://uschpa.admgt.com/index.html

Process Heating:
http://www.process-heating.com/CDA/Archives/8b6e827d50368010VgnVCM100000f932a8c0

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