Introduction • Running out of traditional energy sources such as hard coal, natural gas and crude oil makes us contemplate the future ofworld power industry. • Today’s high standard of life of the industrialized world inhabitants is possible only thanks to the use of energy. • It makes free transport and import of goods from different corners of the world possible. • Constant supply of energy ensures the development of science and technology, theimprovement of medical care. • Finally it lets us enjoy common (from the young generation’s point of view) amenities such as electricity or central heating in the comfort of our own home.
What is geothermal energy ? • Geothermal energy is one of the renewable energy sources. • It relies onthe use of the heat from the earth, mainly in the areas of volcanic and seismic activity. • Rainwater filters in the Earth’s interior where in contact with magma intrusion or active magma focus it heats up to considerable temperature. • As a result it travels to the surface of the Earth as hot water or water steam.
What is Geothermal Energy? Geo:(Greek) - Earth Thermal: Of, relating to, using, producing, or caused by heat.
The Earth • Parts of the earth • Flow of magma • Below surface temperatures gradient from hot to cold • Heat can be ejected as steam or hot water. • Hydrothermal reservoirs, water and hot porous rock. • Yellowstone National Park
Energy, where from? • The Earth’s interior with the temperature of 5400 degrees Celsius, generating the heat flow towards the surface, is the source of geothermal energy. • At first the Earth’s interior heat came from the gravitational contraction during the planet formation. • Nowadays, the most heat (45 to 90%) comes from radioactive decay of potassium and uranium isotopes. • The sources of energy are also party caused by the cooling of the mantle, the inner clash caused by liquid forces and changes in the speed of the Earth rotation. • Some of the inner core thermal energy is transported to the Earth’s crust through the mantle plume, which can cause hotspots and flood basalts.
Geothermal energy sources • Soil and rocks to a depth of 2500m, from which heat for heating purposes using heat pumps is charged with special probes called heat probes • Lower ground water as a heat source for heating pumps used for heating • Hot and warm water, extracted with drilled holes (in the case of water mineralization they are injected back after the use • Water vapor, extracted by means of boreholes which is applicable in geothermal power plants for electricity generation • Salt domes- the energy is discharged through the brine or salt neutral liquids, mainly hydrocarbons, eg isobutane • Hot rocks, from which the energy is received by circulating water under high pressure through a system of natural or artificial crevices in rocks at great depth • This energy is used in geothermal power plants to generate electricity and heating.
Heat from the Earth’s Center • Earth's core maintains temperatures in excess of 5000°C – Heat radial radioactive decay of elements • Heat energy continuously flows from hot core – Conductive heat flow – Convective flows of molten mantle beneath the crust. • Mean heat flux at earth's surface – 16 kilowatts of heat energy per square kilometer – Dissipates to the atmosphere and space. – Tends to be strongest along tectonic plate boundaries • Volcanic activity transports hot material to near the surface – Most is left at depths of 5-20 km beneath the surface, • Hydrological convection forms high temperature -Geothermal systems at shallow depths of 500-3000m.
The use of geothermal energy in the EU • In the European Union geothermal heating plants are already working in Iceland - where 85% of the houses are heated with geothermal energy and 30% of them use electricity generated from geothermal energy . • It is also the case in Greece, Italy, Turkey, Germany and Austria. • The potential areas where you can produce this kind of energy, are found in the northwest and central west coast of Italy, in western Turkey and parts of Portugal, Spain, France and Germany. • The Italian market of geothermal energy isgrowing (the generation capacity could increase up to 200 MWe - 1 500 MWe by 2020. Germany on the other hand have almost 150 plants and pipeline worth 4 billion euros.
Geothermal energy and climate changes • Geothermal energy is used to produce electric energy in 24 countries around the world. • In five of them it makes up between 15% and 22% of all the electric power produced nationwide. • The installed power of 140GWt and production equaling 1100TWh annually in 2050 would result in reducing the emission by 500 million tons of CO2 annually by replacing the natural gas with geothermal energy while 1000 million tons of CO2 annually by replacing coal.
Environmental Effects/ Benefits • Remarkable difference of environmental effects compared to fossil fuels • Leaves almost no footprints • Most hardware used to extract geothermal energy is underground • Minimal use of surface (http://www.geothermal.nau.edu/about/enviroment.shtmlNorthern Arizona University. 2009 Oct 27)
Advantages of geothermal energy • Geothermal energy, like other renewable energy sources, is environmentally friendly, as it causes no pollution. • Its resources are available locally, so it can only be collected near the place of use. • Furthermore, geothermal energy has several advantages over other renewable energy sources. • Geothermal plants, unlike dams or windmill plants, have no negative impact on natural landscape. • In addition, geothermal energy resources, unlike wind energy or solar energy, are always available regardless of weather conditions. What is more, installations based on geothermal energy use are low cost.
Disadvantages of geothermal energy • Disadvantages of geothermal energy include its low availability and the fact that suitable conditions for its use are restricted to only a few locations. • In addition, some harmful gases and minerals may emerge during its collection. • One of these is hydrogen sulphide, which in low concentrations has a characteristic odor of rotten eggs while in high concentrations may be hazardous to human health. • Although geothermal energy is widely spread, its collection is not possible everywhere.
Environmental Effects/ Disadvantages • Fluids drawn from the deep earth carry a mixture of gases e.g. H2S • Pollutants contribute to global warming and acid rain • Construction of plants can adversely affect land stability • Sources may hold trace amounts of toxic chemicals/mineral deposits • Loud Noises • Initial start up cost (expensive) (http://www.geothermal.nau.edu/about/enviroment.shtml> Northern Arizona University. 2009 Oct 27)
What can we do with heat? conventional geothermal plants capture hot water from geysers or steam from vents to spin turbines
GEOTHERMAL EXTRACTION There are three primary ways we can use geothermal energy: for electricity production, for direct-use applications, and for heating and cooling buildings with geothermal heat pumps. 1. Electricity Production 1.1 Dry-steam power plants 1.2 Flashed-steam power plants 1.3 Binary-cycle power plants
1.1 Dry-steam POWER plants Dry steam power plants draw heat from underground reservoirs of steam. The steam is piped directly from wells to the power plant, where it enters a turbine. The steam turns the turbine, which turns a generator. The steam is then condensed and injected back into the reservoir via another well. The Geysers in northern California, the world’s largest single source of geothermal power, uses dry steam.
1.2 Flashed-steam power plants Flashed-steam power plantstap into reservoirs of water with temperatures greater than 182°C. This very hot water flows up through wells under its own pressure. As it flows to the surface, the fluid pressure decreases and some of the hot water boils or “flashes” into steam. The steam is then separated from the water and used to power a turbine/generator unit. The remaining water and condensed steam are injected through a well back into the reservoir
1.3 Binary-cycle power plants Binary-cycle power plantsoperate with water at lower temperatures of about 107° to 182°C. These plants use heat from the geothermal water to boil a working fluid, usually an organic compound with a lower boiling point. The working fluid is vaporized in a heat exchanger and the vapor turns a turbine. The water is then injected back into the ground to be reheated. The water and the working fluid are confined in separate closed loops during the process, so there are little or no air missions.
2. Direct Use Applications Geothermal heat is used directly rather than for power generation Extract heat from low temperature geothermal resources < 150 oC . Applications sited near source (<10 km) Today, most geothermal direct-use applications circulate these fluids through closed-loop, emissions-free systems. The carbon dioxide found in geothermal fluids could prove beneficial to direct-use greenhouse applications. Carbon dioxide is a very effective growth stimulant for plants. Studies have shown that an increase in carbon dioxide from a normal level of 300 ppm to approximately 1,000 ppm can raise crop yields up to 15 percent.
3. Geothermal Heat Pumps The use of geothermal energy through ground-coupled heat pump technology has almost no impact on the environment and has a beneficial effect in reducing the demand for electricity Because of this constant temperature, the energy efficiency of geothermal heat pumps is about 30% better than that of air-coupled heat pumps and 50% better than electric-resistance heating. The need for electrical generation capacity at the central power station is reduced by 2 to 5 kW for each residential installation and by about 20 kW for average commercial installations. Thus, for each 1000 homes with geothermal heat pumps, the utility can avoid the installation of 2 to 5 MW of generating capacity.
Efficiency • Functions like a conventional coal power plant. • Efficiencies vary by • input heat. • At 400 deg. expect ~ 23%, not including parasitic load. • In 2006 the US produced 2850 MW of geothermal electricity
Limitations of surface geothermal • These are surface based • Represent “low hanging fruit” • Most viable sites have been tapped • Not as efficient as Coal, by the numbers
Enhanced Geothermal Systems(EGS) An Idea • Temperature profile • Think about the energy stored in the earth. • How would one take advantage of this?
Enhanced Geothermal Systems in practice • Basically the same technology as surface geothermal for electricity production • Some different nuances • Take advantage of heat ANYWHERE
Nuances • Use drilling technology to access heat of the earth. • Create fractures in rock under ground. • Allows for the flow of water. • Creates an artificial well through which water or fluid can be pumped.
Drilling Depending on depth different solutions are available.
Fracturing • Looking for hot, tectonically stressed, and fractured rock. • over time fractures seal due to secondary mineralization. Low permeability. • Reopen fractures with hydraulic, thermal, and chemical processes.
Enhanced Geothermal Systems in practice The Enhanced Geothermal System designs for the actual electricity generation are similar to surface geothermal. Flash or Steam Plants Dry Steam Power Plants Binary cycle power plant Type of plant depends on conditions