GEOTHERMAL POWER PLANT
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Our earth’s interior - like the sun – provides energy from nature. This heat – geothermal energy – yields warmth and power that we can use without polluting the environment. Geothermal heat originates from Earth’s fiery consolidation of dust and gas over 4 billion years ago. At earth core – 4,000 miles deep – temperatures may reach over 9,000 degrees F
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GEOTHERMAL POWER PLANT
- 1. GEOTHERMAL POWER PLANT By : Muhammad Nawawi Ekawati Prihatini Presented in Professional Management ProgramPresented in Professional Management Program University of CanberraUniversity of Canberra July 12July 12ndnd , 2007, 2007
- 2. OUTLINE Description Technology to Generate Geothermal Power Plan Electrical Capacity and Costs Environmental Impacts Socioeconomic Summary Recommendation
- 3. What is Geothermal Energy? Geo : (Greek) - Earth Thermal : relating to, using, producing, or caused by heat.
- 4. What is Geothermal Energy? Our earth’s interior - like the sun – provides energy from nature. This heat – geothermal energy – yields warmth and power that we can use without polluting the environment. Geothermal heat originates from Earth’s fiery consolidation of dust and gas over 4 billion years ago. At earth core – 4,000 miles deep – temperatures may reach over 9,000 degrees F.
- 5. The Earth Radius of 6370 km Three zones Crust (7 km under ocean, 20-65 km under the continent) Mantle (2900 km, lies under the rust) Solid Magma Chambers Seismic activity Core (center, 4000o C and 3.6 million bars)
- 8. How Does Geothermal Heat Get Up To Earth’s Surface? The heat from the earth’s core continuously flows outward. It transfers (conducts) to the surrounding layer of rock, the mantle. When temperatures and pressures become high enough, some mantle rock melts, becoming magma. Then, because it is lighter (less dense) than the surrounding rock, the magma rises (convicts), moving slowly up toward the earth’s crust, carrying the heat from below. Sometimes the hot magma reaches all the way to the surface, where we know it as lava. But most often the magma remains below earth’s crust, heating nearby rock and water (rainwater that has seeped deep into the earth) – sometimes as hot as 700 degrees F. Some of this hot geothermal water travels back up through faults and cracks and reaches the earth’s 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.
- 9. What can we do with heat? conventional geothermal plants capture hot water from geysers or steam from vents to spin turbines
- 11. How Have People Used Geothermal Energy In The Past? comforting warm waters treat eye and skin disease cooking and medicine heating homes
- 12. How Do We Use Geothermal Energy Today? to generate electricity in geothermal power plants or for energy saving non-electrical purposes. Back
- 13. Technology to Generate Geothermal Power Plant
- 14. Surface Geothermal Systems There are three different types surface of Geothermal system designs : Dry Steam Power Plants Flash / Steam Plants Binary cycle power plant
- 15. Units of Measure Pressure 1 Pascal (Pa) = 1 Newton / square meter 100 kPa = ~ 1 atmosphere = ~14.5 psi 1 MPa = ~10 atmospheres = ~145 psi Temperature Celsius (ºC); Fahrenheit (ºF); Kelvin (K) 0 ºC = 32 ºF = 273 K 100 ºC = 212 ºF = 373 K
- 16. A. Dry Steam Schematic
- 17. Dry Steam Power Plants “Dry” steam extracted from natural reservoir 180-225 ºC ( 356-437 ºF) 4-8 MPa (580-1160 psi) 200+ km/hr (100+ mph) Steam is used to drive a turbo-generator Steam is condensed and pumped back into the ground Can achieve 1 kWh per 6.5 kg of steam A 55 MW plant requires 100 kg/s of steam
- 18. B. Flash or Steam plants Hot, High pressure water Turbines generate electricity Costs 4-6 cents per Kwh.
- 19. Single Flash Steam Power Plants Steam with water extracted from ground Pressure of mixture drops at surface and more water “flashes” to steam Steam separated from water Steam drives a turbine Turbine drives an electric generator Generate between 5 and 100 MW Use 6 to 9 tonnes of steam per hour
- 20. Flash Steam Power Plant
- 21. C. Binary Cycle Power Plant Hot water (100 – 300 deg F) Heat Exchanger Binary liquid lower specific heat (vaporizes)
- 22. Binary Cycle Power Plants Low temps – 100o and 150o C Use heat to vaporize organic liquid E.g., iso-butane, iso-pentane Use vapor to drive turbine Causes vapor to condense Recycle continuously Typically 7 to 12 % efficient 0.1 – 40 MW units common
- 23. Binary Cycle Power Plant
- 24. Efficiency Functions like a conventional coal power plant. Efficiencies vary by input heat. At 400 deg. expect ~ 23%, not including parasitic load. Back
- 25. Electrical Capacity and Cost
- 26. Geothermal capacity Heat flow though the earth’s crust with: Flow rate of 59 mW/m2 or 1.9 x 10-2 Btu/h/ft2 Due to: Convection and conduction from the mantle core Radioactive decay of U, Th, K Useful rock temperature 150-200 C for electricity production 100-150 C for other heating purposes
- 27. Geothermal Sites in US
- 28. Electricity production Different types of cycle give efficiency from 5%-14% depend on temp Electrical output Where output at 40 C output geofluid
- 29. Recoverability ( useful energy) Depth of Slice, km Power available for slice, MWe Amount at 150°C, MWe Amount at 200°C, MWe Amount at 250°C, MWe Amount at 300°C, MWe Amount at 350°C, MWe 3 to 4 122,000 120,000 800 700 400 4 to 5 719,000 678,000 39,000 900 1,200 5 to 6 1,536,000 1,241,000 284,000 11,000 600 6 to 7 2,340,000 1,391,000 832,000 114,000 2,800 7 to 8 1,543,000 1,238,000 415,000 48,000 1,200 8 to 10 4,524,000 1,875,000 1,195,000 1,100,000 302,000 54,000 TOTAL 12,486,000 MWe = ɳth xQ rec x 1MJ/1000kJ x 1/t where Qrec = recoverable thermal energy (heat) in kWs (or kJ) = rho*m*C*∆T ɳth = net cycle thermal efficiency (fraction) t = seconds in 30 years = 30 yr x 365 days/yr x 24 hrs/day x 8
- 30. “Typical” Cost for Geothermal Power Plant Permitting Drilling Steam Gathering Transmission Power Plant equipment & construction Exploration
- 31. Costs of a Geothermal Plant PHASE SUBPHASE COST per kW COST FOR 50 MW PLANT Exploration $150 $7.5 million Site Development Permitting $20 $1 million Drilling $750 $37.5 million Steam Gathering $250 $12.5 million Power Plant equipment & construction $1500 $75 million Transmission $100 $5 million
- 32. Do these cost averages fluctuate depending upon the plant? YES! Factors that impact the cost of geothermal power include... Type of project: expansion of an existing project will require lower exploration costs than “greenfield” projects, where specific resource locations are unknown Plant size: the larger the plant, the less the cost per megawatt (economies of scale) Well characteristics: depth, diameter, productivity Properties of the rock formation
- 33. Cost Factors (continued) Site accessibility and location Time delays Ease with which the resource can be retrieved, influenced by permeability, depth of the reservoir, and pressure Characteristics of the geothermal fluid/steam, including chemistry and temperature Fluctuations in the costs of certain materials, such as steel for drilling
- 34. Cost Factors (continued) Lease and permitting costs/issues Transmission costs Tax incentives, such as the production tax credit (PTC) included in the 2005 Energy Policy Act (EPAct) Financing: types of investors, interest rates, debt periods, rate of return
- 35. Drilling cost Same for oil, gas and geothermal wells Depends on: Well type Depth Location of wells
- 36. Cost and performance of 1MW geothermal plant as a function of temp
- 37. Geothermal energy and economics Reduce in energy price Meet market price after 2nd year long-term stability and characteristic power curve : run all year round
- 38. Cost Factors Temperature and depth of resource Type of resource (steam, liquid, mix) Available volume of resource Chemistry of resource Permeability of rock formations Size and technology of plant Infrastructure (roads, transmission lines)
- 39. Costs of Geothermal Energy Costs highly variable by site Dependent on many cost factors High exploration costs High initial capital, low operating costs Fuel is “free” Significant exploration & operating risk Adds to overall capital costs “Risk premium”
- 40. Cost of Water & Steam Cost (US $/ tonne of steam) Cost (US ¢/tonne of hot water) High temperature (>150o C) 3.5-6.0 Medium Temperature (100-150o C) 3.0-4.5 20-40 Low Temperature (<100o C) 10-20
- 41. Cost of Geothermal Power Unit Cost (US ¢/kWh) High Quality Resource Unit Cost (US ¢/kWh) Medium Quality Resource Unit Cost (US ¢/kWh) Low Quality Resource Small plants (<5 MW) 5.0-7.0 5.5-8.5 6.0-10.5 Medium Plants (5-30 MW) 4.0-6.0 4.5-7 Normally not suitable Large Plants (>30 MW) 2.5-5.0 4.0-6.0 Normally not suitable
- 42. Direct Capital Costs Plant Size High Quality Resource Medium Quality Resource Low Quality Resource Small plants (<5 MW) Exploration : US$400-800 Steam field:US$100-200 Power Plant:US$1100- 1300 Total: US$1600-2300 Exploration : US$400- 1000 Steam field:US$300-600 Power Plant:US$1100- 1400 Total: US$1800-3000 Exploration : US$400-1000 Steam field:US$500-900 Power Plant:US$1100- 1800 Total:US$2000-3700 Med Plants (5-30 MW) Exploration : US$250-400 Steamfield:US$200- US$500 Power Plant: US$850- 1200 Total: US$1300-2100 Exploration: : US$250- 600 Steam field:US$400-700 Power Plant:US$950- 1200 Total: US$1600-2500 Normally not suitable Large Plants (>30 MW) Exploration:: US$100-200 Steam field:US$300-450 Power Plant:US$750- 1100 Total: US$1150-1750 Exploration : US$100-400 Steam field:US$400-700 Power Plant:US$850- 1100 Total: US$1350-2200 Normally not suitable Direct Capital Costs (US $/kW installed capacity)
- 43. Indirect Costs Availability of skilled labor Infrastructure and access Political stability Indirect Costs Good: 5-10% of direct costs Fair: 10-30% of direct costs Poor: 30-60% of direct costs Back
- 46. Solid and Gas Emissions No chance of contamination from solid discharge. Geothermal fluids contains less harmful greenhouse gases. No Nitrogen Oxide and Sulfur Dioxide. Less acid rain. Binary Plants have no Carbon Dioxide, however others have 0.2lb/kW-h.
- 47. Comparison of Gas Emissions
- 48. Technology: Disadvantages and Advantages Disadvantages: For mid to low grade resources, wells deeper than 4 km are required. EGSs are very new, time will be required to develop its potential and stability Advantages: Deep Geothermal energy extraction could use existing drilling technologies for high grade resources. Back
- 50. Landscape Impact and Land Use Requires relatively less land. Less environmental alterations and adverse effects. Produces more power per surface acre compared to nuclear and coal.
- 51. Comparison of Land Requirement for Baseload Power Generation
- 52. Thermal Pollution It is one of the biggest concerns due to considerable loss of thermal heat. Taller cooling towers are needed to contain the waste heat.
- 53. Noise Pollution Noise does occur during initial construction and drilling. Noise is minimum. 0 20 40 60 80 100 120 Source(dB) Air Drilling Mud Drilling Well Discharge Well Testing Heavy Machinery
- 54. Land Subsidence and Induced Seismicity In early days of geothermal energy sinking of land was a major problem (subsidence). This was caused by severe drop in reservoir pressure due more fluid removal. However, now through re-injection we keep the pressure balanced. Possibility of microseismic events from opening of fractures and acoustic noise when drilling.
- 55. Disturbance to Wildlife Habitat and Vegetations Loss of habitat and vegetation is relative minor and non-existence. Although there will be some alteration to the vegetation, most can restored. Available technology and waste management significantly reduces and damage to the ecosystem.
- 56. Geothermal Plants In Harmony with Nature
- 57. Immense potential Although Geothermal Energy is not renewable, the available resource is large 2,000 zettajoules available for extraction. (MIT) Enough to power human civilization for thousands of years 100,000 MWe is projected to be extracted in the next 50 years
- 58. Environment Low risks of water contamination and low air pollution Most of the major noise pollutions are during construction only Seismicity due to EGS operation is minor and not definite Back
- 59. SOCIO ECONOMICS
- 60. What is socioeconomics? The study of the relationship between economic activity and social life. The field is often considered multidisciplinary, using theories and methods from sociology, economics, history, psychology, and many others. Socioeconomics typically analyzes both the social and economic impacts of social activity. (Adopted from Wikepedia)
- 61. Increasing national security Producing Power at home Benefiting rural, economically depressed areas Providing jobs Social Issues
- 62. average number of hours the facility can produce power out of a 24 hour day ability of a facility to generate power during peak hours ability of a facility to increase/decrease generation, or be brought online or shut down at the request of a utility's system operator air emissions, other environmental impacts, and related public health issues Externalities that should be considered include:
- 63. resource availability and quality disposal issues fuel transportation issues land degradation, extent and impact of land use, and zoning water usage seasonal and weather variability employment Back
- 64. In Summary Further development of Deep Geothermal Energy should be highly considered because of its Potential to allow new access to large resources Environmentally friendly traits Competitive costs in the long run Ability to use existing technologies to begin extraction soon Back
- 65. Recommendations An analysis on the reasons to move forward in the development of deep geothermal systems
- 66. ☺Thank You …
Editor's Notes
- Transition, OK, so let’s take a look at how this is possible. What are the characteristics of our planet that would allow us to do this.
- What are the temperatures at the different parts of the earth? The earth is decreasing in temperature. Where did his heat come from? What about radioactive decay, etc. Over the life-time of the earth it is said that it’s temperature has decreased 300 – 400 degrees Celsius. It is still however around 4000 degrees Celsius.
- I. Earth Heat The gradual radioactive decay of elements within the earth maintains the earth&apos;s core at temperatures in excess of 5000°C. Heat energy continuously flows from this hot core by means of conductive heat flow and convective flows of molten mantle beneath the crust. The result is that there is a mean heat flux at the earth&apos;s surface of around 16 kilowatts of heat energy per square kilometre which is dissipated to the atmosphere and space. This heat flux is not uniformly distributed over the earth&apos;s surface but tends to be strongest along tectonic plate boundaries where volcanic activity transports high temperature material to near the surface. Only a small fraction of the molten rock feeding volcanoes actually reaches the surface. Most is left at depths of 5-20 km beneath the surface, where it releases heat that can drive hydrological convection that forms high temperature geothermal systems at shallower depths of 500-3000m.
- Explain the technology. A schematic would be nice. Parallel between coal power plants, nuclear power plants. Talk about harvesting the earth’s energy. How are these things formed?
- Use very hot (more than 300° F) steam and hot water resources (as found at The Geysers plants in northern California) Steam either comes directly from the resource, or the very hot, high-pressure water is depressurized (&quot;flashed&quot;) to produce steam. Steam then turns turbines, which drive generators that generate electricity. Only significant emission from these plants is steam (water vapor). Minute amounts of carbon dioxide, nitric oxide, and sulfur are emitted, but almost 50 times less than at traditional, fossil-fuel power plants. Energy produced this way currently costs about 4-6 cents per kWh. The flash steam power plant uses hot water reservoirs as a source of power. When the hot water comes up from the earth into the flash tank, there is a drop in pressure which causes some of the water to turn into steam. This steam is then used to spin the turbine much like in the Dry Steam power plant. The water is then returned to the earth to be used again later. This is the most used type of geothermic power plant since there are a lot of hot water reservoirs.
- The steam once it has been separated from the water is piped to the powerhouse where it is used to drive the steam turbine. The steam is condensed after leaving the turbine, creating a partial vacuum and thereby maximising the power generated by the turbine-generator. The steam is usually condensed either in a direct contact condenser, or a heat exchanger type condenser. In a direct contact condenser the cooling water from the cooling tower is sprayed onto and mixes with the steam. The condensed steam then forms part of the cooling water circuit, and a substantial portion is subsequently evaporated and is dispersed into the atmosphere through the cooling tower. Excess cooling water called blow down is often disposed of in shallow injection wells. As an alternative to direct contact condensers shell and tube type condensers are sometimes used, as is shown in the schematic below. In this type of plant, the condensed steam does not come into contact with the cooling water, and is disposed of in injection wells. Typically, flash condensing geothermal power plants vary in size from 5 MWe to over 100 MWe. Depending on the steam characteristics, gas content, pressures, and power plant design, between 6 and 9 tonne of steam each hour is required to produce each MW of electrical power. Small power plants (less than 10 MW) are often called well head units as they only require the steam of one well and are located adjacent to the well on the drilling pad in order to reduce pipeline costs. Often such well head units do not have a condenser, and are called backpressure units. They are very cheap and simple to install, but are inefficient (typically 10-20 tonne per hour of steam for every MW of electricity) and can have higher environmental impacts.
- To generate electricity, fluids above 150oC are extracted from underground reservoirs (consisting of porous or fractured rocks at depths between a few hundred and 3 000 metres) and brought to the surface through production wells. Some reservoirs yield steam directly, while the majority produce water from which steam is separated and fed to a turbine engine connected to a generator. Some steam plants include an additional flashing stage. The used steam is cooled and condensed back into water, which is added to the water from the separator for reinjection (Figure 12.2). The size of steam plant units ranges from 0.1 to 150 MWe.
- Uses lower-temperatures, but much more common, hot water resources (100° F – 300° F). Hot water is passed through a heat exchanger in conjunction with a secondary (hence, &quot;binary plant&quot;) fluid with a lower boiling point (usually a hydrocarbon such as isobutane or isopentane). Secondary fluid vaporizes, which turns the turbines, which drive the generators. Remaining secondary fluid is simply recycled through the heat exchanger. Geothermal fluid is condensed and returned to the reservoir. Binary plants use a self-contained cycle, nothing is emitted. Energy produced by binary plants currently costs about 5 to 8 cents per kWh. Lower-temperature reservoirs are far more common, which makes binary plants more prevalent.
- Binary Cycle Power PlantsIn reservoirs where temperatures are typically less than 220oC (430oF). but greater than 100oC (212oF). binary cycle plants are often utilised. The illustration below shows the principal elements of this type of plant. The reservoir fluid (either steam or water or both) is passed through a heat exchanger which heats a secondary working fluid which has a boiling point lower than 100oC (212oF). This is typically an organic fluid such as Isopentane, which is vaporised and is used to drive the turbine. The organic fluid is then condensed in a similar manner to the steam in the flash power plant described above, except that a shell and tube type condenser rather than direct contact is used. The fluid in a binary plant is recycled back to the heat exchanger and forms a closed loop. The cooled reservoir fluid is again re-injected back into the reservoir. Binary cycle type plants are usually between 7 and 12 % efficient depending on the temperature of the primary (geothermal) fluid. http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm If the geothermal resource has a temperature between 100o and 150oC, electricity can still be generated using binary plant technology. The produced fluid heats, through a heat exchanger, a secondary working fluid (isobutane, isopentane or ammonia), which vaporises at a lower temperature than water. The working fluid vapour turns the turbine and is condensed before being reheated by the geothermal water, allowing it to be vaporised and used again in a closed-loop circuit (Figure 12.3). The size of binary units range from 0.1 to 40 MWe. Commercially, however, small sizes (up to 3 MWe) prevail, often used modularly, reaching a total of several tens of MWe installed in a single location. The spent geothermal fluid of all types of power plants is generally injected back into the edge of the reservoir for disposal and to help maintain pressure. In the case of direct heat utilisation, the geothermal water produced from wells (which generally do not exceed 2 000 metres) is fed to a heat exchanger before being reinjected into the ground by wells, or discharged at the surface. Water heated in the heat exchanger is then circulated within insulated pipes that reach the end-users. The network can be quite sizeable in district heating systems. For other uses (greenhouses, fish farming, product drying, industrial applications) the producing wells are next to the plants serviced. http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
- If the geothermal resource has a temperature between 100o and 150oC, electricity can still be generated using binary plant technology. The produced fluid heats, through a heat exchanger, a secondary working fluid (isobutane, isopentane or ammonia), which vaporises at a lower temperature than water. The working fluid vapour turns the turbine and is condensed before being reheated by the geothermal water, allowing it to be vaporised and used again in a closed-loop circuit (Figure 12.3). The size of binary units range from 0.1 to 40 MWe. Commercially, however, small sizes (up to 3 MWe) prevail, often used modularly, reaching a total of several tens of MWe installed in a single location. The spent geothermal fluid of all types of power plants is generally injected back into the edge of the reservoir for disposal and to help maintain pressure. In the case of direct heat utilisation, the geothermal water produced from wells (which generally do not exceed 2 000 metres) is fed to a heat exchanger before being reinjected into the ground by wells, or discharged at the surface. Water heated in the heat exchanger is then circulated within insulated pipes that reach the end-users. The network can be quite sizeable in district heating systems. For other uses (greenhouses, fish farming, product drying, industrial applications) the producing wells are next to the plants serviced.
- What are the typical efficiencies? Number of sites. It would be nice to have data on the lifetime of the plants.
- The cost of geothermal power developments is dependent upon many factors, the most important factors being: · The temperature and depth of the resource. A shallow resource means minimum drilling costs. High temperatures (high enthalpies) mean higher energy capacity.· The type of resource (steam, two phase or liquid). A dry steam resource is generally less expensive to develop as reinjection pipelines, separators and reinjection wells are not required· The chemistry of the geothermal fluid. A resource with high salinity fluids, high silica concentrations, high gas content, or acidic fluids can pose technical problems which may be costly to overcome. · The permeability of the resource. A highly permeable resource means higher well productivity, and therefore fewer wells required to provide the steam for the power plant.· The size of the plant to be built. As with most types of power plant, economies of scale means large power plants are generally cheaper in $/MW.· The technology of the plant. There are a number of geothermal power technologies available, including simple back pressure plant with atmospheric exhaust, conventional condensing plant, binary cycle, combined cycle binary plants, Kalina Cycle, multi flash plants etc. Each technology has advantages and disadvantages and different cost structures.· Infrastructure requirements (access roads, water and power services, proximity to adequate port facilities, proximity to a city). In isolated locations or small islands especially in developing countries, infrastructure may be a significant part of the total cost.· Climatic conditions at the site. As with all types of power plants their cost and performance is dependent on the local climatic conditions. Low ambient wet bulb temperatures for example can lead to a less costly cooling system and a more efficient plant.· Topography of the site. If the geothermal resource is sited in difficult terrain, civil development costs will be higher, pipelines may be more complex, of longer length with greater pressure drops and overall development costs may be higher.· Environmental constraints. Environmental constraints on the siting, construction and operation of the geothermal power station can often result in increased development cost. A typical example may be the requirement for minimal discharge of geothermal gases (in particular hydrogen sulphide) to the environment. This may require the gases to be either reinjected into the reservoir (such as at the Puna plant in Hawaii) or costly hydrogen sulphide abatement systems to be installed.· The proximity of the transmission lines. In isolated areas, it may be a requirement of the project to include for the construction of a lengthy transmission line to enable the power from the station to be fed into a grid servicing a sizeable load, possibly some distance away.· The type of construction contract employed. Turnkey/EPC contracts are becoming very popular, especially with IPP developments as they reduce the financial risk to the developer, enable financing to be more easily achieved as well as giving a single point of responsibility for plant performance. However such implementation methods are generally more costly than the traditional multi-contract approach.· Administration, management, legal, insurance, permitting, financing, local taxes and royalties and other indirect costs. The indirect costs of a power project, especially in developing countries can be a significant proportion of the overall project costs (up to 30%)
- Costs of geothermal electric power are very dependent on the character of the resource and project size. The unit costs of power currently range from 2.5 to over 10 US cents per kilowatt-hour while steams costs may be as low as US$3.5 per tonne. Major factors affecting cost are the depth and temperature of the resource, well productivity, environmental compliance, project infrastructure and economic factors such as the scale of development, and project financing costs.
- Geothermal Energy Cost for Power Generation Geothermal energy development of high temperature (&gt;180oC) for power generation typically involves some risk in the initial investigations to prove the geothermal resource. Investment is required for exploration, drilling wells and installation of plant, but operating costs are very low because of the low cost of fuel. In comparison, fossil fuel station capital costs are usually significantly cheaper than geothermal power stations, but fuel costs are very much higher. Diesel powered generation plant capital costs for example are typically less than 50% of the cost of geothermal plants. However, diesel can cost between US$3 to US$6/GJ. There are many other benefits in utilising an indigenous geothermal energy resource. Geothermal power reduces the national reliance on imported fossil fuels, thereby saving valuable foreign exchange earnings. Due to many influencing factors, geothermal power development project capital costs are very much site and project specific. However, as a general guideline, the following sections give a range of direct and indirect capital costs and operating and maintenance costs under a number of scenarios. All scenarios below are based upon an EPC type project implementation approach, with the detailed engineering included in the direct costs, not the indirect, as would other wise be the case. http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
- Levelised Unit Power CostsThe typical unit cost of power from geothermal plants, based upon a discount rate of 10% are shown in the table below. A capacity factor of 90% has been assumed. These costs are based upon projects constructed in developing countries and therefore indirect costs at the higher end of the scale have been chosen. With the unit cost of diesel generation at least 10c/kWh and up to 20c/kWh, geothermal generation is a very attractive option, especially in remote, off grid areas and small islands where diesel generation is often the only alternative for power generation. Direct use of the low temperature reject water fraction from geothermal power generation can often be attractive. It is advantageous for the power developer to be approached at an early stage to enable any such arrangement to be incorporated into the power plant/steam field designs
- Direct Capital Costs The table below shows indicative direct capital costs (US$/kW) for small, medium and large plants, developed in high, medium and low quality geothermal resources. A high quality geothermal energy resource is taken to mean a resource with high temperature (&gt;250o C) very good field wide permeability (and therefore high well productivity) likely to be a dry steam or two phase reservoir, low gas content and with benign chemistry. A low quality resource is one with reservoir temperature below 150oC, or a resource although with possibly higher temperature, has poor permeability, high gas content and difficult chemistry. The exploration phase is assumed in the costs to be made up of geoscientific surface exploration (US$600,000) and one (small plant development) to five exploration wells, each well costing about US$1.5 M
- Indirect CostsIndirect costs vary significantly depending on the location of the site, its accessibility, level of infrastructure and expatriate requirements. Approximate Indirect costs have been given based upon three different categories of project locations. Location A, is typical project site in a developed country. Infrastructure is in place, skilled labour is available and port facilities and a major city relatively close by. Indirect costs are about 5 - 10% of direct costs. Location B is a typical project site in a more remote area of a developed country, or in an area of a developing nation where infrastructure is of a good standard, there is a pool of skilled labour and the nation enjoys political and social stability. Indirect costs are about 10-30% of direct costs. Location C is a typical project site in a more remote area of a developing nation, where infrastructure is poor, accessibility is difficult, skilled labour is scarce and there is the risk of political instability. Indirect costs are about 30 - 60% of direct costs.
- -Advantages are that deep geothermal energy extraction could use existing drilling technologies for high grade resources. Disadvtanges -required. -This requires new drilling technologies. -new- which means that much time will be required to maximize it’s stability and potential to extract energy.
- Edited acre to surface acre. EGS goes very deep and would probably use more land in volume.
- Edited bigger to taller.
- -While geothermal energy extraction is not renewable, but the available resource is extremely large. -The panel in MIT estimated of around 2,000 zettajoules available for extraction. (enough to power the human civilization for millennia time frames)
- There are possible water contamination and air pollution but compared to existing power plants, EGS are very environmentally friendly.