Geothermal Energy. Dr. Mazen Abualtayef. Environmental Engineering Department Islamic University of Gaza, Palestine

Transcription

1 Geothermal Energy Dr. Mazen Abualtayef Environmental Engineering Department Islamic University of Gaza, Palestine

2 Adapted from a presentation by Professor S.R. Lawrence Leeds School of Business, Environmental Studies University of Colorado, Boulder, CO, USA

3 AGENDA Geothermal Energy Geothermal Overview Extracting Geothermal Energy Environmental Implications Economic Considerations Geothermal Installations Examples

4 Geothermal Overview

5 Geothermal in Context Geo = earth, thermos = heat Geothermal energy is the extractable portion of the heat stored in the ground.

6 Geothermal in Context World energy consumption

7 Geothermal in Context Global geothermal electric capacity

8 Advantages of Geothermal

9 Heat from the Earth s Center Earth's core maintains temperatures in excess of 5000 C Heat originates from radioactive decay of elements Heat energy continuously flows from hot core تدفق الحرارة بالتوصيل Conductive heat flow Convective انتقال حراري 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 Only a small fraction of molten rock actually reaches surface Most is left at depths of 5-20 km beneath the surface Hydrological convection forms high temperature geothermal systems at shallow depths of m.

10 Earth Dynamics

11 Earth Temperature Gradient

12 Geothermal Site Schematic نبع ماء حار Boyle, Renewable Energy, 2 nd edition, 2004

13 Geysers Clepsydra Geyser in Yellowstone 500 geysers in yellow stone park out 1000 geysers worldwide

14 Hot Springs Hot springs in Steamboat Springs area

15 Fumaroles Clay Diablo Fumarole (CA) White Island Fumarole New Zealand

16 Global Geothermal Sites

17 Tectonic Plate Movements Enthalpy: Catchment Boyle, Renewable Energy, 2 nd edition, 2004

18 Extracting Geothermal Energy

19 Methods of Heat Extraction من تشكيل الصخور المحيطة حركة المياه من خالل محاكاة الصخور المتصدعة من المياه الجوفية الحرارية

20 Units of Measure Pressure 1 Pascal (Pa) = 1 Newton / square meter 100 kpa = ~ 1 atmosphere 1 MPa = ~10 atmospheres Temperature Celsius (ºC); Fahrenheit (ºF); Kelvin (K) 0 ºC = 32 ºF = 273 K 100 ºC = 212 ºF = 373 K

21 Plants Types: 1. Dry Steam Power Plants Dry steam extracted from natural reservoir ºC 4-8 Mpa 200+ km/hr 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 Boyle, Renewable Energy, 2 nd edition, 2004

22 Dry Steam Schematic Boyle, Renewable Energy, 2 nd edition, 2004

23 2. 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 to produce each MW of electrical power

24 Single Flash Steam Schematic The steam is condensed, creating a partial vacuum and thereby maximizing the power generated by the turbinegenerator. 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. As an alternative to direct contact condensers shell and tube type condensers are sometimes used. Boyle, Renewable Energy, 2 nd edition, 2004

25 3. Binary Cycle Power Plants Low temps 100 o and 150 o 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 7~12% efficient MW units common

26 Binary Cycle Schematic >2000m Boyle, Renewable Energy, 2 nd edition, 2004

27 Binary Plant Power Output

28 4. Double Flash Power Plants Similar to single flash operation Unflashed liquid flows to low-pressure tank flashes to steam Steam drives a second-stage turbine Also uses exhaust from first turbine Increases output 20-25% for 5% increase in plant costs

29 Double Flash Schematic Boyle, Renewable Energy, 2 nd edition, 2004

30 5. Combined Cycle Plants Combination of conventional steam turbine technology and binary cycle technology Steam drives primary turbine Remaining heat used to create organic vapor Organic vapor drives a second turbine Plant sizes ranging between 10 to 100+ MW Significantly greater efficiencies Higher overall utilization Extract more power (heat) from geothermal resource

31 6. Hot Dry Rock Technology Wells drilled 3-6 km into crust Hot crystalline rock formations Water pumped into formations Water flows through natural fissures picking up heat شقوق Hot water/steam returns to surface Steam used to generate power

32 Hot Dry Rock Technology Fenton Hill plant

33 Soultz Hot Fractured Rock Boyle, Renewable Energy, 2 nd edition, 2004

34 2-Well HDR System Parameters m 2 = 2 km m 3 = 0.2 km 3 Boyle, Renewable Energy, 2 nd edition, 2004 معاوقة لتيار كهربائي Impedance:

35 Promise of HDR 1 km 3 of hot rock has the energy content of 70,000 tons of coal If cooled by 1 ºC Upper 10 km of crust in US has 600,000 times annual US energy (USGS) Between GW power available at existing hydrothermal sites Using enhanced technology Boyle, Renewable Energy, 2 nd edition, 2004

36 Direct Use Technologies Geothermal heat is used directly rather than for power generation Extract heat from low temperature geothermal resources < 150 o C Applications sited near source (<10 km) Using heat pump technology to utilize geothermal heat for air conditioning and refrigeration applications

37 Geothermal Heat Pump

38 Vertical Geothermal Loop Ramallah example Video Installation Video

39 Heat vs. Depth Profile Boyle, Renewable Energy, 2 nd edition, 2004

40 Geothermal District Heating Southhampton geothermal district heating system technology schematic Boyle, Renewable Energy, 2 nd edition, 2004

41 Direct Heating Example Boyle, Renewable Energy, 2 nd edition, 2004

42 Technological Issues Geothermal fluids can be corrosive Contain gases such as hydrogen sulphide Corrosion Requires careful selection of materials and diligent operating procedures Typical capacity factors of 85-95%

43 Technology vs. Temperature Reservoir Temperature High Temperature >220 o C Intermediate Temperature o C Low Temperature o C Reservoir Fluid Water or Steam Water Water Common Use Power Generation Direct Use Technology commonly chosen Flash Steam Combined (Flash and Binary) Cycle Direct Fluid Use Heat Exchangers Heat Pumps Power Generation Direct Use Binary Cycle Direct Fluid Use Heat Exchangers Heat Pumps Direct Use Direct Fluid Use Heat Exchangers

44 Geothermal Performance Boyle, Renewable Energy, 2 nd edition, 2004

45 Current Geothermal Projects

46 Environmental Implications

47 Environmental Impacts Land Air Vegetation loss Soil erosion Landslides Slight air heating Local fogging Ground Reservoir cooling Seismicity (tremors) الزلزالية )الهزات ) Water using water for drilling purpose: Watershed impact Divert streams using water from reservoir: Lower water table هبوط Subsidence Noise -- Disturbance to animals & humans Benign overall بشكل عام غير خطر

48 Renewable? Heat depleted as ground cools Not steady-state Earth s core does not replenish/refill heat to crust quickly enough Example: -- The government of Iceland states It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource. It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW.

49 Geothermal Calculator A geothermal calculator was developed by Mazen Abualtayef and you can find it here ualtayef/files/pvcalculator.xlsx

50 Economics of Geothermal

51 Cost Factors Temperature and depth of resource: A shallow resource means minimum drilling costs. High temperatures mean higher energy capacity Type of resource (steam, liquid, mix): A dry steam resource is generally less expensive to develop as reinjection pipelines, separators and reinjection wells are not required Chemistry of resource: 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 Permeability of rock formations: A highly permeable resource means higher well productivity Size and technology of plant Infrastructure (roads, transmission lines)

52 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

53 Cost of Water & Steam High temperature (>150 o C) Medium Temperature ( o C) Low Temperature (<100 o C) Cost (US $/ton of steam) Cost (US /ton of hot water) Table Geothermal Steam and Hot Water Supply Cost where drilling is required

54 Cost of Geothermal Power Small plants (<5 MW) Medium Plants (5-30 MW) Large Plants (>30 MW) Unit Cost (US /kwh) High Quality Resource Unit Cost (US /kwh) Medium Quality Resource Unit Cost (US /kwh) Low Quality Resource Normally not suitable Normally not suitable

55 Direct Capital Costs Plant Size High Quality Resource Medium Quality Resource Low Quality Resource Small plants (<5 MW) Exploration : US$ Steam field:us$ Power Plant:US$ Total: US$ Exploration : US$ Steam field:us$ Power Plant:US$ Total: US$ Exploration : US$ Steam field:us$ Power Plant:US$ Total:US$ Med Plants (5-30 MW) Exploration : US$ Steamfield:US$200-US$500 Power Plant: US$ Total: US$ Exploration: : US$ Steam field:us$ Power Plant:US$ Total: US$ Normally not suitable Large Plants (>30 MW) Exploration:: US$ Steam field:us$ Power Plant:US$ Total: US$ Exploration : US$ Steam field:us$ Power Plant:US$ Total: US$ Normally not suitable Direct Capital Costs (US $/kw installed capacity)

56 Indirect Costs Availability of skilled labor Infrastructure and access Political stability Indirect Costs Good: 5-10% of direct costs in developed countries Fair: 10-30% of direct costs Poor: 30-60% of direct costs in developing countries

57 Operating/Maintenance Costs O&M Cost (US c/kwh) Small plants (<5 MW) O&M Cost (US c/kwh) Medium Plants (5-30 MW) O&M Cost (US c/kwh) Large Plants(>30 MW) Steam field Power Plant Total

58 Geothermal Installations Examples

59 Geothermal Power Examples Boyle, Renewable Energy, 2 nd edition, 2004

60 Geothermal Power Generation World production of 8 GW 2.7 GW in US The Geysers (US) is world s largest site Produces 2 GW Other attractive sites Rift region منطقة الصدع of Kenya, Iceland, Italy, France, New Zealand, Mexico, Nicaragua, Russia, Phillippines, Indonesia, Japan

61 Geothermal Energy Plant Geothermal energy plant in Iceland

62 Geothermal Well Testing Geothermal well testing, Zunil, Guatemala

63 Heber Geothermal Power Station 52kW electrical generating capacity

64 Geysers Geothermal Plant The Geysers is the largest producer of geothermal power in the world.

65 Geyers Cost Effectiveness Boyle, Renewable Energy, 2 nd edition, 2004

66 Geothermal Summary

67 Geothermal Prospects Environmentally very attractive Attractive energy source in right locations Likely to remain an adjunct مساعد to other larger energy sources Part of a portfolio of energy technologies Exploration risks and up-front capital costs remain a barrier

68 Next Week: BIOENERGY

69 Supplementary Slides Extras

70 Geothermal Gradient

71 Geo/Hydrothermal Systems

72 Location of Resources

73 Ground Structures Boyle, Renewable Energy, 2 nd edition, 2004

74 Volcanic Geothermal System Boyle, Renewable Energy, 2 nd edition, 2004

75 Temperature Gradients Boyle, Renewable Energy, 2 nd edition, 2004

76

77 UK Geothermal Resources Boyle, Renewable Energy, 2 nd edition, 2004

78 Porosity vs. Hydraulic Conductivity Boyle, Renewable Energy, 2 nd edition, 2004

79 Performance vs. Rock Type Boyle, Renewable Energy, 2 nd edition, 2004

80 Deep Well Characteristics Boyle, Renewable Energy, 2 nd edition, 2004

81 Single Flash Plant Schematic

82

83 Binary Cycle Power Plant

84 Flash Steam Power Plant

85 Efficiency of Heat Pumps Boyle, Renewable Energy, 2 nd edition, 2004

86 Recent Developments Comparing statistical data for end-1996 (SER 1998) and the present Survey, it can be seen that there has been an increase in world geothermal power plant capacity (+9%) and utilisation (+23%) while direct heat systems show a 56% additional capacity, coupled with a somewhat lower rate of increase in their use (+32%). Geothermal power generation growth is continuing, but at a lower pace than in the previous decade, while direct heat uses show a strong increase compared to the past. Going into some detail, the six countries with the largest electric power capacity are: USA with MWe is first, followed by Philippines (1 863 MWe); four countries (Mexico, Italy, Indonesia, Japan) had capacity (at end-1999) in the range of MWe each. These six countries represent 86% of the world capacity and about the same percentage of the world output, amounting to around GWhe. The strong decline in the USA in recent years, due to overexploitation of the giant Geysers steam field, has been partly compensated by important additions to capacity in several countries: Indonesia, Philippines, Italy, New Zealand, Iceland, Mexico, Costa Rica, El Salvador. Newcomers in the electric power sector are Ethiopia (1998), Guatemala (1998) and Austria (2001). In total, 22 nations are generating geothermal electricity, in amounts sufficient to supply 15 million houses. Concerning direct heat uses, Table 12.1 shows that the three countries with the largest amount of installed power: USA (5 366 MWt), China (2 814 MWt) and Iceland (1 469 MWt) cover 58% of the world capacity, which has reached MWt, enough to provide heat for over 3 million houses. Out of about 60 countries with direct heat plants, beside the three abovementioned nations, Turkey, several European countries, Canada, Japan and New Zealand have sizeable capacity. With regard to direct use applications, a large increase in the number of GHP installations for space heating (presently estimated to exceed ) has put this category in first place in terms of global capacity and third in terms of output. Other geothermal space heating systems are second in capacity but first in output. Third in capacity (but second in output) are spa uses followed by greenhouse heating. Other applications include fish farm heating and industrial process heat. The outstanding rise in world direct use capacity since 1996 is due to the more than two-fold increase in North America and a 45% addition in Asia. Europe also has substantial direct uses but has remained fairly stable: reductions in some countries being compensated by progress in others. Concerning R&D, the HDR project at Soultz-sous-Forêts near the French-German border has progressed significantly. Besides the ongoing Hijiori site in Japan, another HDR test has just started in Switzerland (Otterbach near Basel). The total world use of geothermal power is giving a contribution both to energy saving (around 26 million tons of oil per year) and to CO2 emission reduction (80 million tons/year if compared with equivalent oil-fuelled production).