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LOW ENTHALPY APPLICATION OF GEOTHERMAL ENERGY PART I Ruggero Bertani Enel – International

LOW ENTHALPY APPLICATION OF GEOTHERMAL ENERGY PART I Ruggero Bertani Enel – International Rome – Italy ruggero.bertani@enel.it Rome, 2007 10 th May. Contents. 1° PART Introduction Geothermal energy basic concepts Electricity generation Binary plants Case studies 2° PART

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LOW ENTHALPY APPLICATION OF GEOTHERMAL ENERGY PART I Ruggero Bertani Enel – International

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  1. LOW ENTHALPY APPLICATIONOF GEOTHERMAL ENERGY PART I Ruggero Bertani Enel – International Rome – Italy ruggero.bertani@enel.it Rome, 2007 10th May

  2. Contents • 1° PART • Introduction • Geothermal energy basic concepts • Electricity generation • Binary plants • Case studies • 2° PART • Low Enthalpy applications • Introduction • Direct Uses • SPA • Heating • Geothermal Heat Pumps • Agriculture • Aquaculture • Industrial applications • Conclusion and case studies

  3. Enel 2006 Results Net installed capacity (MW) 50,776 Domestic 40,475 International 10,301 Electricity Distribution & Sales Enel distribution (TWh)267.6 Domestic 255.0 International 12.6 Enel sales (TWh) 159.9 Domestic 142.7 International 17.2 Customers (millions) 32.5 Domestic 30.4 International 2.1 Netz (km/thousands) 1,179.3 Power plants MW Hydro (616 pp) 18,151 Thermal (53 pp) 28,857 Wind (46 pp) 591 Geothermal (31 pp) 671 Other Renewables (6 pp) 46 Nuclear (2 pp) 2,460 Total production (TWh) 131,4 Domestic 103.9 International 27.5 Gas Distribution & Sales Enel Sales (bcm) 4.5 Customers (millions) 2.3 Gas Pipeline (km/thousand) 31.1

  4. Canada 22 MWHydro, biomass Italy 15,358 MW Hydro, geothermal, wind, solar USA 380 MWHydro, wind Guatemala 69 MW - Hydro Slovakia 2.329 MW Hydro El Salvador 44 MW geo Costa Rica55 MW - Hydro, wind Brazil 97 MW - Hydro Panama300 MW - Hydro Spain900 MW Hydro, wind, cogeneration Chile100 MW - Hydro Over 19.000 MW of renewable energy

  5. Northern Pool SouthEastern EU NorthAmerica Iberia Central EU + Centrel + Italy LatinAmerica • Growth in all technologies & upstream gas in Europe and Russia • Growth in Renewables worldwide A solid international player

  6. Contents • 1° PART • Introduction • Geothermal energy basic concepts • Electricity generation • Binary plants • Case studies • 2° PART • Low Enthalpy applications • Introduction • Direct Uses • SPA • Heating • Geothermal Heat Pumps • Agriculture • Aquaculture • Industrial applications • Conclusion and case studies

  7. Power plant Meteoric water Production wells Steam gathering system Drilling rig Reinjection well Caprock Thickness 500 – 1500 m Impervious rocks Hot fluid Reservoir Porous – fractured rocks Tickness 500 – 1500 m T = 150 – 300 °C Geothermal system Utilization of geothermal energy has been limited to areas in which geological conditions permit a carrier (water in the liquid phase or steam) to 'transfer' the heat from deep hot zones to or near the surface, thus giving rise to geothermal system Heat source Depth 5-10 km T > 600- 700 ° C

  8. Geothermal systems

  9. Temperature use for direct use applications

  10. Utilization of geothermal energy as a function of the resource temperature

  11. Energy saving & pollution avoided • Electric use • Energy saving of fuel oil per year 96,6 million barrels or 14, 5 millions tonnes • Carbon pollution avoided (millions tonnes year) 3 (natural gas) or 13 (oil) or 15 (coal) • Direct uses • Energy saving of fuel oil per year123,4 million barrels or 18,5 millions tonnes • Carbon pollution avoided (millions tonnes year) 4 (natural gas) or 16 (oil) or 18 (coal) Total energy saving of fuel oil per year over 220 million barrels Total carbon pollution avoided per year over 29 (oil) million tonnes

  12. Contents • 1° PART • Introduction • Geothermal energy basic concepts • Electricity generation • Binary plants • Case studies • 2° PART • Low Enthalpy applications • Introduction • Direct Uses • SPA • Heating • Geothermal Heat Pumps • Agriculture • Aquaculture • Industrial applications • Conclusion and case studies

  13. Geothermal system

  14. Germany 8 MW Austria 1 MW Italy 811 MW China 28 MW France 15 MW Turkey38 MW USA 2687 MW Thailand 0,3 MW Iceland421 MW Russia 79 MW Portugal 23 MW Japan 535 MW Mexico 953 MW Philippines 1970 MW Ethiopia 7 MW Guatemala53 MW PapuaNew Guinea 56 MW Costa Rica163 MW Indonesia 992 MW Nicaragua87 MW Kenya 129 MW El Salvador204 MW Australia 0,2 MW New Zealand 472 MW GEOTHERMAL ELECTRICIT WORLDWIDE TOTAL INSTALLED CAPACITY 9,7 GW

  15. Contents • 1° PART • Introduction • Geothermal energy basic concepts • Electricity generation • Binary plants • Case studies • 2° PART • Low Enthalpy applications • Introduction • Direct Uses • SPA • Heating • Geothermal Heat Pumps • Agriculture • Aquaculture • Industrial applications • Conclusion and case studies

  16. Generating electricity from low-to-medium temperature geothermal fluids and from the waste hot waters coming from the separators in water - dominated geothermal fields has made considerable progress since improvements were made in binary fluid technology. The binary plants utilize a secondary working fluid, usually an organic fluid that has a low boiling point and high vapour pressure at low temperatures when compared to steam. The secondary fluid is operated through a conventional Rankine cycle: the geothermal fluid yields heat to the secondary fluid through heat exchangers, in which this fluid is heated and vaporizes; the vapour produced drives a normal axial flow turbine, is then cooled and condensed, and the cycle begins again.

  17. By selecting suitable secondary fluids, binary systems can be designed to utilize geothermal fluids in the temperature range 85-175°C. The upper limit depends on the thermal stability of the organic binary fluid, and the lower limit on technical-economic factors: below this temperature the size of the heat exchangers required would render the project uneconomical. Apart from low-to-medium temperature geothermal fluids and waste fluids, binary systems can also be utilized where flashing of the geothermal fluids should preferably be avoided (for example, to prevent well sealing). In this case, downhole pumps can be used to keep the fluids in a pressurized liquid state, and the energy can be extracted from the circulating fluid by means of binary units.

  18. After long trial and error, binary plant technology is emerging as a very cost-effective and reliable means of converting into electricity the energy available from water-dominated geothermal fields (below 175°C). A new binary cycle system has been developed recently, called the Kalina cycle. The Kalina cycle uses an ammonia-water mixture as the working fluid and takes advantage of regenerative heating. The ammonia-water mixture has a low boiling point, so that the excess heat coming from the turbine’s exhaust can be used to vaporize a substantial portion of the working fluid. This plant is estimated to be up to 40% more efficient than existing geothermal binary power plants.

  19. BOTTOM CYCLE BINARY PLANT In many cases, additional generating capacity may be obtained in a cost-effective manner by repowering existing geothermal power plant utilizing otherwise untapped geothermal energy, without additional wells; For cost effective power generation, the extraction of heat from geothermal fluid must be maximized; Often this repowering also provides concomitants environmental benefits, since it conserves energy while reducing environmental hazardous waste; These plant retrofit additions can be designed at any stage of the life of each generation facility, they are modular and can be realized in different steps; The typical cost is two million USD for MW and the timing for the realization of the entire phases of the project can be very short (one year); Approximately 150 MW are installed worldwide. LOW TEMPERATURE BINARY PLANT • In many cases where it is present a low temperature resource, binary plant technology is the only one feasible for electricity generation from geothermal fluid; • There are about 600 MW of binary plants installed worldwide.

  20. The utilization of geothermal energy for the electricity production reached the value of 9,000 MW in 24 countries; The economics of electricity production is influenced by the drilling costs and resource development; The productivity of electricity per well is a function of reservoir fluid thermodynamic characteristics (phase and temperature); The higher the energy content of the reservoir fluid, the lesser is the number of required wells and as a consequence the reservoir CAPEX quota is reduced: Utilization of low temperature resource can be achieved only with binary plant. Binary plant can be an efficient way for recovery the energy content of the reservoir fluid after its primary utilization in standard flash plant, achieving a better energy efficiency of the overall system.

  21. Reservoir fluid Utilization Energy Content Electricity Production Direct uses of the Heat High Enthalpy Low Enthalpy Steam Dominated Water Dominated BINARY PLANT BOTTOM CYCLE BINARY PLANT

  22. BINARY PLANTS FOR OPTIMIZATION OPTIMIZATION • Bottoming cycle technique is widely used worldwide, as shown in the attached table; • This electricity is produced using the waste water from the separated brine: it can be considered as an un-expensive and rich of value by-product of the primary flash power plant. LOW TEMPERATURE • For temperature below 150°C, the conventional flash is not able to reach satisfactory efficiency: at this temperature, only 10% of steam can be produced at about 1 bar of separation pressure; the steam will have a very low efficiency, due to its low pressure and temperature, for producing 20 MW it will be necessary to mine up to 3,000 t/h of fluid (to be compared with 500 t/h from 300°C liquid reservoir); • The UNIQUE way to exploit the geothermal energy for producing electricity is the use of a binary plant on the pressurized fluid, which will be handled through a closed loop from production and reinjection. • It is a zero emission cycle. The total installed capacity of such binary plants is about 600 MW worldwide.

  23. chimney The hot reinjection fluid at 170°C is approximately 2-3 times the steam fraction, accordingly to the initial fluid temperature; this energy can be utilized using a BOTTOM CYCLE BINARY PLANT • Average value for 20 MW plant (Res. Temp. 300°C) • Fluid extraction 470 t/h • Steam in 140 t/h Fluid (30% of the fluid) • Flash: temperature 170°C and pressure 8 bar • Gas out 4 t/h • Cold Reinjection 40 t/h • Hot reinjection 330 t/h • Cooling tower evaporation 96 t/h (75% of steam) Non condensable gas ~ Gas extractor turbine generator separator Two phase mixture from reservoir Cooling tower condenser Liquid phase for the reinjection at 170°C Cold reinjection (20°) Discarded water Steam and non condensable gas Typical Flash plant from high enthalpy Liquid Reservoir

  24. In El Salvador, our local partner LaGeo installed a new bottom cycle binary plant at the existing old power station of Berlin (2x28 MW, completed in 1999), using the separated water from four wells; it is utilized in two heat exchanger for boiling an organic fluid (Isopentane), which has a low temperature boiling point; the isopentane steam expands into a 9,5 Gross MW turbine, generating 7,8 MW net of electricity, without any additional expenditure from the reservoir development, and achieving a better utilization of the overall energy content of the geothermal fluid. The cost for this unit is 16,5 MUSD, with a very positive return of the investment Total utilized geothermal fluid 1,000 t/h at 180°C; isopentane flow rate 700 t/h, working between 160°C and 44°CC; wet cooling tower; GE turbine, ABB generator; Mexican heat Exchanger; Enex (ICELAND) design and EPC contractor.

  25. Heat Exchanger Turbine Power Plant Housing

  26. Chena Hot Springs is located approximately 100 km northeast of Fairbanks, Alaska, in the interior of the state. In August 2006 a low temperature power plant was commissioned to provide power for the isolated resort. The 200 kW plant, a binary or organic Rankine cycle unit built by United Technology Corporation, is the first geothermal power plant in Alaska, and uses the lowest temperature geothermal resource in the world at 74°C for power generation. The secondary fluid in the plant is R-134a, which has a lower boiling point than water and is heated by geothermal water at 32 l/s through a heat exchanger at 74°C. Cooling water from a shallow well or infiltration gallery is around 4°C, providing a large temperature difference which improves the efficiency of the system. As the resort is isolated from the electric grid, it has used diesel generators in the past, costing around 30 cents/kWh with a daily average cost of $1,000. The new power plant will provide electricity at 7 cents/kWh, a major saving for the resort. Maintenance is estimated to be $50,000 per year. The total unit cost around $1,300 per installed kW. Plans are to add another 200 kW unit, and then shortly to reach one MW.

  27. TURKEY: Salavatli geothermal field is located in one of the most promising geothermal regions, namely on the northern flank of Menderes graben. The Salavatli-Sultanhisar geothermal system was delimited after a resistivity survey. Two wells were drilled in 1987 and 1988 to 1500m and 962m, and temperatures of 170°C were recorded. In the past two years, two more wells were also drilled to the depths 1300m and 1430m for reinjection and stand by production, and both have struck similar temperatures. The geothermal fluid contains an average of 1% of CO2 by weight, which is similar to that of other geothermal fields in the region. An air cooled binary power plant with 7 MWe gross power is being installed. Specific consumption of plant is 500 t/h of water at 156°C, discharged at 76°C, producing 8 MW in winter and 5,3 MW in summer; 600 kW parasitic load of fan cooling.

  28. USA: Enel has finalized the acquisition of four geothermal field in USA; these reservoirs should be exploited through binary plants. The relevant data are collected in the attached table. As working fluid has been selected the isobutane, for achieving better performances in such range of temperatures. The use of isobutane will requires higher operating pressure which could result in slight increase in equipment cost, and it implies an increase of risks concerning safety aspects due to higher operating pressures (near supercritical conditions) and its higher volatility respect to isopentane. All plants will be air cooled, while the Cove Fort units I and II will be water cooled, due to availability of water source.

  29. CONCLUSION The most abundant geothermal resource in the world is given by hot pressurized water. Whereas in the dry steam reservoir (Larderello-Italy, The Geyser-USA) the exploited energy of the fluid can be fully utilized, in all the other situation the majority of the thermal energy from the extracted fluid is lost, being reinjected at high temperature and practically not-used and wasted. The binary plants on the reinjection stream could be a very effective way of producing cheap energy, because there will not be any additional mining costs associated with this extra production The binary plants technology represents an unique way of producing geothermal electricity for medium/low temperature geothermal system, Increasing the overall exploitable potential worldwide

  30. Thanks for your attention For any further information please contact me at the following e-mail address: ruggero.bertani@enel.it

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