GEOTHERMAL POWER PLANTS

Transcription

1 UNU-GTP, KenGen and MEMD-DGSM Short Course on Geothermal Project Management and Development. Entebbe, Nov , 2008 GEOTHERMAL POWER PLANTS Benedikt Steingrímsson Sverrir Þórhallson Einar Tjörvi Elíasson Iceland GeoSurvey (ÍSOR), Reykjavík, Iceland

2 Content Geothermal power generation, history, advantages and concerns Geothermal fields suitible for power generation Overview of power plant designs: World survey of geothermal plants currently in use Prevailing problem types and countermeasures res in operation of power plants. Power plant design parameters

3 Geothermal Power Plant

4 Few historical milestones in Geothermal Power Generation (Present installed power is close to 10,000 MW Geothermalgeneration demonstrated in Larderello, Italy kw plant put into service in Larderello Larderello redeveloped after WW The Wairakei in NZ commissioned 192 MW The Geyser field California i starts t at only 14 MW Námafjall, Iceland 3.2 MW Tivi, i Phillipinesi 330 MW Olkaria, Kenya, 45 MWe

5 Geothermal Power Generation in Iceland Installed power 575 MW in Electricity Generation n (GWh/yea ar) Hellisheiði 213 M W Reykjanes 100 M W Húsavík 2 M W Nesjavellir 120 M W Bjarnarflag 3,2 M W Krafla 60 M W Svartsengi 76,4 M W Year

6 Geothermal Power: Advantages over other renewable energy sources High degree of availability (>98% and 7500 operating hrs/annum common) Low land use Low atmospheric pollution compared to fossil fuelled plants Almost zero liquid id pollution with re injection of effluent liquidid Insignificant dependence on weather conditions Comparatively low visual limpact

7 Environmental Concerns in Geothermal Roads, drilling platforms, pipelines and power lines Pollution of air and waters Geothermal activity alters or vanishes Rare plants and micro biota are lost Geothermal fields are often in natural conservation areas

8 High temperature steam dominated dfields T=240 C and P 35 bar Depth: 1 3 km Related to volcanism and plate boundaries Suitable for electricity production o with conventional o turbines The first fields to be developed for power generation, Larderello, Geysers and Kamojang

9 High temperature liquid dominated fields C Depth: 1 3 km Related to volcanism and plate boundaries Suitable for electricity production with conventional turbines The first wet field to be developed for power generation was Wairakei Nesjavellir, Iceland. 300 C fluid used to produce electricity

10 Medium temperature liquid dominated fields C 1 5 km Mostly found din deep sedimentary basins around the world as well as in volcanic areas High flowrates necessary for electricity Binary systems needed for electricity production Húsavík, Iceland. 124 C water used to produce electricity

11 The three basic turbo generating systems Flashed steam back pressure system; resource temperature range from about 320 C to some 200 C Flashed steam/dry steam condensing system; resource temperature range from about 320 C to some 230 C Binary ayor twin fluid udsyste system (based upon the Organic Rankin or the Kalina cycle); resource temperature range between 100 C to about 200 C

12 Typical Back Pressure Unit Layout

13 Typical Condensing Unit Layout Water Steam Steam Turbine / Generator Electricity Sepa rator Conde enser Cooling Tower Water Production Well T > 230 C Reinjection Well

14 Typical Binary Plant Layout Working Fluid Steam Steam Turbine / Generator Electricity Evapo orator Conde enser Cooling Tower Water Production Well 100 C < T < 200 C Reinjection Well

15 Hybrid Binary/Back Pressure Layout

16 The Nesajvellir Plant Electricity and hot water production

17 Krafla: Single and Twin Pressure Condensing Plant Layout

18 Typical Binary (Kalina) Plant Layout

19 Installed capacity of geothermal power plants. Data from Bertani i(2005, 2007 and 2008). COUNTRY Year: * China Costa Rica El Salvador Ethiopia France (Guadeloupe) Guatemala Iceland Indonesia Italy Japan Kenya Mexico New Zealand Nicaragua Papua New Guinea Philippines Portugal Russia Turkey USA Total:

20 2005 World review of Geothermal Plant types Plant type Installed capacity (MW e ) Percent Number of units Percent Average size Dry steam 2, Single flash 3, Double flash 2, Binary/combined cycle/hybrid Back pressure Total 8, Installed/generated geothermal electricity per continent MWe GWh/year Installed capacity (Mwe) Electricity generation (GWh/year) Africa America Asia Europe Oceania

21 Operation of Power Plants Problems and countermeasures The Problems are found in: Power house equipment: Automatic control and communication system: Cooling system: Particulate and/or droplet erosion: Heat exchangers: Gas evacuation systems: Re injection system:

22 Operation of Power Plants Problems and countermeasures The main problems are related to: 1. Scaling 2. Corrosion 3. Gas emission For countermeasures see the paper

23 Power Plant Design Parameters Resource Type of resource: Steam dominated or liquid dominated Steam conditions: Optimum turbine inlet steam pressure. Gas (% NCG) in steam. Size (thickness and areal extent), and long term capacity, and natural recharge Temperature and pressure of deep resource fluid Chemical composition (liquid and gas phase) of deep fluid Well productivity/injectivity Two phase zones.

24 Power Plant Design Parameters Accessibility Topography of resource area Remoteness from population centres Closeness to nature parks and environmentally restricted areas Market Size, type and security of market Proximity of market Accessibility to existing power transmission lines, substations

25 Power Plant Design Parameters Permits etc. Resource concessions Exploration permits Drilling permits Development permits Environmental Impact Assessment Building and other permits Pre and post investment studies, business plan

26 Summary Geothermal Power Generation is a well known technology which celebrated its 100anniversary in There is a wide range in the properties of the geothermal resources that has to be taken into account when designing the Power Plant. Operational problems are several but can be overcome by proper material selection, correct countermeasures and good maintenance. The world wide installed capacity is now about MW and annual increase has been about 200 MW/year for the last few years this has grown to about 500 MW/year. There is still a lot of unused geothermal power potential in the world

27 The Krafla Geothermal Power Plant Emil Thor Thank you