Transcript
GEOTHERMAL POWER PLANT
By :Muhammad Nawawi
Ekawati Prihatini
Presented in Professional Management Presented in Professional Management ProgramProgram
University of CanberraUniversity of CanberraJuly 12July 12ndnd, 2007, 2007
OUTLINEDescriptionTechnology to Generate Geothermal Power PlantElectrical Capacity and CostsEnvironmental ImpactsSocioeconomicSummaryRecommendation
What is Geothermal Energy? Geo : (Greek) - Earth
Thermal : relating to, using, producing, or caused by heat.
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.
The EarthRadius of 6370 kmThree 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, 4000oC and 3.6 million bars)
Earth Temperature Gradient
Earth Dynamics
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.
What can we do with heat?
conventional geothermal plants capture hot water from geysers or steam from
vents to spin turbines
How Have People Used Geothermal Energy In The Past?
comforting warm waterstreat eye and skin diseasecooking and medicineheating homes
How Do We Use Geothermal Energy Today?
to generate electricity in geothermal power plants or for energy saving non-electrical purposes.
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Technology to Generate Geothermal Power Plant
Surface Geothermal Systems
There are three different types surface of Geothermal system designs :Dry Steam Power Plants Flash / Steam PlantsBinary cycle power plant
Units of MeasurePressure
1 Pascal (Pa) = 1 Newton / square meter100 kPa = ~ 1 atmosphere = ~14.5 psi1 MPa = ~10 atmospheres = ~145 psi
TemperatureCelsius (ºC); Fahrenheit (ºF); Kelvin (K)0 ºC = 32 ºF = 273 K 100 ºC = 212 ºF = 373 K
A. Dry Steam Schematic
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-generatorSteam is condensed and pumped back into the groundCan achieve 1 kWh per 6.5 kg of steam
A 55 MW plant requires 100 kg/s of steam
B. Flash or Steam plants
Hot, High pressure water Turbines generate electricityCosts 4-6 cents per Kwh.
Single Flash Steam Power Plants
Steam with water extracted from groundPressure of mixture drops at surface and more water “flashes” to steamSteam separated from water Steam drives a turbine Turbine drives an electric generatorGenerate between 5 and 100 MWUse 6 to 9 tonnes of steam per hour
Flash Steam Power Plant
C. Binary Cycle Power Plant
Hot water (100 – 300 deg F) Heat Exchanger Binary liquid lower specific heat (vaporizes)
Binary Cycle Power PlantsLow temps – 100o and 150oCUse heat to vaporize organic liquid
E.g., iso-butane, iso-pentaneUse vapor to drive turbine
Causes vapor to condenseRecycle continuously
Typically 7 to 12 % efficient0.1 – 40 MW units common
Binary Cycle Power Plant
EfficiencyFunctions like a conventional coal power plant.
Efficiencies vary by input heat.
At 400 deg. expect ~ 23%, not including parasitic load.
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Geothermal capacityHeat flow though the earth’s crust with:
Flow rate of 59 mW/m2 or 1.9 x 10-2 Btu/h/ft2Due to:
Convection and conduction from the mantle coreRadioactive decay of U, Th, K
Useful rock temperature150-200 C for electricity production100-150 C for other heating purposes
Geothermal Sites in US
Electricity productionDifferent types of cycle give efficiency from 5%-14% depend on temp
Electrical output
Where output at 40 C output geofluid
Recoverability ( useful energy)
Depth ofSlice, km
Poweravailable forslice, MWe
Amount at150°C,MWe
Amount at200°C,MWe
Amount at250°C,MWe
Amount at300°C,MWe
Amount at350°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 3600 s/hr. = 9.46 x 108 s
“Typical” Cost for Geothermal Power Plant
Permitting
Drilling
Steam Gathering
Transmission
Power Plant equipment & construction
Exploration
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 Plantequipment & construction
$1500 $75 million
Transmission $100 $5 million
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 unknownPlant size: the larger the plant, the less the cost per megawatt (economies of scale)
Well characteristics: depth, diameter, productivity
Properties of the rock formation
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
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
Drilling costSame for oil, gas and geothermal wellsDepends on:
Well typeDepth Location of wells
Cost and performance of 1MW geothermal plant as a function of temp
Geothermal energy and economics
Reduce in energy price Meet market price after 2nd yearlong-term stability and characteristic power curve : run all year round
Cost FactorsTemperature and depth of resourceType of resource (steam, liquid, mix)Available volume of resourceChemistry of resourcePermeability of rock formationsSize and technology of plantInfrastructure (roads, transmission lines)
Costs of Geothermal Energy
Costs highly variable by siteDependent on many cost factors
High exploration costsHigh initial capital, low operating costs
Fuel is “free”Significant exploration & operating risk
Adds to overall capital costs“Risk premium”
Cost of Water & SteamCost
(US $/ tonneof steam)
Cost (US ¢/tonne of hot water)
High temperature (>150oC)
3.5-6.0
Medium Temperature (100-150oC)
3.0-4.5 20-40
Low Temperature (<100oC)
10-20
Cost of Geothermal PowerUnit Cost
(US ¢/kWh) High Quality
Resource
Unit Cost (US ¢/kWh)
MediumQuality
Resource
Unit Cost (US
¢/kWh) Low Quality
ResourceSmall plants
(<5 MW)5.0-7.0 5.5-8.5 6.0-10.5
MediumPlants
(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
Direct Capital CostsPlantSize
High QualityResource
Medium QualityResource
Low QualityResource
Small plants (<5 MW)
Exploration : US$400-800 Steam field:US$100-200Power Plant:US$1100-
1300Total: US$1600-2300
Exploration : US$400-1000
Steam field:US$300-600Power Plant:US$1100-
1400Total: US$1800-3000
Exploration : US$400-1000 Steam field:US$500-900Power Plant:US$1100-
1800Total:US$2000-3700
Med Plants (5-30 MW)
Exploration : US$250-400 Steamfield:US$200-
US$500Power Plant: US$850-
1200Total: US$1300-2100
Exploration: : US$250-600
Steam field:US$400-700Power Plant:US$950-
1200Total: US$1600-2500
Normally not suitable
Large Plants (>30 MW)
Exploration:: US$100-200 Steam field:US$300-450Power Plant:US$750-
1100Total: US$1150-1750
Exploration : US$100-400 Steam field:US$400-700Power Plant:US$850-
1100Total: US$1350-2200
Normally not suitable
Direct Capital Costs (US $/kW installed capacity)
Indirect CostsAvailability of skilled laborInfrastructure and accessPolitical stabilityIndirect Costs
Good: 5-10% of direct costsFair: 10-30% of direct costsPoor: 30-60% of direct costs
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Advantages and Disadvantages
Advantages of Geothermal
Solid and Gas EmissionsNo 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.
Comparison of Gas Emissions
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.
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The Environmental Impacts
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.
Comparison of Land Requirement for Baseload Power Generation
Thermal PollutionIt is one of the biggest concerns due to considerable loss of thermal heat.Taller cooling towers are needed to contain the waste heat.
Noise Pollution
Noise does occur during initial construction and drilling.Noise is minimum.
0
20
40
60
80
100
120
Source(dB)
AirDrillingMudDrillingWellDischargeWellTestingHeavyMachinery
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.
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.
Geothermal Plants In Harmony with Nature
Immense potentialAlthough 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 years100,000 MWe is projected to be extracted in the next 50 years
EnvironmentLow 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
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SOCIO ECONOMICS
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)
Increasing national security Producing Power at home Benefiting rural, economically depressed areasProviding jobs
Social Issues
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
aesthetic concerns
Externalities that should be considered include:
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
employmentBack
In SummaryFurther development of Deep Geothermal Energy should be highly considered because of its
Potential to allow new access to large resourcesEnvironmentally friendly traitsCompetitive costs in the long runAbility to use existing technologies to begin extraction soon
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Recommendations
An analysis on the reasons to move forward in the development of deep geothermal systems
☺Thank You …
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