ECEn 490 –Winter 2015 Lecture # 11 Introduction to ECEn 490.
ECEN 5007 - Lecture 9
Transcript of ECEN 5007 - Lecture 9
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ECEN 5007 SOLAR THERMAL POWER PLANTS
Lecture 9: Thermal Energy Storage and Hybridization
July 26, 2012
Manuel A. Silva, Dr.Ing. - Manuel J. Blanco, Ph.D., Dr.Ing.
TWTH 17:00-19:30 - Class Room: ECCR 1B55
Office Hours: TWTH 15:30-16:30
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Dispatchability
The ability to dispatch power. Dispatchable
generation refers to sources of electricity that can be
dispatched at the request of power grid operators;
that is, it can be turned on or off upon demand
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Thermal storage and Hybrization
} STP unique features within the RE technologies:} Thermal energy storage. Thermal energy produced by
the solar fieldcan be stored, decoupling power
generation from solar resource.
} Hybridization. Ability to hybridizewith an alternativeenergy source fossil or renewable fuel.
} Thermal energy storage and/or hybridizationprovide the basis for CSP to be:
} Dispatchable} Stable} Reliable
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Thermal Energy Storage
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} Andasol} Gemasolar
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Why Energy Storage?
} Increase operational stability} Reduce intermittence.} Increase plant utilization and capacity factor} Permits time-shifted operation (decouples electricity
generation from solar energy collection)} Reduce generation cost (as long as storage + solar field
oversizing results cheaper than increasing rated power!)
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Profile of the electricity demand
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Solar-only electricity generation
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Solar + Thermal Storage
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Thermal energy storage
} A fraction of the thermal energy produced at the solar field isstored, increasing the internal energy of the storage medium.
} Sensible heat} Latent heat} (Thermochemical)
} The solar field has to be oversized} Solar Multiple = (thermal power delivered by the field at design
conditions) / (thermal power required to generate rated electric
power)
}SM > 1
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Types of thermal storage
} By utilization} Short term
} Provide operational stability} Medium term
} Increase capacity factor} Shift electrical generation hours
} By type} Direct (same substance as working fluid, does not require HX)} Indirect (different substance, requires HX)
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Technical Requirements for TES materials
} High energy density (per-unit mass or per-unit volume)} Good heat diffusivity and conductivity} Good heat transfer between heat transfer fluid (HTF) and the
storage medium
} Mechanical and chemical stability at operating conditions} Chemical compatibility between HTF, heat exchanger and/or
storage medium
} Reversibility for a large number of charging/discharging cycles} Low thermal losses}
Easy to control
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Thermal storage options
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Solid materials
Liquid materials
Source: Gil, A. et al. State of the art on high temperature thermal energy storage for power generation.
Part 1Concepts, materials and modellization. Renewable and Sustainable Energy Reviews. January 2010
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Thermal storage options - PCM
27/07/12Source: Gil, A. et al. State of the art on high temperature thermal energy storage for power generation.
Part 1Concepts, materials and modellization. Renewable and Sustainable Energy Reviews. January 2010
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Thermal storage past experiences
Source: Survey of thermal storage for parabolic trough power plants, Pilkington Solar Int. (2000)27/07/12
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TES STP commercial installations
} Short term: pressurized water} PS10 and PS20
} Mid term: Molten salt, 2 tank}
Direct (CRS) Gema Solar (Solar Tres)} Indirect (PT) Andasol I
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Short term TES
} Pressurized water} Sliding pressure during discharge} Pressure vessel
PS10 / PS20
Max. pressure: 40 bar Thermal capacity: 20 MWh
(50 min at 50% load)
Total Volume: 600 m3 4 tanks, sequentially
operated
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Molten salt storage, 2 tank, direct
} Thermal capacity proportionalto T
} Hot cold tank design} Commercial (salt widely used
in process industry)
High operation T limited(salt decomposition)
Need for heat tracing(risk of freezing)
Costly equipment(pumps, valves)
Solar Two (Barstow, CA)
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Molten salt TES
} GEMASOLAR (Torresol Energy)
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GEMASOLAR
} Type: 2 tanks, molten salts} Fluid: NO3 mixture
(60% NaNO3 - 40% KNO3)
} Freezing point: 223C} Capacity: 640 MWh
(~15 h full load operation)} Tank size: 14 m high, 23 m diameter} Molten salt mass: 8000 tons approx} T cold tank: 290 C} T hot tank: 565C
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Molten salt TES, 2 tanks, indirectANDASOL and other
Needs oil-to-salt HXs Freezing point = 220 oC T max. limited by HTF Large volumes (small T) Increases investment
Provides large storagecapacity to PT plantsusing thermal oil as HTF
Andasol (Granada, Spain)
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Andasol TES Technical characterisitics
} Type: 2 tanks, molten salts} Fluid: NO3 mixture
(60% NaNO3 - 40% KNO3)
} Freezing point: 223C} Capacity: 1,010 MWh
(~7.5 h full load operation)} Tank size: 14 m high, 37 m diameter} Molten salt mass: 27,500 tons} T cold tank: 292 C} T hot tank: 386C
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ANDASOL
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R&D Activities. Concrete storageDual medium
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R&D activities.Thermocline, phase change, sand storage
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R&D activities. Thermocline} Single tank system, .} Hot and cold fluids separated by stratification;
the zone between the hot and cold fluids iscalled the thermocline.
} Usually a filler material is used to help thethermocline effect.
} Sandia National Laboratories identifiedquartzite rock and silica sands as potentialfiller materials.
} Depending on the cost of the storage fluid,the thermocline can result in a substantiallylow cost storage system.
} This system has an additional advantage: mostof the storage fluid can be replaced with alow cost filler material, for example, quartziterock and sand.
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Thermocline tank operation
HTF from Field
HTF Return
Salt-to-Oil
Heat
Exchanger
Thermocline Tank
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Latent heat storage (Phase change)
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} Isothermal thermal energy storage as the latent heat of phasechangephase change materials (PCM).} Reduced in size compared to single-phase sensible heating
systems.
} Heat transfer design and media selection are more difficult,} Degradation of salts after moderate number of freezemelt
cycles (experience with low-temp salts).
} Phase change materials allow large amounts of energy to bestored in relatively small volumes, resulting in some of the
lowest storage media costs of any storage concepts.
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R&D activities. Phase change.Cascaded LHS
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R&D activities. Phase change. DISTOR project
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R&D activities. Sand (fluidised bed)
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TES costs and benefits
} Improves plant controlability and operability, expanding derange of possible operating strategies
} Facilitates Dispatchability} If adequately designed, can improve
} The efficiency of the plant} The profitability of the project
} Extends lifetime of equipment (reduces the number of strat-stop cycles)
} Increases investment} Oversized solar field}
Tanks, HX, molten salt management equipment, heat tracing, safety} Increases O&M costs
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Simulating operational strategies with EOS
Clear day, summer
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Simulating operational strategies with EOS
Cloudy day, winter
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Gemasolar
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ntral de
17 MWe & 15 horas de almacenamiento. 24h de produccin en veran
Energa trmica delcampo solar
Energa trmicaen el tanque
Produccin de energa
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Hybridization options
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SEGS 30 MW
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Andasol-type plants(thermal storage and auxiliary boiler)
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ISCCS
}3 projects in North Africa (Morocco, Algeria, Egypt)
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Unit #1 (100 kW hybrid GT) (Aora Solar, Israel)
14/7/1038 GEEN 4830 ECEN 5007
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HybridizationCosts and benefits
Improves controlability and operability Faciltates dispatchability Improves plant overall efficiency Improves capacity factor Improves profitability of the plant Extends equipment lifetime Increases investment and O&M costs CO2 emmissions
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