thermodynamic strategies for pumped thermal exergy storage...
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Thermodynamic strategies forPumped Thermal Exergy Storage (PTES)
with liquid reservoirs
Pau Farres-Antunez
Dr. Alex White
Department of Engineering
UK Energy Storage ConferenceBirmingham. 1st December 2016
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Thermo-mechanical energy storage (TMES)
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Thermo-mechanical energy storage (TMES)
Compressed air energy storage (CAES)
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Thermo-mechanical energy storage (TMES)
Compressed air energy storage (CAES) Liquid air energy storage (LAES)
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Thermo-mechanical energy storage (TMES)
Pumped thermal exergy storage (PTES)
Compressed air energy storage (CAES) Liquid air energy storage (LAES)
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Thermo-mechanical energy storage (TMES)
Pumped thermal exergy storage (PTES)
Compressed air energy storage (CAES) Liquid air energy storage (LAES)
➔ High efficiency
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Thermo-mechanical energy storage (TMES)
Pumped thermal exergy storage (PTES)
Compressed air energy storage (CAES) Liquid air energy storage (LAES)
➔ High efficiency
➔ High energy density➔ Geographical
independence
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Solid and liquid storage media
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Solid and liquid storage media
PTES with solid reservoirs
➔ Large heat transfer area➔ Pressurised hot tank➔ Thermal fronts
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Solid and liquid storage media
PTES with solid reservoirs PTES with liquid reservoirs
➔ Large heat transfer area➔ Pressurised hot tank➔ Thermal fronts
➔ Limited temperature ranges➔ Unpressurised tanks➔ Tanks at single temperature
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Solid and liquid storage media
PTES with solid reservoirs PTES with liquid reservoirs
➔ Large heat transfer area➔ Pressurised hot tank➔ Thermal fronts
➔ Limited temperature ranges➔ Unpressurised tanks➔ Tanks at single temperature
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Different cycles
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Different cycles
Gas cycle➔ Sensible heat storage➔ High energy density➔ Low work ratio (~2.5)
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Gas cycle
Supercritical CO2
➔ Sensible & latent heat➔ Moderate work ratio (~5)➔ Low energy density
Different cycles
➔ Sensible heat storage➔ High energy density➔ Low work ratio (~2.5)
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Gas cycle
Supercritical CO2
Steam cycle
➔ Sensible & latent heat➔ Moderate work ratio (~5)➔ Lower energy density (x1/4)
➔ Very high work ratio (>100)➔ Latent heat exchangers in
development stage➔ Requires additional Ammonia
cycle for charging phase
Different cycles
➔ Sensible heat storage➔ High energy density➔ Low work ratio (~2.5)
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Thermodynamic strategies
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Thermodynamic strategies
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Thermodynamic strategies
➔ Increasing the top temperature improves WR (→efficiency) and energy density
➔ A limit for Tmax exists due to constraints on compressor and energy storage materials (e.g. common molten salts)
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Thermodynamic strategies
➔ We can continue to improve WR by lowering Tmin
➔ To do so, we require to incorporate a gas-gas regenerator:
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Thermodynamic strategies
➔ We can continue to improve WR by lowering Tmin
➔ To do so, we require to incorporate a gas-gas regenerator:
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Thermodynamic strategies
Same trend applies to power density!
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Thermodynamic strategies
Compressor/expander losses
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Thermodynamic strategies
Compressor/expander losses
Heat exchanger losses
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Thermodynamic strategies
Compressor/expander losses
Two compressions Heat exchanger losses
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Thermodynamic strategies
Compressor/expander losses
Three compressions Heat exchanger losses
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Thermodynamic strategies
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Thermodynamic strategies
➔ Additional stages at cold side allow to use O2 and further increase WR
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Can we build a HEX with +99% efficiency?
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Can we build a HEX with +99% efficiency?
Bejan (1996):
➔ Entropy generation is due to thermal resistance and pressure loss:
➔ For a given mass flux, exists and optimal that minimises
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Can we build a HEX with +99% efficiency?
Bejan (1996):
➔ Entropy generation is due to thermal resistance and pressure loss:
➔ For a given mass flux, exists and optimal that minimises
We can apply the analysis to a counter-flow HEX, flat plate or shell-and-tube:
➔ and
➔ Use standard heat transfer and flow-friction correlations
➔ Find an analytical expression:
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Can we build a HEX with +99% efficiency?
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Can we build a HEX with +99% efficiency?
Turbulent regime
Laminar regime:
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Can we build a HEX with +99% efficiency?
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Can we build a HEX with +99% efficiency?
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Can we build a HEX with +99% efficiency?
~1000m2/MW and ~1m3/MW at 99% efficiency
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Concluding remarks
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Concluding remarks
● PTES: high energy density and geographical independence
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Concluding remarks
● PTES: high energy density and geographical independence
● Using liquid tanks allows to:
Pressurise working fluid
Have lower self-discharge and a well-defined state-of-charge
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Concluding remarks
● PTES: high energy density and geographical independence
● Using liquid tanks allows to:
Pressurise working fluid
Have lower self-discharge and a well-defined state-of-charge
● Several strategies exist to improve Work Ratio
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Concluding remarks
● PTES: high energy density and geographical independence
● Using liquid tanks allows to:
Pressurise working fluid
Have lower self-discharge and a well-defined state-of-charge
● Several strategies exist to improve Work Ratio
● Designing a HEX with ~99% efficiency is key to success
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THANKS FOR LISTENING!
QUESTIONS?
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References:
Acknowledgements and references
Research Funding:● Peterhouse, Cambridge
Funding to attend UKES2016:● Peterhouse, Cambridge● Cambridge University Engineering Department, Ford of Britain Fund
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Extra slides...
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What is Pumped Thermal Exergy Storage?
Literature uses several names…
PTES: Pumped Thermal Energy Storage
PHES: Pumped Heat Electricity Storage
TEES: Thermo-Electrical Energy Storage
Electricity ElectricityThermal exergy Thermal exergy
Heat pump Heat engineStorage
CHEST: Compressed Heat Energy Storage
SEPT: Stockage d'Electricité par Pompage Thermique
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Can we build a HEX with +99% efficiency?
Turbulent regime
Laminar regime:
Min. Dh limited by min. practical LHigher pressures → Higher L and lower Dh
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