Pumped Thermal Exergy Storage Past, Present and...

Pumped Thermal Exergy Storage Past, Present and Future

Alexander White

Josh McTigue, Pau Farres-Antunez, Haobai Xue

Caroline Willich, Christos Markides (Imperial), Chris Dent (Durham)

Department of Engineering

UK Energy Storage Conference Birmingham. 1st December 2016

What is Pumped Thermal Exergy Storage?

•  The literature uses several names… •  PHES: Pumped Heat Electricity Storage •  TEES: Thermo-Electrical Energy Storage

Work Work + ? Thermal exergy Thermal exergy Heat pump Heat engine Storage

CHEST: Compressed Heat Energy Storage SEPT: Stockage d’Electricité par Pompage Thermique

UKES 2016 Birmingham


Hot Storage

Cold Storage

Combined

CHP

Th

pW

Q0

Qc

CHP

pW

Qh

Qc

Tc

Th

T

CHP

c

pW

Qh

Q0

T0

Possible embodiments of PTES


Possible embodiments of PTES (red = Isentropic’s PHES)

•  Storage type:

-  hot / cold / combined

-  sensible heat / latent heat

-  packed bed / liquid tank / other (e.g., concrete)

•  Thermodynamic cycle:

-  Rankine / Joule-Brayton / other (e.g., transcritical CO2)

•  Compression & expansion:

-  turbomachinery / reciprocating / other

•  Heat exchange:

-  direct (packed bed) / intermediate HX


A (very) brief history of PTES

1852: Kelvin’s “Heat Multiplier”

2007: (Oct): Isentropic’s PHES patent


A (very) brief history of PTES

1852: Kelvin’s “Heat Multiplier”

1924: “Thermodynamic” steam- based storage device (Marguerre)

1977: Forerunner of LAES (Smith) 1978: First solely thermal energy storage system (Cahn)

2007: (Jan): PHES patent (Wolf) 2007: (Oct): Isentropic’s PHES patent

Last Thursday: Isentropic’s SVS engine is “turned over”


Whole-system analysis (Strbac et al 2012)

-0.6-0.4-0.20.00.20.40.60.81.01.2 46 31 25

2 5 10

Annu

al s

avin

g, ´£

bn/y

Installed capacity, GW

Storage cost, ´£/kW.y

savingscost

-0.6-0.4-0.20.00.20.40.60.81.01.2 111 75 41

2 5 10

Annu

al s

avin

g, ´£

bn/y

Installed capacity, GW

Storage cost, ´£/kW.y

Bulk storage (2020) Distributed storage (2020)

•  Savings from distributed storage are greater for a given storage cost

•  Benefits are relatively insensitive to storage efficiency


Cost minimisation and endoreversible stuff (Thess, Guo et al)

Totalcost = Engine

cost+ Cost of heat

exchange + Storagecost

C = keWe + kxAx + ks

Es

ρe

CWe

= ke + kxAxWe

+ kstd

ηe ρe

A crude model of costs:

endoreversible analysis minimises this


Cost minimisation and endoreversible stuff (Thess, Guo et al)

Totalcost = Engine

cost+ Cost of heat

exchange + Storagecost

C = keWe + kxAx + ks

Es

ρe

CWe

= ke + kxAxWe

+ kstd

ηe ρe

A crude model of costs:

endoreversible analysis minimises this

Figure courtesy of Markides


Endoreversible analysis: maximum power of CHE

Q1 = αh(Th −T1)

Q2 = α0(T2 −T0)

W.p eW

.

RHE

T

RHP

h

T0

T2

T1

T3

T4

ηe

* =WpQ1

= 1− T0

Th

Chambadal-Novikov efficiency:

Maximum normalised power:

ψe =

We

(αh +α0)T0

=( Th /T0 −1)2

4

Occurs at T1 /T2 = Th /T0 and α0 = αh


Q4 = k Q1

k = discharge time, td

charge time, tc

Round-trip efficiency:

χ = COPp × ηe =

(k +1)θ − k(k +1)θ +1

where:

θ = Th /T0

eW.p W

.

RHP

T

RHE

h

T0

T2

T1

T3

T4

Q1 = αh(Th −T1)

Q2 = α0(T2 −T0)

Endoreversible analysis: efficiency for hot storage


Q4 = k Q1

eW.p W

.

RHP

T

RHE

h

T0

T2

T1

T3

T4

Q2 = α0(T2 −T0)

Q1 = αh(Th −T1)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 0.5 1.0 1.5 2.0 2.5 3.0

-250 0 250 500

Hot storage

!!R

ound

-trip

effi

cien

cy, r

Temperature ratio, Ts / T0

Storage temperature, oC

Endoreversible analysis: efficiency for hot storage


Q3 = k Q2

Q1 = α0(T0 −T1)

Q2 = αc (T2 −Tc )

.p

.We

WRHP

RHE

3

T4

Tc

T1

T2

T0

T

0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 0.5 1.0 1.5 2.0 2.5 3.0

-250 0 250 500

Hot storageCold storage

Rou

nd-tr

ip e

ffici

ency

, r

Temperature ratio, Ts / T0


Endoreversible analysis: efficiency for cold storage


0.0

0.2

0.4

0.6

0.00 0.05 0.10

-175

-125

-75

100

300500

Rou

nd-tr

ip e

ffici

ency

, r

Normalised power output, se

HotCold

Endoreversible analysis: efficiency vs. power density


Tc= -150oC

0.0

0.2

0.4

0.6

0.00 0.05 0.10

-175

-125

-75

100

300500

Rou

nd-tr

ip e

ffici

ency

, r

Normalised power output, se

HotCold

Combined

Endoreversible analysis: combined hot & cold storage


Exergetic storage density (kWh / m3)

0

50

100

150

200

250

-250 -125 0 125 250 375 500

liquid N2

CAES

hotwaterPHS

PTEShot

PTEScold

Exer

getic

den

sity

, kW

h / m

3



Isentropic’s “SVS” (Scaled Validation Model of PHES)

Hot and cold “layered” thermal stores for a 120 kW system

HOT (500 oC)

COLD (–150 oC)

Efficiency-cost optimisation (packed-bed reservoirs)


valves

86

88

90

92

94

96

98

100

0.75 1.00 1.25 1.50 1.75

Effic

ienc

y (%

)

Normalised cost per unit returned energy

R1: Hot (Argon)R2: Cold (Argon)

Isentropic’s layered store concept GA optimisation for different packed-bed thermal reservoirs (Josh McTigue, 2015)

Open symbols = layered stores


Isentropic’s “SVS” : The Engine

Double-acting “reversible” reciprocating compressor / expander

HOT side

COLD side (below gallery)


PTES is sensitive to all loss parameters (low “work ratio”)

50

60

70

80

90

100

0 5 10 15

Ther

mod

ynam

ic e

ffici

ency

, r

Pressure ratio, `

d = 0.99d = 0.95d = 0.90

50

60

70

80

90

100

0 25 50 75 100

Ther

mod

ynam

ic e

ffici

ency

, r

Pressure ratio, `

d = 0.99d = 0.95d = 0.90

Liquid PTES 2-stage A-CAES

χ = fn Pi , Ti , η j , εk , fl( )

heat exchange effectiveness

polytropic efficiencies pressure loss factors

Compression & Expansion Losses: Valve Losses

P-V diagram from an ‘off-the-shelf’ compressor

“Isentropic”’s cunning valve design

P-V diagram from “Isentropic”’s device


Early prototype piston / valve arrangement for a heat pump

Compression & Expansion Losses: Thermodynamic Losses


10ï2 10 0 10 2 10 410ï3

10ï2

10ï1

10 0

10 1

Loss

Pe

CFD Air rv=6.8

CFD Helium r v=6.8

CFD Helium r v=2.0

Exp. Helium r v=2.0

isothermal adiabatic

slow fast

Load-Integrated Energy Storage (LIES)


Electricity in

Electricity out

Refrigeration and / or cooling

Low-grade heating

More LIES


-200

0

200

400

600

-0.4 -0.2 0

1

2

3

4

Tem

pera

ture

, C

Specific Entropy, KJ/kgK

T-s Diagram

Charge Discharge

-200

0

200

400

600

-0.4 -0.2 0

1

2

3

4

Tem

pera

ture

, C

Specific Entropy, KJ/kgK

T-s Diagram

Charge Discharge

Optimised for work output Lower discharge pressure

qout < 50 oC

qout < 50 oC qout > 75 oC

The UK’s Energy Storage Inventory (data from DOE)


0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1963

1965

1974

1984

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Inst

alle

d ca

paci

ty, G

WPHS Mechanical Batteries

SUMMARY

q  PTES has good potential for distributed storage

q  High power density and efficiency go together for (hot + cold) storage

q  Possible scope for load integration (cooling / heating)

q  Low temperature PTES is probably best used for low-grade heat

q  High compression and expansion efficiencies need to be demonstrated

q  To reap the benefits of a whole-system approach it’s probably best to have a whole system


Pumped Thermal Exergy Storage Past, Present and...

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