High-Temperature Combined Sensible/
Latent-Heat Storage for AA-CAES
Experiments and Simulations
Lukas Geissbühler1, Michael Kolman1, Dr. Giw Zanganeh2, Dr. Andreas Haselbacher1, Prof. Dr. Aldo Steinfeld1
1Professorship of Renewable Energy Carriers, ETH Zurich, 2Airlight Energy Manufacturing SA, Biasca
3
Experimental tests of a combined sensible/latent-heat TES were performed at Airlight Energy SA in Biasca. The
model was compared to measurements for various operating conditions and multiple cycles.
• At present, electricity storage with advanced
adiabatic compressed air energy storage (AACAES) is considered to be the only large-scale
alternative to pumped hydro storage, offering
high cycle efficiency (70-75%) thanks to
incorporation of a thermal energy storage (TES)
system
0.0
1.0
Td ) [ ]
Simulation
Experiment, centerline
Experiment, wall
Td ) [ ]
0.4
Simulation
Experiment, centerline
Experiment, wall
0.2
(T
0.4
0.6
0.8
Td )/(Tc Td ) [ ]
4
Mat. Costs / Net Energy Output [$/kWh]
xxx x
x
x
x x
30
25
20
15
10
5
0
1
(t
2
100
Percentage of total material costs
410
6
7.6
8
9.2
11.4
10
Td,max [%]
4.3
4.7
6.8
80
43
42.5
6.2
6.8
6.5
12
4
Sensible, reference
Combined
5.3
7.3
2
1
39.1
12.3
60.2
37.5
59.5
58.9
32.9
40
49.4
20
48.3
46.6
45
43.1
S14 S10
S8
Concrete
PCM
6
C7
C6
⌘ex > 98.5 %
4
6
8
10
37.8
34.5
33.2
32.4
C5 S2-13 S2-7 S2-6
Insulation
Encapsulation
Rocks
100
8.6
Outlook
• Measure PCM properties
for more accurate
simulations
• Simulation-based
determination of heattransfer coefficients for
different encapsulation
configurations
• Numerical optimization of
TES considering
efficiency and material
costs
3
12
14
16
Td,max [%]
11.3
Thermocouple positions
5
4
0
14
5.6
41.9
60
0
• An unsteady one-dimensional heat transfer
model was developed. The validated model is
used to predict the dynamic behavior of largescale TES systems and compare the combined
storage with the sensible only storage
considering exergy efficiency and material costs
for a given maximum temperature drop during
discharging ( Td,max).
3
Dtpc )/Dtcycle [ ]
5
Percentage of total material costs
4
x
x
0.00
⌘ex > 95 %
836
1083
1237
1303
1348
1270
1680
200
0.20
Eout,cycle = 1000 MWhth
Sensible, reference
Combined
Sensible, double insulation
35
Schematic of combined TES
Partner
0.40
Eout,cycle = 23 MWhth
Insulation
200
0.60
Comparison of material costs and exergy efficiency between sensible only
and combined storages (with AlSi12) for given maximum temperature
drops during discharging at steady cycling.
0
x
x
1.0
0.80
Simulation Results - Large-Scale TES
xxx x
394
0.90
Comparison of experimental (dots) an numerical (lines) results
• An experimental setup was built consisting of a
packed bed of rocks (sensible heat section) and
steel encapsulated AlSi12 PCM tubes (latent heat
section) on top (Etot = 42.3 kWhth). Air at ambient
pressure was used as heat transfer fluid.
Plate
Td )/(Tc
t/Dtc = 1
(T
x/L [ ]
0.6
0.0
0.0
• The system of combined sensible/latent heat
TES is studied using an experimental-numerical
approach
x x
0.95
t/Dtc = 2
Approach:
x
3
2
0.85
1.00
0.8
• However, they are expensive and not well suited
to large temperature ranges
x
1
Simulation
Experiment
PCM
• PCMs have high energy densities
Rocks
0
1.00
Td )/(Tc
t/Dtc = 1
1.0
• Phase change materials (PCMs) can deliver
heat at constant temperature
x
x
x
x
1.0
0.4
0.2
Plate
PCM
0.8
0.0
Concept
• Combined sensible/latent heat TES avoids
disadvantages
0.6
0.6
0.2
• For several applications, this is unfavorable
(thermodynamic power cycles, chemical
reactions)
120
90
0.4
PCM
t/Dtc = 0
(T
• The outflow temperature of a thermocline TES
system with only sensible heat storage material
drops during discharge if the tank is not large
enough and not sufficiently pre-charged
2
0.2
0.8
x/L [ ]
• Thermocline storage has gained increasing
interest as solution for TES with potentially high
efficiency and low costs.
Experimental Results and Model Validation - Labscale TES
Mat. Costs / Net Energy Output [$/kWh]
1 Background
6.7
20
23.6
26.3
80
7.3
9.4
13.9
10.3
15.2
17.1
15.9
60
37.1
14
35.6
34.6
31.9
0
• Experiments with TES for
AA-CAES in tunnel
• Sensible
• Combined
29.8
26.4
40
20
• Simulation of TES for AACAES in tunnel
43
S16
40.7
S8
Concrete
PCM
39.1
S6
37
34.5
30.6
C14
C8
C6
Insulation
Encapsulation
Rocks
References
1. Geissbühler L., Kolman M., Zanganeh G., Haselbacher A., Steinfeld A., Analysis of industrial-scale high-temperature combined
sensible/latent thermal energy storage, to be presented at the ASME-ATI-UIT conference on thermal energy systems, May 2015
2. Zanganeh G., Khanna R., Walser C.,Pedretti A., Haselbacher A., Steinfeld A., Experimental and numerical investigation of
combined sensible-latent heat for thermal energy storage at 575 °C and above, Sol. Energy, 114:77-90, 2015
3. Zanganeh G., Pedretti A., Zavattoni S., Barbato M., Steinfeld A., Packed-bed thermal storage for concentrated solar power – pilotscale demonstration and industrial-scale design, Sol. Energy, 86:3084-3098, 2012
Acknowledgment Funding by the Commission for Technology and Innovation through the SCCER is gratefully acknowledged