High-Temperature Combined Sensible/
Latent-Heat Storage
Experiments and Simulations
Lukas Geissbühler1, Michael Kolman1, Dr. Giw Zanganeh2, Dr. Andreas Haselbacher1, Prof. Dr. Aldo Steinfeld1,3
1Professorship of Renewable Energy Carriers, ETH Zurich, 2Airlight Energy Manufacturing SA, Biasca, 3Solar Technology Laboratory, PSI
3
1 Background
• The outflow temperature of a thermal energy
storage (TES) system with only sensible heat
storage material drops during discharge if the
tank is not large enough and not sufficiently
pre-charged
• For several applications, this could be
unfavorable (thermodynamic power cycles) or
even unacceptable (chemical reactions)
Experimental tests of a combined sensible/latent-heat TES were performed at Airlight Energy SA in Biasca.
The code was compared to measurements for various operating conditions. (Note: ṁd / ṁc = discharging /
charging mass flow rate)
ṁd /ṁc = 1
600
Temperature [ C]
ṁd /ṁc = 1
600
500
580
Concept
400
560
300
540
200
520
100
500
• Phase change materials (PCMs) can deliver
heat at constant temperature
• PCMs have high energy densities
• However, they are expensive and not well
suited to large temperature ranges
• Combined sensible/latent-heat TES avoids
disadvantages
1
2
3
4
5
6
7
0
2
4
6
Time [h]
ṁd /ṁc = 1/2
600
600
10
12
14
16
500
580
Temperature [ C]
8
Time [h]
ṁdisch
· ṁ
ṁd=
/ṁ0.5
1/2
ch
c =
400
560
300
540
200
520
100
Heater
500
1
2
3
4
5
6
7
0
2
4
Time [h]
6
8
10
12
14
16
Time [h]
Comparison of experimental (dots) an simulation (lines) results
Insulation
4
Thermocouple positions
Simulation Results - Large-Scale TES
5
• Numerical study of large-scale TES (rtank = 8 m, height variable)
1. Sensible: Rocks
2. Combined: Rocks with encapsulated AlSi12 on top
Laboratory setup of combined sensible/
latent-heat TES
Perforated
Plate
Ncycles
ṁmax
tc
td
20
30 kg/s
5h
5h
Tc
Td
Tout,max,c
Tout,min,d
231 °C
575/565/
555/550 °C
595 °C 220 °C
Charging
PCM
Height above Tank Bottom [m]
• Compare the necessary tank
sizes for the following conditions:
Air
10
Sensible, 3 Pre-Charge-Cycles
Combined, 1 Pre-Charge-Cycle
8
PCM
charge
6
discharge
4
2
Tmax,discharge = 20 C
0
200
300
400
500
600
Fluid Temperature [ C]
Rocks
Insulation
580
560
Sensible 1 Pre-Charge-Cycle
Sensible, 3 Pre-Charge-Cycles
Combined, 1 Pre-Charge-Cycle
Discharging
540
0
1
2
3
Time [h]
6
Sensible
Combined
1
Normalized Material Costs
Fluid Outlet Temperature [ C]
600
1360 mm
2
Experimental Results and Code Validation - Labscale TES
4
5
0.95
0.9
Outlook
• Investigate alternative
PCMs
• Determine missing
properties for more
accurate simulations
• Upcoming experiments:
• Parametric studies
• Alternative PCMs
• Different storage
configurations
• Optimization of tank
design considering
efficiency and capital
costs
• Advanced adiabatic
compressed air energy
storage (AA-CAES):
Simulation of TES in
tunnel
• Experiments with TES in
tunnel
0.85
0.8
20
25
30
35
40
45
Tmax,discharge
References
394 mm
Air
Schematic of combined TES
Partner
1. Zanganeh G., Pedretti A., Haselbacher A., Steinfeld A., Design of Packed-Bed Thermal Energy Storage Systems for HighTemperature Industrial Process Heat, Appl. Eng., 2014, in press
2. Zanganeh G., Commerford M., Haselbacher A., Pedretti A., Steinfeld A., Stabilization of the outflow temperature of a packed-bed
thermal energy storage by combining rocks with phase change materials, Appl. Thermal Eng., 70:316-320, 2014
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
4. Kenisarin M. M., High-temperature phase change materials for thermal energy storage. Ren. Sust. Energy Rev, 14:955-970, 2010
Acknowledgment Funding by the Commission for Technology and Innovation is gratefully acknowledged