The document summarizes research on performance analysis of high temperature sensible heat storage systems during charging and discharging cycles. The objectives were to develop a thermal model to predict performance, optimize the storage bed design, and analyze performance of beds made of cast steel and concrete. The results show that charging times were 683 seconds for cast steel and 3650 seconds for concrete, with energy storage of 62.85 MJ and 62.39 MJ respectively. Discharging times and energy recovered were also reported. Exergy efficiency was analyzed. Thermal models were validated and provided insights into heat transfer and temperature variations during the cycles.

1. Performance Analysis of High Temperature Sensible
Heat Storage System during Charging and
Discharging cycles
By
Likhendra Prasad, Hakeem Niyas, P.Muthukumar
Department of Mechanical Engineering
IIT Guwahati
4th International Conference on Advances in Energy Research
IIT Bombay

2. Outline of Presentation
• Introduction
• Objectives of present work
• Thermal modelling
• Results and discussions
• Conclusions
12/10/2013
ICAER 2013
2

3. Potential of Renewable Energies
Global Primary Energy Consumption (GPEC)
Solar energy (1800
Wind energy (200
Biomass (20
GPEC)
GPEC)
GPEC)
Geothermal energy (10
GPEC)
Ocean energy (2
GPEC)
Hydro energy (1
GPEC)
Source: Nitsch, 2007
12/10/2013
ICAER 2013
3

4. Solar Power
Solar
Energy
12/10/2013
Solar
PV
Solar
Thermal
Solar
Cell
CSP
ICAER 2013
Solar
Power
4

5. Concentrating Solar Power (CSP)
(a) Parabolic Trough
(b) Linear Fresnel Reflector
(c) Parabolic Dish
(d) Solar Tower
Source: www.csp-world.com
12/10/2013
ICAER 2013
5

6. Solar thermal power plant with TES system
HTF
Steam
Superheater
Turbine
Solar
Boiler
TES
Field
Preheater
P
12/10/2013
ICAER 2013
P
Condenser
6

7. Thermal Energy Storage Methods
• Sensible Heat Storage (SHS) Q   s V C p s Tch ( J )
• Concrete, Cast steel, Concrete, etc.
• Latent Heat Storage (LHS)
Tm
T2
Q    s , pc m V C p s , pcm dT  l , pc m  H f g   l , pc m  C pl , pcm
T1
Tm
• Phase change material (PCM)
• Thermochemical Heat Storage (THS) - Reversible chemical reactions
• Metal Hydrides
12/10/2013
ICAER 2013
7
(J )

8. Materials for SHS
 Requirements of
SHS Materials
OperatingTemper
Specific heat
Thermal
ature (K)
(kJ/kg K)
conductivity
SHS materials
•
Large operating
temperature
(W/m K)
Reinforced concrete
673
1.00
1.5
2200
Silica fire bricks
973
1.00
1.5
1820
Solid NaCl
773
0.85
7
2160
Cast iron
673
0.56
37
7200
Cast steel
973
0.60
40
7800
•
High heat capacity
•
High thermal
conductivity
•
High Density
•
Stability
•
Low cost and availability
High thermal conductivity materials
Low cost and easily available materials
12/10/2013
ICAER 2013
8

9. Objectives of the present work
 To develop a 3-D thermal model for predicting the performances of SHS systems.
 To optimize the number of charging tubes in the storage bed based on charging
time.
 To predict the performance of SHS bed of high conductivity solid material (cast
steel) of capacity 50 MJ.
 To predict the performance of SHS bed of low conductivity solid material
(concrete) of capacity 50 MJ by incorporating the axial fins (copper) on charging
tube surfaces.
12/10/2013
ICAER 2013
9

10. Design and Optimization of SHS model
12/10/2013
ICAER 2013
10

11. Thermal modelling of SHS model
 Assumptions
• The inlet velocity profile of HTF is fully developed.
• SHSM is isotropic.
• The flow is considered as unsteady, laminar and
incompressible.
• Axial Conduction is negligible
 Governing Equations:

Physical model of SHS bed
Fluid flow: Continuity and N-S Eq.

. v  0


Dv
2
f
  P    v
Dt


12/10/2013
Heat transfer: Convection (solid- liquid interface)
Heat transfer: Conduction (solid)
ICAER 2013
Schematic of mathematical model 11

12.  ICs and BCs :
 Performance parameters
•
Charging / discharging time.
•
Energy stored / recovered
•
12/10/2013
Exergy efficiency
Q  s V C p s T ( J )
 Exergy 
Tch  T (t)
Tch  Tatm
ICAER 2013
12

13. Validation of SHS model
Fig.10 (a)
Input parameters for validation [4]
Sl.
Parameters
1
Density of concrete (kg/m3)
2200
2
Specific heat of concrete (J/kg K)
1000
3
Thermal conductivity of concrete (W/m K)
1, 2, 5
4
Diameter of the charging tube (m)
Values
0.02
5
12/10/2013
[31]
623
6
663
13

14. Flow and temperature variation of HTF inside the charging tube
12/10/2013
ICAER 2013
14

15. Heat Transfer into the cast steel bed during charging
12/10/2013
ICAER 2013
15

16. Results and Discussions - Charging
3650 s
683 s
62.39 MJ
Charging time of concrete and cast steel beds
12/10/2013
62.85 MJ
Energy storage rate of concrete and cast steel
ICAER 2013
beds
16

17. Results and Discussions - Charging
4493 s
3650 s
3379 s
Effect of HTF velocity on charging time of
12/10/2013
concrete bed
1400 s
683 s
430 s
Effect of HTF velocity on charging time of cast
ICAER 2013
steel bed
17

18. Results and Discussions - Charging
Axial Temperature variation of HTF during
12/10/2013
charging of concrete bed
Axial Temperature variation of HTF during
ICAER 2013
charging of cast steel bed
18

19. Results and Discussions - Discharging
7200 s
1820 s
59.78 MJ
Discharging time of concrete and cast steel beds
12/10/2013
62.75 MJ
Energy discharge rate of concrete and cast steel
beds
ICAER 2013
19

20. Results and Discussions - Discharging
Effect of HTF velocity on discharging time of
Effect of HTF velocity on discharging time of
concrete bed
cast steel bed
12/10/2013
ICAER 2013
20

21. Results and Discussions - Discharging
Axial Temperature variation of HTF during
12/10/2013
discharging of concrete bed
Axial Temperature variation of HTF during
ICAER 2013
discharging of cast steel bed
21

22. Results and Discussions
Exergy efficiency variation
12/10/2013
ICAER 2013
22

23. Conclusions
•
Thermal models for predicting the charging and discharging characteristics of SHS systems have been developed.
•
The number of charging tubes has been optimized based on the charging time of the SHS bed.
•
Heat transfer enhancement technique is implemented by adding fins on the outer surface of charging tubes.
•
The charging time and energy stored in the SHS bed are found to be 3650 s and 683 s, 62.39 MJ and 62.85 MJ for concrete
and cast steel respectively.
•
The predicted discharging time of SHS beds are 7200 s for concrete bed and 1850 s for the cast steel bed.
•
The energy discharged from the beds in their respective discharging times are found to be 59.78 MJ for concrete bed and
62.75 MJ for cast steel bed.
12/10/2013
ICAER 2013
23

24. References
[1]
Gil A., Medrano M., Martorell I. and Cabeza F. (2010) State of the art on high temperature thermal energy
storage for power generation. Part 1-Concepts, materials and modellization, Renewable and Sustainable Energy
Reviews, 14, pp. 31-55.
[2]
Khare S., Knight C., and McGarry S. (2013) Selection of materials for high temperature sensible energy
storage, Solar Energy Materials and Solar Cells, 115, pp. 114-122.
[3]
Sragovich, D. (1989) Transient analysis for designing and predicting operational performance of a high
temperature thermal energy storage system, Solar Energy, 43, pp. 7-16.
[4]
Tamme, R., Laing, D. and Steinmann, W. (2004) Advanced thermal energy storage technology for parabolic
trough, Journal of Solar Energy Engineering, 126, pp. 794-800.
12/10/2013
ICAER 2013
24

25. References
[5]
Laing, D., Steinmann, W., Tamme, R. and Richter, C. (2006) Solid media thermal storage for parabolic trough
power plants, Solar Energy, 86, pp. 1283-1289.
[6]
Nandi, B.R., Bandyopadhyay, S. and Banerjee, R. (2012) Analysis of high temperature thermal energy storage for solar
power plant, Proceedings of the 3rd IEEE International Conference on Sustainable Energy Technology, pp. 438-444.
[7]
John, E.E., Hale, W. M. and Selvam, R. P. (2011) Development of a high-performance concrete to store thermal
energy for concentrating solar power plants, Proceedings of the 5th ASME International Conference on Energy
Sustainability, pp. 523-529.
[8]
Tian, Y. and Zhao, C.Y. (2013) A review of solar collectors and thermal energy storage in solar thermal
applications, Applied Energy, 104, pp. 538-553.
12/10/2013
ICAER 2013
25

26. THANK YOU
12/10/2013
ICAER 2013
26