Solar thermal storage in power generation using phase ...
Transcript of Solar thermal storage in power generation using phase ...
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Solar thermal storage in power
generation using phase change material
with heat pipes and fins to enhance heat
transfer.
D.J. Malana & R.T. Dobsona
aSolar Thermal Energy Research Group
(STERG), University of Stellenbosch
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Design philosophy and objectives
Use passive natural occurring
phenomena to transfer heat:
• Design and test a modular
PCS module.
• Determine the module’s
thermal characteristics
experimentally.
• Develop a numerical model
and validate it by comparing
it to the module
experiments.
• Use the results to design a
PCS system for a power
generation application.
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Fig 1. Internal energy of wax and water
Fig 2. Rectangular multichannel heat pipes
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Background to phase change storage systems
(PCS)
Different storage
systems:
• Integral storage
• Indirect systems
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Fig 3. A latent heat storage test
section (Robak et al, 2011)
Phase change storage system
advantages
• Stores more heat across smaller
temperature range,
• Saves on premium fuels and
• Increases system reliability and
may improve energy performance.
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Experimental procedure:
• Measure temperatures and flow
rates.
• Calculate energy balance of the
components during the cycle.
Charge up phase
• Heat kettle water to 90°C
• Keep kettle water close to 90°C
until all the wax has melted
Discharge phase
• Extract hot water from kettle
• Cool down wax container with
heat exchanger
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Experimental setup
Fig 4. Experimental setup of the PCS module
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Numerical thermal resistance model 5
• Keep track of the
temperature and state
(is it solid, mixture or
totally liquid) in the
control volumes.
• Change the length of
wax as it melts and
expands or solidifies
and contracts.
Fig 5. Thermal resistive diagram of PCS module
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Power and energy response charge phase6
Fig 6-7. Power and energy response from the charge cycle.
𝑄𝑁𝑡𝑜𝑡𝑎𝑙
𝑄𝐸𝑡𝑜𝑡𝑎𝑙
Fig 8. Experimental setup a
𝑄𝑁𝑎𝑙𝑄𝑁𝑤𝑎𝑥
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Power and energy response discharge phase7
Fig 9-10. Power and energy response from the discharge cycle.
Fig 11. Experimental setup b
𝑄𝐸𝑤𝑎𝑡𝑒𝑟𝑄𝑁𝑤𝑎𝑡𝑒𝑟
𝑄𝐸𝑤𝑎𝑥𝑄𝑁𝑤𝑎𝑥
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Concept development
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Fig 12. System layout of solar tower with latent storage
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Temperatures during the summer solstice
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Fig 13. Temperature variation of the PCS system
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Energy during summer solstice
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Fig 14. Energy variations during simulation
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Power during summer solstice
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Fig 15. Power variation of the PCS system
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Conclusions
• The numerical model correlates well with the experimental
tests.
• Heat is quickly transferred into the wax during the charge
phase and it can be quickly extracted due to the many finned
heat paths.
• Heat pipes and fins are effective in transferring heat to and
from the storage container.
• The numerical storage model was successfully used to
simulate a power plant fitted to the Helio 100 field
• Power may be generated around the clock with the Helio
100 solar field or alternately it may be used as a small
peaking station with the aid of a PCS system
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Thank you!
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Acknowledgements:
Contact details:Author A.
Thermal Energy Research Group
(STERG)
University of Stellenbosch
Stellenbosch
South Africa
+27 (0)21 808 4016
Visit us:
concentrating.sun.ac.za
blogs.sun.ac.za/STERG
All glory to my LORD Jesus Christ
for the opportunity to
do this research.
I also acknowledge
M&M workshop
CHE factory
STERG
NRF
Contact details:
D.J. Malan
Solar Thermal Energy Research
Group (STERG)
Stellenbosch University
South Africa