Concentrated solar power (CSP) has the potential of fulfilling the world’s
electricity needs. Parabolic-trough system using synthetic oil as the HTF with
operating temperature between 300 and 400o C, is the most matured CSP
technology. A thermal storage system is required for the stable and cost
effective operation of CSP plants. The current storage technology is the indirect
two-tank system which is expensive and has high energy consumption due to
the need to prevent the storage material from freezing. Latent heat storage
(LHS) systems offer higher storage density translating into smaller storage size
and higher performance but suitable phase change materials (PCMs) have low
thermal conductivity, thus hindering the realization of their potential. The low
thermal conductivity can be solved by heat transfer enhancement in the PCM.
There is also lack of suitable commercially-available PCMs to cover the
operating temperature range. In this study, a hybrid cascaded storage system
(HCSS) consisting of a cascaded finned LHS and a high temperature sensible
or concrete tube register (CTR) stages was proposed and analysed via
modelling and simulation. Fluent CFD code and the Dymola simulation
environment were employed.
A validated CFD phase change model was used in determining the heat
transfer characteristics during charging and discharging of a finned and unfinned
LHS shell-and-tube storage element. The effects of various fin
configurations were investigated and heat transfer coefficients that can be used
for predicting the performance of the system were obtained. A model of the
HCSS was then developed in the Dymola simulation environment. Simulations
were conducted considering the required boundary conditions of the system to
develop the best design of a system having a capacity of 875 MWhth, equivalent
to 6 hours of full load operation of a 50 MWe power plant.
The cascaded finned LHS section provided ~46% of the entire HCSS capacity.
The HCSS and cascaded finned LHS section have volumetric specific
capacities 9.3% and 54% greater than that of the two-tank system, respectively.
It has been estimated that the capital cost of the system is ~12% greater than
that of the two-tank system. Considering that the passive HCSS has lower
operational and maintenance costs it will be more cost effective than the twotank
system considering the life cycle of the system. There is no requirement of
keeping the storage material above its melting temperature always. The HCSS
has also the potential of even lower capital cost at higher capacities (>6 hours
of full load operation).
| Identifer | oai:union.ndltd.org:CRANFIELD1/oai:dspace.lib.cranfield.ac.uk:1826/9303 |
| Date | 09 1900 |
| Creators | Muhammad, Mubarak Danladi |
| Contributors | Badr, Ossama, Yeung, Hoi |
| Publisher | Cranfield University |
| Source Sets | CRANFIELD1 |
| Language | English |
| Detected Language | English |
| Type | Thesis or dissertation, Doctoral, PhD |
| Rights | © Cranfield University, 2014. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. |
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