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International Journal of Thermal Sciences
journal homepage: www.elsevier.com/locate/ijts
Performance assessment of some ice TES systems
David MacPhee*, Ibrahim Dincer
Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario L1H 7K4, Canada
a r t i c l e i n f o
Article history: Received 20 September 2008 Received in revised form 24 February 2009 Accepted 7 March 2009 Available online 3 June 2009 Keywords: Ice Slurry Encapsulated Thermal Energy Storage Coil Internal External Energy Exergy Efﬁciency Performance
a b s t r a c t
In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efﬁciencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working ﬂuid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efﬁciencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efﬁciencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efﬁciencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities. Ó 2009 Published by Elsevier Masson SAS.
1. Introduction Energy storage is an extremely important part of our society. In almost every facet of science and technology, energy storage plays a signiﬁcant role, whether the energy is needed in chemical, heat, mechanical, electrical or other forms. Though the motivation for the recent technological advancements in the various ﬁelds of energy storage varies, the overall impetus is the same; our energy supply – whether it comes from the earth or the sun, is never a constant. Day turns to night, winds die down, oil ﬁelds eventually run dry, and the geothermal heat from the crust of the earth, although seemingly constant, will eventually diminish. There is, then, a need to store energy, for the purpose of extracting it when it is not readily available. This is clearly evident in solar panels, which convert the sun’s radiation into electricity for later use. In fact, the storage of energy thermally perhaps dates back as far as civilization itself; since the beginning of recorded history, people have been * Corresponding author. E-mail addresses: firstname.lastname@example.org (D. MacPhee), ibrahim.dincer@ uoit.ca (I. Dincer). 1290-0729/$ – see front matter Ó 2009 Published by Elsevier Masson SAS. doi:10.1016/j.ijthermalsci.2009.03.012
harvesting ice to keep things cool when warmer weather approaches. It is this type of thinking which has provided the desire to store many other types of energy from various sources, both for economic and ecologic purposes. For the past few decades, the world’s energy supply has not been keeping up with the increasing demand. Burgeoning countries undergoing industrial reform are consuming an increasing amount of crude oil, coal and...