Exergy Analysis for Utilizing Latent Energy of Thermal Energy Storage System in District Heating

Joong Yong Yi, Kyung Min Kim, Jongjun Lee and Mun Sei Oh
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Joong Yong Yi: Yujin Energy Consulting Co., Gyeonggi-do 14047, Korea
Kyung Min Kim: Korea District Heating Corp., Gyeonggi-do 17099, Korea
Jongjun Lee: Korea District Heating Corp., Gyeonggi-do 17099, Korea
Mun Sei Oh: Korea District Heating Corp., Gyeonggi-do 17099, Korea

Energies, 2019, vol. 12, issue 7, 1-13

Abstract: The thermal energy storage (TES) system stores the district heating (DH) water when the heating load is low. Since a TES system stores heat at atmospheric pressure, the DH water temperature of 115 °C has to be lowered to less than 100 °C. Therefore, the temperature drop of the DH water results in thermal loss during storage. In addition, the DH water must have high pressure to supply heat to DH users a long distance from the CHP plant. If heat is to be stored in the TES system, a pressure drop in the throttling valve occurs. These exergy losses, which occur in the thermal storage process of the general TES system, can be analyzed by exergy analysis to identify the location, cause and the amount of loss. This study evaluated the efficiency improvement of a TES system through exergy calculation in the heat storage process. The method involves power generation technology using the organic Rankine cycle (ORC) and a hydraulic turbine. As a result, the 930 kW capacity ORC and the 270 kW capacity hydraulic turbine were considered suitable for a heat storage system that stores 3000 m 3 /h. In this case, each power generation facility was 50% of the thermal storage capacity, which was attributed to the variation of actual heat storage from the annual operating pattern analysis. Therefore, it was possible to produce 1200 kW of power by recovering the exergy losses. The payback period of the ORC and the hydraulic turbine will be 3.5 and 7.13 years, respectively.

Keywords: district heating; latent energy; power generation; thermal energy storage (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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