Evaluation of CO2 heat pump water heater model for operational planning

Yasuaki Bando, Hironori Hattori, Yoshiharu Amano

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Energy management is systematic activity to improve energy performances of target system, and it has already been introduced in the industrial and commercial field. Energy management system is expected to solve operational planning problem and report or suggest opportunities for performance improvement. In recent years, CO2 heat pump water heater (HPWH) is attracting attention as one of the high-efficiency devices to meet domestic hot water demand. Equipment model is required to reflect the characteristics of the actual equipment’s performance and to have a simple structure to apply to operational planning problem and should diagnose the changes with the performance degradation overtime. However, few studies have been reported which proposes the thermodynamically-sound model of HPWH for energy management. In this paper, we proposed a simple model suitable for solving operational planning problem and diagnosing aging deterioration or degradation of equipment in energy management system. Firstly, we constructed function model consisting of a heat pump unit (HP) and a hot water storage tank (ST). HP model is simply composed of start-up, steady state, and shut-down status-transition model. The steady state model is constructed based on the Lorentz efficiencyand theoretical maximum coefficient of performance (COP) for trans-critical heat pump cycle. The Lorentz efficiency is identified by experiment on typical domestic hot water demand with variation of ambient temperature, inlet/outlet water temperature at the gas-cooler. While the heat pump system is operating, unit COP of the HP is influenced on the thermal stratification of ST. The ST model is a simplified model that can describe temperature distribution in ST. Secondly, we validated the model. Proposed model reproduced experimental values with sufficient accuracy for day-ahead planning problem. Finally, we confirmed that the proposed model is preferable in its simplicity and robust performance for wide temperature range by comparing with a conventional statistical regression model.

Original languageEnglish
Title of host publicationECOS 2018 - Proceedings of the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems
PublisherUniversity of Minho
ISBN (Electronic)9789729959646
Publication statusPublished - 2018 Jan 1
Event31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2018 - Guimaraes, Portugal
Duration: 2018 Jun 172018 Jun 21

Publication series

NameECOS 2018 - Proceedings of the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems

Conference

Conference31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2018
CountryPortugal
CityGuimaraes
Period18/6/1718/6/21

Keywords

  • Energy management system
  • Heat pump water heater
  • Lorentz cycle
  • Operational planning

ASJC Scopus subject areas

  • Environmental Science(all)
  • Energy(all)

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  • Cite this

    Bando, Y., Hattori, H., & Amano, Y. (2018). Evaluation of CO2 heat pump water heater model for operational planning. In ECOS 2018 - Proceedings of the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2018 - Proceedings of the 31st International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems). University of Minho.