Optimal system design and operation-control method for evacuated solar thermal collector system to obtain hot water near 100°C

Shigeki Hirasawa, Tsuyoshi Kawanami, Katsuaki Shirai

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

Abstract

We have been developing a high performance solar thermal collector system to obtain hot water near 100°c. We studied the effect of system structures and operation-control methods on the thermal performance of collectors and cost to produce the required amount of heated water through numerical simulations. Four types of thermal collector system structures were examined: (1) a natural convection collector system that collected heat by natural convection of water between the collector plate and the heat storage tank, (2) a heat pipe collector system that collected heat using a heat pipe between the collector plate and the heat storage tank, (3) a water-circulating collector system that circulated water between the collector plate and the heat storage tank with a pump, and (4) an accumulating heated water collector system that supplied new water and accumulated heated water in the heat storage tank. Three operation-control methods were evaluated for the accumulating heated water collector system: (1) the flow rate of the water was controlled to keep a constant outlet-temperature of the heated water, (2) the flow rate of the cooling water was controlled proportionally to match the solar radiation rate, and (3) the flow rate of the water was constant without control. The effects of change in actual daily solar radiation during four seasons were assessed. The results from calculations revealed that the effect of system structures and control methods on the thermal efficiency of the collectors and cost to produce the required amount of heated water was small. The accumulating heated water collector system effectively used solar energy during the day, and the other types effectively used solar energy in the evening. The best method of control to minimize outlet-temperature fluctuations in the heated water and to make the tank-temperature approach the usage temperature was control method (2) (i.e., control with solar radiation).

Original languageEnglish
Title of host publicationOPT-i 2014 - 1st International Conference on Engineering and Applied Sciences Optimization, Proceedings
EditorsN. D. Lagaros, Matthew G. Karlaftis, M. Papadrakakis
PublisherNational Technical University of Athens
Pages129-139
Number of pages11
ISBN (Electronic)9789609999465
Publication statusPublished - 2014 Jan 1
Externally publishedYes
Event1st International Conference on Engineering and Applied Sciences Optimization, OPT-i 2014 - Kos Island, Greece
Duration: 2014 Jun 42014 Jun 6

Publication series

NameOPT-i 2014 - 1st International Conference on Engineering and Applied Sciences Optimization, Proceedings

Other

Other1st International Conference on Engineering and Applied Sciences Optimization, OPT-i 2014
CountryGreece
CityKos Island
Period14/6/414/6/6

Keywords

  • Cost
  • Optimal operation control
  • Optimal system design
  • Solar thermal collector
  • Temperature
  • Thermal efficiency

ASJC Scopus subject areas

  • Computer Science Applications
  • Software
  • Engineering(all)

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  • Cite this

    Hirasawa, S., Kawanami, T., & Shirai, K. (2014). Optimal system design and operation-control method for evacuated solar thermal collector system to obtain hot water near 100°C. In N. D. Lagaros, M. G. Karlaftis, & M. Papadrakakis (Eds.), OPT-i 2014 - 1st International Conference on Engineering and Applied Sciences Optimization, Proceedings (pp. 129-139). (OPT-i 2014 - 1st International Conference on Engineering and Applied Sciences Optimization, Proceedings). National Technical University of Athens.