Direct Solar Thermal Energy Storage Using a Semitransparent Phase Change Material

Research Project

Project/Area Number	01550729
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	化学工学
Research Institution	Gifu University
Principal Investigator	NISHIMURA Makoto Gifu Univ., Fac. Eng., Professor, 工学部, 教授 (10021627)
Co-Investigator(Kenkyū-buntansha)	BANDO Yoshiyuki Gifu Univ., Fac. Eng., Assoc. Professor, 工学部, 助教授 (60144002)
Project Period (FY)	1989 – 1990
Project Status	Completed (Fiscal Year 1990)
Budget Amount *help	¥2,000,000 (Direct Cost: ¥2,000,000) Fiscal Year 1990: ¥800,000 (Direct Cost: ¥800,000) Fiscal Year 1989: ¥1,200,000 (Direct Cost: ¥1,200,000)
Keywords	Heat storage / Latent heat storage / Phase change material / Solar thermal energy / Volume heat trap / 輻射伝熱 / 温度分布
Research Abstract	The latent heat storage of a volume heat trap (VHT) type was proposed as a new passive system of solar thermal energy storage, in which a plane layer of a semitransparent phase change material (PCM) is directly heated and melted by the sun. The performance was investigated in the indoor and the outdoor experiments and analyzed theoretically. Those of the latent heat storage of surface heat trap (SHT) type and the sensible heat storage of VHT type were examined in parallel. Paraffin wax was used as a PCM and the time changes of temperature distributions in the collector during heat storage weremeasured. The tilt angle of the collector and the thickness of PCM were varied. In the theoretical analysis, the basic equations were derived by assuming the two-dimensional fluid flow and heat transfer and by applying the concept of overall specific heat, and were solved numerically. The effects of the tilt angle and the thickness of PCM on the time changes of temperature distribution and heat storage efficiency were discussed. As a result, the following conclusions were obtained. 1) The calculated results reasonably expressed the tendencies of the experimental data so that the present theoretical analysis was considered to be valid. 2) The latent heat storage of VHT type was superior in performance to the latent heat storage of SHT type and the sensible heat storage of VHT type. 3) In the latent heat storage of VHT type, the internal heating and the heat and fluid flow by natural convection affected the characteristics of heat storage. 4) In the outdoor experiments, the most suitable tilt angle was found to be solar incidence angle at the time of culmination.