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Energies 2016, 9(12), 1077; doi:10.3390/en9121077

Laboratory Experiment and Numerical Analysis of a New Type of Solar Tower Efficiently Generating a Thermal Updraft

1
Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
2
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: Brian Agnew
Received: 15 October 2016 / Revised: 5 December 2016 / Accepted: 8 December 2016 / Published: 16 December 2016
(This article belongs to the Special Issue Thermally Driven Systems)
View Full-Text   |   Download PDF [9450 KB, uploaded 16 December 2016]   |  

Abstract

A new type of solar tower was developed through laboratory experiments and numerical analyses. The solar tower mainly consists of three components. The transparent collector area is an aboveground glass roof, with increasing height toward the center. Attached to the center of the inside of the collector is a vertical tower within which a wind turbine is mounted at the lower entry to the tower. When solar radiation heats the ground through the glass roof, ascending warm air is guided to the center and into the tower. A solar tower that can generate electricity using a simple structure that enables easy and less costly maintenance has considerable advantages. However, conversion efficiency from sunshine energy to mechanical turbine energy is very low. Aiming to improve this efficiency, the research project developed a diffuser-type tower instead of a cylindrical tower, and investigated a suitable diffuser shape for practical use. After changing the tower height and diffuser open angle, with a temperature difference between the ambient air aloft and within the collector, various diffuser tower shapes were tested by laboratory experiments and numerical analyses. As a result, it was found that a diffuser tower with a semi-open angle of 4° is an optimal shape, producing the fastest updraft at each temperature difference in both the laboratory experiments and numerical analyses. The relationships between thermal updraft speed and temperature difference and/or tower height were confirmed. It was found that the thermal updraft velocity is proportional to the square root of the tower height and/or temperature difference. View Full-Text
Keywords: solar tower; diffuser; thermal updraft; laboratory experiment; computational fluid dynamics (CFD) solar tower; diffuser; thermal updraft; laboratory experiment; computational fluid dynamics (CFD)
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Ohya, Y.; Wataka, M.; Watanabe, K.; Uchida, T. Laboratory Experiment and Numerical Analysis of a New Type of Solar Tower Efficiently Generating a Thermal Updraft. Energies 2016, 9, 1077.

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