Experimental validation of theoretical heliostat wind loads

In the current concentrated solar power (CSP) context central receiver systems seems to be the most promising technology with the highest cost reduction potential. In the construction of such plants the solar field represents one of the largest investments, a fact which has made cost reduction of these elements become the main target for many actors of the solar thermal sector. Therefore, the design of cost efficient heliostats has become a major interest. One of the design challenges is to develop a heliostat which is able to withstand all foreseen mechanical loads, while at the same time have reduce costs by avoiding unnecessary safety margins. To achieve this goal a good knowledge of expected wind loads onto the support structure and drive mechanism is crucial. In this paper a heliostat prototype, equipped with measuring devices, is deployed to a test site in order to measure the true mechanical stresses suffered due to varying wind loads. These data together with the information about wind speed and direction is then used to validate theoretical loads determined via formulations extracted from wind tunnel experiments. It is shown, that for low turbulence conditions the theoretical values correspond well to the measured values; however, for turbulent wind conditions a significant difference is detected. As those conditions are difficult to simulate in wind tunnels or CFD simulations, this shows the importance of on-site testing of new heliostat designs. (C) 2015 The Authors. Published by Elsevier Ltd.