Commissioning of a Preheat Strategy of a Molten Salt Test Receiver

Abstract

Solar power tower plants that are operated with molten salt offer the advantage that the molten salt can be used as a heat transfer medium as well as storage medium. Consequently, solar energy can be stored easily and efficiently in only one loop without transformation losses. Furthermore, by using large-scale storage facilities, almost a 24/7 base load operation is possible. Since the molten salt begin to crystallize at temperature of 238 °C, the absorber tube must be preheated before the plants’ operation can begin. During the preheating a subset of heliostats will be aimed on the receiver surface to ensure a solar flux density that leads to tube temperatures above the solar salt crystallization point. Since the absorber tubes are empty during the preheating, there is a risk of high temperature gradients and transients and thus high thermal stresses that may lead to fatigue damage. To prevent this, a preheating strategy for a molten salt test receiver was developed and tested, taking into account ambient conditions and time. The present work shows the results of the commissioning of the developed preheating strategy and discusses its potential for improvement.