Solar Tower System Temperature Range Optimization for Reduced LCOE

New heat transfer and storage media offer for solar tower systems a much broader temperature range. Higher temperatures allow the integration of steam power cycles with increased efficiency. The present study evaluates modular solar tower plants using solid particles as heat transfer medium (HTM), allowing temperatures up to 1000°C. In a parameter study the influence of upper and lower HTM temperature on levelized cost of electricity (LCOE) is evaluated. The results show a significant impact of the HTM temperature selection, mainly governed by the HTM temperature difference. A high temperature difference results in reduced LCOE. The most important factors for this reduction are the cost decrease of particle inventory, storage containment, and particle steam generator. This decrease is partially offset by an increase in heliostat field and tower cost. The results indicate that the use of solid particles for high efficiency steam power cycles offers unique advantages due to the wide temperature range of the particles

DESIGN AND COST STUDY OF IMPROVED SCALED-UP CENTRIFUGAL PARTICLE RECEIVER BASED ON SIMULATION

A numerical model of the CentRec® receiver has been developed and validated using the measurement data collected during the experimental test campaign of the centrifugal particle system at the solar tower Jülich. The model has been used to calculate the thermo-optical efficiency of a scaled-up 20 MWth receiver for various receiver geometries. A cost function has been deduced and was used to perform a technoeconomic optimization on an LCOH (levelized cost of heat) basis of the CentRec® receiver concept. Attractive LCOH as low as 0.0209 €/kWhth for a system with thermal storage, or as low as 0.0150 €/kWhth for the LCOH without storage, are predicted. This study has shown that the optimal configuration from an LCOH perspective for a 20 MWth centrifugal particle receiver reaches specific receiver costs of 35 €/kWth. Hereby the costs of the receiver can be reduced by 60 % compared to the original configuration

Review of heliostat calibration and tracking control methods

Large scale central receiver systems typically deploy between thousands to more than a hundred thousand heliostats. During solar operation, each heliostat is aligned individually in such a way that the overall surface normal bisects the angle between the sun’s position and the aim point coordinate on the receiver. Due to various tracking error sources, achieving accurate alignment ≤1 mrad for all the heliostats with respect to the aim points on the receiver without a calibration system can be regarded as unrealistic. Therefore, a calibration system is necessary not only to improve the aiming accuracy for achieving desired flux distributions but also to reduce or eliminate spillage. An overview of current larger-scale central receiver systems (CRS), tracking error sources and the basic requirements of an ideal calibration system is presented. Leading up to the main topic, a description of general and specific terms on the topics heliostat calibration and tracking control clarifies the terminology used in this work. Various figures illustrate the signal flows along various typical components as well as the corresponding monitoring or measuring devices that indicate or measure along the signal (or effect) chain. The numerous calibration systems are described in detail and classified in groups. Two tables allow the juxtaposition of the calibration methods for a better comparison. In an assessment, the advantages and disadvantages of individual calibration methods are presented