Evaluation of annual efficiencies of high temperature central receiver concentrated solar power plants with thermal energy storage

The current study has examined four cases of a central receiver concentrated solar power plant with thermal energy storage using the DELSOL3 and SOLERGY computer codes. The current state-of-the-art base case was compared with a theoretical high temperature case, which was based on the scaling of some input parameters and the estimation of other parameters based on performance targets from the Department of Energy SunShot Initiative. This comparison was done for both current and high temperature cases in two configurations: a surround field with an external cylindrical receiver and a north field with a single cavity receiver. The optical designs for all four cases were done using the DELSOL3 computer code; the results were then passed to the SOLERGY computer code, which uses historical typical meteorological year (TMY) data to estimate the plant performance over the course of one year of operation. Each of the four cases was sized to produce 100 MWe of gross electric power, have sensible liquid thermal storage capacity to generate electric power at full rated production level for 6 hours, and have a solar multiple of 1.8. There is a fairly dramatic difference between the design point and annual average performance. The largest differences are in the solar field and receiver subsystems, and also in energy losses due to the thermal energy storage being full to capacity. Another notable finding in the current study is the relatively small difference in annual average efficiencies between the Base and High Temperature cases. For both the Surround Field and North Field cases, the increase in annual solar to electric efficiency is < 2%, despite an increase in thermal to electric conversion efficiency of over 8%. The reasons for this include the increased thermal losses due to higher temperature operation and operational losses due to start-up and shut-down of plant sub-systems. Thermal energy storage can mitigate some of these losses by utilizing larger thermal energy storage to ensure that the electric power production system does not need to stop and re-start as often, but solar energy is inherently transient. Economic and cost considerations were not considered here, but will have a significant impact on solar thermal electric power production strategy and sizing. (C) 2013 D. Gill. Published by Elsevier Ltd.