Final Test and Evaluation Results from the Solar Two Project

Abstract

Solar Two was a collaborative, cost-shared project between 11 U. S. industry and utility partners and the U. S. Department of Energy to validate molten-salt power tower technology. The Solar Two plant, located east of Barstow, CA, comprised 1926 heliostats, a receiver, a thermal storage system, a steam generation system, and steam-turbine power block. Molten nitrate salt was used as the heat transfer fluid and storage media. The steam generator powered a 10-MWe (megawatt electric), conventional Rankine cycle turbine. Solar Two operated from June 1996 to April 1999. The major objective of the test and evaluation phase of the project was to validate the technical characteristics of a molten salt power tower. This report describes the significant results from the test and evaluation activities, the operating experience of each major system, and overall plant performance. Tests were conducted to measure the power output (MW) of the each major system, the efficiencies of the heliostat, receiver, thermal storage, and electric power generation systems and the daily energy collected, daily thermal-to-electric conversion, and daily parasitic energy consumption. Also included are detailed test and evaluation reports.

Storage capacities required for a solar thermal plant to avoid unscheduled reductions in output

“…The current analysis extends the range of storage efficiency below the 98% minimum of daily thermal storage efficiency for a commercially operated solar power tower reported by Bradshaw et al (2002) to the range from 94-100%. This is because the storage efficiency can be expected to decrease as the storage temperature is increased in future power plants to temperatures above those of the molten-salt systems currently employed (typically 565°C) to achieve more efficient power cycles.…”

“…Recent developments in TES technologies have resulted in them achieving relatively high daily thermal storage efficiencies, of around 98-99% for molten-salt storage systems in commercial solar power towers operating at approximately 565°C (Bradshaw et al, 2002;Kolb, 2011;Ehrhart and Gill, 2013). However, it is to be noted that at significantly higher operating temperatures (e.g.…”

Off-design performance of concentrated solar heat and coal double-source boiler power generation with thermocline energy storage

“…The operation temperature of molten salt in SPT plant is around 290-565 C [21]. Two integration schemes with a 660MW supercritical boiler have been proposed [16].…”

“…In Scheme I, the molten salt exchanger just transports heat to the superheat steam, like the superheater in Solar Two [21]. Therefore, the design data of exchanger in Solar Two can be used in this part.…”

“…1. The heat transfer fluid in the thermal receiver of SPT is selected as liquid molten salt, which has excellent thermal properties both for heat transfer and thermal energy storage [21,22]. The solar heat is introducedto the boiler by the molten salt heat exchanger (MSHE).…”