Increasing the efficiency of parabolic trough plants using thermal oil through external superheating with biomass

Abstract

It is well understood that the cost of concentrating solar power (CSP) will need to decrease quickly to ensure competitiveness with photovoltaic (PV) systems and other forms of power generation. Research and development on CSP plant components is crucial in order to reduce costs but is typically time consuming. New CSP plant concepts combining proven technologies with CSP represent another option that can be implemented quickly.This paper investigates the use of several biomass materials to externally superheat steam in conventional parabolic trough plants. Currently, parabolic trough plants are easiest to finance and external steam superheating can overcome the lower efficiencies compared to other CSP technologies. Seven scenarios, each air and water cooled, with steam parameters ranging from 380°C at 100bar to 540°C at 130bar have been modeled, and the results presented here are based on a 50MWe plant with 7.5h molten salt thermal storage.Our results show that the peak solar to electricity net efficiency increases up to 10.5% while the specific investment can decrease immediately from AU$8.2m/MWe to AU$6.3m/MWe, a 23.5% reduction. That is significant considering the expected 17–40% CSP cost reduction targets by the end of this decade. The modeling shows that even major fuel and water price changes are significantly less relevant than small changes in the agreed electricity purchase price.The technical, economic and environmental analysis reveals that external superheating with biomass can provide significant benefits, is able to use a variety of fuels and despite a limited global market, could immediately enable the implementation of several hundred MWe of CSP capacity at lower cost.