Evaluation of the performance of hybrid CSP/biomass power plants

Abstract

The fundamental benefit of using renewable energy systems is undeniable since they rely on a source that will not run out. Nevertheless, they strongly depend on meteorological conditions (solar, wind, etc.), leading to uncertainty on the instantaneous energy supply and consequently to grid connection issues. An interesting alternative concept is renewable hybridisation. It consists in the strategic combination of different renewable sources in the power generation portfolio by taking advantage of each technology. Hybridisation of concentrating solar energy with biomass denotes a powerful way of assuring system stability and reliability. The main advantage is dispatchability through the extension of the operating range. In this article, two 1 MWel hybrid power plants are presented and assessed. In case 1 the purpose is only power generation and in case 2 the use of Combined Heat and Power. Both systems were designed as a scale up and enhancement of a prototype, installed in Tunis under the REELCOOP project. Technical and economic performance were evaluated trough numerical simulation and levelised cost of electricity calculation. Simulations were carried out under the assumption of 16 hours of continuous load demand per day (6 to 22 h). Case 1, with a power block higher efficiency, leads to an annual average system efficiency of about 13.7%. The use of heat in case 2, increases system efficiency to 33.8%. Capital expenditure varies from 9.5 M€ (case 1) to 11.3 M€ (case 2). Despite the lower electrical conversion efficiency of case 2, and its higher capital expense, the levelised cost of electricity is lower (126 €/MWhel) than in case 1(173.1 €/MWhel). Both results are attractive considering the small scale of the power plant. This outcome is a consequence of hybrid operation, enhancing power block and system efficiency, and also reducing cost by equipment sharing (i.e. power block).