Towards Cost-competitive Solar Towers – Energy Cost Reductions based on Decoupled Solar Combined Cycles (DSCC)

AbstractA preliminary analysis of the potential for cost reduction of the innovative decoupled combined cycle concept for Solar Towers was presented in SolarPACES 2012 [1]. This work has been continued with a more detailed analysis of the cost-competitiveness of the decoupled solar combined cycle (DSCC) concept and is presented in this paper.Solar towers that use a combined Brayton – Rankine cycle, in which the Brayton cycle is decoupled from the Rankine cycle by means of the thermal storage system, have shown up as a cost-effective alternative due to their increased flexibility in the design and operation leading to better efficiencies and reduced costs. This paper is focused in the Levelized Cost of Energy (LCOE) reduction that can be achieved by a mid-scale DSCC Solar Tower plant based mainly on already existing components and concepts, alongside simple and short term technological developments.Since today's costs of medium size gas turbines are very competitive, while the specific cost of steam turbines still decreases significantly with size, this paper presents the analysis of a multi-tower system using several small Brayton cycles feeding a single oil-based storage system that, in turn, is used to drive a superheated Rankine cycle in a decoupled way (Fig. 1).This paper presents a stochastic analysis of the cost and performance of the proposed DSCC plant by providing probabilistic cost and efficiency distributions to the most sensitive figures. The results obtained show that the DSCC concept has the potential to achieve cost reductions in the LCOE in the order of 25% with a probability greater than 90%, based upon short term technological developments and adaptations