Techno-economic optimization of molten salt solar tower plants

Abstract

In this paper the results of a techno-economic analysis of improved and optimized molten salt solar tower plants (MSSTP plants) are presented. The potential improvements that were analyzed include different receiver designs, different designs of the HTF-system and plant control, increased molten salt temperatures (up to 640°C) and multi-tower systems. Detailed technological and economic models of the solar field, solar receiver and high temperature fluid system (HTF-system) were developed and used to find potential improvements compared to a reference plant based on Solar Two technology and up-to-date cost estimations. The annual yield model calculates the annual outputs and the LCOE of all variants. An improved external tubular receiver and improved HTF-system achieves a significant decrease of LCOE compared to the reference. This is caused by lower receiver cost as well as improvements of the HTF-system and plant operation strategy, significantly reducing the plant own consumption. A novel star receiver shows potential for further cost decrease. The cavity receiver concepts result in higher LCOE due to their high investment cost, despite achieving higher efficiencies. Increased molten salt temperatures seem possible with an adapted, closed loop HTF-system and achieve comparable results to the original improved system (with 565°C) under the given boundary conditions. In this analysis all multi tower systems show lower economic viability compared to single tower systems, caused by high additional cost for piping connections and higher cost of the receivers.

Solar tower system temperature range optimization for reduced LCOE

“…An advanced subcritical steam power cycle with reheat and multiple preheating stages is assumed, as described in [4]. In the steam generator high pressure steam is heated from 261°C to 620°C, in the reheat section the intermediate pressure steam is heated to 620°C.…”

Using corrugated tubes in external molten salt receivers

“…Within the HPMS (High Performance Molten Salt) project different receiver concepts for a 700 MW th molten salt system have been evaluated [1]. The ASTRID code [2] was used for the design of the receiver by optimizing the thermo-hydraulic layout in a first step.…”

“…The wall thickness of the tube was set to 1.5mm for all variations. The heat flux on the tube outside was modeled using a similar circumferential distribution as in reality but homogenous along tube length (see (1) and Fig. 4).…”

Power-to-heat in CSP systems for capacity expansion

“…Thus the power cycle could be run on full load. 2 Further specifications can be found in the Appendix.…”

“…In this chapter a conclusion of the modelling work of the subsystems is given, as well as a detailed description of the annual yield calculation model. A general overview of the workflow of the annual yield calculation model is depicted in Figure 3 [2].…”