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.
In this paper results from an ongoing research project (HYGATE) are presented, which is performed to reduce the levelized cost of electricity (LCOE) and to increase the CO 2 reduction potential of the solar-hybrid gas turbine plant concept (SHGT). Key improvements are the integration of thermal energy storage and the reduction of the operating temperature of the gas turbine to 950°C. As a result the solar receiver can provide the necessary temperature for solar-only operation of the plant at design pointwithout using the auxiliary burner. Annual performance calculations and an economic analysis of four different plant concepts were performed. Those concepts were analyzed using innovative power block processes. In general, such systems offer reliable and dispatchable power with low specific CO 2 emissions. A substantial decrease of CO 2 emissions has been achieved all along the four variants compared to results of a previous project [1]. Compared to the defined reference molten salt solar tower the solar-hybrid gas turbine plants as of now yield higher plant efficiencies, but have a slightly lower potential for CO 2 reduction. Among the SHGT plants the variants including a bottoming Organic Rankine Cycle (SHORCC and SHORCC-R) achieve the highest efficiencies but have significantly higher LCOE, caused by the high costs of the ORC components which are not yet commercially available in the required dimensions. The solar-hybrid combined cycle plant (SHCC) and solar-hybrid gas turbine plant with quasi isothermal compression and recuperation (SHGT-ICR) perform best among the SHGT plants in terms of LCOE, and can be considered an interesting alternative to molten salt tower plants. Taking into account other factors, such as plant complexity and water consumption, an isothermal solar gas turbine plant shows the most potential advantages. However, the SHCC has the highest technological maturity and is a likely candidate for a future demonstration plant.
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