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Beside continuous implementation of concentrating solar power plants (CSP) in Europe, which stipulate cost reduction by mass production effects, further R&D activities are necessary to achieve the cost competitiveness to fossil power generation. Therefore the cost range of 15–20 cents€/kWh for the currently planned CSP systems in Europe has to be decreased by a factor of 2–4. The European Concentrated Solar Thermal Roadmap (ECOSTAR) study that is conducted by leading CSP research institutes in Europe intends to stipulate the direction for R&D activities in the context of cost reduction. It uses a common methodology approach, based on an annual performance model to identify the most essential technical innovations that will reduce the cost of seven different CSP system concepts, which are currently under promotion world wide. The potential of innovative concepts for solar light weight concentrators, low-cost thermal energy storage concepts, solar receivers/absorbers and power cycles are in the main focus of interest. The results of the study include a description of the value of CSP power, the sensitivity of the electricity cost information, a list of innovations that have been investigated and recommendations for the focus of further R&D work.

Besides continuous implementation of concentrating solar power plants (CSP) in Europe, which stipulate cost reduction by mass production effects, further R&D activities are necessary to achieve the cost competitiveness to fossil power generation. The European Concentrated Solar Thermal Roadmap (ECOSTAR) study that was conducted by European research institutes in the field of CSP intends to stipulate the direction for R&D activities in the context of cost reduction. This paper gives an overview about the methodology and the results for one of the seven different CSP system concepts that are currently under promotion worldwide and considered within ECOSTAR. The technology presented here is the parabolic trough with direct steam generation (DSG), which may be considered as an evolution of the existing parabolic systems with thermal oil as heat transfer fluid. The methodology is explained using this exemplary system, and the technical improvements are evaluated according to their cost-reduction potential using a common approach, based on an annual performance model. Research priorities are given based on the results. The simultaneous implementation of three measures is required in order to achieve the cost-reduction target: Technical improvement by R&D, upscaling of the unit size, and mass production of the equipment.

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.

Existing solar thermal power plants are based on steam turbine cycles. While their process temperature is limited, solar gas turbine (GT) systems provide the opportunity to utilize solar heat at a much higher temperature. Therefore there is potential to improve the efficiency of future solar thermal power plants. Solar based heat input to substitute fuel requires specific GT features. Currently the portfolio of available GTs with these features is restricted. Only small capacity research plants are in service or in planning. Process layout and technology studies for high solar share GT systems have been carried out and have already been reported by the authors. While these investigations are based on a commercial 10MW class GT, this paper addresses the parameterization of high solar share GT systems and is not restricted to any type of commercial GT. Three configurations of solar hybrid GT cycles are analyzed. Besides recuperated and simple GT with bottoming Organic Rankine Cycle (ORC), a conventional combined cycle is considered. The study addresses the GT parameterization. Therefore parametric process models are used for simulation. Maximum electrical efficiency and associated optimum compressor pressure ratio πC are derived at design conditions. The pressure losses of the additional solar components of solar hybrid GTs have a different adversely effect on the investigated systems. Further aspects like high ambient temperature, availability of water and influence of compressor pressure level on component design are discussed as well. The present study is part of the R&D project Hybrid High Solar Share Gas Turbine Systems (HYGATE) which is funded by the German Ministry for the Environment, Nature and Nuclear Safety and the Ministry of Economics and Technology.