Fraunhofer-Led ‘HybridKraft’ Project Pioneers Cost-Effective Electricity Generation with Solar Thermal Power and Photovoltaics

© Fraunhofer ISE The electric heater is tested in closed-loop operation with the molten salt storage tank in the pilot plant at Fraunhofer ISE

The German Federal Ministry of Economics and Climate Protection is funding the pioneering “HybridKraft” project, spearheaded by the Fraunhofer Institute for Solar Energy Systems ISE. The project aims to develop a cutting-edge electric heater for molten salt storage tanks, designed to be compatible with large-scale power plants. By combining solar thermal power plants, photovoltaics, and storage, the project seeks to achieve a cost-optimized system that ensures stable electricity generation.


The “HybridKraft” project capitalizes on the advantages of both solar thermal power plants and photovoltaic systems. During daylight hours, electricity predominantly comes from the photovoltaic system, while after sunset, the stored thermal energy in the molten salt storage tank, sourced from the solar thermal power plant, is employed to generate electricity through a turbine. An innovative feature of this hybrid approach involves using surplus photovoltaic electricity to electrically heat the molten salt storage tank on days with ample solar radiation, enhancing the system’s efficiency.

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The project focuses on testing an electric heater for liquid salts in combination with linear concentrating thermal Fresnel collectors. This technology enables the optimization of the heat transfer fluid’s exit temperature from the receiver, thanks to the use of PV current. As a result, the molten salt’s storage density, the turbine’s operating temperature, and the overall system efficiency are enhanced.


The project’s ultimate goal is to develop a one-megawatt solar-powered heater prototype, which will undergo testing in Fraunhofer ISE’s pilot plant with a molten salt storage tank in closed-loop operation. Based on the prototype’s design, test results, and simulation studies, the team plans to create a design for large-capacity electric heaters suitable for various locations and applications.

Industrial Applications and Collaborative Efforts:
Beyond solar thermal power plants, the electric heater’s versatility holds promise for industrial applications where surplus electricity from renewable sources is available. The surplus electricity can be efficiently converted into heat, catering to high-temperature industrial processes ranging from 150 to 550 degrees Celsius. Additionally, the heat can be stored in a Carnot battery for subsequent reconversion into electricity.

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Frenell GmbH, John Cockerill UVK GmbH, and BASF Stationary Energy Storage GmbH have joined forces as project partners to develop the components and integrate them into solar thermal power plants. BASF Stationary Energy Storage GmbH, a wholly owned BASF subsidiary, is entrusted with reviewing specifications, exploring electro-chemical storage options, including sodium-sulfur batteries, and adapting their design to meet power plant requirements.

The “HybridKraft” project represents a significant step towards cost-effective and stable electricity generation by combining solar thermal power plants, photovoltaics, and innovative storage solutions. The development of a powerful electric heater for molten salt storage tanks holds promise for large-scale power plants and industrial processes, bringing Germany one step closer to achieving its climate-neutral goals. The collaborative efforts of Fraunhofer ISE and its project partners ensure that this technology will soon find practical applications in various locations and industries.

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