The goal of E²PHEST²US project is to design and realize innovative components for solar radiation concentrating systems able to efficiently generate at the same time both electricity (thermal-to-electrical efficiency of 35%) and heat power (standard efficiency of 65%), and reliably work at high temperatures (800-1000 °C), recovery and exploit residual heat at intermediate temperature.
The conversion will be based on the development and tailoring of:

• Efficient concentrating solar system, able to feed a high amount of solar radiation power to the conversion module;
• Optically efficient solar absorber receiver, able to transform the radiation energy into thermal energy and work at high temperatures (> 800 °C);
• Innovative two-stage solid state active module, based on the combination of thermionic and thermoelectric conversions, for the thermal to electrical energy conversion;
• Monolithic integration of absorber, two stage conversion module and heat recovery system;
• Hybrid cables carrying electricity and fluids.

The new-concept module, able to produce low-voltage/high-current electrical and thermal energy, should be realized within 36 months.
The conversion module size will be 5x5 cm and absorber/module depth of about 2 cm. The estimated input heat flux will be about 30 W/cm2 and an output electrical power up to 260 W and thermal power up to 320W are expected. The thermionic stage will be able to supply up to 215 W of the electric power, while the thermoelectric stage around 45 W (absorber temperature around 800 °C).
Therefore the main activities planned in  the frame of E²PHEST²US  will deal with:

• Optimization of the concentrating solar system in terms of mechanics, optics, tracking system, wirings, integrated circuits.
• Investigation, selection and preparation of the absorbing materials composing the solar radiation receiver. Innovative preparation methods will be explored to produce new ceramic materials characterized by nanostructures, multilayered structures, graded porosities, etc, with suitable mechanical properties (low thermal expansion variation and high thermal stability). Absorber mechanical and micro-structural properties will be tailored and other physical functional properties investigated (i.e. resistance to high temperature and to thermal cycles, corrosion and oxidation, electrical and thermal conductivity, optical absorption, etc).
• Investigation of the best design to efficiently capture concentrated solar radiation and convert it into thermal energy.  
• Realization of the thermal-to-electrical module, constituted by a thermionic and/or a thermoelectric  active solid-state converters and/or a combination of them. The integration of the first conversion stage, able to exploit the thermionic effect, with the second stage, that recovers the residual thermal energy by means of the Seebeck effect, can allow to harvest additional electrical energy.
• Design of the heat recovery system: selection of vector fluids and their integration with the converters.
• Design and manufacturing of a hybrid cable providing for simultaneous transfer of electricity and fluid.
• Identification and definition of technological drawbacks to scale up the absorber/multigenerative module.