Research activities

07 Jun

Research activities

Hybrid thermionic near-field thermophotovoltaic converter

The conversion of thermal energy, available or stored at high temperature, into electrical energy would make it possible to overcome the problem posed by the intermittency of solar or wind energy. One possible solution is based on thermoelectric conversion, which takes advantage of the thermal gradients established in solids. Alternatives related to the emission by thermal sources, by means of photons in so-called thermophotovoltaic devices or by means of electrons in so-called thermionic devices, are also under study. If the distance between the thermal source and the thermophotovoltaic converter is decreased below the micron, then the photon transfer increases due to near-field effect (tunneling) and the electrical power generated by photoconversion also increases.
A novel concept, proposed by researchers at the Instituto de Energia Solar (Madrid, Spain) and the Centre for Energy and Thermal Sciences of Lyon (Villeurbanne, France)*, consists in combining the two types of near-field thermophotovoltaic and thermionic devices in a single hybrid device. The new hybrid converter would achieve higher conversion efficiencies and power output than the separate converters. It is known that the resistive losses are severe for thermophotovoltaic cells, in particular because of the high flux of photons in the near field, similarly to the case of concentrated solar cells. It turns out that the novel thermionic-photovoltaic hybrid device seems to totally bypass this crucial problem. The work on this new concept has just been published in an article in the journal Nano Energy.
Practical implementation is now envisaged. Near-field thermophotovoltaic converter and far-field thermal-thermophotovoltaic prototypes are already under development, respectively in the DEMO-NFR-TPV project funded by the French National Research Agency (ANR) and in the AMADEUS project funded by the European Commission H2020 programme. The next challenge will be to combine the achievements of these two projects to realize the hybrid converter in the near field.
This work is mentioned in a news article of the CNRS and an in article of Industrie et Technologies (both in French).

* Researcher in-charge : R. Vaillon (
R. Vaillon recently joined the Institut d’Electronique et des Systèmes (IES) in Montpellier.

 Reference : Thermionic-enhanced near-field thermophotovoltaics. A. Datas and R. Vaillon. Nano Energy (2019). DOI: 10.1016/j.nanoen.2019.04.039

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