A concentrated solar reactor harnesses the sun's energy by concentrating sunlight with mirrors to obtain high temperatures and provide carbon-free energy for endothermic reactions. REACSOL, an Instituts Carnot research project, a concentrated solar reactor was built at Liten in Grenoble and tested for the gasification of biomass on a solar concentrator at CNRS-PROMES in Font Romeu in Southwestern France.

Nearly 100 tests were completed on the continuously-fed reactor, giving the researchers an opportunity to compare different protocols and assess the influence of parameters like temperature (tests were carried out at 1,200 °C to 1,400 °C); the direct or indirect absorption of the concentrated solar energy; the addition of water vapor or CO2 to the process; and types of lignocellulosic material. The results showed that using solar energy to provide heat for the gasification reaction substantially improves yields. The energy required for the reaction is provided by the sun rather than by the oxidation of a portion of the biomass being processed. The researchers also reported complete conversion of the biomass, with carbon conversion rates in excess of 95%. Finally, the process resulted in part of the solar energy being stored as high-quality syngas.

The tests confirmed the feasibility of converting solid biomass into gas using a solar reactor. Modelling of the reactions and transfers will provide insights into how the technology can be extrapolated and scaled up.