Direct solar air heating inside small-scale linear Fresnel collector assisted by a turbocharger: Experimental characterization

Abstract

In recent years many efforts are being made to replace fossil fuel with renewable energy sources in the industry, both for electricity and heat production. Several high-energy demanding processes use hot air as heat and moisture carrier in the low and medium temperature range, for which solar air heaters offer great potential. Among solar energy technologies, Linear Fresnel collectors can provide heat in the medium temperature range at a decreasing cost. Direct air heating inside Linear Fresnel collector avoids the use of a liquid heat transfer fluid and the heat exchanger, reducing installation and maintenance costs, as well as residues. In this innovative technology, an automotive turbocharger reduces auxiliary energy consumption for air pumping through the solar collector, which would be unsustainable at medium and large scale. It configures an original open-to-atmosphere Brayton cycle with null power efficiency. In this study, an experimental investigation is carried out on the first small-scale prototype solar field of 79.2 m2 area. It allows characterizing the thermal and mechanical behavior of the turbocharger, besides tuning and validating the numerical model implemented. Especial attention is given to the diabatic behavior of both turbomachines and to establish the limiting efficiency of the turbocharger as forefront research.