Experimental evaluation of a non-isothermal high temperature solar particle receiver

The experimental evaluation of a solar particle receiver is reported. Concentrated irradiation was converted into thermal energy in a gas flow by a cloud of radiation absorbing sub-micrometre carbon particles. Average solar concentration was 2500 on an 80 mm diameter aperture. Cloud particle mass fractions were in the range of 0.2-0.5%. Exit gas temperatures exceeding 2100 K were measured with nitrogen, 1900 K with CO2, and 2000 K with air, which is 1000 K higher than previously reported using a particle receiver. The air heating tests reveal that the particle/gas heat transfer exceeded the oxygen/ carbon oxidation rate up to 2000 K. A carbon particle mass fraction of less than 0.5% in the gas stream ensures that the heated air contains only a negligible amount Of CO2 and NOchi. The axial receiver cavity wall temperature increased with distance from the aperture, peaking at 60% of the total cavity length, and then slightly decreasing towards the exit plane. At steady conditions, the wall temperatures in the gas exit plane were at least 100 K cooler than the gas's, alleviating structural constraints associated with conventional volumetric receivers. Estimated radiation to thermal energy conversion efficiencies surpassed 80% at the highest mass flow rates. The receiver accumulated over 12 net hours at temperatures above 1700 K without any major failures. (C) 2003 Elsevier Ltd. All rights reserved.