Concentrating solar power (CSP) systems represent a zero emission method for conversion of sunlight to electricity. CSP systems use an array of mirrors to concentrate sunlight on the surface of a heat exchanger and heat a working fluid. These heat exchanger surfaces must have high absorptivity and low emissivity in the solar spectrum. In addition, they must be capable of extended operation at temperatures in excess of 600°C. Initial development of solar selective coatings using the air plasma spray process will be discussed. Eight different coating materials were deposited onto 304L stainless steel substrates. Solar absorptance and emittance were measured from each coating in three conditions: as-deposited, after heat treatment at 600°C for six hours, and after polishing to a 1 µm finish. A figure of merit based upon solar power tower (SPT) operation was calculated from these data and compared to the industry standard solar selective coating for SPT receivers, Pyromark Series 2500 high temperature paint. This comparison shows that Ni-5Al, 80WC-20Co, and CeO plasma-sprayed coatings all have potential as solar selective surfaces for SPT receivers.

A Sulzer-Metco 6P Powder Flame Spray Torch spraying an alumina-titania ceramic powder RX60 6-axis robotic was characterized using an Accura G3(Tecnar Automation; Quebec, Canada) and a DPV-2000 (Tecnar Automation; Quebec, Canada). The two sensors were mounted side-by-side and a robot was used position the torch in relation to each sensor. Process gas flows were set using laminar flow element mass flow controllers. Accura and DPV measurements of particle temperature (Tp) and particle velocity (Vp) were made in succession at each operating condition without changing torch operating conditions. Data for a single designed experiment was collected with both sensors allowing for comparison of the two sensors across the operating space of a typical powder flame spray process.