  Spectrally selective solar absorbers (SSAs), harvesting sunlight into heat,
are the key to the concentrated solar thermal systems. Current SSAs' designs
using photonic crystals, metamaterials, or cermets are either cost-inefficient
or have limited applicability due to complicated nanofabrication methods and
poor thermal stability at high temperatures. We present a scalable-manufactured
blackbody cavity solar absorber design with nearly ideal properties. The unity
solar absorptivity and nearly zero infrared emissivity allow for a stagnation
temperature of 880C under 10 suns. The performance surpasses those
state-of-the-art SSAs manufactured by nanofabrication methods. This design
relies on traditional fabricating methods, such as machining, casting, and
polishing. This makes it easy for large-scale industrial applications, and the
"blackbody cavity" feature enables its fast-integration to existing
concentrated solar thermal systems.
