Static Diffuse Solar Concentrators

   Static Diffuse Solar Concentrators

A vertical surface sees the sky and ground equally and a ground surface with a reflectivity of 1 doubles the solar input. An equatorially facing wall and a snowfield are close to ideal.

Diffuse surfaces are typically much cheaper than specular surfaces and are less sensitive to dust and damage.

TiO2 filled paints with solar reflectivity’s >90% have been available for more than 100 yrs.

The sun occupies 40% of the sky dome over the course of a year allowing a static concentrator to provide 2.5 X direct solar concentration (1/0.4).

Further static concentration can be achieved by microspheric PV cells. An aluminum foil with hemispherical bumps covered with Perovskite PV and concentric high index glass cover can increase concentration by the square of the glass refractive index. Glasses with nd>2 are available at low cost and are used in great quantities as microspheric retroreflectors in roadway surfaces.

The theoretical limits of static concentration are >10X as some portions of the sky dome can be dismissed as less economically efficient and glasses with much higher than nd2 are available.

PV efficiency increases with increasing flux.

Vertical PV has improved heat xfer, reduced dust, dirt, and snow accumulation, and greatly reduced hail damage.

Bifacial perovskite panels with 25um glass cover will become available and can be hung from wires that that act as electrical and structural conduits.