PV module concentrates sunlight, lets light through for windows

A see-through photovoltaic (PV) module for window-integrated use developed at the Nagaoka University of Technology (Niigata, Japan) contains a low-concentration prism concentrator that allows direct solar radiation to be focused onto PV solar cells while diffuse solar radiation is transmitted to a building’s interior. The arrangement is efficient because direct solar radiation is (on sunny days) far more intense than diffuse solar radiation. The geometry and tilt are set such that the device functions without adjustment for a large part of the yearly sun path.

The prisms concentrate light via total internal reflection, which fails (due to the geometry) for most diffuse sunlight angles. After ray-trace modeling, the team constructed a test module with acrylic-resin prisms and single-crystalline silicon PV cells. The cell area was 57.5% of the total module area; the device was tested against a conventional module. A pyranometer measured the broadband solar irradiance incidence on the modules, and a pyrheliometer measured the direct normal incidence; the diffuse component of the solar irradiation was the difference between the two. The test module generated 1.15 times more electrical power than the conventional module, using only 63% of the cell area. The test module’s generation was twice that of the control per amount of light absorbed. Contact Noboru Yamada at [email protected].