Analysis of a hybrid solar window for building integration

• Spectral band splitting allows heating and daylighting in a hybrid window.
• The window uses moveable truncated CPCs with a reflective mirror film.
• Adjustable operation allows higher solar heat gain for passive space heating.
• The solar window performs as well as commercial windows.

The technical performance of a hybrid ‘solar window’ that provides heating in addition to daylighting is evaluated. A wavelength selective film is coupled with a compound parabolic concentrator (CPC) to reflect and concentrate the infrared portion of the solar spectrum onto a tubular absorber while transmitting the visible portion of the spectrum into the interior space. The optical performance of the CPC/selective film is predicted using a Monte Carlo Ray-Tracing model. An adaptive concentrator geometry based on asymmetrical truncation of CPCs is analyzed for vertical windows and horizontal skylights. The predicted visible transmittance is 0.66–0.73 for single glazed windows and 0.61–0.67 for double glazed windows. The solar heat gain coefficient and the U-factor are comparable to existing glazing technology. The annual thermal efficiency for double glazed windows/skylights based on use in Minneapolis, MN is 24–26%.