09.09 Photovoltaics

Categories: Advanced Glazings

Introduction
It might be argued that with the advent of photovoltaic technology it is no longer necessary to use advanced glazings.  However, passive advanced glazings will always have the advantage that they work regardless of the weather; photovoltaics only generate power when the sun is shining, and may ultimately lead to significant problems of demand management because the greatest power output is often generated when it is least needed.  Controlling the energy input to a building is often preferable to allowing the energy in and then using generated power to remove it (using free summer power to cool a building for example may lead to a demand for the same levels of comfort in winter, therefore increasing the wintertime power demand).

This is not to say that photovoltaics should not be used, but they should be part of an integrated solution to the building design.  Indeed, the combination of photovoltaics on the opaque facade and electrochromics on the transparent facade may be a highly desirable way in which to clad a building.

Photovoltaics have found another application which impacts directly on the use of advanced glazings - photovoltaic modules are readily mounted on external shading devices, so that the intercepted solar energy is used to provide useful electricity for the building occupants (Goethe and Kwasny [1993]).  Ultra-thin photovoltaic cells have also been developed so that glazings containing photovoltaics can be used directly - this is particularly valuable for overhead glazings, where the patterns caused by the photovoltaic cells do not detract from the view.

For more information a useful guide to photovoltaic technology is given in EAB-OPET [1993], and some of the issues are discussed by Schmid [1994], Toggweiler [1994], Goethe [1994] and Benemann [1994].