Development, testing and evaluation of energy savings potentials of photovoltachromic windows in office buildings. A perspective study for Australian climates

PhotoVoltaChromic (PVC) cells are among the emerging smart windows technologies with an interesting potential of building integration. PVC technology combines ElectroChromic materials with Dye Sensitized Solar cells in order to have a self-powered adaptive transparent film. The main advantage of this technology is to have an automatic control – potentially manually overridden – of colouration process, depending on levels of solar irradiance. Moreover, a PVC window can operate, at the same time, as a photovoltaic cell, producing energy exceeding the amount required for the colouring process. In the current study, for the first time, the full potential of PVC windows in office buildings is assessed. For this analysis, a PVC cell with a Visible Light Transmittance (VLT) variable between 16.9% and 31.5% has been selected. Australia has been considered as reference location, due to the presence, in its territory, of different climatic regions, ranging from tropical/subtropical climates to the temperate ones. The results show a strong dependence of potential energy savings on Window-to-Wall Ratio (WWR) and solar irradiance on windows. In cooling dominated climates, the adoption of PVC windows has been demonstrated to be always beneficial, even with very low WWR and/or non-optimal exposures, achieving overall energy savings of up to 20%. In heating dominated climates, adoption of PVC windows should be carefully considered, as it is highly beneficial when large glazed surfaces are present. In this case annual total energy savings up to the 32% can be predicted in comparison with buildings equipped with standard clear windows.