Page - 54 - in Water, Energy, and Environment - A Primer

foot before they would be competitive…’ At that time EC windows were in the range of $50–100/square foot, with commercial buildings on the lower end of that range and residential applications on the higher end. Another approach being taken by a few EC window companies is to add an EC film to existingwindows,which is also capable of reducing energy costs. Howmuch energy canECwindows save? TheNREL study, using a model to evaluate the performance of EC windows in a single-family traditional new home in Atlanta, predicted that whole-house energy demand could be reduced by 9.1% andwhole-house electricity demandby13.5%. Note: some thought has been given to combining electrochromic windows and solar PV cells so that instead of uselessly reflecting away sunlight, darkened smart windows could soak up that energy and store it for use at another time. It’s easy to imagine windows that capture some of the solar energy falling on them during the day and storing generated electricity in batteries that can power lights inside your home at night. However, a window can’t be 100 percent transparent and work as an efficient solar panel at the same time. The incoming energy is either transmitted through the glass or absorbed and stored, but not both. Awindow that doubles as a solar panel would of necessity involve a compromise: a darker window even when clear and less efficient at capturing energy than a good solar panel. Nevertheless, R&D on this concept is underway, and we can probably look forward to dual-purpose windows in the future. 5.6 ENERGYEFFICIENCYIN INDUSTRY Currently, the industrial sector consumes just over half of all global energy and feedstock fuels. Sector demand is expected to grow over the next few decades, with themost rapid growth occurring in the use of feedstocks for petrochemicals. It will Water,Energy, andEnvironment–APrimer54