A study led by the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) has shown that the use of thermochromic windows in office buildings could improve energy efficiency in all climate zones in the United States by regulating indoor temperatures, resulting in significant energy savings.
A thermochromic window based on the absorption of solar energy using perovskite materials transitions from a transparent state to a visible absorbing or reflecting state. This technology relieves the heating load in warm climates and the cooling load in colder regions.
Lance Wheeler, the lead researcher on the project, said switching to thermochromic windows would result in substantial annual energy savings, with the main savings coming from tall glass office buildings requiring less heat in cold or seasonal climates. If all employees in a simulated office building drove an electric car for a distance equivalent to the average U.S. commute, the annual energy could be used to fully charge each employee's car.
The researchers used a 12-story building as a model with a window-to-wall ratio of 95 percent. They simulated building energy use over the course of a year at 15-minute intervals in eight climate zones across the United States, including Hawaii, Arizona, California, Colorado, New York, Wisconsin, Minnesota and Alaska.
They determine:
Thermochromic double pane glass increases building energy efficiency compared to double pane glass in each area.
Energy savings are greater in cold regions.
Thermochromic double pane glass is even better than triple pane glass in the hottest climate zones.
The researchers note that triple-glazed windows save more energy than thermochromic double-glazed windows in cooler climates, but adding thermochromic laminate to create three Laminated glass windows provide the greatest annual energy savings.
