A team of researchers from the National Renewable Energy Laboratory (NREL) and the University of Wisconsin, Stout, have said glass-walled buildings can be made 40% more energy efficient through the addition of thermally efficient photovoltaic (PV) windows.

The U.S. Department of Energy’s (DOE) Building Technologies Office funded the research.

Buildings usually account for roughly more than a third of the world’s energy consumption as well as global carbon dioxide emissions.

The researchers said that by combining PV with high thermal performance window technologies, new buildings have a chance to become crucial in combatting climate change.

Lance Wheeler, a scientist at NREL, along with his twin brother Vincent from Wisconsin University, primarily conducted the study to develop a software called PV window to allow users to model the design of PV windows for building simulations.

It outlines building design rules that can yield a structure with net-zero and net-positive energy consumption.

The team found that energy use increases when a building has more windows than wall space. However, the energy use drops when the ratio is increased along with the inclusion of PV glazing.

On its discovery, the team said that if PV glazing technology is coupled with photovoltaic panels on the outside of the building, particularly facing east and west, to capture early morning and late day, the buildings can reach net zero.

Referencing the Freedom Tower in New York, which has millions of square feet of glass, Wheeler said if fully glazed, the building “could be a power plant in itself.”

PV Glazing

For the study, the researchers considered buildings with a window-to-wall ratio of 95% – dubbed “highly glazed” — to understand the impact glazing has on overall building energy performance.

The study identified that improving glazing technologies, such as triple-pane windows, helped lower the buildings’ energy consumption.

The team simulated the impact of three different types of PV glazing technologies in eight cities across different climates.

It was noted that highly glazed buildings require considerable energy to cool the occupants as many windows let sunlight stream through and raise the temperature.

Photovoltaic windows can provide thermal insulation for a building and use the absorbed energy to generate electricity.

Over a year, a clear trend emerged in PV generations in climates with weather that changes with the season.

For instance, the simulations revealed that in a city like Denver, onsite PV generation daily could cut 50% of the average building electricity load for a heavily glazed 12-story structure.

The team also identified that PV windows in Denver could eliminate up to 2 million kilograms of carbon dioxide emissions annually.

The researchers noted that the technology could also be paired with rooftop solar to increase the amount of electricity generated, with the potential to create more power than a building needs by using high-efficiency PV windows and unique building geometry.

“We should be building highly efficient buildings… if we choose to keep making these buildings, we’ve got to reconcile their lower performance somehow, and PV windows are one way to do that,” Wheeler said.

In October, a new study by the National Renewable Energy Laboratory (NREL) revealed that distancing rows of solar panels apart can help maintain the module temperature, which usually increases when solar modules are exposed to direct sun for a long time leading to a decrease in module efficiency.

Recently, a team of researchers from the Gwangju Institute of Science and Technology (GIST), South Korea, claimed that using a certain amount of deionized (DI) water prevents the aggregation of organic materials in solar cells, resulting in better performance.