Solar Window Glaze Innovation a 'Significant Breakthrough'
Originally published by: Proud Green Building — January 5, 2018
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A group of National Renewable Energy Laboratory (NREL) scientists recently made a significant breakthrough in solar window efficiency.
The NREL scientists created solar windows that use thermochromism — the property of substances to change color due to a change in temperature — to transform from transparent to tinted, and convert sunlight into electricity in that tinted state.
The innovation, called SwitchGlaze, could be one of the next commercial successes coming from Energy Department national laboratory research, the agency reports. The SwitchGlaze team has been able to explore the market potential of its new technology through Technology-to-Market’s Energy I-Corps, a training program for national lab researchers that aims to accelerate industry offtake of DOE technologies.
With support from the department’s Building Technologies Office (BTO), the researchers spent two months learning the industry landscape for solar windows, and determining how to best transition their technology from the lab to the marketplace.
While the technology offers something new and exciting to the market, solar windows have been around for decades. Initial efforts integrated conventional fully-opaque solar cells into windows and shades. This was followed by semi-transparent designs when thin film solar technology took hold. The latest technologies included fully-transparent, infrared light-absorbing designs.
What makes their technology unique? Below are five facts about solar windows and how the new innovation works.
1. It looks like an ordinary window. SwitchGlaze windows may look ordinary, but they are far from it. The technology absorbs some of the sunlight as it is transmitted through the window and converts it into electricity. The windows act like solar cells, providing a flexible clean energy solution for modern building design.
2. It “switches” with changes in temperature. SwitchGlaze solar windows are designed to tint (the switch) at warmer temperatures, especially on hot days when the sun is shining. After the switch to a tinted state occurs, SwitchGlaze windows absorb and convert sunlight into electricity the same way conventional rooftop solar panels do.
3. It’s thermochromatic. SwitchGlaze windows use temperature-triggered thermochromatic tinting. This is what allows for the partial absorption of sunlight and transforms the windows into efficient solar cells. SwitchGlaze initially converts sunlight into electricity at an efficiency of 11.3 percent. Conventional rooftop solar panels are roughly 20 percent efficient, with a theoretical maximum of 32 percent. Meanwhile solar windows that only convert visible light are limited by a theoretical 10 percent efficiency.
4. It will be cost-efficient. The cost of adding SwitchGlaze solar cell layers to traditional windows is predicted to be a fraction of the cost, which could be cancelled out by solar energy payback. The most expensive parts of conventional rooftop solar panels, the glass that encapsulates the panel and the transparent metals, are already in standard high-performance windows.
5. It’s an evolving technology. Building design is constantly evolving from static to dynamic. Just like lighting set to motion sensors provides lighting when needed by responding to occupant need, this dynamic technology responds to sunlight to improve building efficiency and provide on-site energy generation. Buildings of the future will be more energy-efficient, comfortable and durable as dynamic technologies are integrated. SwitchGlaze is in the proof-of-concept stage, with more work to be done before it will be commercially available.