Innovative smart windows cool buildings and generate electricity without external power

Tokyo, Japan (SPX) Aug 26, 2024 - As global temperatures rise, the demand for cooling inside buildings has surged, leading to increased energy consumption. Traditional windows, which often absorb significant amounts of solar heat while reflecting little, contribute to this inefficiency. In response, energy-efficient windows are being developed to enhance thermal comfort while also reducing reliance on conventional cooling systems, thus addressing both climate change and energy sustainability challenges.

A research team led by Professor Seung Hwan Ko from the Department of Mechanical Engineering at Seoul National University has developed multifunctional smart windows that can cool indoor spaces without consuming electricity and generate power from raindrops. These windows also include a transparent heater to remove frost in cold weather, showcasing a versatile, next-generation energy-saving device.

Research Innovations

The smart windows integrate three critical functionalities:

1. Radiative Cooling: The windows lower indoor temperatures on sunny days by emitting heat without requiring external power, thus providing energy-efficient cooling.

2. Electricity Generation: On rainy days, the windows harness the friction generated by raindrops to produce electricity, further contributing to energy self-sufficiency.

3. Frost Removal: The windows use a transparent heating mechanism to rapidly clear frost, ensuring visibility in cold conditions.

Technical Approach

The smart windows are constructed with a layered structure of silver and indium tin oxide (ITO), materials known for their electrical conductivity and optical properties. The design allows the windows to selectively reflect near-infrared sunlight, minimizing indoor heat absorption while maintaining transparency. The windows' ability to generate electricity comes from the friction created by raindrops interacting with the electrode material on the window surface. Additionally, the same transparent electrodes provide Joule heating, which efficiently melts frost or ice.

Performance and Potential Impact

In tests, the smart windows were able to maintain indoor temperatures approximately 7 degrees Celsius lower than standard windows under direct sunlight. During simulated rainy conditions, they generated 8.3 watts per square meter of power with a single raindrop and removed frost twice as quickly as conventional windows using Joule heating.

Professor Ko commented on the significance of this technology, stating, "This achievement of presenting next-generation smart window technology optimized for responding to the depletion of fossil fuels and global warming offers valuable insights into the technological advancements for Plus Energy buildings and the eco-friendly electric vehicle industry. Smart windows are expected to be applied across various industries because they address environmental pollution, reduce cooling energy, and overcome the limitations of conventional battery technologies through self-power generation."

The development of these multifunctional smart windows is a major step forward in the quest for Plus Energy Buildings (PEBs), which not only minimize energy consumption but also generate their own power, contributing to greater energy independence.

Research Report:Energy-saving window for versatile multimode of radiative cooling, energy harvesting, and defrosting functionalities