Passive Day Cooling can Reduce Energy Consumption in Any Weather, Study Says

A technology with great potential for long-term energy consumption reduction is passive day cooling. Doing so prevents buildings from becoming overheated by solar radiation and releases built-up heat without using any additional energy.

Thanks to a test system developed by researchers at the University of Bayreuth, regardless of whether or environmental factors, materials used for passive cooling can now be consistently characterized and compared.

A standardized, universally applicable test system for comparing high-performance cooling materials is being developed, and the measurement setup described in Cell Reports Physical Science is the first step in that direction.

Global Warming vs. Passive Cooling

Prof. Dr. Markus Retsch, Chair of Physical Chemistry I at the University of Bayreuth, said that using more fossil fuels on a global scale continues to contribute to global warming and is a major factor in the heating up of many cities. Retsch is the leader of the study.

Using passive cooling techniques to cool buildings during the day has a great deal of potential to become a reliable tool for energy conservation. As a result, many technologically intriguing materials and classes of materials have been developed for the dissipation of heat, but it is still difficult to determine and compare their performance precisely.

The laboratory setup created by the research team aids in overcoming this challenge. It is a test system that, regardless of the weather, significantly contributes to the characterization of currently available cooling materials and the design of new ones.

Simulations

The most significant elements that affect passive cooling performance are modeled by the laboratory-based test system. Therefore, the sun simulator is an aluminum dome cooled with liquid nitrogen, which is a changeable filter that only permits light rays of specific wavelengths to pass through. Essential elements include the flow of a heatable gas that can be used to regulate the ambient temperature.

This makes it possible to simulate on a small scale the intensity of solar radiation, the temperatures affecting the cooling materials, and other environmental influences.

These variables are constantly changing outdoors and are therefore uncontrollable, but the new Bayreuth measurement setup allows for a highly precise setting of these variables. As a result, regardless of time, location, or weather, the test results can always be replicated. There is no other way to compare cooling materials under the same circumstances and to accurately characterize their properties and behavior.

The measurement setup is reliable, economical, and has the benefit of being easily repeatable without a lot of technical work.

The Bayreuth researchers have shown the test system's high performance and dependability on three different materials, including a silicon wafer coated with graphite; a polydimethylsiloxane (PDMS) film applied to a silver mirror, and a polydimethylsiloxane (Ag) mirror.

They measured the materials' cooling performance while also testing the materials' heating and cooling properties, Science Daily reports.

Dr. Qimeng Song, a postdoc at the research group led by Retsch, emphasized that their measurement setup is the first step toward making consistent performance comparisons in both cooling materials that have been created all over the world under a variety of very different climatic and weather conditions. Such a test system is a crucial requirement for passive cooling to become a widely used technology for significantly reducing energy consumption. Song is the first author of the study.