Timed Capsule Professor Darkwa (left) and research assistants examine phase-change material they’ve engineered to store and release a room’s excess heat.
Courtesy University of Nottingham Timed Capsule Professor Darkwa (left) and research assistants examine phase-change material they’ve engineered to store and release a room’s excess heat.

Imagine window treatments or painted walls that could store excess heat in a room and release that heat when the room gets a bit chilly. Several companies are currently working to bring this scenario closer to reality. National Gypsum, for instance, is currently testing ThermalCORE, wall panels treated with Micronal, a BASF-produced microscopic acrylic “phase-change material” (PCM) that helps maintain a comfortable interior environment as room temperatures fluctuate during the day.

On the other side of the globe, researchers at the University of Nottingham in Ningbo, China, have been toiling for eight years on a composite PCM whose “unique advantages” offer a higher energy storage capacity and faster heat transfer, according to Professor Jo Darkwa, the team’s leader and director of the university’s Center for Sustainable Energy Technologies.

In the lab, the PCM looks like an oversized Alka Seltzer, but could be made larger or small enough to be sprayed onto surfaces depending on use. Darkwa says the material may eventually be combined with gypsum drywall, paint, laminated transparent sheets for window blinds, and other residential products.

In essence, Darkwa explains, the material is engineered so that it stores or releases heat by solidifying or melting at constant temperatures.

“For heating applications, it can store any excessive solar or internal sundry heat gains when a preset room temperature is exceeded and then releases the heat back when the temperature falls below a preset room temperature,” he says.

For cooling applications, the material could be used to reduce the amount of solar heat gains through walls, roofs, and windows into rooms, thereby minimizing the total cooling loads of air conditioners by as much as 65 percent. “Depending on the internal environmental conditions in a room, additional cooling by air conditioning may not even be necessary,” says Darkwa, except to control humidity and air movement.

All told, the application of this material has the potential to cut a building’s energy consumption by 35 percent. And given that construction produces more carbon emissions than any other industry in the world, the commercialization of this type of PCM could have a significant impact on curtailing energy usage and the pollutants that are emitted due to that usage.

Darkwa and his team have been conducting life-cycle analyses to determine how the addition of the PCM would affect the overall cost of the product.

Their research already has financial backing from China’s public and private sectors, and Darkwa tells Builder that some kind of product—such as a solar photovoltaic efficiency enhancement application—could be on the market within the next two years.