Imagine a building that can heat itself in winter and cool itself in summer without using any electricity.
A research team in South Korea has created exactly that.
They have developed a three-dimensional smart energy-saving device that automatically switches between heating and cooling based on sunlight and temperature—no power source required.
Their work was published in the journal Advanced Materials and led by Professor Kim Bong-hoon from DGIST, in collaboration with researchers from KAIST, POSTECH, Kyung Hee University, and Kongju National University.
Buildings use a huge amount of energy—about 30% of the world’s total energy consumption. Most of this, around 70%, goes to heating and cooling. This contributes heavily to greenhouse gas emissions and air pollution.
Because of this, many scientists and engineers are looking for environmentally friendly ways to control indoor temperatures more efficiently.
However, most existing heating and cooling systems depend on electricity, and even “smart” systems often have limited automatic control.
Professor Kim’s team has created a device that could change this. Their 3D smart structure responds naturally to sunlight—opening or closing depending on the angle of the sun—allowing it to automatically switch between cooling and heating modes.
The design is inspired by traditional architecture techniques, where the shape and angle of roof eaves change based on the region’s latitude to control sunlight and indoor temperature.
The key to this technology is a material called a shape memory alloy, or SMA. This special metal changes shape when the temperature changes.
In this device, the SMA allows the structure to open or close on its own without motors, wiring, or an external power source.
When the device is closed, its surface reflects sunlight and releases heat through mid-infrared radiation. This activates cooling mode, helping keep the inside of a building cooler.
When the device opens, a black surface that absorbs heat becomes exposed, allowing the structure to warm up and support heating.
The researchers tested the device in real outdoor environments under different angles and weather conditions. They found that it consistently and reliably controlled heating and cooling, regardless of the building design it was applied to. This means the device could potentially be attached to many different types of structures—from homes and office buildings to factories and even outdoor facilities.
Professor Kim noted that this work points toward a new generation of energy-saving building technologies that don’t require electricity.
Since the study was featured on the cover of a major scientific journal, the team hopes to continue developing practical versions of the device that can help reduce energy use in cities and industrial areas.
Their innovation shows that sometimes the most sustainable solutions come from letting nature—and smart materials—do the work for us.
