Researchers at Texas A&M University have developed a novel phase-change material (PCM) that could be used to construct buildings which are capable of passive internal temperature regulation.
Once mixed with normal building materials, the team’s unique wax-filled resin can be DIW 3D printed into structures which change shape in order to absorb thermal energy. At present, the composite can be added to paints and used for decorative home heat deflection, but with further iteration, its creators say that it also holds potential for building houses that are better able to withstand extreme weather.
“We’re excited about the potential of our material to keep buildings comfortable while reducing energy consumption,” said Dr. Peiran Wei, a research scientist at Texas A&M’s Soft Matter Facility. “We can combine multiple PCMs with different melting temperatures and precisely distribute them into various areas of a single printed object to function throughout all four seasons and across the globe.”
Climate change and PCMs
As climate change begins to wreak havoc upon the world’s weather patterns, the homes of millions of people have become more susceptible to temperature fluctuations than ever before. To combat this, heating, ventilation and air conditioning or ‘HVAC’ systems are often used to regulate heat within residential settings, but such devices tend to be power hungry and energy inefficient.
Making matters worse, HVACs also rely on greenhouse materials known as refrigerants to generate cool, dry air, thus they effectively contribute to the very global warming they’re built to address. As a result, significant research is now being poured into finding more efficient methods of thermal regulation, and PCMs have shown particular potential as a passive means of achieving this.
In effect, PCMs are able to store heat by converting from a solid into a liquid upon absorbing it, while doing the opposite to release it, meaning that they can regulate temperature without needing external power. However, manufacturing such composites currently requires a ‘shell’ to be added around each individual PCM particle, limiting the amount that can be added to existing building materials.
According to Ciera Cipriani, a NASA Space Technology Graduate Research Fellow at Texas A&M, the process is like using a pot to boil an egg, but by innovating upon the way PCMs are produced, it could be possible to manufacture them at scale and in a way that allows them to operate within a broader temperature window.
“Imagine filling a pot with eggs and water,” explains Cipriani. “If each egg has to be placed into an individual container to be hard-boiled, fewer eggs will fit in the pot. By removing the plastic containers, the veritable shell in our research, more eggs, or PCMs, can occupy a greater volume by packing closer together within the water/resin.”
A wax-based building material
Taking inspiration from similar previous studies, the Texas A&M team mixed a light-sensitive liquid resin with a phase-changing paraffin wax powder, to create a novel 3D printable ink. In doing so, the researchers were able to skip several existing PCM production steps including encapsulation, as the resin acts as both the outer ‘shell’ and building material simultaneously.
By locking PCM particles inside individual ‘pockets,’ this approach also allows them to undergo a phase change and manage thermal energy, without leaking and creating a safety hazard. However, the team’s mixture initially proved to be soft, paste-like and malleable, thus to make it 3D printable they cured it with ultraviolet light to solidify it and make it end-use ready.
To test the efficacy of their novel composite, the engineers later used it to 3D print a miniature house model, and raised its temperature by placing it into an oven. Compared to samples produced using conventional building materials, the PCM-based model proved able to maintain a temperature that was up to 40% hotter or cooler than that measured outside.
Moving forwards, the researchers now intend to experiment with PCMs other than paraffin, with the aim of developing enhanced composites that can operate at broader temperature ranges and manage more thermal energy at once.
“PCMs are an attractive option for passively controlling building heating and cooling,” concluded the team in their paper. “PCMs with different melting points can be simultaneously integrated into resin and printed without detriment to the structure or integrity… our approach is compatible with a wide range of photopolymer matrices and PCMs.”
Construction material advances
The Texas A&M team isn’t the first to think of using 3D printing to construct temperature regulating housing, as Microlight3D has also received EU backing to develop a concrete for creating ‘self-cooling’ buildings. Working with five European universities, the firm essentially aims to design a microstructured material that combats the phenomenon known as ‘urban heat islands.’
In a similarly sustainability-minded project, scientists at the Swinburne University of Technology and Hebei University of Technology have turned demolition waste into a novel eco-friendly printing material. Composed of recycled concrete, ceramsite particles, and sand, the team’s material exhibits a self-supporting ‘skeletal’ effect.
On a more commercial level, BigRep and Forward AM launched a new Concrete Formwork filament in May 2021, which is designed to enable the creation of more complex precast concrete supports. When deployed alongside BigRep’s STUDIO G2 3D printer, the firms say their material can be used to build architecture at vastly reduced costs and lead times.
The researchers’ findings are detailed in their paper titled “Thermal energy regulation with 3D printed polymer-phase change material composites,” which was co-authored by Peiran Wei, Ciera E. Cipriani and Emily B. Pentzer.
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Featured image shows the Texas A&M team’s 3D printed test sample on top of a stack of wood. Photo via Texas A&M University.