Wearable Fabrics and Solid-State Chillers Challenge the Air Conditioner

Air conditioning has quietly become one of the planet’s most problematic technologies. Traditional cooling and refrigeration now account for an estimated 10 percent of global greenhouse gas emissions, a share that is rising and set to double by 2050. Worse, the story is circular: as cities grow hotter, people install more air conditioners, which expel waste heat and consume electricity generated largely from fossil fuels, further warming the urban environment. A comprehensive review published in Frontiers in Thermal Engineering argues that breaking this vicious cycle demands a fundamental redesign of how humans achieve thermal comfort, spanning everything from next-generation cooling fabrics to refrigerant-free space chillers.

The review, led by Elisa Y. M. Ang of the Singapore Institute of Technology together with Aminu Yusuf of Istanbul University-Cerrahpasa and colleagues, is unusual in that it unites two research streams that are typically treated in isolation: personal cooling devices that chill the skin directly, and large-scale alternatives to the vapor-compression systems that dominate buildings. Database searches reveal an exponential increase in publications on human cooling technology, reflecting a rapidly growing field driven by climate realities. Even with dramatic emissions cuts, climate scientists widely agree that dangerous levels of heat and humidity are likely to become more common, making sustainable cooling a survival issue rather than a luxury.

Conventional air conditioning is an especially wasteful way to keep people comfortable. Because cooling is delivered to entire rooms, up to 70 percent of the energy can be wasted on empty space rather than human bodies. Personal cooling devices, or PCDs, promise to sidestep this inefficiency by targeting the skin itself, and they can also provide relief where air conditioners cannot follow, from construction sites and sports fields to outdoor medical settings. Yet the technology remains immature. To ground their assessment, the authors conducted a medium-scale market and user survey in which 56 participants evaluated three commercial products: a fan-based vest, a flow thermoelectric vest, and an ice-packed vest.

The thermoelectric vest, which exploits the Peltier effect to produce solid-state, tunable cooling, received the highest overall satisfaction rating at 3.93 out of 5. By contrast, the ice-packed vest was repeatedly described as heavy and uncomfortable because of condensation buildup, while the fan vest offered limited cooling and raised safety concerns about exposed blades. Even the best-performing device suffered from roughly three hours of battery life, high production costs, and added weight, which is a serious drawback for outdoor or industrial workers who need continuous cooling across a full shift. The authors caution that their survey was limited in sample size and trial duration, so the findings should not be overgeneralized, but the conclusion aligns with prior evaluations: no commercial personal cooling device is yet adequate as a stand-alone replacement for space cooling.

On the passive side of the field, however, remarkable progress is emerging from materials science. Phase change materials such as paraffin waxes and hydrated salts absorb body heat as they melt, sustaining cooling for up to two hours in optimized vests, though low thermal conductivity, leakage, and long recharge times remain obstacles. Evaporative approaches, which exploit water’s high latent heat, struggle in humid climates and leave wearers wet. The most striking advances come from radiative cooling textiles. Human skin, with an emissivity above 0.95, radiates heat in the mid-infrared range of 7 to 14 micrometers, and engineered fabrics can amplify this pathway. One bioinspired metafabric with a dual-gradient Janus design achieves 99.4 percent solar reflectance and 0.94 mid-infrared emittance, delivering a 17.8 degrees Celsius skin temperature reduction under intense sunlight while wicking sweat at a rate of just 0.5 milliliters per hour.

Smart fabrics are also learning to adapt. A sandwich-structured nanofibrous textile reported in 2025 combines a cooling side with 97.9 percent solar reflectance and a heating side made of carbon nanotubes absorbing 88.4 percent of sunlight; flipping the fabric switches between modes. Other designs draw inspiration from the Namib Desert beetle, using circular and triangular patterns to transport sweat continuously and reducing skin temperature by 1.3 degrees Celsius compared with cotton. Thermochromic fabrics that reflect sunlight and reverse moisture transport under hot conditions point toward garments that respond dynamically to the environment rather than offering static regulation. Meanwhile, thermoelectric garments are being rebuilt for the body: multi-stage coolers, flexible heatsinks made from hydrogel and nickel foam, and paraffin-graphene composites have demonstrated sustained on-skin cooling of 7 to 11 degrees Celsius, though the underlying bismuth telluride materials are nearing their efficiency limits and new compounds such as n-type PbS are being explored.

Because personal devices cannot yet replace whole-building cooling, the review devotes equal attention to the supply side. Here the verdict is sobering: quantitative comparisons of fourteen space-cooling technologies found vapor-compression still superior in coefficient of performance, exergetic efficiency, and power density, and it retains the highest overall sustainability score when scalability and maturity are counted. The realistic near-term path is therefore greener refrigerants, including flammable hydrocarbons like R290 and R600, alongside emerging cycles that must close the efficiency gap. Solid-state options include magnetocaloric cooling, which exploits temperature changes in gadolinium-family alloys under varying magnetic fields; electrocaloric cooling, based on dielectric materials responding to electric fields; and elastocaloric cooling, in which shape-memory alloys like nickel-titanium release and absorb latent heat under mechanical stress. All are refrigerant-free but remain limited by material costs, fatigue, and modest temperature spans.

Among the more promising newcomers, membrane heat pumps stand out. Identified by the U.S. Department of Energy in 2014 as one of the top three technologies for high energy savings, they separate moisture from air across water-vapor-selective membranes, avoiding the heavy condensation penalty of conventional systems and using only water as the working medium. Thermodynamic models suggest a potential coefficient of performance between 10 and 40, though prototypes currently achieve less than 3 due to vacuum pump inefficiencies, and even a 10 percent drop in water vapor rejection pushes performance below 3. Radiant cooling, which chills occupants directly through temperature-controlled surfaces rather than conditioning air, has demonstrated energy savings up to 50 percent and is already installed in landmark buildings such as the Pearl River Tower in Guangzhou, though condensation in humid climates remains the central engineering challenge.

Complementary, city-scale strategies multiply these gains. District cooling systems, proven in the Gulf Cooperation Council region where air conditioning consumes up to 70 percent of Saudi household electricity, achieve coefficients of performance of 4 to 6 and cut energy use by 30 to 50 percent through load sharing, and fifth-generation networks with bidirectional heat exchange can save up to 40 percent of electricity. Snow storage in Sweden, Norway, and Japan offers free seasonal cooling, while cool roofs stay 28 to 33 degrees Celsius cooler than traditional surfaces and green infrastructure intercepts 70 to 90 percent of incoming solar radiation through canopy shade, with building energy savings of 20 to 80 percent. In Singapore’s Cool Canyon experiments, cool surfaces cut sensible heat release by 30 percent and lowered afternoon air temperature by up to 2 degrees.

The review’s integrated perspective carries clear implications. For engineers, hybrid strategies combining localized and space-based cooling can deliver meaningful savings without sacrificing comfort. For manufacturers, the priorities are durability, flexibility, and heat rejection in wearables, whose performance is still measured by standards designed for uniform indoor environments and which often overestimate real-world cooling. For policymakers, the authors argue, localized cooling needs its own tailored standards, alternative technologies belong in energy codes, and district-scale low-carbon infrastructure deserves targeted incentives. Achieving this will require broader field trials, standardized evaluation metrics, and life-cycle assessments to bridge the gap between laboratory demonstrations and deployable, climate-resilient cooling.

Subject of Research: Alternative personal and space cooling technologies for sustainable thermal comfort

Article Title: Human cooling solutions: alternatives to conventional cooling solutions

Article References: Ang, E. Y. M., Yusuf, A., Soh, C. B., & Wang, P. C. (2026). Human cooling solutions: alternatives to conventional cooling solutions. Frontiers in Thermal Engineering, 6, Article 1602847. https://doi.org/10.3389/fther.2026.1602847

Image Credits: AI Generated

DOI: 10.3389/fther.2026.1602847

Keywords: human cooling, personal cooling devices, radiative cooling, thermoelectric cooling, vapor compression, solid-state cooling, membrane heat pumps, district cooling, urban heat island, phase change materials, cooling fabrics, thermal comfort