Keeping buildings cool is becoming one of our fastest growing and energy-intensive challenges. A startup based in Hong Kong pioneers for an answer already existing in nature– the outer layer of a tiny ant that survives one of the hottest places on Earth. Dr. Martin Zhu and his co-founder mimicked the heat-repelling biology of the Saharan silver ant to develop cooling technology that remains electricity-free.

Cooling maintains around 10% of global electricity demand. In the hottest regions, cooling can account for over 70% of peak electricity demand. 

The biological inspiration behind i2Cool’s technology, the Saharan silver ant, has evolved to be a solution in the transition to zero-energy cooling. The ant endures desert heat through its surface hairs with a distinctive structure that reflects solar energy and emits body heat as radiation in a specific wavelength range. This wavelength passes through the atmosphere into outer space, effectively cooling the ant without any energy input. 

The team replicates this using engineered nanoparticles embedded in various materials, like paint coatings, window films, ceramics, and textiles. The i2Cool’s research team integrated this heat transfer principle to produce a multi-component and multi-scale solution, efficient in solar reflectivity and mid-infared emissivity of up to 95%.

The most significant advantage of passive radiative cooling is that it requires no energy input, unlike traditional air conditioning. This technology can reduce surface temperature up to 42 ℃ and save air conditioning energy consumption by up to 40%.

In addition, since this solution is passive, requiring no electricity to run, the technology can be used off-grid or in energy-poor areas. This means the technology has the potential to democratize access to cooling in the regions of the world that need it most, but currently have the least access.

A constraint of passive radiative cooling is that the material may need to be redesigned for different climates, as Dr. Zhu acknowledges. Temperature swings and humidity in different regions require different nanoparticle structures, which is costly to implement and adjust for. This may be fine in areas near the equator where cooling demand is relatively consistent, but in seasonal climates like Russia, Canada, or the U.S., radiative cooling solutions run the risk of overcooling. 

Another drawback could be the varying and longer payback times from saved energy costs that has the potential to deter building owners from using the technology. For example, vehicle payback is under six months, while building applications take two to three years. This has the potential to deter building owners from using the technology. 

Dr. Martin Zhu sees zero-energy cooling as a powerful tool to reduce the global need for air conditioning, rather than an outright replacement. For him, this technology democratizes access to cooling while innovatively requiring no ongoing energy. This is a part of a broader vision for climate equity, sustainably leveraging technology as a means of supporting marginalized communities.

Dr. Martin Zhu is the Co-Founder and CEO of i2Cool, a company specializing in electricity-free cooling technology. He focuses on commercializing passive radiative cooling technology, reaching more than 30 countries.

For a transcript, please visit climatebreak.org/zero-energy-cooling-with-martin-zhu/