Mirror-Like Tiles Made with Nanotechnology Could Solve the Cooling Crisis
The climate is changing, and for many regions in the world, this means extreme warming. As temperatures rise, so too will the demand for air conditioning. However, continued use of current refrigerants will only exacerbate climate change and exert more pressure on energy grids.
Yet, a new technology kindled at Stanford University in 2012 promises to replace air conditioning by using nanotechnology and radiative cooling. SkyCool Systems is working to create a low-energy solution to cooling the built environment, one that could potentially replace modern air conditioners altogether, Popular Science reported.
What is Radiative Cooling?
Radiative cooling is the phenomenon by which everything on Earth releases heat as infrared. These infrared waves are sent into space, providing a cooling effect. Radiative cooling is powerful at night when the sun is absent and cannot resupply the lost heat. It’s the reason why your car’s windshield can freeze over, even if the temperature never drops below zero. Some engineers are hoping to channel this phenomenon for air conditioning, sending excess heat back into space.
Humans have used radiative cooling before; there is evidence showing desert-dwellers using radiative cooling to make ice at night. However, the question that plagued scientists for years was whether radiative cooling could happen in direct sunlight. This prompted Aaswath Raman, co-founder of SkyCool Systems, to search for an answer.
The Cooling Crisis
The vicious cycle of warming temperatures and increased air conditioning is one of the main drivers of the “cooling crisis.” In the coming decades, we may face a situation where we can't meet the demand for air cooling.
Air conditioning and refrigeration accounted for 11% of greenhouse gas emissions in 2018, according to the Birmingham Energy Institute. The American Department of Energy reported that air conditioning emitted almost 700 million metric tons of greenhouse gas emissions each year. The International Energy Agency estimates that running air conditioners will be one of the top drivers for electricity in the coming decades. This increased energy demand will only exacerbate climate change.
Additionally, air conditioners use hydrofluorocarbons (HFCs) as refrigerants, which are another greenhouse gas. Hydrofluorocarbons were introduced after the Montreal Protocol banned chlorofluorocarbons (CFCs). CFCs were damaging the ozone layer, so HFCs were proposed as a solution. HFCs, however, are potent greenhouse gases, several thousand times more potent than carbon dioxide.
Only 15% of the world’s population currently uses air conditioning, but that number is rising rapidly. In addition, as temperatures increase due to climate change, air conditioning use increases along with it. Higher air conditioning use leads to more energy use, which fuels carbon emissions and stress on electric grids. Raman hopes that SkyCool Systems can provide an alternative to air conditioning units, especially for smaller homes in warming regions.
SkyCool Systems vs. The Greenhouse Effect
SkyCool Systems, a California-based start-up, is looking to solve the cooling crisis. SkyCool harnesses radiative cooling to keep buildings cool with less demand on air conditioners. SkyCool installs mirror-like tiles on rooftops that send heat back to space to keep buildings cool.
SkyCool's product relies on a material produced using nanotechnology. Raman and his team created a thin film with unique optical properties that help emit infrared heat. The film keeps the infrared waves within the range that allows them to exit the atmosphere instead of getting stuck in the greenhouse effect. This creates a cooling effect as it reflects 97% of the sun’s rays.
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Raman’s team also ran a trial to cool water pipes under their SkyCool system. After noticing a cooling of 9 degrees Fahrenheit, Raman proposed that they could connect the water pipes to the condenser of an AC unit, which would reduce the energy demand of the unit.
SkyCool has implemented a small number of its systems, like one at a grocery store in Stockton, CA. The store experienced 15% lower energy use after installing the system, a promising result for radiative cooling.
Radiative Cooling Has Limitations
Radiative cooling does not work equally well in all climates. The best climates are dry ones that don’t have much cloud cover, like California. Water molecules trap infrared; therefore, radiative cooling is less effective in humid climates. It’s yet to be determined how much cooling SkyCool’s systems can achieve in humid climates.
The current barrier to radiative cooling replacing traditional air conditioning is cost and availability. Like most new technologies, radiative cooling has potential but would need to become cheaper to manufacture and install. SkyCool’s current installations function more as real-world experiments. The adoption rate will be based on cost, availability and how willing people are to try something new. Air conditioning has been the same since the twentieth century, and radiative cooling may seem a little too-good-to-be-true for some consumers.
SkyCool’s technology could be installed for less than 6.25 USD per square meter, which is low enough to cover energy savings over five years. SkyCool’s current focus is manufacturing, having already changed its material to be better suited to mass production.
There are a handful of other start-ups that are researching and creating films for radiative cooling systems. Some engineers also advocate for using special reflective paint that would be cheaper. Raman stated that the paint would only supplement air conditioning, instead of SkyCool, which could replace air conditioning.
A Piece of the Cooling Puzzle
Radiative cooling is an exciting frontier for engineering, one which is desperately needed as the planet warms. If SkyCool and its competitors can provide a practical air conditioning supplement, they could offset a looming energy crisis. Even reducing the stress on air conditioning units could help alleviate the cooling problem — even better if the systems can fully replace air conditioning.
SkyCool has a product that can alleviate the cooling burden but cannot completely meet the world’s increasing cooling demands. SkyCool claims to save two to three times the energy solar panels generate, but the systems don’t have universal applications, such as in humid climates. However, if used in conjunction with air conditioners and even as replacements in some cases, radiative cooling could reduce the stress on our already burdened energy grid.
Watch Aaswath Raman talk about radiative cooling technology:
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