When you think of hot, sweltering, summer days, what comes to your mind? Sipping ice-cold lemonade or eating delicious ice cream from the refrigerator, while lounging indoors in an air-conditioned room, right?
However, did you know that cooling appliances like fridges and air conditioners use a significant amount of energy worldwide?
In 2020, it was estimated that about 392 billion kilowatt-hours of electricity were used by American residential and commercial sectors. Worldwide, 20% of total electricity is currently used to cool spaces. Without action to address energy efficiency, energy demand for space cooling will more than triple by 2050. Yet, at the same time, lack of access to cooling spaces is also responsible for nearly 40% of all global heat-related deaths.
As climate change makes heatwaves longer, hotter, and more dangerous, innovators in the US and Saudi Arabia are developing new cooling methods that can help us stay safe and reduce carbon emissions.
What are these innovations and how can they help save energy? Let’s take a look.
Mirror, mirror - which is the whitest paint of them all?
Researchers at Purdue University have developed a white paint that reflects 98.1 % of all sunlight that falls on it!
Not only did this paint win the Guinness World Records for the “world’s whitest paint,” a building coated with this paint will not require central air conditioning. Currently, available paints don’t cool surfaces and reflect about 80-90% of sunlight.
After seven years of research, Mechanical engineering professor Xiulin Ruan and his team developed a paint that reflects 98.1% of all sunlight that falls on it. They chose a paint with a very high concentration of barium sulfate and experimented with different-sized particles that scatter different wavelengths of sunlight.
Because the paint retains less heat than it reflects, it can cool down surfaces below surrounding temperatures. The results are fantastic - just covering a roof area of 1000 square feet will generate a cooling power of 10 kilowatts, which makes it more powerful than central air conditioners.
Cooling Without Electricity!
In the meanwhile, researchers at Saudi Arabia's King Abdullah University of Science and Technology (KAUST) are developing a cooling system that could function without electricity.
Since large parts of the Middle East lack water and electricity but have abundant sunshine, the KAUST cooling system uses the energy from sunlight to cool down! The system is based on phase change, a natural phenomenon that occurs when salt is added to water. As salt crystals dissolve in warm water, they absorb energy, cooling the water.
After experimenting with different salts for their cooling system, the researchers decided on ammonium nitrate, which is cheap, widely available, and highly soluble. Within 20 minutes of adding ammonium nitrate, the system cools to about 3.6ºC and sustains a temperature below 15ºC for over 15 hours! This technology can be used for both cooling spaces and food, after which the ammonium nitrate can be reused again for another cooling cycle.
Commercializing these technologies will be a major step towards reducing greenhouse emissions and combating climate change. Hopefully, very soon, we can eat ice cream in a cool room without leaving a carbon footprint!
Sources: Interesting Engineering, National Geographic, Guardian, iea.org