Solar water cooler could significantly lower energy costs

Current cooling systems consume nearly 15 percent of all electricity and account for more than 10 percent of total global greenhouse gas emissions.
By Joseph Scalise | Sep 07, 2017
A new solar water cooler developed by researchers at Stanford University may help save on energy costs and lower the money it takes to run industrial-scale air conditioning and refrigeration, according to a new report published in Nature Energy.

Like solar water heaters, the new machine sits on top of a roof and is made up of three components. The first is a plastic layer topped with a silver coating that reflects almost all incoming light. The second piece is a snaking copper tube that funnels water through the device and heats the plastic, while the last is a thermally insulating plastic housing that goes around the entire device.

All three pieces work together to cool water. To do this, the plastic in the device radiates the heat in the device out at a wavelength in the middle region of the infrared (IR) spectrum, which is not absorbed by the atmosphere. Once that happens, the outer casing ensures that almost all of the heat radiated away is from the water inside the device and not the air around it.

To test the unique machines, the team placed three cooling panels on top of a building at Stanford and ran water through them at a rate of roughly 0.2 liters every minute. After three days of testing, the process cooled water nearly 5 degrees Celsius below the ambient temperature. Then, researchers followed up on those findings by modeling how the panels would behave if put into a typical air conditioning unit for a two-story building in Las Vegas, Nevada. That showed the setup would lower air conditioning electrical demand by 21 percent over the summer.

"It's an excellent paper," says Ronggui Yang, a mechanical engineer at the University of Colorado in Boulder who was not involved in the study, according to Science."It shows a promising direction for real world use."

Current cooling systems consume nearly 15 percent of all electricity and account for more than 10 percent of total global greenhouse gas emissions. As a result, this new technology could be a big step towards saving future energy costs and cutting back on global energy use.

"This research builds on our previous work with radiative sky cooling but takes it to the next level," said study co-author Aaswath Raman, a researcher at Stanford University, in a statement. "It provides for the first time a high-fidelity technology demonstration of how you can use radiative sky cooling to passively cool a fluid and, in doing so, connect it with cooling systems to save electricity,"

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