Wasted Heat from Air Conditioners Raises Temperatures at Night in Urban Areas

Researchers at the Arizona State University have found that warm air from air conditioners during night raises night time temperatures. The wasted heat makes urban areas warmer and increases cooling demands.

"We found that wasted heat from air conditioning systems was maximum during the day, but the mean effect was negligible near the surface. However, during the night, heat emitted from air conditioning systems increased the mean air temperature by more than 1 degree Celsius (almost 2 degrees Fahrenheit) for some urban locations," said Francisco Salamanca, a post-doctoral research scientist at Arizona State University's School of Mathematical and Statistical Sciences.

The study is published in the Journal of Geophysical Research Atmospheres.

For the study, researchers looked at the energy consumption at Phoenix metropolitan area. The city is located in Sonoran desert.

Air conditioning systems use a large amount of energy and put strain on electrical grids. Researchers developed computed models to study the effects of wasted heat on temperature in the urban areas. They accounted for building shapes, cooling needs, wind speed and other factors that could have affected the results.

Researchers found that air conditioning during the night increases temperatures and led to an additional need of cooling. This effect was seen only during night time. During the day, the amount of heat generated by ACs was negligible when compared to the Sun's energy.

Our work demonstrates 1 degree Celsius (almost 2 F) local heating of urban atmospheres in hot and dry cities due to air conditioning use at night. This increase in outside air temperature in turn results in additional demands for air conditioning," Salamanca said in a news release.

According to researchers, reusing the wasted heat could help reduce energy demands and keep urban areas cool.

Research has shown that climate change will lead to frequent hotter nights in the future.