http://mv-voice.com/print/story/print/2007/08/17/the-ac-paradox


Mountain View Voice

- August 17, 2007

The AC paradox

Air conditioners actually raise outside temperature, requiring even more power

by Forrest Linebarger

A recent study concluded that air conditioners were increasing the outside air temperature in Tokyo by two to four degrees Fahrenheit. The study was conducted by Dr Yukitaka Ohashi of Okayama University of Science and published in the Journal of Applied Meteorology and Climatology.

The temperature increase was not merely due to the transferring of hot air from inside buildings to the outside, but also to the large amount of heat created during the consumption of electricity. Air conditioners have long been known for their huge power demands, but the heat generated thereby, and its ramifications, are just beginning to be understood.

The additional heat caused the air conditioners to use more energy. In fact, an extra four degrees Fahrenheit of ambient outside temperature in Tokyo alone means an additional 1.6 gigawatts of power is expended to run the air conditioners.

It is a vicious cycle.

To put 1.6 gigawatts into perspective, the largest power plant in California, Duke Energy plant at Morrow Bay, produces 1.2 gigawatts of power. In other words, it takes almost one and a half extra power plants just to cover the energy required to cool Tokyo's buildings the four degrees caused by air conditioners in the first place. This energy, 1.6 gigawatts, is enough power to run 1.2 million households in the Bay Area.

Why do we care about Japan? Well, air conditioners in Japan are not much different from the ones we have here. The U.S. uses more electricity than any other country in the world. The average U.S. household uses 2.4 times the energy of a Japanese household.

In temperate climates like the Bay Area's, air conditioners were rarely installed until recent decades. They are fast becoming ubiquitous. According to the California Energy Commission, air conditioners use approximately one third of the state's total electrical demand on hot days, 16 gigawatts of electricity the amount of power produced by 15 large power plants.

Air conditioning is also changing where we live. The availability of air conditioning has added more housing in the hottest parts of the state, most notably in the scorching Central Valley.

Most of this extra energy is being produced by coal and natural gas power plants, both prodigious producers of greenhouse gases. If your head is beginning to spin, it may be because you're jumping ahead and completing the circle: Greenhouse gases add to global warming. Global warming increases air conditioner and therefore electricity use.

There is one wonderful way to stop this vicious cycle: stop using air conditioning.

Today we can design green homes that cost the same as traditional homes but provide amazingly comfortable natural cooling without the use of air conditioning. Even if you don't live in a fancy new green home, you can you can apply many natural cooling principles in your existing house.

The use of generally lighter-colored materials for roofing, exterior paint and paving surfaces will cool your environment. The greater solar reflectivity a material has (also known as its "albedo"), the better it diverts heat away from your home. Absorption of solar radiation by dark materials has been shown to raise temperatures in cities across America in a process called the heat island effect.

Vegetation also provides cooling though a process called evapotranspiration. This is a fancy name for the water that evaporates from plants through the pores in their leaves. The water draws heat as it evaporates, and cools the surrounding air in the process. A single mature, properly watered tree with a crown of 30 feet can evapotranspire up to 40 gallons of water a day. This is equivalent to removing all the heat produced in four hours by an electric space heater.

You can also use whole-house fans in your attic to circulate cool air into your home in the cool morning and evening hours. If you keep your house closed in the midday, usually the cool air introduced during the night can keep a home cool all day. If you don't have a whole-house fan, window fans or swamp coolers will also do the trick.

Most people find naturally cooled air to be more comfortable. In fact, studies have shown that people feel comfortable across a wider range of temperatures when exposed to natural, non-conditioned air.

Keep cool this summer, the natural way.

Forrest Linebarger is CEO and chief designer at VOX Design Group Inc. in Mountain View. He can be reached at forrest@voxdesigngroup.com or at (650) 694-6200, ext. 511.

Comments

Posted by Joe, a resident of Cuesta Park
on Aug 22, 2007 at 4:01 pm

Vicious cycle indeed.