20 June 2010

Stella, We Can Save 90% On Air Conditioning Bills!

When it comes to home comforts, few inventions can beat the air conditioner for its ability to help us tolerate the dog days of summer. The problem is, when it comes to energy-guzzlers, few inventions can beat the air conditioner.

But the National Renewable Energy Laboratory has invented a new air conditioning system that uses 50 to 90 percent less energy than the best available units. The Desiccant-Enhanced eVaporative air conditioner -- DEVap -- combines membranes, evaporative cooling and liquid desiccants in a way that has never been done before.

NREL mechanical engineer Eric Kozubal, who co-invented the system, says the goal is to revolutionize cooling while removing millions of metric tons of carbon from the air. It cools and dries the air in one step. Evaporative cooling, blowing air across a wet surface to promote evaporation, has long been used in swamp coolers, as Technology Review notes. The DEVap takes it a step further, dividing air into two streams that are separated by a polymer membrane.

Water passes through one airstream, making it cooler and wetter. The cooler air cools the membrane, which cools the air on the other side, without making that side any more humid.
Another process dries the air, making the system effective even in humid locales -- a big step toward reducing refrigeration-based air conditioning, which is used in most of the country and is responsible for about 5 percent of the nation's energy consumption. _Popsci
If you live in the hot, humid "big easy" otherwise known as N'wollens, staying cool through the muggy warmth of sprummerautumn can be expensive. But scientists at the US National Renewable Energy Lab have updated an old idea and brought it into the modern age -- by combining dehumidification with a "swamp-cooler" style evaporative cooler. By updating the technology, NREL researchers promise to cut 90% off the cost of cooling for New Orleans and other similar sweltering tropical and quasi-tropical warm spots.
What's new, Kozubal says, is a design that manages to merge evaporative cooling and desiccant drying into a cost-effective system. "It makes this type of air conditioning viable for commercial and residential processes for cooling," he says.

The industry is working on a variety of methods to improve the efficiency of air conditioning, Jacobi says, from the use of heat exchangers to improvements in the compression systems of traditional machines. "It's an area of great importance to the nation, because about a third of our nation's energy use is in buildings."

The U.S. uses about 100 quadrillion British Thermal Units each year, according to the U.S. Energy Information Administration. Up to 40 percent of that is used in buildings, with about 5 percent going to air conditioning. Kozubal says his system could cut that in half in less-humid areas and by up to 90 percent where humidity is high. "When you talk about a technology that can save 2 to 3 percent of the nation's entire energy supply, that's quite a lot," he says.

The desiccant used in the system is relatively harmless (calcium chloride is used in road salt), though its corrosiveness requires that metal be eliminated from the hardware. What's particularly attractive is that it replaces the chlorofluorocarbons that are used as the refrigerant in traditional air conditioners. Those CFCs can easily leak, and every kilogram of them provides the same greenhouse gas effect as about 2,000 kilograms of carbon dioxide.

Kozubal says it might take about five years to develop the system to a point where NREL can hand it off to industry for commercialization. The system is designed to replace existing systems without many changes, so it could be phased in as people upgrade their old air conditioners.

The desiccant can be reused simply by heating it up to boil off the water it's absorbed. In an industrial setting, that might be done using waste heat from another industrial process. In the home, natural gas or solar energy would work. In fact, Kozubal says, the setup could make solar thermal energy systems, which absorb sunlight to heat a home and its water, more cost effective. During hot summer days, solar energy that might otherwise go to waste could therefore actually help keep a building cool. _TechnologyReview

It is not the combination of evaporative cooling and dehumidification that is new. It is the way in which the two processes are combined into one integrated system.

Air conditioning has always been a huge obstacle to comfortable living off-the-grid for those living in the Eastern part of the United States. Too much power is required to cool a home in a hot humid environment, to expect a small solar or wind off-grid system to be able to keep up. But cut that power requirement by 90% and suddenly a lot of people who thought they'd never be able to comfortably declare independence from the power utility are suddenly emancipated.

Just let him in, Stella. He can explain. Everything.

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3 Comments:

Blogger SwampWoman said...

Woohoooo! Sign me UP for the first unit!

Sunday, 20 June, 2010  
Blogger George said...

Traditional evaporative coolers become ineffective as the humidity and dew point increase.

When it's 105 here and the humidity is 2% the cooler pumps 62 degree air into the house.

When the summer monsoon hits it's time for the AC.

Monday, 21 June, 2010  
Blogger al fin said...

Yes. When I lived in the desert a swamp cooler worked fine.

Air conditioners cool, dehumidify, filter, and circulate the air.

That may be why it has taken so long for engineers to come up with a more economical substitute.

Monday, 21 June, 2010  

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