10 Jul 2012

Cooling a Warming Planet: A Global Air Conditioning Surge

The U.S. has long used more energy for air conditioning than all other nations combined. But as demand increases in the world’s warmer regions, global energy consumption for air conditioning is expected to continue to rise dramatically and could have a major impact on climate change.
By stan cox

The world is warming, incomes are rising, and smaller families are living in larger houses in hotter places. One result is a booming market for air conditioning — world sales in 2011 were up 13 percent over 2010, and that growth is expected to accelerate in coming decades.

By my very rough estimate, residential, commercial, and industrial air conditioning worldwide consumes at least one trillion kilowatt-hours of electricity annually. Vehicle air conditioners in the United States alone use 7 to 10 billion gallons of gasoline annually. And thanks largely to demand in warmer regions, it is possible that world consumption of energy for cooling could explode tenfold by 2050, giving climate change an unwelcome dose of extra momentum.

The United States has long consumed more energy each year for air conditioning than the rest of the world combined. In fact, we use more electricity for cooling than the entire continent of Africa, home to a billion people, consumes for all purposes. Between 1993 and 2005, with summers growing hotter and homes larger, energy consumed by residential air
China is expected to surpass the U.S. as the world’s biggest user of electricity for air conditioning by 2020.
conditioning in the U.S. doubled, and it leaped another 20 percent by 2010. The climate impact of air conditioning our buildings and vehicles is now that of almost half a billion metric tons of carbon dioxide per year.

Yet with other nations following our lead, America’s century-long reign as the world cooling champion is coming to an end. And if global consumption for cooling grows as projected to 10 trillion kilowatt-hours per year — equal to half of the world’s entire electricity supply today — the climate forecast will be grim indeed.

Because it is so deeply dependent on high-energy cooling, the United States is not very well positioned to call on other countries to exercise restraint for the sake of our common atmosphere. But we can warn the world of what it stands to lose if it follows our path, and that would mean making clear what we ourselves have lost during the age of air conditioning. For example, with less exposure to heat, our bodies can fail to acclimatize physiologically to summer conditions, while we develop a mental dependence on cooling. Community cohesion also has been ruptured, as neighborhoods that on warm summer evenings were once filled with people mingling are now silent — save for the whirring of air-conditioning units. A half-century of construction on the model of refrigerated cooling has left us with homes and offices in which natural ventilation often is either impossible or ineffective. The result is that the same cooling technology that can save lives during brief, intense heat waves is helping undermine our health at most other times.

The time window for debating the benefits and costs of air conditioning on a global scale is narrowing — once a country goes down the air-conditioned path, it is very hard to change course.

Air Conditioners in China Office Building
ChinaFotoPress/Getty Images
Air conditioners on an office building in China’s Fujiang Province
China is already sprinting forward and is expected to surpass the United States as the world’s biggest user of electricity for air conditioning by 2020. Consider this: The number of U.S. homes equipped with air conditioning rose from 64 to 100 million between 1993 and 2009, whereas 50 million air-conditioning units were sold in China in 2010 alone. And it is projected that the number of air-conditioned vehicles in China will reach 100 million in 2015, having more than doubled in just five years.

As urban China, Japan, and South Korea approach the air-conditioning saturation point, the greatest demand growth in the post-2020 world is expected to occur elsewhere, most prominently in South and Southeast Asia. India will predominate — already, about 40 percent of all electricity consumption in the city of Mumbai goes for air conditioning. The Middle East is already heavily climate-controlled, but growth is expected to continue there as well. Within 15 years, Saudi Arabia could actually be consuming more oil than it exports, due largely to air conditioning. And with summers warming, the United States and Mexico will continue increasing their heavy consumption of cool.

Countries are already struggling to keep up with peak power demand in hot weather. This summer, India is seeing a shortfall of 17 gigawatts, with residential electricity shut off for 16 hours per day in some areas. China is falling short by 30 to 40 gigawatts, resulting in energy rationing and factory closings.

In most countries, the bulk of electricity that runs air conditioners in homes and businesses is generated from fossil fuels, most prominently coal. In contrast, a large share of space heating in cooler climates is done by directly burning fuels — usually natural gas, other gases, or oil, all of which have somewhat smaller carbon emissions than coal. That, together with the energy losses involved in generation and transmission of electric power, means that on average, an air conditioner causes more greenhouse emissions when pushing heat out of a house than does a furnace when putting the same quantity of heat into a house.

Based on projected increases in population, income, and temperatures around the world, Morna Isaac and Detlef van Vuuren of the Netherlands Environmental Assessment Agency predict that in a warming world, the increase in emissions from air conditioning will be faster than the decline in emissions from heating; as a result, the combined greenhouse impact of heating and cooling will begin rising soon after 2020 and then shoot up fast through the end of the century.

Refrigerants — fluids that absorb and release heat efficiently at the right temperatures — are the key to air conditioning and refrigeration, but they can also be serious troublemakers when released into the atmosphere. Refrigerants such as chlorofluorocarbons (CFCs) that harm the stratospheric ozone layer are being phased out under the 1989 Montreal Protocol; however, most ozone-friendlier substitutes are, like CFCs,
The U.S. experience provides little hope that renewable energy can satisfy a growing share of air conditioning demand.
powerful greenhouse gases.

Most prominent worldwide in the new generation of refrigerants are compounds known as hydrofluorocarbons (HFCs). They have a smaller climate-warming potential than do the ozone-depleting compounds they are replacing, but they still have hundreds to thousands of times the greenhouse potency of carbon dioxide (on a pound-for-pound basis, that is; carbon dioxide is released in vastly larger quantities and has a larger total impact.) Rapid growth in air conditioning threatens to swamp out the marginal climate benefits of replacing current refrigerants with HFCs.

According to a recent forecast by Guus Velders of the Netherlands’ National Institute for Public Health and the Environment and his colleagues, refrigerants that accumulate in the atmosphere between now and 2050 (increasingly HFCs, mostly from refrigeration and air conditioning) will add another 14 to 27 percent to the increased warming caused by all human-generated carbon dioxide emissions. Recent years, therefore, have seen a research stampede to find refrigerants with lighter greenhouse potential. Several promising candidates have been discarded on the basis of flammability, toxicity, ozone depletion, or other problems. None of the remaining prospects is ideal in all respects.

One important consideration is efficiency. A refrigerant that has smaller direct greenhouse potential than those currently in use but that exchanges heat less efficiently — causing an air conditioner to consume more energy for the same amount of cooling — could have a larger total climate impact.

Isaac and Van Vuuren predict that even if demand for air conditioning is satisfied with successively more efficient generations of equipment, global electricity consumption for home cooling will still rise eightfold by 2050, which is not much better than the tenfold increase that would occur without efficiency improvements. A similar dominance of growth over efficiency has prevailed in the United States. From 1993 to 2005, energy efficiency of air-conditioning equipment improved by almost 30 percent, but household energy consumption for air conditioning doubled.

There is hope that renewable energy could satisfy a growing share of air-conditioning demand, but there is little inspiration to be drawn from the U.S. experience. Here, renewable electricity production from wind, solar, biomass, and geothermal sources could expand to five times its current
Is it fair to expect people in Mumbai to go without air conditioning when so many in Miami use it freely?
production (an increase that the Environmental Protection Agency does not expect to be achieved until 2030) and still not cover the nation’s air-conditioning demand, let alone other needs. Today, worldwide renewable production is estimated at about 750 billion kilowatt hours, which, I estimate, covers about three-fourths of current global air-conditioning demand. The International Energy Agency predicts that renewable generation will expand to six times its current output by 2050. But even if that is achieved, renewable sources will still be satisfying only three-fourths of air-conditioning demand.

Each supply-side option has its own problems. Attempts to catch up with cooling demand by expanding hydroelectric power generation have caused serious ecological disruption and displacement of many millions of rural people in India, China, Brazil, and other countries. And we see hints that proliferation of air conditioning will provide an incentive to revive and expand nuclear power. Last month, in the face of strong opposition from the public, Japanese Prime Minister Yoshihiko Noda announced that his government was ending the moratorium on nuclear energy generation that had been in place since the tsunami disaster at the Fukushima Daiichi nuclear power plant in 2011. Noda acknowledged that the timing of the restart of two reactors in western Japan was no accident; the additional power will be needed to satisfy the summer surge in air conditioner use.

In thinking about global demand for cooling, two key questions emerge. Is it fair to expect people in Mumbai to go without air conditioning when so many in Miami use it freely? And if not, can the world find ways to adapt to warmer temperatures that are fair to all and do not depend on the unsupportable growth of air conditioning?

Currently, efforts to develop low-energy methods for warm climates are in progress on every continent. Passive cooling projects in China, India, Egypt, Iran, Namibia, and other countries combine traditional technologies — like wind towers and water evaporation — with newly designed, ventilation-friendly architectural features. Solar adsorption air conditioning performs a magician’s trick, using only the heat of the sun to cool the indoor air, but so far it is not very affordable or adaptable to home use. Meanwhile in India and elsewhere, cooling is being achieved solely with air pumped from underground tunnels.


The New Story of Stuff:
Can We Consume Less?

The New Story of Stuff: Can We Consume Less?
A new study finds that Britons are consuming less than they did a decade ago, Fred Pearce writes, with similar patterns being seen across Europe. Could this be the beginning of a trend in developed countries? Might we be reaching “peak stuff”?
But non-refrigerated climate control, especially in hot climates, cannot consistently achieve comfort that satisfies the industrial definition; in other words, it doesn’t produce the kind of cool, still, dry air that prompts many Americans to wear sweaters at work in July. A shift toward natural cooling will mean relying on humans’ well-proven capacity to adapt to variable conditions. Studies in the tropics have found, for example, that office workers are well satisfied with natural ventilation and warmer temperatures, if they have not already been conditioned by air conditioning.

Whatever course the world follows in adapting to a hotter planet — universal high-efficiency air conditioning; tighter construction; all-out pursuit of renewable, hydroelectric, or nuclear energy; or rebuilding and retrofitting entire societies for non-refrigerated cooling — the cost in both money and physical resources will be staggering. Deciding on the best strategy, and soon, will be crucial.


Stan Cox is the author of Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World (and Finding New Ways To Get Through the Summer). He is a senior scientist at the nonprofit Land Institute in Salina, Kansas.

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I live in tropical North Queensland, Australia, yet almost never use air conditioning: ceiling fans and open windows that allow cross-breezes to cool the house is cheaper and more environmentally responsible.

Posted by Jewel Rainbow on 10 Jul 2012

Proper housing design for passive cooling is obviously essential. Giant houses probably have to go — price electricity accordingly.

Posted by SqueakyRat on 12 Jul 2012

My apartment in "sustainable" NYC does not afford cross-ventilation (all the windows are on one side of the apartment) and breezes rarely travel through my open windows.

Posted by Georgia on 12 Jul 2012

In dry climates like California, efficient evaporative cooling systems work very well, even when the temperature rises above 100F. Add shade from mature trees and appropriate architectural features such as were common on older bungalow homes, and we very rarely need energy-intensive air conditioning to keep our home below 80F. It seems such a waste of money and energy when I hear the constant drone of our neighbors' air conditioning.

Posted by Michael Kunz on 12 Jul 2012

Do most of the developing countries need air-conditioning at all? Traditional houses with cross ventilation and Mud offer promise. Only thing is we have to modernise the traditional systems. There is Rocky Mountain Institute's Zero Energy House, Mud houses in Rajasthan (India).

The Eastgate Centre in Harare, Zimbabwe, typifies the best of green architecture and ecologically sensitive adaptation. The country’s largest office and shopping complex is an architectural marvel in its use of biomimicry principles. The mid-rise building, designed by architect Mick Pearce in conjunction with engineers at Arup Associates, has no conventional air-conditioning or heating, yet stays regulated year round with dramatically less energy consumption using design methods inspired by indigenous Zimbabwean masonry and the self-cooling mounds of African termites!
Termites in Zimbabwe build gigantic mounds inside of which they farm a fungus that is their primary food source. The fungus must be kept at exactly 87 degrees F, while the temperatures outside range from 35 degrees F at night to 104 degrees F during the day. The termites achieve this remarkable feat by constantly opening and closing a series of heating and cooling vents throughout the mound over the course of the day. With a system of carefully adjusted convection currents, air is sucked in at the lower part of the mound, down into enclosures with muddy walls, and up through a channel to the peak of the termite mound. The industrious termites constantly dig new vents and plug up old ones in order to regulate the temperature.

The Eastgate Centre, largely made of concrete, has a ventilation system which operates in a similar way. Outside air that is drawn in is either warmed or cooled by the building mass depending on which is hotter, the building concrete or the air. It is then vented into the building’s floors and offices before exiting via chimneys at the top. The complex also consists of two buildings side by side that are separated by an open space that is covered by glass and open to the local breezes.
Air is continuously drawn from this open space by fans on the first floor. It is then pushed up vertical supply sections of ducts that are located in the central spine of each of the two buildings. The fresh air replaces stale air that rises and exits through exhaust ports in the ceilings of each floor. Ultimately it enters the exhaust section of the vertical ducts before it is flushed out of the building through chimneys.

The Eastgate Centre uses less than 10 percent of the energy of a conventional building its size. These efficiencies translate directly to the bottom line: Eastgate’s owners have saved $3.5 million alone because of an air-conditioning system that did not have to be implemented. Outside of being eco-efficient and better for the environment, these savings also trickle down to the tenants whose rents are 20 percent lower than those of occupants in the surrounding buildings.


Dr.A.Jagadeesh Nellore(AP),India
E-mail: anumakonda.jagadeesh@gmail

Posted by Dr.A.Jagadeesh on 13 Jul 2012

'In fact, we use more electricity for cooling than the entire continent of Africa, home to a billion people, consumes for all purposes'.

And much of this over-consumption is totally unnecessary. On visits to the U.S. I have, while indoors, shivered in summer and sweated in winter.

Posted by Chris Chatteris SJ on 13 Jul 2012

Here are some traditional methods used to cool the buildings as well as heat it. The west spends more energy on heating while the east spends more energy on cooling.
Something as simple as using a white elastomeric roof coating can keep your home 7 degrees cooler. Thousands of years ago, ancient civilizations like the Egyptians and Greeks used this technique to keep their homes cooler. If you are considering this, review the cost of an elastomeric coating, estimated to be about 50 cents a square foot, balanced against the cost of air conditioning.
A whole attic house fan also reduces the need for air conditioning. estimates that the cost to use a whole house fan at one to five cents an hour, compared to 25 cents an hour for air conditioning. Consider where you would locate an attic fan and if the air flow would help cool the entire house. Also, an attic fan does best when the outside air temperature is cooler than that in the house so it is more effective in the early morning and evening.

Passive solar homes are designed to catch and hold heat in the winter and stay cool in the summer. For example, they have large, south-facing windows and interior surfaces that retain heat like tile or concrete. Trees are planted to strategically shade the house in summer and block the winter wind. Deep overhangs and eaves also shelter the house. If you are considering passive solar strategies, review your existing home layout and capitalize on those features which would allow you to take advantage of the sun. Or, if you are building a new home, seek out solar heating home plans that incorporate features like these.

The buildings in the Iranian desert regions are constructed according to the specific climatic conditions and differ with those built in other climates. The desert buildings are equipped with air traps, arched roofed, water reservoirs with arched domes and ice stores for the preservation of ice. The operation of modern coolers is similar to the old Iranian air traps which were built at the entrance of the house over underground water reservoirs or ponds built inside the house.

Lofty walls, narrow and dry streets, highly elevated air traps, big water reservoirs and arched roofed chambers, are the outstanding features of desert towns in Iran

I have a fan and ceiling fans. We've been putting the fan in front of an open door in the hopes it will pull out the hot air during the day and pull in the cool air at night, obviously turning the fan the appropriate direction.

Close curtains and blinds during the day and don't open windows or doors open thinking it'll let in cool air. If you can paint the outside of your house white as this will reflect the suns light and heat.

One more thing for tropics to get cool. Put a Polyethylene sheet on the roof and spread thin layer of sand and soil. Plant horizontal root spreading plants like Coriander. They won’t spread deep root and the greenery reduces temperature inside the house considerably. During rainy season the whole thing can be rolled and removed. Also convex shaped clay covers coated with white wash reduce temperature considerably because of white color reflection of sunlight, thickness of the clay cover and air trapped between the clay cover and roof which acts as insulator.

Dr.A.Jagadeesh Nellore (AP), India

Posted by Dr.A.Jagadeesh on 14 Jul 2012

Private transport use with AC for commutes prevents acclimation that happens naturally during spring on a walk, cycle or jog to walk.

There is an argument to lift target indoor temperatures gradually toward summer and have a couple of morning hours with reduced A/C output at higher target as people start the day with lower core body temperatures.

During fall / early winter target temperatures can be lowered economically and "optimum off"
strategies can used to control ventilation and reduce air changes. Lowering ventilation at start
and end of day rates can also reduce winter heat loads.

Related comment and views is available at http://blog.

Posted by james Ferguson on 15 Jul 2012

"In most countries, the bulk of electricity that runs air conditioners in homes and businesses is generated from fossil fuels, most prominently coal. In contrast, a large share of
space heating in cooler climates is done by directly burning fuels — usually natural gas, other gases, or oil, all of which have somewhat smaller carbon emissions than coal. That, together with the energy losses involved in generation and transmission of electric power, means that on average, an air conditioner causes more greenhouse emissions when pushing heat out of a house than does a furnace when putting the same quantity of heat into a house."

This is a deeply flawed comparison.

The number of degrees cooled in a hot climate is generally far less (say, 95 down to 72F) than degrees warmed in a cold climate (say, 32 up to 68F). The text above implies this hasn't been taken into account given the "same quantity of heat into a house" note on the comparison. Your comparison is like saying it's more efficient to light a house with halogen than a stadium with LEDs.

Heating requirements also rise as temperatures plunge, generally along with the sunset. Solar energy, which is quickly approaching competitive efficiency in some markets, correlates in abundance with high temperatures. It's also a technology that deploys well directly on or near buildings in hot, sunny locales in ways that mitigate transmission costs and efficiency losses.

Heating, even when derived directly from fuels, will always carry either an energy transportation cost or storage costs because it's counter-cyclical with the primary on-site renewable energy source (solar).

Finally, because air conditioning generally correlates with peak power usage, some of the cleanest plants tend to come online to provide the marginal increase in generation needs. The dirtiest plants tend to be the cheapest to run, so they provide a much greater fraction of energy generated at night (when power usage is lower) than they do during the day. The
marginal power used by an air conditioner should map better to a natural gas plant's output than a coal plant's.

Posted by David Strauss on 19 Jul 2012

Dr.A.Jagadeesh Nellore wrote:

Some wise words.

Many years ago similar words were said to me by a professor at a theological seminary “Wisdom is to Take the Best of the Old and Combine it with the Best of the New.”

Dr. Nellore can you direct me to anywhere that I can read more on this? I’m emailing you as well as I’d really like to find out more on this. I feel that the lack of emphasis on energy efficiency and reforestation were strategic mistakes in this battle and is why we are now unlikely to meet the 2017 deadline to stop a +2C world.

Taking on the coal, oil, gas industries head on was always doomed to fail. They have too much money, too many political connections, and too few morals to be stopped.

Litigation for damages is the only way some justice will be delivered for humanity. Recent cases against the tobacco and asbestos companies have provided powerful precedents that will enable individuals, companies and eventually countries to be held to account in courts of law.

Posted by Matthew Rosenbaum on 21 Jul 2012

See also SSPP blog post "Warming the Planet by Cooling Off"

Posted by sustainability: science, practice, & policy on 14 Aug 2012

Dr A.Jagadeesh Nellore suggests nice traditional technics to avoid electric coolers in developing countries. I disagree with the way you phrase it. We should all go for this kind of buildings, not just developing countries. And if we can't go for it don't ask them to do it.

The reality in most developing countries is quite different from what you depict. Everywhere I travelled, which incldues Afghanistan, DRCongo, Niger, Panama, Mali, Iran, Senegal, ..., new buildings use western style concrete intensive techniques with almost no attention paid to natural cooling opportunities. And this is especially true for the richest houses who are the most likely to be equipped with electric coolers. The model is rather to build as cheap as possible and as modern as possible. And I do not blame them for this.

Posted by David Hercot on 31 Aug 2012

Even in the Chicago area, summer heat gain through the windows is significant, and in the U.S. sunbelt with longer summers, solar screens are sometimes used to reduce the heat gain and thus electricity for air conditioning. The screens are mounted outside the window and maintain a view, darken the room some, and are intended for permanent installation.

Another option for reducing electricity for air conditioning are solar grates. Mounted outside the window and using selective reflectivity, the grates pass visible light and block most of the infrared light while maintaining a view, even at night. The room is quite bright with diffused light thus allowing artificial lights to be turned off during sunlit hours. (Think cool and bright). Grates are designed for seasonal use and are normally stored in cool weather to allow free sunlight heating during winter. Grates can be applied to all window types, and are robust and easily installed. Maintenance is nil. Both screens and grates have attractive payout periods. Ref. USP "Grate sunshade".

Posted by H. Cochran on 07 Nov 2012



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