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All About: Waste heat

  • Story Highlights
  • Globally homes responsible for 19 percent of greenhouse gas emissions
  • Household energy use to increase by 15 percent by 2015
  • Recycling waste heat could slash fossil fuel usage by half
  • CHP-generated CO2 emissions 49 percent lower than standards power stations
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By Rachel Oliver
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(CNN) -- There's no place like home -- especially when it comes to affecting the environment, it seems.


A power plant in Shaanxi Province, China. The Asian nation is trying to cut per capita energy consumption.

For all the bad mouthing we dish out to the auto and manufacturing industries for the foul pollutants they force us to breathe, a wealth of evidence is suggesting that we should be looking a little closer to home for the other villains of global warming.

It turns out that our homes gobble up 25 percent of the world's energy and are to thank for 19 percent of global greenhouse gas emissions (that's 4,400 million metric tons of carbon dioxide, or CO2), according to a recent McKinsey report, "Curbing Global Energy Demand: The Energy Productivity Opportunity."

That figure is expected to reach 21 percent by 2020 if we carry on the way we are going. It could, of course get much higher, depending on how quickly the developing world adopts the same consumer-led lifestyle as the West. (India and China's emissions per capita, for example, are expected to double by 2020).

As it stands now, the U.S. residential sector is the largest single consumer of energy on Earth, with American homes spewing out 25 percent of global home-related greenhouse gas emissions. But by 2020, developing China -- which is currently emitting 18 percent -- will have surpassed the United States, says McKinsey, taking 26 percent of the world's share.

So where is this need for energy coming from? Basically, from all the things we feel we can't live without -- our fridges, microwaves, air conditioning units, heating systems and dishwashers. But mostly, it's our heating and cooling systems, which use up 60 percent of a household's energy needs.

Home appliances are now the fastest-growing consumers of energy in the world, after cars, according to the WorldWatch Institute -- although houses overall emit more greenhouse gases than cars. In developed countries, home appliances generally account for 30 percent of all electricity consumed, emitting 12 percent of global greenhouse gases in the process.

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By 2015, says ASE, household energy use will be nearly 15 percent higher than it is today. But, again, with the developing world jumping on the consumer bandwagon, those figures could get even bigger still. In places like India, for example, sales of refrigerators ("by far the single biggest consumer of electricity in the average household," according to LiveScience) are expected to grow by nearly 14 percent every year, says WorldWatch.

The demand our buildings are putting on the energy sector and consequently the environment is bad enough, some say, but it wouldn't be so bad if at least that energy was being used efficiently -- that is to say, if it was being used at all.

Power stations and manufacturing plants -- which deliver the energy to our houses -- waste a staggering amount of energy. In the U.S., plants waste two-thirds of the energy they produce, the waste heat being enough, according to the UK's New Statesman, to power the entire Japanese economy.

Greenpeace has calculated that in the UK -- where power stations also discard two-thirds of the energy they produce -- the amount of waste heat there could provide hot water and heating for every building in the country.

Recycling this wasted heat, environmentalists say, could slash the amount of fossil fuels the U.S. burns for electricity in half. Governments around the world are now figuring how to use this waste heat to make homes more energy-efficient, with some countries more ahead of the curve than others.

One way of achieving this is by building more Combined Heat & Recovery (CHP) plants. CHP has won many supporters in the environmental movement and it is not hard to see why. It employs the art of recycling energy -- as in using the same energy twice. The idea is to reuse the thermal energy byproduct of the electric energy the plants are generating (ie that two thirds of energy that is getting wasted) for thermal-related uses such as space heating, hot water and air conditioning -- the very items that send electricity bills through the roof.

The result: more energy-efficiency and decreased usage of fossil fuels. According to Greenpeace in the UK, CHP plants can be as much as 95 percent energy-efficient, compared to standard power plants which are around 38 percent-efficient. And according to the Environmental and Energy Study Institute, "a generalized estimate" of CHP-generated CO2 emissions is 49 percent lower than that of a standard power station.

Countries that have embraced CHP include Holland and Denmark, which now both get at least half of their energy from CHP plants.

The Washington-based Environmental and Energy Study Institute has strongly come out in support of CHP and is pushing for the proliferation of CHP plants in the U.S., blaming "major policy and regulatory barriers" over the past 15 years for hampering its development thus far. Its arguments for the continued creation of CHP plants are fairly compelling:

"CHP...could literally save billions in new capital investment, reduce power costs, reduce security vulnerabilities, improve reliability and power quality, avoid transmission losses, reduce water used by power plants, cut fossil fuel use, cut greenhouse gas emissions and cut other pollutants."

One of the things holding back development, it says, is it costs the electricity providers. "Electricity utilities typically perceive CHP as a competitive threat, to the extent that it reduces their electricity sales, and hence, their revenues," says the Institute.

There is also the matter of investing in the construction of more power plants, in addition to adapting current ones. For CHP to work, its plants need proximity to the people they are providing energy to -- basically, because heat doesn't travel long distances very economically. (According to energy expert Thomas Casten, heat takes seven times as much energy to travel as electricity).

So one of the main downsides of CHP is, you need to build more power plants. But the upside is clean energy -- and a lot of it. According to Grist, since it invested in installing waste-heat recovery boilers, one coke oven plant in the U.S. state of Virginia now produces as much clean energy (1.6 billion kilowatt hours) as the entire amount generated by grid-connected solar power worldwide in 2004.

Another upside, CHP proponents say, is you can now put them in your homes, which means no need for the power plant. Micro-CHP units are now cropping up on the market for people to install in their own homes, no bigger in size than a dishwasher. They have been around in Japan -- the world's leading market for Micro-CHP boilers -- for some time and have in the past year also stirred up interest in the UK.


For other countries though, heat recovery is old news. The concept of heat recovery was being championed by Sweden as far back as 1979, when it was facing its own energy crisis. One of the ways it dealt with it was to refit individual homes with heat recovery systems, in various shapes and sizes.

Today, 90 percent to 95 percent of new homes in Sweden feature heat pumps, which not only are used for recirculating waste heat for the purpose of heating and hot water systems, but conversely are also employed for cooling uses too. E-mail to a friend E-mail to a friend

(Sources: McKinsey Global Institute; Green Energy News; WorldWatch Institute; Solar Energy International; Union of Concerned Scientists; Alliance to Save Energy; LiveScience; Grist; New Statesman; Greenpeace; Environmental and Energy Study Institute;; Christian Science Monitor; ScienceDirect; European Heat Pump Network)

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