IMPROVING ENERGY EFFICIENCY

What is energy efficiency? Doing more with less. Energy efficiency is the percentage of total energy input into an energy conversion device or system that does useful work and is not converted to low-quality, essentially useless heat. Improving the energy efficiency of a car motor, home heating system, or other energy conversion device involves using less energy to do more useful work.

You may be surprised to learn that 84% of all commercial energy used in the United States is wasted! About 41% of this energy is wasted automatically because of the degradation of energy quality imposed by the second law of energy. However, about 43% is wasted unnecessarily, mostly by (1) using fuel-wasting motor vehicles, furnaces, and other devices and (2) living and working in leaky, poorly insulated, poorly designed buildings.

The energy conversion devices we use vary in their energy efficiencies. We can save energy and money by buying more energy-efficient cars, lighting, heating systems, water heaters and appliances. Some energy-efficient models may cost more initially, but in the long run they usually save money by having a lower life cycle cost: initial cost plus lifetime operating costs.

The net efficiency of the entire energy delivery process for a space heater, water heater, or car is determined by the efficiency of each step in the energy conversion process. For example, the sequence of energy-using (and energy-wasting) steps involved in using electricity produced from fossil or nuclear fuels is:

Extraction ® Transportation ® Processing ® Transportation to power plant ® Electric generation ® Transmission ® End use

The analysis shows that the process of, for example, (1) converting the high-quality energy in nuclear fuel to high-quality heat at several thousand degrees in the power plant, (2) converting this heat to high-quality electricity, (3) transmitting the electricity to users, and (4) using the electricity to provide low-quality heating a house to only about 20 ^оC is very wasteful. Burning coal or any fossil fuel at a power plant to supply electricity for heating water or space is also inefficient. Using electricity to heat a house (resistance heating) costs about twice more per unit of energy than heating with oil or with an efficient natural gas furnace.

How can we save energy?

Could we recycle energy? No. The second law of energy tells us that we cannot recycle energy. But we can slow the rate at which waste heat flows into the environment.

For a house, the best way to do this is to insulate it thoroughly and to eliminate air leaks. The energy efficiency of existing house can be improved significantly by (1) adding insulation,
(2) plugging leaks, and (3) installing energy-saving windows. About one-third of heated air in the U.S. homes and buildings escaped through closed windows and holes and cracks. Replacing all windows with low-E (low emissivity) windows would cut these expansive losses by two-thirds and reduce CO₂ emissions. Widely available super insulating windows insulate as well as 8 ¾ 12 sheets of glass. Although they cost 10 ¾ 15% more than double-glazed windows, this cost is paid back rapidly Because of tough energy-efficiency standards, the average Swedish home consumes about one-third as much energy as the average American home of the same size.

Another way to save energy is to buy the most energy-efficient appliances and lights. Replacing a standard incandescent bulb with an energy-efficient compact fluorescent bulb saves about $48 ¾ 70 per bulb over its 10-year life. If all households in the US used the most efficient frost-free refrigerator now available, 18 large (1,000 megawatt) power plants could close. Microwave ovens could cut electricity use for cooking by 25 ¾ 50%. Increased use of Internet for business can help saving energy and reduce emissions of carbon dioxide and other air pollutants.

There are three important ways to save energy (and money) in industry:

• Cogeneration, or combined heat and power (CHP) systems, in which two useful forms of energy (such as steam and electricity) are produced from the same fuel source. These systems have an efficiency of up to 80% (compared to about 30 ¾ 40% for coal-fired boilers) and emit two-thirds less carbon dioxide per unit of energy produced. Cogeneration has been widely used in Western Europe for years, and its use in the USA and Chine is growing. In Germany, small cogeneration units that run on natural gas or liquefied petroleum gas (LPG) supply restaurants, apartment buildings, and houses with all their energy. In 4 ¾ 5 years, they pay for themselves in saved fuel and electricity.
• Replacing energy-wasting electric motors. Most of these electric motors are inefficient because they run only at full speed. Each year a heavily used electric motor consumes 10 times its purchase cost in electricity ¾ equivalent to using $200.000 worth of gasoline each year to fuel a $20.000 car. The costs of replacing such motors with new adjustable-speed drive motors would be paid back in about 1 year and save an amount of energy equal to that generated by 150 large (1.000-megawatt) plants.
• Switching to high-efficiency lighting (see above).

Why aren't we doing more to reduce energy waste? The major reasons are as follows:

· A glut of low-cost fossil fuels. As long as energy is cheap, people are more likely to waste it and not make investments in improving energy efficiency.

· Lack of sufficient tax breaks and other economic incentives for consumers and businesses to invest in improving energy efficiency.

· Lack of information about the availability of energy-saving devices and the amount of money such items can save consumers by using life cycle cost analysis.

Date: 2016-01-14; view: 862