Energy Conservation

Energy conservation is the practice of decreasing the quantity of energy used. It may be achieved through efficient energy use, in which case energy use is decreased while achieving a similar outcome, or by reduced consumption of energy services. Energy conservation may result in increase of financial capital, environmental value, national security, personal security, and human comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy costs and promote economic security. Industrial and commercial users may want to increase efficiency and thus maximize profit.

Transportation

The transportation includes all vehicles used for personal or freight transportation. Of the energy used in this sector, approximately 65% is consumed by gasoline-powered vehicles, primarily personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.

The two oil supply crisis of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight which originated in the late 1970s, along with the transition to front wheel drive. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.

In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy. Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy. While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved. The gas-guzzler tax ended the reign of large cubic-inched engines from the muscle car era.

Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders. In recent years telecommuting has also become a viable alternative to commuting for some jobs, but in 2003 only 3.5% of workers were telecommuters. Ironically, hundreds of thousands of American and European workers have been replaced by workers in Asia who telecommute from thousands of miles away.

Fuel economy-maximizing behaviors also help reduce fuel consumption. Among the most effective are moderate (as opposed to aggressive) driving, driving at lower speeds, using cruise control, and turning off a vehicle's engine at stops rather than idling. A vehicle's gas mileage decreases rapidly highway speeds, normally above 55 miles per hour (though the exact number varies by vehicle). This is because aerodynamic forces are proportionally related to the square of an object's speed (when the speed is doubled, drag quadruples). According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph (8.0 km/h) you drive over 60 mph (97 km/h) is similar to paying an additional $0.30 per gallon for gas. The exact speed at which a vehicle achieves it's highest efficiency varies based on the vehicle's drag coefficient, frontal area, surrounding air speed, and the efficiency and gearing of a vehicle's drive train and transmission.

Residential sector

The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories. Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation. On average, about half of the energy used in U.S. homes is expended on space conditioning (i.e. heating and cooling).

The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified". Beyond these minimum standards, the Environmental Protection Agency awards the Energy Star designation to appliances that exceed industry efficiency averages by an EPA-specified percentage.

Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources. The average size of homes built in the United States has increased significantly, from 1,500 sq ft (140 m²) in 1970 to 2,300 sq ft (210 m²) in 2005. The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.

As furnace efficiency gets higher, there is limited room for improvement--efficiencies above 85% are now common. However, improving the building envelope through better or more insulation, advanced windows, etc., can allow larger improvements. The passive house approach produces super insulated buildings that approach zero net energy consumption. Improving the building envelope can also be cheaper than replacing a furnace or air conditioner.

Even lower cost improvements include weatherization, which is frequently subsidized by utilities or state/federal tax credits, as are programmable thermostats. Consumers have also been urged to adopt a wider indoor temperature range (e.g. 65 °F (18 °C) in the winter, 80 °F (27 °C) in the summer).

One underutilized, but potentially very powerful means to reduce household energy consumption is to provide real-time feedback to homeowners so they can effectively alter their energy using behavior. Recently, low cost energy feedback displays, such as The Energy Detective or wattson, have become available. A study of a similar device deployed in 500 Ontario homes by Hydro One [2] showed an average 6.5% drop in total electricity use when compared with a similarly sized control group.

Standby power used by consumer electronics and appliances while they are turned off accounts for an estimated 5 to 10% of household electricity consumption, adding an estimated $3 billion to annual energy costs in the USA. "In the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off."

Commercial sector

The commercial sector consists of retail stores, offices (business and government), restaurants, schools and other workplaces. Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings. Lighting, at 25%, plays a much larger role than it does in the residential sector. Lighting is also generally the most wasteful component of commercial use. A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.

Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997). Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts. As a result, fluorescent lighting (about four times as efficient as incandescent) is the standard for most commercial space, although it may produce certain adverse health effects. Potential health concerns can be mitigated by using newer fixtures with electronic ballasts rather than older magenetic ballasts. As most buildings have consistent hours of operation, programmed thermostats and lighting controls are common. However, too many companies believe that merely having a computer controlled Building automation system guarantees energy efficiency. As an example one large company in Northern California boasted that it was confident its state of the art system had optimized space heating. A more careful analysis by Lumina Technologies showed the system had been given programming instructions to maintain constant 24 hour temperatures in the entire building complex. This instruction caused the injection of nighttime heat into vacant buildings when the daytime summer temperatures would often exceed 90 °F (32 °C). This mis-programming was costing the company over $130,000 per year in wasted energy (Lumina Technologies, 1997). Many corporations and governments also require the Energy Star rating for any new equipment purchased for their buildings.

Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months. An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.

Recent advances include use of occupancy sensors to turn off lights when spaces are unoccupied, and photo sensors to dim or turn off electric lighting when natural light is available. In air conditioning systems, overall equipment efficiencies have increased as energy codes and consumer information have begun to emphasise year round performance rather than just efficiency ratings at maximum output. Controllers that automatically vary the speeds of fans, pumps, and compressors have radically improved part-load performance of those devices. For space or water heating, electric heat pumps consume roughly half the energy required by electric resistance heaters. Natural gas heating efficiencies have improved through use of condensing furnaces and boilers, in which the water vapor in the flue gas is cooled to liquid form before it is discharged, allowing the heat of condensation to be used. In buildings where high levels of outside air are required, heat exchangers can capture heat from the exhaust air to preheat incoming supply air.

Industrial sector

The industrial sector represents all production and processing of goods, including manufacturing, construction, farming, water management and mining. Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years. For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%. These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.

Another example for efficiency improvements is the use of products made of High temperature insulation wool (HITW) which enables predominantly industrial users to operate thermal treatment plants at temperatures between 800 and 1400°C. In these high-temperature applications, the consumption of primary energy and the associated CO₂ emissions can be reduced by up to 50% compared with old fashioned industrial installations. The application of products made of High temperature insulation Wool is becoming increasingly important against the background of the currently dramatic rising cost of energy.

The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related.) In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.

To conserve energy, some industries have begun using solar panels to heat their water. Unlike the other sectors, total energy use in the industrial sector has declined in the last decade. While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations overseas.

Never before has the demand for energy been as high -- and never before have homeowners become so increasingly aware of the energy savings possible with landscaping. Although it is not possible to control temperature, wind, and other natural elements, certain landscape practices can help modify the climate in and around the home.

By placing trees, shrubs, vines and landscape structures properly, homeowners can reduce the energy required to keep homes comfortable during winter and summer. Along with the reduction of energy bills, a well-planned landscape adds beauty, interest and increased property values.

Although homeowners have intuitively used landscaping to save energy for many years, we are only beginning to realize the magnitude of the savings possible. According to one government study, winter heating bills may be reduced by as much as 15 percent, while summer cooling energy needs may be cut by as much as 50 percent.

Houses gain or lose heat in 3 basic ways:

• air infiltration - passage of air through cracks and around doors or through open windows and doors. The average home loses 20-30% of heat in winter by air infiltration;
• heat conduction - conduction of heat through materials of which the house is built. Controlling the temperature difference and air movement between inner and outer surfaces of walls, floors and ceilings is the best opportunity for reducing heat conduction. Heat conduction represents up to 50% or more of the total heat exchange between a home and the outside environment;
• solar radiation - heat is transmitted into homes by penetration of the sun's rays. Up to 90% will be transmitted into the living area if rays are received perpendicular to a single pane. Sunlight will be increasingly reflected by the glass as the sunlight departs from the perpendicular.

The role of landscape vegetation in conserving energy varies with the different microclimates across North Carolina. In the cooler, northwest areas of North Carolina, where enormous amounts of energy are consumed in winter heating, control of air infiltration is paramount. Hotter southeastern areas place more emphasis on use of shade to control heat conduction and reduce the need for summer air-conditioning. Three basic landscape applications which have proven to save energy are: (1) the use of shade trees, (2) windbreaks, and (3) the use of foundation plants.

Trees.

Trees can reduce summer temperatures significantly. Shading the roof of a house from the afternoon sun by large trees can reduce temperatures inside the home by as much as 8 to 10 degrees F.

Deciduous trees provide summer shade, then drop their leaves in the fall. This allows the warmth of the sun to filter through their bare branches in winter and helps warm the home. If a home can be situated to take advantage of shade from existing trees on southeast and west exposures, energy expended to cool the house can be reduced.

If there are no existing trees, the owner can select and place trees that ultimately will provide shade. The temptation is to plant the fastest growing species available. However, this is usually a poor choice for several reasons. Trees that grow at more moderate rates usually live longer, are less likely to break in wind and ice storms, and are often more resistant to insects and diseases.

A carefully selected and planted tree with a moderate growth rate often will respond to good care by increasing its rate of growth. Recommended shade trees for North Carolina would include: Red Maple, Sugar Maple, Pecan, Birch, White Ash, Ginkgo, Honeylocust, Sweetgum, Tulip Poplar, Blackgum, Sycamore, White Oak, Red Oak, Willow Oak, Water Oak, Bald Cypress, Linden, Zelkova, River Birch, and Hickory.

Smaller trees such as Crape Myrtles and Dogwoods can be planted closer to the house and used for shading walls and window areas. Since they are deciduous, they will provide shade during the summer and allow light and sun to penetrate during the winter season. (See HIL #621, "The Use of Small and Intermediate Size Trees in the Landscape".)

Always remember proportions. Ask the nurseryman or county agent How fast? and How large? a certain tree will grow.

Another way to reduce energy consumption with trees and shrubs is to provide shade for the outside protection of a split system air conditioner. A study by the American Refrigeration Institute shows that shading of this type can reduce the temperature inside the home as much as 3 degrees F. However, shrubs planted near the compressor should not obstruct the air flow or access for service. In addition to reducing energy consumption, screening outdoor air conditioning equipment with plantings enhances the esthetic value of the home.

Espaliers and Vines.

In addition to shading roof areas, plants can protect walls from heat and cold. Vines, shrubs and certain trees can be used as espaliers (plants trained to grow flat against walls). The foliage cover insulates the wall against summer heat and cold winter winds. Trees, shrubs and vines can be highly effective in reducing noise and dust pollution.

Overhead Structures.

Arbors and slatted wooden overhead structures can be effective either attached or adjacent to the home or farther out in the landscape. If adjacent to the home, they provide the bonus of shading walls and windows, thus reducing heat and glare and providing cool, restful sitting and viewing areas. Carolina Jasmine, ivy, wisteria or grape vines are popular vines which are well adapted to most of the state.

Protection From the Wind.

Although hedges have been utilized for many years, their value has increased with the advent of higher fuel costs. Winter winds in North Carolina usually blow from the northwest and accelerate the rate of air exchange between a house and the outdoor environment. Savings of up to 23 percent have been recorded in comparing completely exposed homes and a house landscaped to minimize air infiltration. Summer winds normally blow from the south or southwest with generally positive effects on human comfort. Tall trees on the south and west can reduce temperature while allowing breeze to pass beneath and through the foliage canopy.

Planning Windbreaks.

Windbreaks obstruct and redirect the flow of wind. As wind strikes an obstruction, it can move over, around or through it. The extent of protection on the leeward side is related to the height and length of the windbreak. Impenetrable windbreaks create a strong vacuum on the protected or leeward side, which reduces the protection. Windbreaks composed of living plants allow some of the wind to penetrate, which makes them more effective.

Several evergreen trees which grow into large windbreaks and also screen objectionable views are: Hemlock, Cedar, Southern Magnolia, White Pine, Loquat, and Deodar Cedar.

Most homeowners need to consider the size requirements of the living hedge. 6-12 ft evergreen shrubs for good windbreaks are: Camellia, Sasanqua, Cleyera, Elaeagnus, Holly varieties, Ligustrum, Waxmyrtle, Oleander, Osmanthus, Photinia, Pittosporum, and Viburnum. If space is limited for a hedge, consider some type of construction fence or wall.

Other Types of Windbreaks.

In addition to traditional windbreaks, shrubs can also be used closer to the home for winter protection. This is more practical for small areas and subdivision lots where space does not allow the use of conventional windbreaks. For this type of protection, a combination of dense evergreen plants and groundcovers are most appropriate. They should be planted close enough to eventually form a solid wall and far enough away from the house (about 4 to 5 feet, minimum) to create a dead air space. This relatively still or dead air has much less cooling power than moving air which can decrease the loss of that through the walls.

Evergreen shrubs which should be considered as foundation plantings would include many dwarf or slow-growing types. This would include Dwarf Hollies, Boxwoods or Junipers.

Good landscaping practices offer one of the most practical methods of reducing energy consumption in homes. When the homeowner considers the added benefits of the increased real estate value and more attractive homes and communities, the investment becomes an even greater bargain.