The topics of global warming, the Greenhouse effect, reducing energy usage and rising energy costs can be found just about every day in the media. There are plenty of opportunities to work to reverse the negative environmental and economic trends, ranging from better insulation in facilities with higher thermal efficient windows and doors to using vehicles with better mileage or mass transit. Each has its own merits and limitations. A bus may be “eight times more efficient per person than a personal light truck,” according to the U.S. Department of Energy, but an electrical contractor isn’t likely to need 45 people going to the job site at one time nor would want to carry all tools and supplies needed for the job on the local city bus.
By the numbers
Focusing on the electrical aspects as related to energy efficiency also will lead to a substantial list of possibilities for improvements around the world but especially in the United States. According to the World Fact Book, the United States is No. 1 in several areas, including the No. 1 consumer of electricity at 3.9 TW/hr, or 23 percent of the world’s consumption in 2005. Though the United States also has the largest gross domestic product (GDP) (21 percent of world’s GDP), it also has the largest electrical consumption per person, at 12.6 megawatt-hours (MWh) per person annually. That is approximately double what countries with comparable GDP per capita have, such as Germany and the United Kingdom. Not surprising is the statistic that the GDP per electric consumption is significantly less than those comparable industrial countries, or $5.14/kilowatt-hour (kWh) for Europe versus $3.63/kWh for the United States, according to the World Fact Book. In other words, the U.S. economy is only 70 percent as efficient with electricity in producing goods and services as are comparable countries.
That certainly sounds like an opportunity to improve, save significant money and help the environment. At an average cost of 8.91 cents per kWh, according to www.eia.doe.gov/cneaf/electricity/epm/table5_6_a.html, that would come to approximately $100 billion in savings if the efficiency could be raised to comparable levels. Given that the United States is the largest single emitter of carbon dioxide from the burning of fossil fuels with 71.4 percent of the electricity generated from such in 2005, according to the World Fact Book , the effect on the environment from coal-fueled generating plants producing over 1,000 g CO2eq/kWh (grams of carbon dioxide equivalent per kilowatt-hour of electricity generated), according to www.parliament.uk/documents/upload/postpn268.pdf, is around 200 million tons of CO2 that could be reduced from emissions into the atmosphere.
What those numbers mean for the EC
So, that’s all some fun with numbers, but how do we get down to really doing something about this?
The first step in making a real difference is to know what, where and how the electricity is being used now. An electrical energy audit is a relatively straightforward process that the facility electrician or an outside electrical contractor could perform. A walk-through of a facility following the one-line diagram of the electrical infrastructure is used to determine where you need to monitor. A discussion with the facility manager will let you know which type of loads are fed by each distribution point, which will be helpful in analyzing the results from the audit. If you are using an instrument that can simultaneously measure demand, energy and power quality, you can get a two-for-one audit for the customer. In numerous occasions, power quality phenomena, such as harmonic currents, can be a significant contributor to the inefficiencies.
Once the data is all collected, it is good to do a “test of reasonableness” to help ensure that the results are understandable and explainable. There are numerous Web sites and tools on the market to do so. A good place to start is the DOE’s Energy Efficiency and Renewable Energy Web site. For example, if you were monitoring a commercial facility with significant information technology (IT) equipment, such as printers, personal computers and copy machines, you could use the report on the Web site (www.eere.energy.gov) titled, “Energy Consumption by Office and Telecommunications Equipment in Commercial Buildings Volume I and Volume II,” which shows where the energy is consumed overall in the facility (about 25 percent in HVAC and lighting each and 6 percent in IT) and what each type of IT equipment typically consumes (22 percent, 20 percent and 12 percent for monitors and displays, PCs and workstations, and servers, respectively). Note that this data is a little dated, as newer LCD displays use significantly less in power, which operate typically around 100W and less than 5W when in “idle” mode.
After you have identified which equipment in which area is the major consumer of the electricity, you can either directly monitor the equipment for its efficiency or work off the manufacturer’s data sheets. Many types of equipment have a range of efficiency ratings depending on how heavily loaded the equipment is. Some equipment is run continuously, though the actual need for such is not continuous. Light-level and motion sensors could be installed to shut down some of the lighting when it is not needed due to adequate sunlight or no one in the area.
Another common reduction in energy can be achieved by replacing old induction motors with energy-efficient motors. Electric motors are estimated at consuming more than half the electricity in the United States, and according to www.copper.org, “it is estimated that the NEMA Premium motor program could save over 5,800 GWh (5.8 billion kWh) of electricity and prevent the release of nearly 80 million metric tons of carbon into the atmosphere over the next 10 years. … Energy-efficient motors pay for themselves in a few years or sometimes even a few months, after which they will continue to pile up savings worth many times their purchase cost for as long as they remain in service.”
Additional energy reduction can be achieved using variable or adjustable-speed drives (VSDs or ASDs) to power the motors with only as much energy as needed to meet the demands of the load, such as an HVAC system, rather than running the fans and compressors at full speed. According to an article in Building Design + Construction, “An EPA study showed that VSDs … provided average energy savings of 52 percent.” For more on this, see story on page 174.
Other low-hanging fruit include the replacement of incandescent and older fluorescent lighting with more efficient luminaries, zoning HVAC to match the occupancy, and identifying and replacing equipment with low power factor where cost-effective. Add a master on/off switch that can turn off unnecessary equipment and lighting at night in one quick flip of the switch, including such equipment as vending machines. In many facilities, all lights are left on until the cleaning crews come through hours after the work force has left. In one such facility, the lighting load accounted for nearly half of the facility load, and reducing the lit time from 13 to 10 hours saved 12 percent of the electric bill.
There also are more efficient Energy Star power transformers on the market. A transformer’s efficiency is based on a number of factors, including percent loading relative to nameplate rating and the harmonic current levels, especially the higher order harmonic currents, since the losses go up as the square of the harmonic number. Since a transformer’s life expectancy is often several decades, the operating savings calculation versus replacement cost must take that into account, as well. A couple of a percent savings may not seem to be worth the hassle, but every little bit helps. And it pays back year after year.
Each of these various savings in electrical energy are typically in the 1 to 5 percent range of the total electrical energy costs. But the effects are cumulative for each step undertaken and will pay back in operating costs reductions every year. In addition, since much of the inefficiencies result in heat, reducing the losses means less work for the air conditioning systems, hence even further savings. It all goes to the bottom line and not up into the atmosphere, greener on both accounts.
BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.