5. - 11. ICESR 08-14-2007 - Laserfiche WebLink

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MISCELLANEOUS IMPROVEMENTS Power Factor Correction By eliminating a power factor correction penalty, electric bills in many ice arenas can be reduced without changing the amount of electric used by the arena. Often when older electric motors are used to operate equipment they have low power factors. The power factor is the ratio of actual power being used in a circuit (in kilowatts) to the power which is apparently being drawn from the line (in kilovolt-ampere). The actual power is the "real" power that performs useful work such as causing a motor to rotate or creating heat in a resistive element. Apparent power is the power required to establish an electrical field for the motor. The apparent power is used by the motor and returned back into the electrical system to establish a circuit. The apparent power level is used by the utility to size all system components from generation capacity and distribution lines to transformers at the building site. Electric utilities penalize customers for low power factors because they have to have generate more electric than what is required by their customers. Low power factors can usually be corrected by installing capacitor banks at the point where the supply of electricity enters the building. Capacitor banks act as storage devices that store current needed by the electric motor and release the current to the motor at the correct time thereby improving the overall power factor of the building. Power factor correction is typically performed if utility bills indicate that the overall power factor for the site is below 90 - 95 percent, depending on the utility. Not all utilities charge power factor penalties. Power factor correction equipment can be installed by most electricians and ranges in price based on the voltage supplied to the building, amount of capacity needed to correct the problem, and the total electrical load of the building. Typical paybacks are less than 5 years for a building with a power factor of 80 percent or lower. High Efficiency Motor Replacement About half of the world's electricity is used by motors. The electric bill for America's motor driven systems is about $90 billion per year. Given the significant amount of energy and money devoted to motor-driven systems, even modest improvements in their efficiency hold the promise of huge savings. The electric motors currently being used in arenas for refrigeration systems, pumps, and exhaust fans have a large impact on total arena electrical consumption. Electric motors are relatively cheap to purchase and extremely expensive to operate. The cost of electricity to run a typical commercial or industrial sector motor with a duty factor of at least 4,000 hours per year is equivalent to ten times its capital cost. The replacement of an older standard efficiency motor with a new high efficiency motor may result in double savings. First, savings will occur by significantly reducing energy consumption. High efficiency motors will use less energy than an older motor with the same horsepower rating and load. Second, if an arena is charged a power factor correction penalty by their electric utility, this penalty will likely be eliminated by replacing older motors. Older motors have power factors in the range of 70 to 80%. New high Page 14 Energy Improvements in Minnesota Public Ice Arenas Project Center for Energy & Environment