Power Factor Case Study - Southwest Wisconsin Technical College

摘要

Southwest Wisconsin Technical College is a public institution serving southwest Wisconsin, specifically all of Crawford, Grant, Iowa, Lafayette, and Richland counties and part of Dane, Green, Sauk, and Vernon counties. 90% of all Southwest Tech graduates are employed within 6 months, and 67% of those graduates work in the Southwest Tech district. Southwest Tech has an enrollment of 1800 students and employs approximate 200 mil time staff. To meet the growing needs of the residents and businesses in southwest Wisconsin, the college passed a $40M property tax referendum to expand and renovate the campus. The expansion and renovation project included renovating exiting educational space and construction of a new Child Care Center, Health Science Center and Auto/Ag Center. It also included the construction of an 80 acre Public Safety Training Complex with a shooting range, an EVOC Track, and a Live Fire Training Facility. This added 150,575 square feet to the campus, or a 37% increase. The acreage of the campus more than doubled to 135 acres. The project included the following energy efficient and environmental upgrades: Trane building automation system, including touch screen energy tracking software for educational use, variable frequency drives, lighting retrofits, motion sensors on lighting, day lighting, new HVAC systems, boiler replacements, waste oil heater Ag Lab, building envelope improvements, storm water management improvements, new LED exterior parking lot and area lighting, ice storage system in the Health Sciences Center, submetering system for electric and natural gas energy management, new roofing with higher R values, waterless urinals, low water toilets, motion sensors on water faucets, replacement of large water heaters, and interior LED lighting fixtures. All new construction met or exceeded LEED Silver standards. Southwest Tech worked with the State of Wisconsin's Focus on Energy program to obtain $70,000 in grants to help with the cost of the energy efficient upgrades. The engineering calculations show a reduction of 487,760 KWh and 27,468 therms with the energy efficient upgrades included in the project. This is a $70,750 annual energy savings. After completion of the expansion project, utility bills show an actual reduction of 252,060 KWh from the period prior to the expansion. With a 37% increase in square footage, Southwest Tech was able to reduce actual consumption of electricity by 11%. Despite these improvements, poor power factor was impacting the utility bills in the Agriculture/Automotive Center (1700), the Health Science Center (1600), and the Industry Center (500). The power factors ranging from 60% to 70% were costing the organization thousands of dollars a month in utility penalties. Depending upon the rate structure of your electric utility, you may be able to save a substantial amount of money on your electric bill. Pay-back period for an equipment purchase including installation cost may be less than six months to a year. Utility rate structures that account for reactive power consumption, by either a KVA or var demand usage, or a power factor penalty are the ones that can provide this payback. Other ancillary benefits to be gained by correcting power factor are:, lower energy losses, better voltage regulation and released system capacity. All electric equipment requires "vars" - a term used by electric power engineers to describe the reactive or magnetizing power required by the inductive characteristics of electrical equipment. These inductive characteristics are more pronounced in motors and transformers, and therefore, can be quite significant in industrial facilities. The flow of vars, or reactive power, through a watt-hour meter will not affect the meter reading, but the flow of vars through the power system will result in energy losses for both the utility and the industrial facility. Some utilities charge for these vars in the form of a penalty, or KVA demand charge, to justify the cost for lost energy and the additional conductor and transformer capacity required to carry the vars. In addition to energy losses, var flow can also cause excessive voltage drop, which may have to be corrected by either the application of shunt capacitors, or other more expensive equipment, such as load-tap changing transformers, synchronous motors, and synchronous condensers (Northeast Power Systems, 2012).