As I walked through a 10-year-old school building recently with the district energy manager, I pointed out to him the often-overlooked "little things" that increased energy waste daily in the operation of the school. I told him these inefficiencies and waste seem insignificant, but when added up in a school or across the district, they amounted to a significant waste of energy and money annually.
Our walk took us past the locked door of an electrical room. I mentioned to him behind this door probably existed a small gold mine. As the door opened and we took our first footsteps in, we felt a sudden increase in temperature.
I pointed out the "pot of gold" — an electrical distribution transformer (EDT), a gray box at the end of the room. He was confused, so I proceeded to explain what made this a pot of gold.
Most power comes into a school rated at 480/277 volts, and it is transformed down to 120/208 volts providing the electricity to the outlets in the classrooms and throughout the building. This power is essential for teaching tool devices and systems used on a daily basis the teachers and students.
The increase in temperature, I explained, indicated wasted energy or inefficiency. The wasted energy is due to several factors, but the key ones are no load losses, electricity needed to energize the transformer (24/7), loading significantly below design levels and the incorporation of electronics into the teaching tools.
EDTs up to this time only supplied electricity to teaching tools with linear loads — TVs, radios and record players, tape machines, adding machines, slide projectors, incandescent lamps, typewriters, etc.
Teaching tools introduced in '80s and '90s increased the use of more integrated circuits — computer chips and the like — resulting in an increase in nonlinear loads like computers, instant-on TVs, copy machines, dot-matrix printers, wireless phones, DVD players, etc.
Now in the 21st century, more and more nonlinear loading is being introduced into the school building and teaching tools: flat-screen computer monitors, flat-screen TVs, LCD projectors, CFL lamps, smart boards, tablets, smartphones, wireless networks and more.
As our walk-through continued, I explained that the U.S. Department of Energy (DOE) realized as the 20th century was ending that EDTs were a significant source of wasted energy in our nation. In the late 1990s, they began a study to improve the design of EDTs and their operating efficiencies at lower loads.
EDTs are designed to achieve maximum efficiency based on linear loads at 35 percent. A 1999 DOE study found loads in schools averaging about 16 percent. I further provided him with recent test results in schools across the country:
- 75 kVa in New Jersey — 6.6 percent
- 150 kVa in Connecticut — 4.2 percent
- 15 schools in Arizona: 75 kVa — 7.5 percent; 112.5 kVa — 7.7 percent and 225 kVa — 13.4 percent
In 2004, a preliminary report was issued with a design selected with the lowest life cycle cost (LLCC). At the time, it was determined that if one could replace all existing EDTs in the nation (44 million-plus) with the LLCC design, the energy saved would equal nine days of electrical generation in the nation annually or about 2.6 percent of all energy generated.
While continuing our walk-through, I continued to find "little things," and during this time he asked questions about the energy savings potential of replacing existing EDT with new LLCC units. I told him before I could answer his question, I would have to bring him up-to-date on recent developments.
The DOE made its final ruling on EDTs in 2013. It now mandates an improved design, but still designed to 35 percent loads and linear — still a significant improvement in efficiency and energy savings. This requirement goes into effect on Jan. 1, 2016
There are currently transformers manufactured that exceed the minimum efficiency requirements of DOE 2016 mandate for not only linear but also nonlinear loads. We took an inventory of the number and sizes of EDTs and found four, about average for elementary schools built today. The annual energy savings potential for this number ranged from 20,000 to 40,000 kWh.
As the walk-through completed, we sat down to discuss what was observed, recommendations and answers to any questions. He was interested in the 2016 requirement for EDTs and asked what are the key factors he should include to receive 2016 EDT in future new or renovation projects.
I provided him the following information as a minimum:
- Seek out current manufacturers that meet 2016 requirements including nonlinear loads;
- Efficiencies must exceed 2016 minimum standards;
- No load losses must comply with NEMA ST20;
- Efficiency at low and under nonlinear loads must meet minimum requirements;
- K-7 efficiency under 16.7 percent, 25 percent, 50 percent, 75 percent and 100 percent load profiles;
- Testing under both linear and nonlinear loads to verify performance; and
- Submittal of performance requirements in writing.
I summed up information about transformers with the following: Once installed, they require no maintenance, are 99 percent reliable, consume electrical energy with or without loads (no load losses) and have a normal life as long as the building.
I concluded with the following: "New 2016 EDTs meeting the outlined requirements above will result in the establishment of a firm foundation for accomplishment and sustaining of net-zero performance now and in the future."
