Energy reduction techniques employed at the huge research and development center save $1.4 million per year.
AT&T has been involved in a corporate-wide energy savings plan since those bleak, oil-shortage days of the early 1970s. Because AT&T operates hundreds of facilities throughout the country, reductions in energy usage. especially a reduction in electric power use, result,in millions of dollars saved on a corporate-wide basis.
Examples of the effectiveness of AT&T's energy-saving methodology are the programs that have been implemented at AT&T Bell Laboratories, Murray Hill, N.J. Over the years, various energy-saving endeavors have been tried; however, the most effective measures have been accomplished in recent years, resulting in a significant increase in dollars saved.
Multiple power-reduction ideas
The total electric power cutbacks carried out recently at Bell Labs will result in an annual power bill savings of at least $1.4 million. This is the result of a team effort by facility engineers and maintenance and operations personnel as well as various department managers. Budd Sauselein, P.E., a facilities engineer and certified energy manager, worked closely with in-plant mechanical, control, and installation people as well as with plant management and outside contractors. He points out that the major facets of the plan are:
* AT&T corporate support for energy savings;
* Retrofit of lighting throughout the facility;
* Installation of premium-efficiency (PE) motors;
* Use of variable frequency drives;
* Use of computer monitoring and control;
* Implementation of a demand limiting/power curtailment plan;
* Diversification and control of chiller plants; and
* Electric and fuel rate restructuring.
* Lighting retrofits
The replacement of inefficient lamps has been a general policy since the early 1970s; however, recent advances in lighting technology spurred Sauselein into action. He began by trying pilot tests with various types of equipment to see which was the most effective, efficient, reliable, and had the fastest payback.
Also, it was vital that Bell Labs technical people not be disturbed. Therefore, lighting changeouts had to be carried out in a quick and essentially invisible manner. This also applied to any retrofit, be it an energy-saving installation, an operations change, or a maintenance procedure.
Original lighting in the facility was predominately two- and four-lamp fluorescent units furnished with 4-ft, T-12 lamps and magnetic ballasts. Also, nearly 1400 75W incandescent lamps were installed in high-hats in lobbies, meeting rooms, the cafeteria, and other public places.
After testing various brands of lamps, reflectors, and ballasts, Sauselein decided to retrofit the majority of existing fluorescent fixtures with 32W T8 lamps and electronic ballasts (Photos 2 and 3). But as often found in retrofit work, all did not go smoothly.
[Photos 2 and 3 OMITTED]
For example, in one 40-year-old building, the existing two-lamp fixtures were found to be very inefficient, so new fixtures with the new system were scheduled to be installed. When refurbishing started, installers found that sprinkler piping above the ceiling made fixture replacement difficult. To simplify the work, Sauselein decided to keep the old fixture cans in place and retrofit the units with single-lamp inserts coated with a white metal powder finish, and acrylic plastic diffusers.
Light output of the new units is excellent due to the high efficiency reflectors and the color-rendering index of the new T8 lamps. Electric energy used by each fixture having the new single-lamp/electronic ballast system was reduced from 96W to about 32W. This results in a 67% reduction in power consumption while providing much better light output.
The total kW reduction obtained with this system at the facility is 1150kW. Considering usage per one eight-hr shift, the total saved is 9200kWh per day or about 2.3 million kWh per year (250 days per year). At 7 cents per kWh, the annual energy savings on lighting alone comes to more than $161,000. And this does not include demand reduction savings.
Another lighting retrofit project included the removal of more than 1400 75W incandescent PAR lamps from high-hat fixtures throughout the facility. These lamps were replaced with 13W compact fluorescent lamps, resulting in an approximate reduction of 86.8kW. Based on the same usage and cost criteria, the approximate savings is more than $12,000 yearly.
Additional savings accrue from the installation of two-level switching to control office lights and infrared occupancy sensors in rest rooms, storage areas, mechanical rooms, and other appropriate locations.
PE motors
Whenever a 25-hp or larger, frequently running, standard-efficiency motor burns out, it's usually replaced with a PE motor. Such motor replacements are carefully checked to be sure the application is appropriate for a PE motor and that payback will not exceed two years. In most instances, a utility rebate helps to defray the initial cost of the motor.
Most new large motors are specified to be of energy-efficient design where application is appropriate. For example, PE motors are installed on a cooling tower serving the facility's revamped cooling system. Ten 2-speed PE motors, each driving a cooling fan, are installed on the cooling tower roof (Photo 4). These motors, each rated 75 hp, 460V, have nominal efficiencies of 93.6 on high speed (1775 rpm) and 91.7 on low speed (885 rpm). The benefit of two speeds is noteworthy because this characteristic allows the system to run one or more motors at half speed when demand is reduced. This results in very large power savings because of the change-of-speed to energy-cubed relationship of variable torque loads. For example, when motor speed is reduced 50%, motor horsepower is reduced from 75 hp to 9.4 hp. This is calculated by cubing 0.5 (0.5 x 0.5 x 0.5 = 0.125) and then multiplying by the motor's horsepower (0.125 x 75=9.4 hp).
[Photo 4 OMITTED]
Numerous new PE motors are also installed in the new steam-driven chiller plant. These include eight 250 hp,460V vertical condenser water pump motors (Photo 5) that have efficiency ratings of 95.8 nominal and 93.4 guaranteed minimum. Also, seven 200 hp, 460V primary chilled-water system pump motors (Photo 6) have efficiency ratings of 96.2 nominal and 95.8 guaranteed minimum.
[Photo 5 and 6 OMITTED]
Other typical installations are at two of seven secondary chilled-water stations. One station uses three new 125-hp, 460V PE motors (Photo 7). An adjacent station has three motors each rated 50 hp. These have efficiencies of 95.4 nominal and 95.0 guaranteed minimum.
[Photo 7 OMITTED]
Most of the larger motors are controlled by solid-state starters so that redundant motors in the system can be operated in steps as per the plant operating plan as well as to assure maximum reliability. As a result, motors are started and stopped more frequently; thus a "soft-start" method was deemed to be best.
Variable-frequency drives
Some of these motors are powered by variable-frequency drives (VFDs), resulting in significant power savings when running at lower speeds because of the speed/cubic power relationship discussed earlier. These VFDs range in size from 80kVA drives powering 75 hp pump motors to 300kVA units. A typical VFD installed in a motor control center is shown in Photo 8.
[Photo 8 OMITTED]
Computer monitoring and control
Computerized control and monitoring of all systems is the responsibility of John Anderson, operations supervisor. He utilizes several computer software systems, some of which are developed in-house by a computer programmer while others are commercial systems modified to meet facility operation and energy-management requirements.
Computer operations are headquartered in a main control room (Photo 1) with satellite control functioning from two remote locations.
[Photo 1 OMITTED]
The most comprehensive program is a building-management system that monitors and controls the refrigeration/chiller plant systems, pumping stations, and electrical equipment and systems. Also, computer control is applied to the facility HACR (heating, air conditioning and refrigeration) system, which has many large motors and equipment that can be remotely monitored and controlled, providing significant energy savings.
There are two main computer control systems in the control room. The original system is a pen-touch, screen-based system, upgraded to a pen-and-mouse system. It presently has 10,000 points, upgradable to 27,000 points. This system monitors and controls motors, pumps, valves, dampers, and temperature levels throughout the HACR system. It also monitors security functions and controls lighting.
A newer windows-based system currently has 1500 points and controls a new chiller plant, including pumping stations. A software gate between the two systems allows for some redundancy.
Also, computers are used to monitor power on each of the 12 main 13kV feeders that supply 45 substations. This feature eventually will become part of a planned sub-metering system. In the future, excessive power usage can be identified and corrective action taken.
The computer monitoring and control is vital to the controlled reduction of power demand, resulting in significant savings both day-to-day and in a utility power-curtailment plan.
Demand limiting
Demand charges by the utility make up a substantial part of the monthly electric bill. A demand charge is what a utility charges a facility for the maximum power (kW) used for a particular period. At Bell Labs, this charge is based on the highest 15-min power-usage period occurring during the month between 8 a.m. and 8 p.m., Monday through Friday. Each month, a new demand charge is determined. The demand rate at Bell Labs is close to $10 per kW. For example, if on duly 20 between 2 p.m. and 2:15 p.m., the maximum power used (or demanded) from the utility is 15,000kW, and it's the highest for the month, the demand charge for that month would be $150,000. If during the following month on a particular day during a 15-min period, the demand is 17,000kW, the demand charge would be $170,000 for the month, and so on.
It's easy to see that a great amount of money can be saved by keeping energy demand down as much as possible. At the same time, it's essential that workers, particularly creative scientists and development engineers, not be disturbed. As a result, steps taken to reduce demand are very carefully analyzed to obtain the most benefit with the least disturbance.
The most effective procedure that results in the greatest demand reduction is the change-over of chillers from electric to steam-driven absorption. The facility's four electric chillers, each rated 2000 tons, are driven by 1400 hp, 4160V motors. Four units that remain steam-driver are 1500-ton absorption chillers and are dual source units that can be fueled by oil or gas. If the electric chillers can betaken off-line, demand is reduced by approximately 5200kW (based on .65kW per ton).
Also, computer monitoring and control of equipment and systems determines what is doing what, and allows selective removal of least-needed equipment.
Curtailment program with utility
The facility recently entered into a demand-curtailment agreement with the local utility. This plan was developed and implemented by Eugene Dimond, P.E., John Anderson, certified energy manager, and John Godown, shift supervisor. Typical loads that can be shed include motors that drive nonessential air-handler units, fans, pumps, or other noncritical loads. Lighting is turned off in selected areas. Also, base demand is "automatically" lowered by using higher efficiency equipment throughout the facility. In addition, the raising of air-temperatures in selected locations reduces operation of chiller equipment, greatly reducing demand.
The program requires that Bell Labs reduce demand at the utility's request in return for a rebate that ranges from $2 per kW to $25 per kW. The plan is in effect from June to September, not to exceed 25 days per year, on whatever day the utility needs a reduction in power. The dollar rate returned to Bell Labs depends on how much the facility is able to reduce load on those designated, high-demand days.
According to Eugene Dimond, the program results in a payment to Bell Labs that could be as much as $300,000 annually. An accompanying demand graph, on page 34, shows how demand is reduced and how the program works.