Electric power is expensive, often unreliable, and sometimes dirty. Using too much power, losing power, or running on unclean power can adversely affect the operation of your plant. Accordingly, several companies serving our industry are more than happy to sell you hardware, software, and energy management services that will analyze and optimize your power consumption.
Frank Hein, principal engineer at Abbott Laboratories, North Chicago, Ill., has installed an advanced energy optimization system from Pavilion. "With all elements of the program in place, Abbott expects to save at least $273,000 per year, based on the current production rate," he says.
However, as Bela Liptak says, before you can control something, you have to measure it. Here's how and why to make power measurements (Figure 1) and do your own analysis and optimization. As we can see from Abbott's results, the payoff can be enormous.
Problems With Power
Electric power is expensive. "Manufacturing plants consume the most electricity in the United States, totaling more than $3.3 billion per year," says Dick Eshelman, vice president of engineering solutions at Rockwell Automation. "From downtime due to dirty power to avoiding peak demand charges, reducing energy-related expenses starts by understanding when, where, and how much energy is being consumed, and turning that knowledge into results."
Demand charges can be substantial. Although they vary from utility to utility, essentially the utility determines how much power your plant needs, sizes its substations accordingly, and then hits you with a significant surcharge (the peak demand rate) if you use too much power at any point in time. Exceed the peak demand rate one time in a month, and you get charged for it.
Therefore, the first energy monitoring program most plants install is a load-shedding system that measures and tracks electrical power consumption on a real-time basis. The system uses the same technique as the utility does to calculate peak demand, and sheds loads (turns off systems) to keep from exceeding the critical demand level.
If you do not understand your utility's tariff structure, it might be a good idea to get a copy of the rules and see how your energy bills are calculated.
Utilities are beginning to have problems delivering power, say market researchers at Frost & Sullivan. "Insufficient power infrastructure and the growing load on energy utilities are driving the end user market to uninterruptible power supply (UPS) systems. In the absence of clean and consistent power, UPS systems are needed to decrease downtime and protect sensitive equipment," says analyst Farah Saeed.
Is your incoming power clean and consistent? If not, it could cause severe problems. Richard Brown, engineer at ABB, says voltage sags and interruptions can cause havoc in a manufacturing line. He provides this list of potential problems for people in the semiconductor industry:
- A 20 msec. voltage sag to 65% will cause electronic controllers to crash.
- A 200 msec. voltage sag to 50% will cause an entire process to crash.
- An interruption lasting several minutes can cause problems with air and water filtration systems.
- Longer interruptions can affect critical temperature and humidity tolerances in a process.
"Because of the high economic cost of power quality disturbances, many sensitive facilities are beginning to ask electric utilities to guarantee levels of reliability in their energy contracts," says Brown. "Although not widespread at this time, such guarantees are already in effect for several car manufacturing facilities in Michigan. If a factory experiences a power quality disturbance that disturbs the production process, it receives a large credit on its energy bill."
California companies faced electric supply problems every day in 2001, as the energy crisis there reached epidemic proportions. At Cargill's salt plant in Newark, Calif., interruptions in the power supply caused production delays, leading some longtime customers to switch to alternate suppliers. "Our electricity costs doubled here, even with the incredible energy conservation measures we put in," says Lori Johnson, public affairs manager at Cargill Salt.
You need to monitor your incoming electric power to see if you have problems, avoid demand charges, decide what kind of protective and backup equipment to install, and catch your utility with its electric pants down.
Mike Powell, president of eLutions, says his company's EP Web monitoring and control software was installed in a chocolate manufacturing plant and quickly uncovered a severe problem during training. "The client's energy manager discovered a utility feed that had a 1 MW variance when compared to the other two feeds," Powell explains.