Nissan Plant Reduced Energy Expenditure 30% With Daily Power-Down Regimen

Reducing energy consumption by using programmable logic or automation controllers.

Abstract

Industrial Energy Management: Accumulation Chain Conveyors, Overhead Lighting, And Compressed Air Are Among Areas Addressed.

What industries would find this most relevant?

Automotive or transportation

Consulting, business, or technical services

Electrical equipment

Which of your engineering specialties does this project best illustrate?

Automated assembly

Installation and start-up

Robotics

Describe the nature and scope of the project in greater detail

In the manufacturing environment, manual processes used to stop and restart equipment can be costly due to manpower demands. The energy cost of keeping equipment running continuously may be less than that of paying employees for a daily power-down regimen. But given rising energy costs, it’s hardly an ideal solution.

Depending on the amount and nature of the equipment installed in a facility, an automated solution may be the most economically viable one. Fortunately, the modern manufacturing environment has the luxury of using many of the original “smart home devices,” with programmable logic or automation controllers (PLC or PAC).

With some creativity and a slight change in a company’s mindset, any manufacturing plant can become an energy efficient facility using minimal resources to accomplish the task. Once an energy program begins, and the benefits are realized, the savings can be used as investments to fund future projects.

PLCs are now standard on most major pieces of equipment purchased for modern manufacturing, and they provide almost infinite flexibility for modifying equipment operations. These devices are instrumental as a foundation for an automated energy reduction effort.

In fact, without purchasing a single additional component, PLCs in existing equipment panels can be used to immediately generate cost savings. Using existing inputs on machinery for monitoring the equipments’ primary function, the absence of machine or operator movement can also be monitored. If no movement is detected for a predetermined amount of time, select processes can be stopped in a controlled manner, and utility savings will begin to accumulate.

Step by step:

The first step in any plant’s energy-savings development plan should be to identify the energy consumers that can be idled during non-production times without causing quality, production, or safety concerns. Many different motors, heaters, lights, and compressed air lines are energized continuously in a typical plant. Each hour a component runs without producing product is money spent in the form of utility usage that has no added value. Yearly utility budgets can be adversely affected by this wasted energy use.

Not long ago, the Nissan manufacturing plant in Smyrna, Tennessee (NNA-S) was faced with the challenge of reducing energy consumption without taking on additional resources. The 25-year old plant consumed virtually the same amount of utilities during an idled state as it did at full production. After implementing countermeasures, the Smyrna plant was able to eliminate energy consumption by over 30 percent. The plant later was named a 2010 and 2011 Energy Star Partner of the Year by the U.S Environmental Protection Agency. Although many opportunities for energy efficiency existed, the most conspicuous areas of impact were the accumulation chain conveyors, overhead lighting, and compressed air services.

Miles of conveyors ran day and night, regardless of production hours. After some planning, key inputs were identified to monitor movement throughout the chain systems using a timer for each chain motor. If one of the switches on the conveyor is made, the timer resets and begins the timing process again. If the timer exceeds the defined preset value, the conveyor motor is stopped.

Each of these conveyors supplies product to a production line. When the manufacturing line begins to run production, and the supply conveyor is in a no-activity shutdown state, an alarm sounds and the conveyor restarts. This practice was developed as a standard logic routine and replicated throughout the plant. In fact, any machine that was equipped with a PLC and inputs had a version of the standard program implemented.

Looking at lighting:

Automated lighting shutdown was the next step in energy reduction strategy. Several products are currently on the market that will work with an equipment PLC to automatically turn off select lighting. Circuit breaker manufacturers have lighting panel solutions that receive inputs to monitor the running state of equipment. The task-lighting panels in the plant were changed to the smart panels, and the task lighting was automatically shut down several minutes after production had stopped for breaks and lunches. This alone produced an immediate and dependable reduction in electrical consumption.

The Body Assembly department at NNA-S also implemented a very creative automatic light reduction program. The overhead lighting was automatically shut down over robot cells when safety fences were active because robots do not need light to work. The lights automatically turn on for operators when set-up or maintenance is performed.

Although conveyors and lighting were the first areas modified because of their visibility, compressed air is also a large electrical consumer that is often overlooked.

Compressed air is one of the most inefficient energy sources in any facility. Pneumatic devices need a constant supply of compressed air to maintain a load. Most industrial compressors are very large and consume many kilowatts, especially in large facilities that have expansive air line systems. The larger the system, the larger the compressor’s electrical load. Larger systems also provide more potential for air leaks that further compound the problem.

Fortunately, automatically reducing pneumatic supply is a very simple solution. An electrically actuated ball valve can be placed in any pneumatic supply line. Using a version of the standard shutdown logic implemented on the conveyors, inputs can be monitored, and the valve can be turned off during non-production times. All compressed air consumption is immediately stopped. When a pneumatic supply is eliminated, compressor load is reduced, which ultimately saves kilowatt hours and money.

Conclusion:

At first, the task of plant-wide energy reduction may seem overwhelming and could meet much initial resistance. However, using machinery PLCs, inputs and outputs already installed, a viable energy reduction program can be implemented without expending many additional resources.

Once the benefits become apparent, creativity and imagination are the only limiting factors on how far an automated utility conversation program can go. As long as safety considerations are met, any machine can be stopped in a controlled manner to provide long-term maintenance benefits, create a quieter factory, produce an environmental performance improvement, and ultimately, a significantly lower utility budget.