Four Steps to Achieving Active Energy Management

Oct. 1, 2009
The overall goal of an energy-efficient DC should be continuous improvement.

Energy efficiency can be an intimidating subject for managers of warehouses and distribution centers (DCs). In lieu of quantifiable data, most managers have an inkling that plenty could be done to increase their facility’s energy efficiency. After all, who hasn’t walked into an empty room and noticed the lights were on, or watched empty conveyors running endlessly? However, the constraints of available time and budget often make addressing energy usage challenging, particularly in trying economic times.

While there are many ways to improve an existing warehouse or DC’s energy efficiency instantly by varying degrees, the overall goal should be continuous improvement. That means energy efficiency should be viewed by facility managers as the end result of a strategic energy management plan. The most effective plans comprise four basic steps:

1. Measure energy use;
2. Fix the basics;
3. Automate where appropriate;
4. Monitor and control.

Carefully constructed, such a plan incorporates a keen understanding of ownership and management’s energy efficiency goals, including budgetary parameters and payback threshold, along with appropriate product solutions and technologies. In short, it will foster a mindset of ongoing energy planning and accountability while avoiding energy and cost savings erosion that will occur over time unless such a strategic plan is put in place.

Step 1: Measure Energy Use

Anyone who has gone on a diet can attest to the chagrin of getting on a scale and realizing it’s time to make healthier eating choices. Energy can be the same way. It can be shocking for managers of warehouses and DCs to realize the current state of their facility’s usage, which leads to the inevitable question of what to do.

Before doing anything, however, it’s critically important to establish an energy usage baseline because it can suggest the most effective course of action. Additionally, without a baseline, there will be no way to know later whether energy efficiency measures identified as part of a strategic energy management plan are working. Thus, the first step entails collecting data from major energy consumers and analyzing the impact of those consumers on total consumption. One of the most effective methods of accomplishing this is through power metering and monitoring.

Power meters are devices typically installed at various points within a facility’s power distribution system. The role of power meters is simply to record how much electricity is used on a circuit, which can provide a facility manager critical data about the areas within a facility that need to be addressed. Power monitoring is also effective because, in addition to metering electricity usage, these devices also measure power quality. Poor power quality, or power that’s rife with voltage sags and swells, can have a negative effect on facility components and contribute to substandard performance and unplanned downtime—a crucial issue for warehouses and DCs with deadlines to meet. Special software converts the raw usage data from power meters and monitors into historical data that can be studied to identify areas that require attention.

It’s also important to note that facility managers have the option to contact the local utility to schedule an energy audit when they realize energy usage and related costs have reached unacceptable levels. While an energy audit can provide a snapshot of the current state of a facility’s energy usage, unless it drives a strategic plan that is focused on continuous improvement, it will ultimately be of little value.

Step 2: Fix the Basics

When they realize that facility-wide energy usage requires attention, some warehouse and DC managers elect to address the easiest fixes first. This can include installing more energy-efficient lighting fixtures and luminaires, increasing insulation, or deploying power factor correction devices. While these tactics can translate into substantial savings, continuous energy improvement over the lifecycle of the facility and changing conditions should be the ultimate goal, which is best facilitated through automation and regulation.

Step 3: Automate Where Appropriate

The nature of warehouses and DCs requires facility managers to look at both the building envelope and its processes when planning and implementing a strategic energy management plan. The good news is there are automation options for both that create energy and cost savings that are more substantial than passive measures. Lighting control systems, for example, can automatically turn interior and exterior building lights on and off based on a pre-set schedule, instead of relying on personnel (including facility managers) to remember.

But perhaps the most crucial components for any warehouse or DC are motors. On the facility side, motors power everything from the pumps and fans for the facility’s water and HVAC systems, respectively, while on the process side, conveyors simply won’t run without them. Fortunately, automation technologies can adjust motor and energy usage, which can translate into significant savings.

For example, a conveyor system may turn on and off hundreds of times throughout a typical shift. Every time it starts, the current in-rush to the motor that powers the conveyor may spike at 2A before settling back to operational amperage of 1A. However, application of a variable frequency drive or an electronic soft starter can limit that current spike to perhaps 1.2A. Significant savings can be realized when that action is compounded over time with all motors that power processes within a facility. On the facility side, deploying variable frequency drives to slow down motors in conjunction with dampers to alter the building’s airflow can significantly increase the energy efficiency of an HVAC system.

Sometimes, automation can be used to change habits in a warehouse or DC. Consider the fact that many facilities have begun using lift trucks with AC motor technology; obviously, the batteries that power those vehicles must be charged. Deciding to do so when the local utility is facing peak demand will drive up energy costs, so an appropriate solution could be using a remotely operated circuit breaker to prevent charging. The combination of a programmable logic controller (PLC) and a human-machine interface (HMI) could also be used to remind the operator about appropriate charging times later in the shift (when peak demand has passed). Red and green stack lights could also be used as visual cues.

These measures facilitate an active approach to energy management because they can be adjusted based on new energy efficiency opportunities that arise in the future. One recent example is demand response, a scenario where a facility owner or manager signs an agreement with the local utility to receive a signal from the utility when electrical rates reach a preset ceiling.

Step 4: Control

A strategic energy management plan helps ensure energy and cost savings don’t erode over time. Power meter installations, monitoring services, energy efficiency analysis and energy bill verfication can all help achieve this end, but one of the most effective ways is through an enterprise energy management (EEM) system, a tool that delivers business intelligence to company stakeholders, including employees, investors and customers.

An EEM system can be especially effective in a warehouse or DC because it can track all forms of energy usage (water, compressed air, gas and steam, in addition to electricity). Additionally, many EEM systems can model energy efficiency, allowing users to normalize energy consumption based on various drivers, including volume of products being handled or outside air temperature, among others. EEM systems can also benchmark facilities against each other, so best practices can be identified and shared with underperforming facilities. A system could also be used to model one utility rate against another, or quantify payback on energy efficiency measures that are implemented.

Components like electronic motor starters have become robust enough to facilitate the flow of energy information that can lead to not only critical energy decision making, but also predictive maintenance. For example, a motor starter can monitor how much power each of a motor’s phases are using; if one phase becomes unbalanced, that information can be sent to the facility’s energy management or supervisory control and data acquisition (SCADA) system via PLC, which can calculate how much power is being used. If a motor is using more power than anticipated, it could mean that the motor is simply dirty and needs to be cleaned.

Making the Decision

A strategic energy management plan should address both short-term improvements as well as future strategies to implement as energy prices fluctuate. A well considered plan should have clear actions in mind and reflect good decisions that can be somewhat independent of current energy prices.

Most of all, a strategic energy management plan should be realistic, and the best way to ensure that is to have a strong understanding of a facility ownership’s return on investment tolerance. If ownership demands a one-year payback on energy management technologies, the plan will look much different than if a three-year payback is acceptable. Having this information in hand during the initial research phase can help resources better assist in plan development. Appropriate resources can include industry associations, like the Material Handling Industry of America, the local utility and suppliers of the full gamut of energy management technologies.

David Voynow is market segment manager for material handling in the North American operating division of Schneider Electric, a global specialist in energy management.

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