With energy savings, there’s intent and then there’s plan. Industrial facilities in the United States show a sustained interest in energy management. That’s the intent: Reduce overall energy usage or sustain usage but increase the amount produced per kW used.
The plan? Sometimes that’s a problem.
In manufacturing, a plan will only stick if it has both the wisdom of experience guiding the vision and the ROI numbers to back up the effort. But in energy, there just isn’t the body of research out there for an industrial plant manager to use to set baselines for what “reasonable” energy usage looks like in a manufacturing facility. So, how to assess what portion of current energy usage is reasonable and what is wasteful, or of that wasteful portion, what provides high enough ROI to address?
The ROI under discussion here is the cost per kWh as charged by the utility. Those units carry a different rate depending on time of day and year. Reducing that expense is the savings. The investment is the materials and labor required to change energy consumption. The return is the period of time it takes for the reduced utility bill to pay for the investment. The gravy comes after the expense is paid off.
Returning to the issue of the plan, how then to draw up an ROI estimate when there is no industry standard for reasonable energy usage?
Profiling industrial energy usage
Industrial energy usage varies based on multiple variables:
load type and size
operational schedule, both hours per week and intensity of loading
number of workers
The answer is: Don’t try to manage every kW consumed by your facility. This is the “wisdom of experience” part of the equation. Divide the facility into the electrical infrastructure and then key systems.
Energy savings start with two basic tactics:
(1) general inspection of key systems and
(2) targeted data gathering, including logging energy usage at the main service entrances and at the key loads.
Identify how much a system is specified to consume, determine how much it is currently consuming, and identify wasteful practices, either in the hours and type of operation, or in the equipment and system itself. To achieve the savings, the facility must address the waste, either by changes in operation, in maintenance, or in equipment and controls.
Before we explain how to trace energy consumption, let’s revisit how we define and measure energy.