While we’ve seen many examples of good practices in energy saving and efficiency initiatives and hear much discussion about the merits of energy management systems (EMS), energy management currently lacks a formal framework that integrates the supply chain and plant life cycle issues with manufacturing operations and business functions.
For example, while advanced control and real-time process optimization solutions often include energy consumption as variables for optimisation, if the process units themselves were not designed to optimise energy efficiency, much opportunity for saving energy is lost.
Furthermore, automation suppliers are just now beginning to explore the potential energy savings that can be realised by integrating plant electrical control and process control systems.
And enterprise solution suppliers have only recently begun to explore how their production management and enterprise asset management (EAM) solutions can be extended to help users measure and manage energy consumption.
As a result, energy management and energy efficiency initiatives are often incomplete and insufficiently coordinated. This can be very costly for manufacturers, and will only increase as both energy costs and costs associated with carbon emissions rise.
Here, we’ll explore briefly several different dimensions of energy management as they map against ARC Advisory Group’s three-dimensional, Collaborative Manufacturing Model (CMM) shown below.
Status quo of energy management in manufacturing
According to an ongoing ARC survey, many end users have implemented "homegrown" EMS solutions. Clearly, compared to commercial solutions based on industry standards, homegrown solutions tend to be more costly (if not impossible) to support over time. Not surprisingly, most homegrown solutions never grow beyond being point solutions.
This situation is regrettable because energy is the second largest expense for industry and end users end up paying too much for their often-ineffective homegrown solutions.
While many users in the discrete manufacturing industries have only just recently started to look closely at their energy bills, users in the energy-intensive process industries have been scrutinising their energy costs for several decades.
Most energy-intensive operations experience considerable variability in energy consumption due to changing operating conditions, equipment degradation, fluctuating market demand, and inefficient control strategies.
As a result, plants typically use more energy than necessary, yet are unable to improve efficiency because they lack real-time performance information.
Energy management along the supply chain axis
Comprehensive energy management involves both sourcing and logistics. From a sourcing point of view, many companies now buy "green" and use Energy Star and other labels as a reference point for consumers. Sourcing raw materials also includes purchasing electricity and fuel.
Whether they purchase or generate their own electricity and/or process steam, manufacturers need to balance short-term, mid-term, and long-term supply and demand to optimise energy consumption.
The short term relates to optimisation of the process, varying from real-time to horizons of a few hours. The middle term relates to taking production fluctuations and small equipment changes into account, while the long term relates to large fluctuations, such as created by plant revamps.
Energy management along the life cycle axis
The ultimate energy efficiency of the production and energy generation processes begins with conceptual equipment and process design. Heat recovery and heat integration at the equipment-, plant-, and site-wide levels should be taken into account, along with product packaging and recycling.
Energy-efficient equipment, such as variable speed drives and more efficient pumps and motors, plus more efficient lighting and HVAC in the production areas, can reduce energy consumption to a significant degree over the long-term plant life cycle.
The trend in the process industries is toward high-yield, combined heat and power generation plants and the highly energy efficient production processes.
In discrete and hybrid industries, rising energy prices also put pressure on variable costs and lead to new product designs that incorporate alternative raw materials that are less energy-intensive, or demand a less energy-intensive production process.
Energy management along the business/automation axis
The most diverse and challenging aspects of energy management are in the business domain and in production execution. In the business domain, strategies are defined for global energy management. Here, EMS implementation depends on corporate long-term investment decisions, ideally made in collaboration with plant management.
In daily operations, energy usage should be monitored and, for complex processes, optimised in close to real time. In this domain, process operations and control are intimately connected.
Most energy-intensive operations, such as those found in a refinery or chemical plant, experience considerable variability in the consumption of energy due to changing operating conditions, equipment degradation, fluctuating market conditions, plus poorly tuned control loops, inappropriate control strategies and/or lack of process optimisation.
When real-time information is not available, or if control applications are not easily maintainable or adaptable, plants use more energy than necessary.
At the automation level, EMS remains a work in progress. Using PLCs to control power in individual energy-consuming devices, such as electric motors, is still in its infancy.
At the enterprise or production management level, several suppliers offer solutions that enable manufacturers to measure and monitor energy consumption in a real-time manner using real-time and other data collected from control and asset management systems.
An adaptive framework needed
The different domains are intimately related: demand and supply balancing intersect with process life cycle improvements and maintenance. Efficient processes are more complex and require more complex control solutions.
Investments in these solutions are costly and must be coordinated with longer-term initiatives. Excellent short-term process optimisation and energy management practices exist, but these may lack coordination with initiatives in other domains and on long-term time scales.
Users need an adaptive implementation framework for energy management that coordinates initiatives in different domains across different time scales, with a strategy, a management system and competence centres for sharing best practices.