Measure energy consumption to know how to reduce it

In this installment of What Works, industrial energy consumption reduction starts with measurement.

Energy costs were high on the agenda for automotive component- and system-maker Inergy Automotive Systems when, in 2008, the company launched a program to optimize and reduce its energy consumption as part of the sustainable development policy within the group. Inergy is a global company that develops and manufactures fuel systems and in particular, advanced plastic fuel tanks. Inergy Automotive Systems was founded in 2000 as a joint venture combining the plastic fuel systems operations of Plastic Omnium and Solvay S.A. Today, the company is a Tier 1 supplier of plastic fuel systems to car manufacturers.

Headquartered in Paris, Inergy employs approximately 4,000 people worldwide and operates 24 manufacturing facilities in 18 countries. In 2009, Inergy manufactured 9 million fuel systems to car manufacturers.

Not all of the discoveries were associated with the detail of the manufacturing process; normal commercial-building systems are just as effective at wasting energy.

The project, Inergy Energy Consumption Optimization (INeco), was developed to improve energy efficiency in the context of the group’s total usage of around 228,000 Megawatt-hours of electricity. Almost all of the company’s energy input is electricity, which is approximately the same amount of power that a European town of 60,000 people would use. An early step was to put in place a series of energy audits for the major manufacturing processes in use at Inergy’s plants, beginning with the facility at Pfastatt, France.

The first audit, in 2009, had the objective of gathering detailed information about the energy consumption over a period of three weeks, analyzing the data and using the results as the basis of action plans. Naturally, each plant had electricity metering at the level of input from the grid for billing purposes, but required a sub-metering system to gather instantaneous current data at the level of individual machines and processes. The project’s nature demanded a temporary setup for an energy audit in an existing factory; therefore, it had to be easy and fast to install and uninstall.

Installing the monitors

A traditional cabled solution was initially considered, but this proved too difficult and expensive to install for such a short period. There were few plug-and-play measurement solutions available, and the only realistic candidate that emerged was LEM’s Wi-LEM, wireless local energy meter. Wi-LEM’s energy meter nodes are current transducers that feature split cores; they can be clamped around a conductor with no need to disconnect anything for the purposes of installing continuous-loop sensors or in-line current sensors. They gave Inergy the freedom to install the measurement node at the most convenient access point in each power cabinet and required no downtime. The systems’ measurement nodes exceed the demands of the IEC 62053-21 standard for accuracy in energy measurements, achieving 1% accuracy or better.

The LEM wireless energy monitors are portable enough for short-term projects, and a mesh-network configuration can produce points of redundancy that are self-organizing.
The LEM wireless energy monitors are portable enough for short-term projects, and a mesh-network configuration can produce points of redundancy that are self-organizing. Source: LEM

The wireless part of the Wi-LEM designation refers to its transmission of data by a wireless mesh network. Wireless operation means no cabling is required in any of the temporary deployments, and the mesh network between measurement nodes and the central data collection point is self-organizing. Cable-free installation does not mean that the system can only be used for temporary installations. Many users will want to follow up a detailed energy-use survey by installing long-term monitors at key nodes to ensure that savings are maintained, and that wasteful usage patterns do not re-establish themselves. In keeping with the latest practices in factory-data-collection system installation, robust wireless mesh networking is also ideal for long-term use. “The system is really fast and straightforward to install, and the mobile solution was important for us,” says Joseph Brossard, Inergy’s utilities and energy saving leader, who also is one of the managers of the INeco project.

In September 2009, the first Wi-LEM temporary network of 40 measurement points was deployed in the Pfastatt facility. The Wi-LEM was installed using a three-phase delta configuration with a measurement range of up to 2,000 A. These transducer nodes use LEM’s Rogowski coils, which feature a perfect loop technology with no discontinuity coil clasp. Measurement frequency for this exercise was set at 240 current values per day for the three weeks, yielding a substantial volume of data — more than 200,000 instantaneous current values. The Inergy team then designed a strategy to extract the maximum information and value from that data set. A first, precautionary step was to apply a quick “sanity check” on the data. The cumulative current measurements converted to power consumed ought to correspond to the amount billed by the utility supplier. The figures agreed within 3%. Reassured the data was sound, the team went on to the analysis phase of the project.

Analyzing the data

Collected data was placed in a single large database that also contained minute-by-minute information on the processes in the plant — which systems were in use, which product was being manufactured — at every moment corresponding to the current data points. Fuel tank manufacturing at Inergy is based on a blow-molding process; some of the energy-intensive aspects include heating of molding material, supply of compressed air and cooling after molding. Analysis of the data revealed that the blow-molding machines account for 45% or the company’s total energy usage: before the audit, the exact value hadn’t been known. Compressors that deliver the 13-bar pressures needed for the molding consume large amounts of energy, and the analysis showed that much of that energy was wasted by air leakage. Energy consumption measured on the chilled water process — chillers and pumps — has been compared to theoretical energy consumption. The resulting measures to optimize performance following this discovery led to discussions with equipment suppliers on how their machines could reduce energy usage. Not all of the discoveries were associated with the detail of the manufacturing process; normal commercial-building systems are just as effective at wasting energy, if not properly managed. Figures from the database showed Inergy that some of its HVAC and lighting systems were set to run continuously, irrespective of whether the areas they served were staffed or needed controlled conditions.

After completion of the Pfastatt audit, the portable nature of the Wi-LEM units proved their worth by being removed from the first site and reinstalled in two successive audits at Inergy plants in Anderson, South Carolina, and Ramos, Mexico. The initial experience with the Wi-LEM local energy meters was repeated. The team also found that the radio signal range of the wireless network was more than sufficient and even in the electrically noisy industrial environment there were no problems with the data transmission. The aggregated data led to the conclusion that substantial energy-cost savings of around 15% are possible.

Inergy plans to audit six more of its sites in 2010 and to complete a company-wide program, leading to an action plan with investment allocated where it is shown to be needed. Already, however, the INeco plan can demonstrate savings that amount to millions of euros from the three audits.

“The benefits of energy submetering are clear,” explains Broussard. “You can only manage what you measure. The Wi-LEM local energy meter has been crucial to what we have achieved so far. We will be offering our sites Wi-LEM kits to allow them to measure and manage their energy consumption after the initial audits and follow up on their progress.”

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