A strategic approach to energy management

Fabio Mielli.

What’s the most common challenge faced by mining companies today when embarking on a mission to reduce their use of electrical energy? They don’t have sufficient information to accurately forecast energy use or to make decisions that would help them reduce their consumption.

It’s a significant problem – and a significant opportunity if the right measures can be put into place. In the US for example, although fossil fuels represent the largest portion of a mine’s total energy use at 35%, it is followed very closely by electricity at 32%. According to a study by the US Department of Energy,¹ the two types of electrical systems that offer the greatest potential for reducing energy use in the coal mining industry are grinding and ventilation. That’s because both have inherent complexity, which is difficult to optimise, and they usually work at close to full capacity.

From such studies, it can be noticed that in addition to the savings achieved directly via improvements in equipment efficiency, there are significant energy savings to be gained by implementing energy management and energy integration strategies. But these strategies are difficult, if not impossible, to achieve without accurate energy information, which can be identified under one of the three following categories:

• There is no information available at all, or it is managed manually and not made available to everyone who needs it.
• Information is not granular enough and there is insufficient power information for the entire facility.
• Energy data is not linked to the process with which it is associated or provided in context with how it was used.

Fortunately, there are a number of technologies that can deliver actionable energy data so it can be used as part of a systematic strategy to reduce electrical energy usage.

Energy strategy and lifecycle

The first step in taking control of energy management is to start with a strategy. Without a strategic plan and roadmap, most actions can only bring short-term results.

Also, it’s important to note that an energy programme is an ongoing cycle where actions are routinely re- evaluated and fine-tuned against desired objectives.

Passive vs active energy management

Some strategies employ passive solutions such as installing high efficiency devices or using passive power factor correction. In these cases most actions are associated with systems that use less energy due to the nature of their design. On the other hand, active energy management uses strategies, such as motor controls, ventilation controls or process optimisation, that require constant monitoring and intervention to achieve the best results.

Energy management/production systems

Energy systems are great tools to get energy information about some loads, but most of them lack the capability to connect energy consumption with process or mine information. Energy management systems tied directly to mine production systems, for example, are able to provide consumption data within a more meaningful context, such as:

• Real-time energy consumption.
• Energy consumption forecasting based on specific parameters.
• Establishing optimal energy consumption targets for each mine area.
• Identifying and quantifying consumption above targets.
• Identifying and analysing root causes of over-consumption.
• Reporting of over-consumption and changes in daily consumption.
• Understanding energy drivers such as process variables linked to energy consumption.
• Real-time calculation of sustainability Key Performance Indicators, such as kWh/t.
• Providing validated data to justify future capital investments and/or process changes.
• Creating energy models to forecast energy consumption and to determine energy targets.

Smart meters

Smart meters are at the core of an energy efficiency strategy because they are able to deliver rich information from critical mine loads. These include voltage, current, neutral and earth current, power, frequency, power factor, demand, energy, time-of-use metering, and harmonics.

Smart mining breakers

Another way to obtain actionable energy data is smart mining breakers. Besides their typical protection capabilities and robustness for harsh coal mine environments (like trailing cable protects), these breakers are able to deliver energy information thanks to integrated meters:

• kWh meters helps optimise costs and their allocation.
• Harmonic distortion rates show the quality of the electrical supply.
• Alarm notifications help secure operational control and maintenance planning.
• Continuously activated event logs and tables ensure equipment operates correctly, thus maximising energy efficiency.

Advanced breaker trip units can provide different levels of functionality. The simplest units provide basic overcorrect protection, including long-time, instantaneous and optional short-time adjustments for overloads and short circuits. Advanced units offer sophisticated functions, such as ground fault protection and zone selective interlocking.

Power quality and reliability

Mine power systems can be vulnerable to power quality problems. Poor power quality can come from the utility or be caused by equipment within the mine. Either way, it can affect production – tripping breakers, shutting down equipment, degrading motor performance or causing damage to sensitive devices.

The most common method for electrical network reliability is measuring the total number of outages and the duration of those outages over a specified time. This information is used for fault analysis to help improve reliability. The data is then used to identify root causes and to proactively avoid potential faults. Pre-fault and post-fault analyses are both effective ways to improve the reliability of power quality and the distribution network.

Sophisticated power quality monitoring and reporting provides the information needed to validate compliance, improve system stability, and minimise unplanned downtime. Such systems help track and investigate frequency stability, voltage variations, imbalances, harmonics and other conditions to maintain a high level of power quality and to resolve issues before a problem develops.

Conclusion

Ongoing, strategic actions and new technologies can significantly contribute to the energy optimisation, quality and savings in mining operations. It is also important to choose a trusted engineering partner with proven energy consulting experience. Properly integrating the right tactics with the right partner can help optimise energy consumption throughout the mine’s entire lifecycle and improve safety, productivity and cost efficiency, as well as reducing its environmental impact.

Note

1. BCS Inc., Mining Industry Energy Bandwidth Study (US DoE Industrial Technologies Program; June 2007).

Edited by Jonathan Rowland.

About the author: Fabio Mielli is the Mining Offer Manager at Schneider Electric.

Read the article online at: https://www.worldcoal.com/mining/18082015/a-strategic-approach-to-energy-management-2749/