Energy Eficiency

Can process automation increase energy efficiency?

06.01.2013 | Bonavita, N., ABB, Genova, Italy

Energy efficiency doesn’t imply producing less to reduce energy consumptions, but rather improving plant productivity and effectiveness, allowing plants to produce the same amount of product with fewer resources.

Keywords: [control system] [automation] [process control] [spare parts] [legacy systems]

Energy efficiency is a fundamental element in the journey toward a sustainable energy future. As global energy demand continues to grow to meet the needs and aspirations of people across the globe, actions to increase energy efficiency are essential.

Optimizing energy utilization is of paramount importance in the industrial sector. Energy efficiency doesn’t imply producing less to reduce energy consumptions, but rather improving plant productivity and effectiveness, allowing plants to produce the same amount of product with fewer resources.

Therefore, in industry more than anywhere else, energy efficiency has heavy implications (and brings large promises) on both profitability and sustainability. From a profitability perspective, energy represents the most relevant operating expenses in many industrial productions; an effective usage of energy represents an attractive, low-hanging fruit in any cost-reduction-oriented policy.

However big the impact on the bottom line, the outcomes of energy efficiency programs extend beyond accounting books. The last decades have seen environmental regulations grow stronger. Being in compliance with environmental regulations is by no means a secondary concern for any production site; rather, it is a basic requirement to operate and succeed. Energy efficiency is a technology-driven, politically neutral practice that should be viewed as the main sustainability enabler in the industrial world.

Performance improvements

Heavy industry (manufacturing) is the single largest energy consuming sector in the world. Looking at US data, in 2008 it represented over 30% of total energy consumption with about 30 QBtus.

Taking the US as a reference, it is possible to see that process industries like oil and gas, mining, pulp and paper, and chemicals are the most energy-intensive (Fig. 1). This means that no serious energy efficiency program can be designed and deployed without taking into consideration actions in the process/manufacturing industries sector.

Fig. 1. Industrial energy intensity vs.

energy consumption.

The industrial community has understandably focused on improving energy efficiency mainly in electrical components and equipment, which is basically low-hanging fruit in the quest to quickly reduce energy costs. When looking at energy savings per year, as estimated by the International Energy Agency (Fig. 2), it should be noted that, although motor systems provide the highest potential savings contribution with about 7 exajoule (1 exajoule is equal to the yearly production of 47 660-MW power plants), the sum of other items (from combined heat and power to steam systems, from process integration to increased recycling) is bigger than that, with a sum of about 8.5 to 9 exajoule.

Fig. 2. Savings from the adoption of best

practices in commercial technologies for

the manufacturing industries.

Process automation can contribute to improving the energy efficiency of industrial production plants in many ways. Implementing better monitoring, control and optimization strategies improves energy performance directly, through reduced waste (very often associated with undue oscillations in main process parameters), and indirectly, through better maintenance practices that help to prevent an increase in energy use due to plant downtime and the resulting startup and shutdown processes, as well as defective products.

With energy consumption emerging as a top priority for process and plant managers, much room for improvement is available, providing opportunities for advanced automation suppliers. In fact only a minority of process plants have proper energy monitoring tools, able to provide real-time energy-related key performance indicators (KPIs) to control room operators, and even less benefit from advanced process control (APC) strategies able to reduce waste and consumption.

Determine ideal conditions

A modern industrial plant is an extremely complex system that can be run over an almost innumerable range of operating conditions, each characterized by specific energy consumption. Achieving optimum efficiency is the dream of every plant manager. This dream is a never-ending pursuit to be continuously executed and monitored, using reliable real-time process data.

Determining and maintaining ideal operating conditions is a key challenge that requires the involvement of the latest automation technologies, each one contributing to allow not only the acquisition, processing, storage, retrieval and visualization of data, but also the implementation of automatic control strategies that can expand the achievement envelope in terms of production, safety and energy efficiency. The challenge extends beyond technology, involving also organizational and even psychological aspects that actually impact and limit production and energy efficiency.

One such aspect is related to an underlying and unexpressed conflict of interest between plant managers and plant operators. Given the many risks involved in industrial plants, it is natural that a plant operator seeks to preserve a safety margin from the danger zone (safety, economic and environmental). And it is quite normal that the operator is inclined to overestimate this safety margin’s size, placing the operating point centrally in a comfort zone. Fig. 3 represents this tendency in the case of an operator summoned to control a distillation column with multiple constraints. The obvious behavior will be to operate the plant by keeping a reasonable margin (the orange area in Fig. 3) from the limits, even if this means operating considerably away from the economic optimum. The fewer the details available, the bigger the operator’s comfort zone extension will become.

Fig. 3. Operator’s comfort zone in

standard conditions.

Exploiting advanced automation technologies, it is possible to

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