Energy efficient plant of the future

By 2020, process plants will consume much less energy than their present-day equivalents, thanks to much greater use of automation, as well as intelligent systems and devices in areas, including pumps, compressors and heat exchangers.

This is the dominant opinion among leading end users and suppliers in the process industries about how rising energy costs and related regulatory pressures are likely to shape process facilities over the next decade.

Perhaps the most important reference point for such trends is the Hannover Messe, whose partner organisation, the German Electrical and Electronic Manufacturers’ Association (ZVEI), tracks the impact of energy costs on the market for process automation technologies.

Prof Reinhard Hüppe, executive vice-president industry, and managing director, automation division, at ZVEI, estimates that energy consumption accounts for around 20% of the manufacturing costs in complex chemical plants, rising up to 50% in some instances in the metal industries, such as for the production of steel, copper and aluminium.

Structured analysis
In Germany alone, Hüppe reckons that better use of process automation could help companies save around 50 billion kWh of energy equivalent a year from electricity and primary energy sources such as coal, oil and gas - around 10 billion kWh from electricity, with greater impact from primary energy sources translating to a further 40 billion kWh of electricity.

Achieving such savings by 2020, however, will require greater consistency in the use of process automation. This, said Hüppe, should be based on a structured analysis, which differentiates between measures focused on the technical infrastructure of the production process and those that optimise the production process itself.

“All production-related processes and procedures must be configured to optimise energy use to harness this potential,” he added. “The technical capabilities already exist, but must be put to better use.”

Energy costs will also force changes in pump technologies over the next 10 years. Pumps account for 20-25% of the energy consumed in the process sector. Estimates also show that pump-system operators, again in Germany alone, could save 14 billion kWh per year - or €1.12 billion - through better use of technology.

Christoph Pauly, a spokesman for pumps manufacturer KSB, therefore, foresees much wider availability and use of pump-selection software, matching impeller diameter to actual operating conditions, and variable-speed pump sets, as well as extremely energy-efficient motors.

“Hydraulic optimisation of a planned system begins with correct pump selection in order to avoid the common mistake of over-sizing,” explains Pauly. “In this context, pump selection software allows the user to gain access to expert know-how: pump systems can be designed and selected according to commercial or technical parameters.”

The KSB spokesman, however, identifies pump speed control as offering the most potential savings: “What is perfectly normal in other areas - matching power input to actual demand - is still far from standard practice in many branches of industry.”

A detailed analysis of a pump’s operating behaviour often reveals that it is not running in its optimum energy-efficient mode. This, said Pauly, is often because it is being operated at off-design conditions, due either to system over-sizing or normal temporary variations in flow rate arising from system processes.

“If power input is not adjusted to demand via some form of system control, valuable energy is wasted,” Pauly said. “In the case of closed-circuit systems, energy savings of up to 60% can be achieved, depending on load profile.”

Major energy savings are also likely to be seen in the area of compressors, where Peter Lattaway, product support manager, Atlas Copco, expects process plant operators to make great strides in switching from their old fixed-speed compressors to new variable-speed drive (VSD) models over the next decade.

“There is a far greater recognition of the cost of compressed air in the process industry now, although there is always the need for intelligent decision-making as opposed to a one-size-fits-all approach,” commented Lattaway.

“Statistics show that sales of VSD units are increasing as time goes on,” the Atlas Copco manager continued. “They are becoming an accepted technology and you have to ask yourself the question, ’in the future will all compressors have VSDs?’”

Heat recovery
Lattaway also cites heat recovery from compressors as an emerging technology that is likely to attract wider adoption in the process industries by 2020. The best energy savings from this technology are likely to be from a water-cooled machine feeding into an application such as boiler pre-feed water heating, he suggests.

“Under specific circumstances, 100% of the input electrical energy can be captured in the form of hot water and the potential opportunities for saving energy through this technology are, at present, only having the surface of them scratched,” said Lattaway.

In some applications though, the inherent inefficiencies in use of compressed air as a power medium - and the friction losses in transmission - will see a move to transmitting power via electricity.

According to Rotork, which supplies electric valve actuators, the electric motor drive has been transferred from the compressor to the actuator, eliminating all the intermediate conversions and transmissions, together with their attendant losses.

“When considering the large number of process control valves in a plant and compounding this with their constant movement, the elimination of compressed air in a plant can be significant and can result in a much more productive and cost-effective operation,” said a Rotork spokesman.

Further significant energy savings can be achieved from greater use of plate heat exchangers instead of tubular exchangers. In one specific example, Alfa Laval estimates that this could save the world’s sugar refining industry well over 200 million in annual energy costs.

“The difference in efficiency levels - thermal efficiency is 200-300% greater in sugar applications - means that they could employ lower-grade heat sources such as condensate or low-pressure vapour in place of expensive steam for many parts of the process,” says Ian Forrester of Alfa Laval in the UK. Refiners, he adds could reduce steam needs by as much as 5%, with the steam saved used to generate electricity.

Energy management is also central to efficiency efforts over the next decade, according to Alan France, operations director of Idhammar Systems. He expects to see a much greater degree of sophistication in this area, for example, by linking energy meters to overall equipment effectiveness (OEE) applications.

“OEE software already includes the asset structure, running hours and a product count,” said France. “If we then include the output from a number of meters, at least at line level, we can ’read’ the electricity consumption at defined intervals and compare the value to products produced. We can then consolidate the values at higher levels for effective site reporting,” he said.

Going a bit further by linking meters at asset level, can provide even more opportunities for analysis, said France. “We can then see, for instance, which machines consume the most energy and which should be switched off during a breakdown.”

However, as with this and many other energy-saving technologies, the pace of adoption will depend heavily on the regulatory and investment environment that develops between now and 2020.

Costs on the rise
For his part, ABB energy spokesman Steve Ruddell believes that legislation and rising costs will mean those who do not embrace energy-saving technologies will simply be out of business.

“Already the cost of CO2 is set at £12 per tonne and is expected to rise soon,” said Ruddell. “Now that the government has declared this as a tax, what is stopping them raising the figure to £20 per tonne?”

For Ruddell, the biggest energy-saving technologies, without question, remain variable-speed drives and IE3 motors. There is, he said, just nothing else that comes close in the short term.

“Within the UK’s electric motor installed base, there are currently too many plants still failing to have an effective motor management plan in place,” he noted. “Such a plan would save UK industry millions, not just in energy efficiency, but in avoiding the inefficiencies of unplanned stoppages or outages.”

While expecting new International Efficiency (IE) levels to have a major impact, Ruddell went on to caution against seeing efficiencies as the ’Holy Grail’ and ignoring the many other considerations that will make a plant super-efficient. This includes in areas such as industrial automation, robotics, life-cycle services and developments within established technologies.

“The humble electric motor may be well over 100 years old and functioning in the same way, but the materials, components and technology used today make this device one of the most efficient and reliable on the market. The fact is they are designed to last in excess of 25 years, if, just like your car, they are maintained correctly.”

Dominic Molloy, UK head of sales at Rockwell Automation, expects to see significant progress towards energy-efficient technologies by 2020, due, chiefly, to two driving forces: Carbon Reduction Commitment (CRC) legislation and the competitive advantages of reducing spending on energy.

Given the technology and solutions now available in the marketplace, Molloy believes an ideal environment now exists for plant operators to improve efficiency, reduce energy costs and become less vulnerable to future fluctuations in energy costs.

According to Molloy, significant energy efficiencies can be achieved with the latest software offerings, which include functions and metrics to help optimise performance, simplify real-time control, remote management and demonstrate compliance.

“By integrating such software with variable-speed and other energy-efficient drives, controls and hardware and creating energy-usage profiles to assess and predict requirements, plant operators are looking to drive down energy use and costs and improve efficiency simultaneously,” he said.

In terms of progress towards energy efficiency for the sake of the CRC, Molloy expects some of the most important developments to be around the expansion of power production from alternative power sources.

“With technical developments in the harnessing of wind, wave and solar power, plans to increase the energy production from such renewable sources could become a fundamental factor, alongside energy-efficient modern manufacturing and automation techniques, helping the plant of the future to get more for less and meet their own CRC requirements,” Molloy concluded.