Energy focus: power play
24 Feb 2016 by Louisa Hearn
Energy efficiency hasn't always been top of mind for plant managers tasked with keeping process equipment running around the clock.
But the times have changed, and the rising cost of energy has pushed this issue to the top of the corporate agenda.
New regulations in the form of Energy Savings Opportunity Scheme (ESOS) are coming into force, mandating all large businesses in the UK to undertake comprehensive audits of energy use.
From an energy usage point of view, a chiller can be one of the most energy-intensive pieces of equipment to run
Richard Metcalfe, sales director at ICS Cool Energy
This makes selection and optimisation of equipment in energy-intensive industries a crucial consideration, say industry experts.
In October last year, the European chemical industry council, Cefic, awarded Trinseo Benelux with a commendation for achieving energy efficiency through steam re-compression.
The emulsion polymer manufacturer was praised for the creative re-use of steam previously blown off to the atmosphere at its site in Terneuzen in the Netherlands.
Both free cooling and heat recovery are two very commonly used methods of energy management within the process industries, says Richard Metcalfe, sales director at ICS Cool Energy.
Not all pieces of equipment are equal, however, with some eating up far more energy than others.
“From an energy usage point of view, a chiller can be one of the most energy-intensive pieces of equipment to run,” he says.
This is because it incorporates a compressor, which consumes a large amount of energy.
Often referred to as the UK industry’s fourth utility, industry estimates say compressors may account for 10% or above of the total electricity consumed in the industrial sector.
“In my opinion we need to see a much greater shift towards the wider integration of compressor technology which embraces the principal of variable speed drives,” says Metcalfe.
“Whilst these are available as an added extra on some chillers, along with the introduction of inverter-driven screw compressors or digital scroll compressors, I would say the technology needs to become the norm in order for the process industry to really achieve noticeable and sustained energy savings from chiller-based cooling systems.”
Compressed costs
As an accredited supplier with the Carbon Trust, energy management is a very big deal for compressor supplier Atlas Copco.
The company supplies compressor technology for a wide range of users from the wastewater to food and pharmaceutical sectors.
“They are designed to deliver compressed air that mirrors the air demands of the factory,” says Ken Revell, business line manager for Atlas Copco’s Compressor Technique Service division.
“There is rarely a compressor system that doesn't need some sort of energy management thought applied to it. This may just be an adjustment of pressure bands – it’s clever, easy and available.”
Incorrect sizing or specifying the wrong type of compressor can commonly lead to higher energy consumption, says Revell.
“This means the art of specification based on the needs and design of the system is of key importance.”
Once you have got all the right equipment specified, the next part is looking after that system, and the company is building smart technology into some of its equipment to make that possible.
Leaks are another common issue that can also severely impact efficiency, and an additional challenge is to keep airflow as smooth as possible.
“The effect of leaks on an electricity bill on comp can be enormous,” says Revell.
“If you’ve got too many filters or dryers in a system each one creates a little pressure drop. Each of these mean the compressor must work even harder to get compressed air to where it is needed.”
Ignoring system maintenance will invariably end up costing the user more – not just in energy - but in the wear and tear on the machine, he warns.
Compressors also offer opportunities for energy recovery, and Atlas Copco’s Thermo Kit technology provides a package of energy recovery components to provide supplementary hot water at no additional cost.
“Everything we put into a compressor turns into heat so it is very simple for us to add an energy recovery system to recapture 80% of this to be used or stored for preheating industrial boilers, or to take directly into a process,” says Revell.
The company also supplies variable speed drive (VSD) compressors, such as the GA VSD+ range which it says can reduce energy consumption by as much as 50% on average, compared to idling compressors.
Variable-speed savings
Another company championing variable speed drive technology with the process industries is power management company, Eaton.
According to Stuart Greenwood, product marketing manager for Industrial Control and Automation at Eaton, by managing the speed of motors used to run process equipment, a variable speed drive can provide a vital part of the energy management puzzle.
“Pumps and fans are particularly susceptible to huge energy saving potential when used with variable speed drives,” he says.
One reason for this, he adds, is that when many motors are produced – especially in pump applications – they are often over engineered.
“This inbuilt inefficacy exists because they tend to do far less work than they have been designed for.”
While variable speed drives are becoming increasingly commonplace, there is still a huge potential saving to be made in process industries.
While the benefits are self-evident, VSDs are yet to fulfill their potential in many sites of the associated training needs for using their often-complex keypads.
“One barrier to their adoption is that variable speed drives are not generally very simple things to use,” says Greenwood.
To address this issue, Eaton has recently launched a smaller, simple-to-use variable speed drive category that ships without a complex keypad.
A new compressor based on innovative new blade technology has been undergoing trials in the UK.
Developed by engineering startup, Lontra, the Blade Compressor is a compact, double acting rotary compressor that has recently demonstrated energy savings of over 21% in reference sites.
While traditional screw compressor technologies are prone to leakage and often require oil to run, blade technology has an inherent geometry that results in a far better seal, says Steve Lindsey, chief executive of Lontra.
One of the first reference sites to trial the technology is Severn Trent Water, which was seeking an alternative to the traditional blowers and compressors used to pump air into wastewater to feed the micro-organisms that clean it.
Severn Trent part-funded the full scale trial alongside the Carbon Trust at its Worcester Wastewater Treatment Works.
“To make the test as representative as possible, only the existing blower and motor were replaced, with the Lontra Blade Compressor fitted into an existing enclosure and running from an existing variable speed drive,” says Mark Jones, Severn Trent’s wastewater research and development manager.
“This ensured that only the gains in the blower technology - and not those from optimising the supporting systems and drives - were captured.”
Following the trial, the water company says it concluded the Blade Compressor was “a game-changer for the global water and wastewater utility businesses, delivering a step change reduction in electricity usage, maintenance costs and CO2 emissions”.
It reports energy savings of up to £1.8 million per year when rolled out across its network of wastewater treatment works, business-wide reduction in CO2 emissions of 3%, and a reduction in maintenance costs.
While the technology is only currently available to the water sector, it is expected to be more widely rolled out to industrial applications in the future.
