Lowering energy consumption with variable speed compressor technology

Published:  11 July, 2022

Colin Mander, Business Line Director at CompAir, discusses the role that variable speed compressors can play in helping businesses to reduce their electricity consumption. Indeed, every kWh in electricity saved now, will contribute to even greater savings with the current and unprecedented increase in electrical costs.

Industrial compressed air applications consume 11.71 TWh of electricity per year, accounting for as much as ten per cent of all the energy consumed by industry.1 As energy prices continue to rise at an unprecedented rate, many operators are seeking innovative ways to cut their electricity consumption from compressed air.

At the same time, sustainability has become one of the leading factors for decision-makers when selecting a new air compressor. In addition to cost and performance considerations, determining a compressor’s impact on the environment is now a major consideration in the purchasing decision.

Traditionally, compressors have used fixed speed motors, which means they run at a consistent speed, and produce a fixed amount of compressed air per minute, regardless of air demand. In most scenarios, it is unlikely that the exact amount of compressed air generated will be required. This means the compressor can potentially be creating compressed air that ends up being wasted.

In addition, fixed speed compressors run unloaded, as the stress of an engine start-up would put pressure on the motor. This can be a waste of energy as the machine is running without producing any compressed air. In contrast, variable speed compressors have the ability to start and stop under full system pressure. They use an intelligent drive system to constantly alter the speed of the motor and to match the air generated to the required process demand. This allows for the required high speeds for compression, while generating sufficient flow to meet plant requirements, hence minimising power consumption.

This technology can potentially have a big impact on businesses productivity, efficiency and sustainability levels. When compared with a fixed speed compressor, a variable speed model can achieve energy savings of up to 30 per cent, and can help reduce power surges, avoiding peak currents from starting the compressor’s motor.

Furthermore, precise electrical controls ensure motors can be easily slowed down, stopped, or revved up, and the risk of leaks is minimised through the lower system pressure that is achieved with a variable speed drive. Minimising leaks in a compressed air network is another key benefit, and one of the most important energy saving measures for businesses. The Carbon Trust reports that a 3mm hole could cost over £1000 a year in wasted energy2 – not to mention the associated impact on the environment, from generating all this lost energy.

Energy savings in action

The Metal Drum Company, a manufacturer of steel drums, is one such organisation to have benefitted from installing variable-speed compressors, saving £23,000 per annum.

Thanks to a programme of energy-efficiency improvements, The Metal Drum Company is benefitting from a new, CompAir L160 RS, variable-speed drive machine at its main Chilton site, delivering payback in just 3.5 years; alongside a smaller L75 machine, offering 3.7 years’ payback at its Hull facility - from CompAir distributor, Air Compressors and Blowers North (ACB)

Specifying the system

During the wrapping and painting process, The Metal Drum Company has a high demand for air, which was proving costly. With the rising price of energy, alongside the environmental demands being placed on manufacturers, the company approached ACB to see if a programme of compressed air system improvements could be made to help reduce electricity consumption.

The original 110 kW, fixed-speed machine had already been replaced for a CompAir L160 oil-lubricated compressor, to help increase capacity, and had been providing reliable performance for over 20 years, with minimal maintenance issues. But, with its belt drive and fixed-speed operation, the compressor could only run at a constant speed, consuming 160 kW of electricity, regardless of the demand for air generation.

The same scenario applied at the Hull facility, where a CompAir L75 fixed-speed compressor had been running reliably for 10 years, but with no speed-regulation available on the drive.

Engineers from ACB carried out energy data logging on both sites, which showed that each compressor was running continuously, when actual demand was between 50-60 per cent. A speed-regulated, direct drive compressor solution was proposed, which would ensure that each machine was optimised to meet the peaks and troughs in air demand.

The compressed air solution

The CompAir L160 RS has proved ideal for the larger air volumes required at the Chilton site, with predicted energy savings of £15,000 per annum.

The L75 RS compressor at the Hull site is on track to achieve energy savings of £8000 per annum. With higher air delivery, a new, compact footprint of only 2.23m2 and a lower noise level, the unit has been installed in the main production area, without any concerns. The new machine offers efficiency improvements of up to 6.8% over previous models, and a higher flow rate up to 6 per cent from the brand new airends, delivering significantly lower lifetime costs.

In conclusion

Variable-speed compressor technologies are already well-proven and can deliver significant energy cost savings. As the rising costs of energy continue to impact on business profitability it is well worth considering how variable-speed compressors, alongside fixedspeed units to handle the base load could prove beneficial.

1 British Compressed Air Society – Taskforce10 campaign – The Facts https://taskforce10.bcas.org.uk/facts/

2 The Carbon Trust, ‘How companies can save money from thin air’, https://www.carbontrust.com/news-andevents/news/how-companies-can-savemoney-from-thin-air

The recent COP 26 summit, coupled with rising energy bills is driving more and more businesses to consider their electricity consumption, alongside their impact on the environment. Compressed air generation is said to account for as much as 10% of all the electricity consumed by industry, so CompAir is incentivising its customer to lower their energy bills and their carbon footprint, by investing in the latest energy-efficient compressed air technology.

A new environmental campaign in partnership with Carbon Footprint, which commits to planting one tree for every CompAir or Hydrovane variable-speed compressor sold in the UK.

The campaign aims to plant hundreds of trees before the end of the year, across a variety of regions in the UK - one for each energy-efficient compressor purchased. In addition, the company will be supporting a biodiversity reserve project in Rimba Raya in Borneo, Indonesia, with the aim of offsetting 200 tCO2e of its own emissions from its operations.



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