Key points
Standfirst
Energy costs have more than doubled in the past year alone, which, coupled with the world’s climate crisis, is placing every-increasing pressure on process industry operators to minimise site electricity consumption and reduce carbon emissions.
For compressed air users, this urgency is felt even more, with compressors typically using as much as 10% of all the annual electricity consumed by industry.
Colin Mander, Business Line Director at Ingersoll Rand and CompAir discusses the benefits of investing in variable-speed drive technology for compressed air systems.
The scale of the challenge
For many years, the industry has used a formula to calculate compressed air cost of ownership, comprising capital investment and installation at 10%, maintenance at approximately 8% and energy costs making up the largest proportion at 82%.
This breakdown has served many customers well, enabling them to make informed choices about how to lower running costs. This is especially the case when considering the cost of capital equipment and the potential payback that can be achieved by investing in an energy-efficient machine.
However, customers now need to re-evaluate the way that they assess their compressed air energy costs. Total running costs over the last ten years for a 160-kW compressor have more than doubled. Put simply, for every £100,000 spent on compressed air previously, around £82,000 of this was the energy costs. Now, this figure has risen to £91,000.
One way to mitigate this risk is to invest in variable-speed compressor technology; an option now available on many compressed air systems as new or retrofitted.
Waste not, want not
One of the best ways to minimise compressed air energy consumption is to limit avoidable waste. Poor housekeeping practices and inefficient processes can be one of the biggest contributors to energy waste in a typical factory.
The British Compressed Air Society (BCAS) 10% Taskforce campaign highlights this important issue, offering numerous energy saving tips to cut the amount of compressed air wastage by 10%.
The Society states that: “According to a report entitled ‘Compressed Air Systems in the European Union’, when looking at the most important energy savings techniques available to compressed air users, ‘the energy savings amount to 32.9%, achievable over a 15-year period”.
The report highlights that a 3.8% contribution to this overall percentage, the third highest energy-saving measure on the list, can be achieved through the improvement of drives, including variable/adjustable speed options.
Fixed vs variable
A fixed speed motor, as the name implies, runs at a constant speed, regardless of air demand. There are many benefits to fixed speed compressor technology if the air demand is constant and unchanging. However, this isn’t always the case.
Compressed air is generated at a fixed rate per minute, but this can mean that more air is generated than the process requires, effectively creating air, and consuming energy that could end up going to waste.
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 further waste of energy as the machine is running without producing any compressed air.
Variable speed compressors avoid this issue by matching the output with the demand created and could 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.
When compared with a fixed speed compressor, a variable speed model can achieve energy savings of up to 30%, 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 £1,000 a year in wasted energy[1] – not to mention the associated impact on the environment, from generating all this lost energy.
At-a-glance
The benefits of variable-speed technology for compressed air systems
- No need to unload – compressors can start and stop under full system pressure
- Reduced power costs – no loss of energy through running unloaded
- Reduced power surges – avoid peak currents from starting air compressor motor
- More energy efficient – save 30% of the energy used by a typical fixed speed compressor.
- Precise electrical control – motor speeds can be slowed down, brought to a halt or revved up.
- System leaks minimised – lower system pressure reduces the risk of leaks
Ingersoll Rand and CompAir is incentivising its customers 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, 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.
[1] The Carbon Trust, ‘How companies can save money from thin air’
