A well-managed compressed air system can save more than 20% of the electricity used to power it.
Get the best from your compressed air system
Air compressors usually convert just 15% of electrical energy into compressed air energy. The other 85% is converted to heat, which is often wasted. A well-managed compressed air system can save 20% or more of the electricity used to power the system, and a heat recovery system can recover 70% of wasted heat to offset boiler use or other process heat needs.
The most likely areas of energy waste in air compressors are off load running, leakage, excess system pressure drop and inappropriate operating pressure. If a skilled technician isn’t servicing your system, it’s likely your compressor is wasting energy and costing you money.
Check air demand
When you’re reviewing your compressed air system, start with what’s driving demand for compressed air and then examine ways to optimise supply.
- Air leakage - air leaks commonly contribute 20% to 30% of compressed air demand, but a well-managed system will have less than 10% leakage. Repairing leaks almost always has a very short payback period.
- Inappropriate use and artificial demand - includes using high pressure air for cleaning, using high pressure air where only low pressure air is needed, or using compressed air in mechanical applications where an electric drive is used.
- Peak and non-production demand - peak demand, or the maximum airflow demanded at one time, determines the compressed air supply capacity.
- Fluctuating demand - large fluctuations in demand from equipment attached to a system can cause large pressure drops across that system.
- Pressure regulators - minimising supply pressure needed for air-driven equipment can cut demand.
- Air network considerations - pressure drops in the network are common. Typical causes include rust, undersized pipes or pipe constrictions and unnecessary deviations, and partly blocked filters.
- Measuring flow and pressure - use the equipment specification and use profiles of each piece of equipment to estimate the network airflow demand.
Compressors need to accommodate the pressure and flow requirements of the network. It’s important that your compressors are correctly sized to meet demand on the system. Other factors influencing supply-end efficiency include:
- Controlling multiple compressors - arranging ‘run order' to match air supply to demand and make sure machines are operating at their optimum efficiency. For example base demand could be met with a fixed speed machine and any peaks in demand supplied with a variable speed compressor.
- Variable speed compressors - variable flow compressors match air supply to demand (eliminating off load running) and are typically more efficient than fixed flow machines where air demand is variable.
- Compressor supply pressure - for every 1 bar the compressor is set over the required pressure, the system loses about 7% efficiency.
- Drier selection and sizing - over-drying the air wastes energy. A faulty drier can cause excessive pressure drops.
- Environment and maintenance - air compressors are often installed in service areas with boilers, pumps and chillers. Radiant heat affects air compressor efficiency, generally by 1% for every 3°C the intake air is above outside ambient air temperature.
Recover excess heat
About 85% of energy used to run an air compressor turns into heat. So it’s worth exploring ways to use this waste heat. Examples include ducting hot air from cooling vents to working areas and using a heat exchanger to heat water. Consider heat recovery opportunities if you’re looking at a new compressed air system.
Funding for compressed air systems
Part-funding is available for compressed air audits conducted by approved EECA programme partners, according to audit standards and guidelines specified by EECA.