Four tips for saving on compressed air energy

Hurll Nu-Way Pty Ltd
Friday, 17 January, 2014

Energy consumption and energy efficiency are of primary concern to many compressor users. There are many well-known methods for keeping on top of energy consumption - fix the leaks, change the filters, regularly maintain your compressor, ventilate, recover generated heat, invest in VSD - however, there are some less famous yet clever ways to cut your bills down further.

1. Use two compressors instead of one. If you have a required capacity of 10.5 m3/min, instead of investing in a 75 kW screw compressor with VSD (with a capacity of 11.7 m3/min), an alternative option is to purchase a 55 kW machine for base load supply and combine it with a small piston compressor to cover peak demand. To begin with, initial investments can be much lower in this scenario. Secondly, significant energy savings can be made by reducing the base load operating pressure. A rule of thumb is that every 2 psi increase in operating pressure requires an additional 1% in operating costs of energy, and vice versa.

Another example is combining a fixed speed with a VSD unit. This configuration allows for nearly 100% turndown capabilities (as would be the case for a single large VSD unit with twice the capacity). In this example, all the benefits of a single-duty, large VSD unit can be achieved for a smaller upfront cost by combining a smaller VSD unit with a fixed-speed unit for base load supply.

2. Energy savings with fixed speed compressors. Although variable speed units are generally believed to be the best option to achieve energy savings, they may not be the best option for your scenario. If your compressor operates most of the time at full load, look for a modern fixed speed compressor possessing energy-saving features. A good example is the Hitachi Hiscrew compressors series NEXT. With increased capacity, an energy-saving cooling fan system and Ecomode operation, there are many energy-saving features to be found in the fixed-speed models.

Also, by lowering the cut-off pressure as per the load ratio of your compressor, you’ll get a combination of relatively low initial investments (compared to a VSD unit), with 2-4% energy savings through the lifespan of the equipment. These savings could save you several thousand dollars per year.

3. Not all VSDs are the same. New VSD compressor models feature constant pressure control, which maintains constant pressure at all times without a pressure drop. This reduces pressure undershoot under fluctuating load situations and enables the minimisation of control pressure setting to reduce power consumption. Hitachi VSD models have the ability to operate in PQ wide mode, giving the ability to operate at 105% flow capacity (at slightly reduced pressure) or at a higher than specified pressure (at a reduced flow rate) and still be energy efficient.

4. Air auditing. The last point won’t be a revelation. The importance of air auditing is hard to overestimate, with over 70% of the total costs of the compressor being energy consumption. Contact Hurll Nu-Way to discuss this option.

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