Compressed air: Opportunities for savings

According to the manufacturers’ organisation EEF, energy affordability is a concern for 83% of manufacturers*. Compressors – which account for around 10% of the total electricity consumed in the industrial sector – can be an ideal place to start making savings. 

It’s important to ensure that the compressor installed has been sized correctly, and is suitable for the site’s manufacturing processes. For example, we found that one company running a 75kW compressor could actually fulfil its compressed air requirements with a 45kW machine, with estimated savings being in the region of £10,000 a year. Furthermore, it is all too common to find standard industrial compressors (i.e. those capable of producing 8-13bar) being used for low pressure duties, such as the transportation of bulk materials – which is a very inefficient practice. 

Equally, while variable speed compressors can reduce the cost of producing compressed air (offering typical savings of 30% or more), this type of compressor will only save energy if there are true variable peaks and troughs in the demand for air – and only when these variations fall within the efficient working band of the compressor.

Air consumption profiles are recorded and measured over a seven-day period, followed by discussions to identify unusual patterns or planned process changes. Investing in a more detailed energy audit, which should always be carried out in accordance with the international standard ISO 11011:2013, Compressed air – Energy efficiency – Assessment, can paint an even clearer picture, providing data from which a decision on replacement equipment can be made.

If a new compressor is required, opting for the most efficient one available, rather than basing the decision on purchase price, will pay dividends, because the main cost will always be the energy required to produce the compressed air. The initial purchase price actually makes up a very small part of the total lifetime costs of the equipment, and a slightly higher-priced compressor could pay for itself in just a matter of months by reducing energy consumption. 

At Mattei we have continued to invest heavily in the research and development of our already very efficient compression units (air-ends), and have now taken them a step further with the launch of the Maxima Xtreme. I believe it is the most energy efficient fixed speed compressor available, with a specific energy efficiency of just 5.2kW/m³/min. This is around 1.5kW/m³/min better than a good average screw compressor and around 0.8kW/m³/min better than the best figures claimed by the most efficient. This may not sound a lot, but for a compressor delivering 16m³/min on a 24/7/365 basis this could save around 112,000kWh per annum over its nearest rival.

Leaks are also a common problem affecting compressor efficiency. No matter how energy efficient a compressor is, if it is feeding a system full of leaks it won’t run efficiently. In many companies, more than 30% of air generated by a compressor is wasted through leaks. 

We often see compressed air systems with around 150 to 300 leaks, and a company using 50 cubic metres of compressed air per minute could potentially save around £63,000 by repairing them. This is a simple and cost-effective exercise (the average cost of a Mattei leak detection survey is less than 10% of the overall leakage costs). Pipe runs also need to be suitably designed and laid out, as excessive lengths and bends lower system efficiency. 

Compressed air is an essential part of many commercial and industrial processes – and producing it uses a lot of energy. In terms of making energy savings and reducing fuel bills, a manufacturer’s compressed air system can therefore be a good place to start.