With energy efficiency being high on everyone’s agenda, businesses are understandably searching for ways to reduce their energy costs and carbon emissions. 

While many have already put processes in place to reduce their energy use, carbon emissions and costs, the Government’s mandatory Energy Savings Opportunity Scheme (ESOS) aims to ensure that efficiency is front of mind for every major consumer of energy.

ESOS requires eligible companies to carry out an audit of the energy used by their buildings, industrial processes and transport to identify cost-effective energy saving measures every four years*. It applies to large UK undertakings and their corporate groups. It mainly affects businesses but can also apply to not-for-profit bodies and any other non public sector undertakings that are large enough to meet the qualification criteria.

A large undertaking is defined as any UK company that either employs 250 or more people or has an annual turnover in excess of 50 million euro and an annual balance sheet total in excess of 43 million euro, or an overseas company with a UK registered establishment which has 250 or more UK employees (paying income tax in the UK).

And for large undertakings with manufacturing facilities, compressors can be a good place to start making savings. After all, compressed air is often considered to be industry’s fourth utility, and compressors account for around 10% of the total electricity consumed in the sector.

There are many approaches that can be taken to reduce the amount of energy a compressed air system uses, and one effective measure is heat recovery. Compressors generate a lot of heat (around 90% of the electrical input used to power a compressor’s motor is turned into heat), but fortunately around 80% of this waste heat can be recovered and put to good use.  

It is possible to use the recovered heat for local space heating, but in many cases this is not practical. For example, if the heat is needed on the opposite side of the factory to the compressor, it will be a costly exercise, and won’t actually be that efficient. Alternatively the waste heat can be used to generate hot water, which can actually reach temperatures of up to 90ºC. The hot water can be used for a number of purposes, such as to pre-heat boiler-feed water or for sanitary use. 

However, although this type of system can deliver energy savings, the benefits can only be realised if a factory or plant has a constant need for space heating or hot water (a compressor generally runs all year, so it is more efficient to have a continuous demand) – which isn’t always the case. 

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We see the Xpander as an important breakthrough, as where there isn’t always a need for heating and hot water in a factory, there will always be a need for electricity. 

The prototype is based on the Organic Rankine Cycle (ORC) – a ‘steam’ cycle employing organic fluids instead of water that can generate electricity from waste heat.  So far, ORC has been used in medium-sized applications where high temperature waste heat (i.e. 150 to 500°C) is available. But Mattei’s Xpander is a high efficiency ORC based system that allows the recovery of energy from very low temperature waste heat (i.e. 80 to 150°C) – meaning it can be used in a greater number of applications. 

Designed to work with air compressors of 50-100kW, the Xpander recovers heat from hot compressor oil, which is ordinarily cooled by a fan, and converts it into electrical power. It can produce 3kWe, which can be fed back into the compressor. When the Xpander is cooling the oil, the compressor’s normal fan cooling system can be turned off, saving a further 2kW. The overall reduction in the specific energy efficiency of the compressor is around 6%. 

With spiralling energy costs, carbon emission reduction commitments and ESOS to consider, heat recovery should be a key consideration for any business running a compressed air system. Conventional heat recovery can only deliver savings if there’s a need for space or water heating, but by generating more useful electrical energy from waste heat, Mattei’s Xpander will ensure that a greater number of businesses can reduce their energy costs and carbon emissions.