This page contains a Flash digital edition of a book.
BSEE ENERGY MANAGEMENT


Advertising: 01622 699116 Editorial: 01354 461430


THE ROAD TO HEAT RECOVERY Compressors are the starting point


on output.


Energy efficiency is an increasingly high priority for businesses, and for those that run a compressed air system, heat recovery can play an important role. Andy Jones, Managing Director at Mattei, discusses the options.


Commonly referred to as the industry’s fourth utility, compressed air is estimated by the Carbon Trust to account for 10 per cent of the total electricity consumed in the industrial sector, which means improved efficiency in this area translates to a big impact on the carbon footprint of the industry as a whole.


I


With this in mind, compressors are a great starting point for businesses looking to reduce energy costs and shrink their carbon footprint. In fact, insight from the ESOS assessments carried out among manufacturing businesses suggests that compressed air is often an area where energy efficiency can be improved.


There are numerous ways in which the efficiency of the average compressor can be improved, and one of the most fruitful is heat recovery. The reason for this is that compressors generate a high level of waste heat in the course of standard operation, amounting to around 90 per cent of the electrical input used to power a compressor’s motor being lost as heat. However, by exploring the options currently available on the market, a major proportion, up to approximately 80 per cent, can be recovered. This recovered heat can then be used productively for space or water heating, therefore reducing fuel consumption and consequently lowering energy costs and carbon emissions.


Cost efficient


Not only is heat recovery an effective way to save energy, it is also cost efficient. A heat recovery system that recovers warm air can pay for itself in under a year, and if the compressors in question run for long periods of time, the savings can be very significant.


According to the Carbon Trust, a 55kW/350cfm compressor will have 88,000kWh of heat available per year (if the compressor operates for 2,000 hours a year), resulting in potential savings of £2,588 if gas heating was replaced (based on a boiler efficiency of 85 per cent and a gas cost of 2.5p/kWh). For a 110kW/700cfm compressor, the potential savings increase to £5,176. Likewise, the payback period for hot water systems is about two years. The hot water can reach temperatures of up to 90ºC, and can be used for a number of purposes, such as to pre- heat boiler-feed water or for sanitary use. However, having said all of this, using the recovered heat for local space or water heating is not always practical. When considering heat recovery, it is important to assess how much heat is available and at what temperature, and, importantly, where and when the heat will be used.


For example, if the heat is needed on the opposite side of the factory to the compressor, heat recovery will be a costly exercise, and won’t actually be that efficient. And the benefits can





n the current climate, where energy use and carbon emissions are under the spotlight, manufacturers and business owners must consider how they can improve the efficiency of their operation without compromising


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. Overheating the premises can also be an issue, especially in summer months, therefore during these warmer periods times the warm air will need to be ducted externally thus reducing the potential annual savings. As using waste heat from compressors for space or water heating is not always practical, the compressed air industry is seeing the development of a new process that generates more useful electrical energy instead.


For example, Mattei’s R&D team has developed the Xpander which uses waste heat to generate electrical energy. We see the product 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 Xpander 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 500ºC) 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 150ºC) – meaning it can be used in a greater number of applications.


Electrical power


According to the Carbon Trust, a 55kW/350cfm compressor will have 88,000kWh of heat available per year (if the compressor operates for 2,000 hours a year), resulting in potential savings of £2,588 if gas heating was replaced (based on a boiler efficiency of 85 per cent and a gas cost of 2.5p/kWh).


’ 30 BUILDING SERVICES & ENVIRONMENTAL ENGINEER OCTOBER 2017


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 improvement in the specific energy efficiency of the compressor is around six to eight per cent. Heat recovery is only one part of the picture however, and there are other ways to improve the efficiency of a compressed air system. Leak detection and repair and equipment updates (if required) are other important avenues to take. In many companies, 30 per cent of the air generated is wasted through leaks, which can prove costly over time. According to the Carbon


uMattei compressors: There are many examples of manufacturers achieving substantial savings through updating the compressors in their factories and processing plants.


Trust, even a small leak (just 3mm) could cost more than £700 a year in wasted energy – and we often see compressed air systems with around 150 to 300 leaks. Our advice is to check for leaks frequently and carry out an annual leak detection survey – the cost of which is less than 10 per cent of the overall leakage costs.


Meanwhile, we have many examples we can cite where manufacturers have achieved substantial savings through updating the compressors in their factories and processing plants. However, before a business invests in new compressors, it’s important to understand how much compressed air is being used, and how much it costs.


The most straightforward way to evaluate compressed air needs and the efficiency of the system is through data logging. This involves recording and measuring air consumption profiles over a seven-day period, and some discussions to identify unusual patterns or planned process changes. Investing in a more detailed energy audit, carried out in accordance with the international standard ISO 11011:2013, Compressed air – Energy efficiency – Assessment, can paint an even more realistic picture about compressor efficiencies, as can flow monitoring. Alongside other energy saving measures, heat recovery should be a key consideration for any business running a compressed air system. However, conventional heat recovery can only deliver savings if there’s a need for space or water heating, whereas Mattei’s Xpander will ensure that a greater number of businesses can reduce their energy costs and carbon emissions by generating more useful electrical energy from waste heat.


www.mattei.co.uk VISIT OUR WEBSITE: www.bsee.co.uk


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48