FEATURE ENERGY AUDITING & SURVEYING
Using energy audits to save resources when using compressed air systems
Mark Whitmore, General Manager at BOGE, outlines the cost-effective ways to reduce energy consumption while maintaining efficiency and performance of a compressed air system
I
t takes the output of one and a half power stations to run all the UK’s compressed air
applications every year. Sadly, more than half that energy is wasted. It’s an astronomical amount of energy: 10TWh, equivalent to 5 million tonnes of carbon dioxide being released into the atmosphere; and, because of typical system inefficiencies – such as leaks or supercharging – only about 45% of the input energy is used to compress the air. The other 55% is typically wasted. Energy is by far the largest ongoing cost for a
compressed air system – and can be more than the initial outlay on it. However, easy alterations can help to cut the energy needs of compressors by up to 50%. Just as well considering that compressed air typically accounts for nearly one-third of a site’s total electricity usage. In an attempt to reduce his huge drain on energy resources ISO 11011: 2013 Standard was introduced. The standard sets out the requirements for conducting and reporting the results of a compressed air system assessment - also known as an audit - for the entire system. It sets requirements for analysing the data from the audit, reporting and documenting the findings, and identifying an estimate of energy savings that result from the assessment process used.
LEAK DETECTION One of the biggest fault areas is leakage. The Carbon Trust estimates that a 3mm hole in a compressed air line could cost a business as much as £700 a year in wasted energy. However, the problem could easily be prevented with regular pressure checks or by conducting a leak detection survey. As air escapes through a
energy and service costs. Maintenance is cheaper with fewer compressors – and is a key part of the strategy. Another way of reducing energy costs is to
introduce heat recovery. Around 90% of the electrical energy used in a compressor is lost as heat – and almost all of it can be recovered for use elsewhere in the plant, such as heating rooms or even water. A system like the BOGE Duotherm can recover up to 75% of the electrical power, helping to reduce utility bills and lessen environmental impact.
leak hole it creates a tiny sound that is inaudible to the human ear but easily detectable by specialist ultrasound detection equipment – which transforms it into an audible sound and indicates it optically. Leaks can be detected from a long
distance – up to 15m – which is useful in places that are not easily accessible or visible. Once leaks have been identified, a maintenance schedule must be put in place to plug them and ensure future leak detection surveys are conducted - otherwise the benefits will be short-lived. A compressed air energy audit can also
identify whether a line is running at excessive pressure. Lowering system pressure can mean that fewer compressors are needed – with consequent reductions in
Figure 1:
An audit or leak detection survey is integral to running energy-efficient
compressed air systems
CLOSE CONTROL Further savings can be achieved when two or more compressors are operated via a central controller. Modern electronic controllers provide much greater energy saving in two ways: by maintaining pressure in a much narrower range (by constantly monitoring pressure and switching compressors on and off as needed); and by predicting the best combination of compressors to use, in order to meet demand – which is particularly useful if using a combination of fixed speed and variable speed machines, as it minimises off-load and part- load running of the compressors. With continuing pressure on profit
margins, and mandatory measures in place to cut emissions, running energy-efficient compressed air systems will continue to be a priority. An audit or leak detection survey cannot make utility bills disappear – but it can help to take a chunk out of them.
BOGE
www.boge.com/uk 01484 719921
Top tips for boosting efficiency
1. Demand analysis/leakage measurement Considering the energy demands of compressors is not enough: leaks have a huge effect on energy consumption – and reducing them offers massive saving potential. To do this, the optimal running of the compressors must be determined, based on demand analysis and regular leak measurements. 2. System design Efficient operation of individual components is only the first step towards energy savings. Optimal interaction of these components – and aligning the entire system to specific needs – has a positive effect. Intelligent design of the process chain helps optimise both energy and resources.
3. System Renewal For older compressed air systems, a complete overhaul can be useful –
depending on the technical state of the system and its energy efficiency. Modern compressors have high-efficiency motors and air-ends, with modern fans and heat recovery. Investing in new plant – often supported by government – can quickly pay for itself.
4. Intelligent control An optimal ratio for load and idle times can be achieved through intelligent control systems, which select the most efficient air compressor combination according to demand. This keeps idle time and pressure at an optimum level. In addition, the parameters of your system become more apparent.
5. Heat Recovery During air compression, much of the energy is converted into heat. Modern, efficient systems ensure that this energy is not wasted. Up to 94% of the heat generated in a compressor can be recovered – then routed to where it is needed, or used in the form of hot water.
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AUTUMN 2015 | ENERGY MANAGEMENT
/ ENERGYMANAGEMENT
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