Purchasing decisions for capital investment projects in a business are rarely signed off by just one person. At any given time there are likely to be several potential investment options available, with each department having their own ideas as to where spend should be allocated.
Even the most well intended proposal can be rejected out of hand if certain stakeholders do not fully understand or appreciate a problem, its solution, or the subsequent benefits. This can make it a challenge for energy managers to win over colleagues when investing in energy saving initiatives, particularly when it comes to upgrading equipment that typically operates behind the scenes.
There are an estimated 10 million electric motors installed in the UK, accounting for a quarter of all electricity used in industry1. More than 90 percent of these motors are run with no variable speed control. And while not all motors can benefit from variable speed control, the vast majority can, presenting a huge opportunity to save energy.
Energy efficiency can sometimes suffer from being disconnected from the strategic aims of business. Employee wages, for instance, typically comprise a far larger proportion of overall operating costs. When looking for ways to save money, there can be a perception that improving energy efficiency will make minimal difference to the overall balance sheet, if at all.
Even when there is investment in energy saving, this tends to focus on more visible improvements like LED lighting and building management systems (BMS), or modifying employee behaviours, rather than motor-driven applications hidden away in plant rooms.
In many companies, only a small number of employees will be able to tell you anything about the electric motors used in a facility, let alone how many there are, where they are installed, how they are operated and, crucially, how much energy they use. In commercial buildings for example, motors are rarely seen or heard unless something has gone wrong. To that end, variable speed drives (VSDs) are not generally front of many employees’ minds when it comes to energy saving initiatives.
This lack of awareness means that companies could be missing out on the significant energy savings that VSDs can deliver. It is, therefore, important that energy managers are able to build a compelling business case so that others can understand the potential benefits.
Building the business case
VSDs not only significantly reduce energy costs with comparatively little investment, but also provide additional benefits for other stakeholders. Furthermore, with some government energy efficiency schemes like Enhanced Capital Allowances (ECAs) soon to be discontinued, time is running out to achieve maximum return on VSD investment.
In building a compelling business case, an energy assessment is one way of getting the relevant information to the right stakeholders. This is an appraisal of your installed motor-driven applications, focusing primarily on variable torque applications such as centrifugal fans, pumps and compressors. Some VSD providers will carry out such an assessment free of charge, subject to terms and conditions, and it takes place over the course of just half a day. In some cases they may even be able to provide a trial, whereby a VSD is supplied on a short-term basis to determine actual VSD performance in-situ on a given application.
Crunching the numbers
An energy assessment provides the hard proof required to bring all stakeholders on board. The finance department, for instance, will generally have little interest in how a VSD works, or technical details like power curves and the cube law, but it is interested in how much money it can save. There are countless examples of real-life success stories which can be used to prove the case, across a broad range of industries and applications.
CBRE, a building maintenance contractor, undertook an energy assessment at a 17 floor, 46,500 square metre office development near Canary Wharf in London. When the building was completed in 1989, only the most energy intensive applications were speed controlled. Some 20 years later, CBRE was keen to improve energy use on other applications including hot water and chilled water pumps and air extraction systems. 18 VSDs ranging from 5.5 kW to 37 kW were installed resulting in a saving of £15,000 on electricity costs within six months of commissioning, with a payback time of 18 months.
Anglian Water asked its VSD supplier to perform an energy assessment on pumps controlling reservoir boreholes at two sites in Suffolk. It was found that the actual demand for pumping capacity was some distance lower than what the borehole was actually delivering, with no means of slowing the pumps down to adjust flow rates. A 132 kW drive was recommended, which also built additional redundancy into the system, improving reliability. Anglian Water is now saving £2,000 a year on electricity costs, with the £7,000 project investment expected to pay for itself within three and a half years.
Bedford Hospital discovered, thanks to an energy assessment, that it could save £15,000 a year on air handling costs with the installation of four VSDs. In fact, while the energy assessment predicted a speed reduction of 15 percent, the actual reduction was 20 percent, with reduced running noise and maintenance requirements thanks to the reduction in wear on components. Payback time was around one year.
Bourne Leisure, which owns several national hotel and leisure brands, saw how successful VSDs had been at one of its swimming pools, and wanted to see how much energy saving could be attained at another pool elsewhere. The predicted energy savings of £4,899 per annum identified in the assessment were exceeded once the installation was complete, giving a payback of less than six months.
Greenwich University conducted energy assessments on air handling units at three campuses in an effort to reduce its energy bill while cutting CO2 emissions. A total of 44 installations were identified that could benefit from VSD installation, equating to £10,472 a year in energy savings, while reducing carbon emissions by over 57 tonnes per annum. Further projects were identified beyond the initial rollout that are predicted to achieve additional savings of £4,000.
Finance & compliance
The financial department needs to know what the value of an investment is, and its expected return. On a typical fan application a VSD will recoup its upfront cost within two years, but this can be as little as six months. Once the payback time has been reached, the drive will continue to deliver cost savings in perpetuity compared to a motor run without a VSD.
Schemes like ESOS and SECR can also be leveraged as part of any VSD investment proposal. These schemes are widely considered to be well intentioned, but some have criticised the lack of incentive to actually implement any energy saving opportunities identified in any reports. VSDs are exactly the kind of low hanging fruit that these schemes are designed to encourage. Indeed, VSDs from several manufacturers are included on the Carbon Trust’s Energy Technology List (ETL), which allows companies to claim tax relief as part of the Enhanced Capital Allowances (ECA) scheme.
Maintenance and operations
As well as reducing energy, VSDs can also enhance productivity. The precise motor speed control provided by a VSD means that ramping up and down is much smoother, preventing jolts on start up and shutdown, or when transitioning between different speeds. PID control is a feature which provides constant feedback to ensure that a motor is operating at the correct speed at all times regardless of conditions, ensuring that HVAC systems accurately maintain the required temperature, for example.
The smoother motor operation achieved by a VSD reduces the strain on components like gearing and bearings, and can ultimately reduce the need for motor repairs, limiting the cost and frequency of downtime. This frees up maintenance engineers to concentrate on other priority tasks.
The biggest leap forward in VSD technology in recent years is the digitalisation of the powertrain. A powertrain comprises a VSD, motor, bearing and load, be it a fan, pump or otherwise. Traditionally, mechanical items like motors, bearings and the load would require manual visual inspection to check their status and condition. Smart sensor technology now allows parameters to be monitored in real-time to provide enhanced performance and energy efficiency data. This data can then be turned into meaningful information, and displayed to the relevant persons in a format they can comprehend. This means that the energy manager can see at a glance how much energy an application is saving, the financial officer can see the monetary savings in real-time, while the maintenance manager can see where action is required to prevent breakdowns.
Manufacturers are increasingly recognising that many stakeholders in the decision-making process do not know nor care how a VSD works. An energy assessment means that they don’t have to. The bespoke nature of an assessment, which is carried out on-site on real applications, means that stakeholders can see exactly what the actual impact will be, how much money will be saved, and the likely payback times. With employees at all levels of organisations increasingly being required to squeeze more out of less, VSD manufacturers are equipping energy managers with the tools to help build a consensus on energy saving investments, and expedite upgrade processes.
Steve Hughes has worked in ABB for 23 years in sales and channel management roles for both variable speed drives and instrumentation products. Whilst working in the drives business Steve was an integral part of ABB’s energy efficiency campaign when it began almost 20 years ago in the year 2000.