Time for another examination

Time for another look

You’ve already looked at ways in which you can save energy. But, with the seemingly unending increases in energy prices, it could be time to look again, says Alan Baird

Alan Baird

Country manager of Danfoss Drives UK

www.danfoss.com

he UK Quarterly Energy

TPrice Review released at the end of September 2022 makes sobering reading. It reports that UK electricity prices for non-domestic consumers were, on average, 45 per cent higher in Quarter 2 of 2022 than they were in the same quarter of the previous year. For small/ medium consumers, the situation was even worse, with prices 57 per cent higher.

With this in mind it would be easy to think that, even before the present crisis, organisations would have been availing themselves of every possible opportunity to find ways of saving energy. Research shows otherwise.

Eff ective opportunity

One of the most effective tools for identifying opportunities to save energy is an energy audit, for which, according to the Government, “the various activities and processes that make up an organisation’s energy consumption are audited by a trained assessor, who then makes tailored energy savings recommendations based on the audit.” When the UK government looked at the uptake of energy audits in 2017, it found, astonishingly, that only 9 per cent of SMEs (organisations with fewer than 250 employees) had undertaken one, and it seems that there had been little improvement by 2020.

Low uptake of energy audits

What are the reasons for the low uptake of energy audits? One of the most frequently encountered is the belief that “we don’t need one”. Those with responsibilities for energy management in buildings and businesses often feel that they are themselves in the best position to identify opportunities for saving energy. There is some justification for this point of view, and it is certainly possible for them to identify some of the opportunities. Substituting LED light bulbs for less efficient types and mandating that equipment must be switched off out of working hours are typical examples.

Some energy-saving opportunities are rather harder to see, however, which is why the government definition quoted earlier states that energy audits should be carried out by “a trained assessor.” This is no reflection on the capabilities of the organisation’s energy manager, it simply recognises that specialist expertise is needed to maximise energy savings and, to a lesser extent, that an external assessor will have the benefit of looking at systems and procedures with fresh eyes.

One area where expert assessment can bring big benefits is in relation to the drives used to control motors. Again, there may be some who are thinking “we don’t need this – our organisation doesn’t have motors and drives.” Think again! All but the very smallest organisations are likely to have motors and drives in their HVAC systems even if they’re used nowhere else. Such motors and drives are a classic case of “out of sight, out of mind.” But that doesn’t stop them guzzling energy!

Worst-case conditions

Until comparatively recent, motors in HVAC systems in particular often had very basic controls – they could either

One of the most frequent excuses for not having an energy audit is 'we don't need one'

Even where motors are already controlled by variable speed drives, an energy assessment is worthwhile

run at full speed or stop. However, these motors are necessarily sized for worst-case conditions which means that for 90 per cent of the time or more they are running faster and using more energy than needed. This is significant, because the energy used by a motor is proportional to the cube of its speed or, to put it another way, reducing the speed by 20 per cent cuts the energy usage by 50 per cent. Clearly, there are big savings to be made, and these are easily realised by installing variable speed drives.

Small, inexpensive changes

Even in installations where motors are already controlled by variable speed drives, an energy assessment by a drives specialist is definitely worthwhile, as this will often spot ‘lowhanging fruit’ – small and inexpensive changes that will deliver significant energy savings.

Of course, believing that energy audits are unnecessary is not the only reason that organisations shun them. There are also concerns about cost and disruption. Both of these are groundless fears. Companies like Danfoss Drives that have a strong commitment to protecting the environment will carry out energy audits at very low cost or, in some cases, free of charge. This does, of course, lead on to another issue: how can the improvements be financed? With the current high energy prices, this question may be somewhat easier to answer than in the past, as payback periods will be shorter.

Very quickly paid back

However, even before the present energy crisis, investments in energy saving measures usually paid off very quickly, as illustrated by a recent audit carried out by Danfoss. We were invited to carry out an energy audit at a higher educational establishment which is not, perhaps, the most obvious place to look for energy saving drive applications. We discovered that six pump motors in the HVAC installation had very basic controls. Replacing these with variable speed drives has given projected energy savings of almost £20,000 per year. Since the total cost of fitting the new drives was also £20,000, we confidently predicted that the investment would be repaid in a year. Of course, the recent huge increases in energy prices mean that this period will now be even shorter. ■