Drives and controls - Don't waste the hard lessons of this recession

Typography
Articles

The electrical industry could be at the forefront of helping organisations recover from the economic downturn, by installing energy saving equipment and green technologies that will also help with carbon reduction requirements. So says Jeff Whiting of Mitsubishi Electric

Global greenhouse gas emissions are down 3% on last year, according to the International Energy Agency. Unfortunately this is not a massive triumph of green technologies, but is a reflection of the reduced economic activity brought about by the worldwide recession. This has given us a bit of a breathing space in which to reassess our position in regards to global warming. And we must be careful not to waste this advantage with a headlong rush to rebuild things as they were.

Instead we need to take time to work out how we can do things better this time around. We won't get everything right, but the world needs to change and electrical engineers can play a vitally important part in building a better tomorrow.

In a recession there is simply less work available, so businesses have to make financial savings. Ten or twenty years ago this tended to mean job cuts; but modern businesses run pretty lean and recognise that losing people also means losing skills that may never be replaced. So savings need to be found elsewhere.

A big cost for most businesses is energy bills - and these can be controlled!

Here we have a conjunction of an economic need to cut power bills and a social drive to become more energy efficient. Good housekeeping - switch things off, turning things down, checking the insulation - will pay worthwhile dividends. But the real benefits come with a long term commitment to control energy usage (and therefore costs) on an on-going basis.
Probably the technology with the best energy saving potential is variable speed inverter drives, which are fitted to electric motors to control speed, and therefore costs. Electrical engineers have long known the basic rule that the energy saving is proportional to the cube of the speed reduction, which means that a small reduction in speed will give a huge reduction in running costs and energy used. Traditionally, financial managers have often only looked at initial capital outlay, not recognising the short payback and significant savings that can be achieved with such systems.

A climate of change
However with climate change now so high on the agenda, traditional thinking is being turned on its head. Governments around the world are introducing laws and guidelines to promote the adoption of inverters. 

One clear example of this in the UK is the new Part L of the Building Regulations, which recommends inverters should be fitted to all pump and fan motors over a moderate 1.1kW. Doing this will improve the efficiency grade of the building and actually improve the value of the building asset. 

A modern medium sized office building, for instance will have literally hundreds of motors tucked away behind access panels. Every fan has its own motor; pumps in the air conditioning, heating and water supplies are often motor driven: high powered extracts in the kitchens - motors are everywhere.

Let's look at a typical example. A 100kW motor is not a cheap thing to buy. There are more costs in installing and commissioning it. Then there is regular maintenance. And, not least, it will be running up the energy bill every time it is used. And the last cost is by far the largest one!

Such a motor will have a typical working life of 15 years. And it is of such a size it is likely to be assigned a duty where it is running 24/7. In this case its total energy consumption would work out at £75,000 per year.

Interestingly, most systems have some sort of mechanical damping device to control or limit flow as motor systems are generally sized for ‘worse case plus' conditions they are never required to operate at. Include an inverter and you can control the speed thereby reducing the flow, but with the added benefit of significantly reducing the power requirements. Usually you would expect to find the motor never needs to run at more that 80-90% top speed. Often you can run it at a far lower speed, say 25-50%, and you could turn it right down or right off at weekends, bank holidays and possibly other times too.

Do this and energy consumption would reduce significantly, possibly 50-70% - that is to say a saving of maybe £50,000 each and every year of its operational life. An inverter can be programmed to make all these speed changes automatically.

But what of the initial capital outlay? Well most retrofit inverter installations will pay for themselves in 12-18months, fast enough to impress even the grumpiest of accountants. Further, there are now grants available and financial plans that mean you pay for the inverter as you achieve your energy savings. 

Inverter installation costs are, naturally, far less if they are designed into new build projects, and the payback time is therefore reduced significantly.

While there are many motors in an office, there are significantly more in a factory with lots of production plant or in a hospital with all its high tech medial apparatus, or in a leisure facility housing exercise equipment, catering, computer games etc.

In fact, the manufacturing and production industries are by far the biggest users of energy, consuming about 40% of the total generation capacity. 70% of this figure (i.e. 30% of the total) is used to run electric motors, of which only 17% are fitted with energy saving inverters.

And while you may think that 17% is a poor, it is streets ahead of the figure for inverter take up by other sectors of the economy.

Culprits unmasked
Until global warming was recognised as the crisis it so nearly is, for some reason government guidelines always fought shy of drives, not recommending them with the enthusiasm that might have been expected. But now the tide has turned.

In a recent revison of the McKinsey report, the management consultants re-aligned the inclusion of inverters as being one of the most cost effective measures, creating a big impact on CO2 levels and global warming.

The government is advised by McKinsey & Company, the international management consultants, who for some reason did not acknowledge the full carbon and money saving potential of drives until their most recent publication.

Their initial report: Pathways to a low carbon economy: Version of the global greenhouse gas cost abatement curve, includes the McKinsey greenhouse gas abatement cost curve.

A cost curve is a typical tool of management consultants - and let it be said - they are often very useful, condensing complex and multi-dimensional information into a simple two-axis graph. The problem with cost curves is users know how difficult they are to compile and that management consultants charge a lot for them, so they are pre-disposed to trust them and therefore use them blindly without questioning their accuracy.

Unfortunately Version 1 of the McKinsey curve presented variable speed inverter drives as an energy saving solution with significant cost! A new Version 2 curve, now in circulation puts drives right at the top of the energy saving ranking, recognizing the high level of savings that are achieved with such systems. The savings are only bettered only by a wholesale switch to LED lighting and thermal insulation of commercial buildings. Drives are seen as greener than other industrial efficiency improvements, electricity from landfill gas, biofuels, geothermal and next generation hydroelectricity schemes.

Let's look at some details of the report. The analysis finds that if no attempt to curb emission is made, they will grow by about 40% by 2030. There is potential, if everyone pulls together, to turn this around to a 35% reduction. This would cost about £200bn annually, or 1% of global GDP, and would hold global warming to just under 2°C, a critical figure if icecap melting and desert growth are to be contained.

The International Energy Agency's report suggests the recent recession has bought us a couple of years on these figures. Unhappily, I would predict at least two more recessions before 2030, which might win us another six years (thereby giving us time for yet another recession and three more years).

The report goes on to define four categories of abatement opportunities: energy efficiency, low carbon energy supply, terrestrial carbon (agriculture, forestry), and behavioural change. Of these energy efficiency has the most promise; it could account for about a third of all potential savings, uses mainly proven technologies and does not rely on changing human behavior.

McKinsey looked at carbon reduction on a global scale, but this is not a scale familiar to most working engineers. They look at a rather smaller world; refurbishing some building controls, a single production plant or design of a machine.

Until recently it was unheard of that customers or bosses asked for a reduced carbon footprint. But they are now being forced to do so (although it is often presented as a financial saving).

Electrical engineers will be the ones who lead the widespread adoption of inverters and other green technologies. And now with business minds so focused on cost control is a good time to get a firm foothold in what will become a staple of the sector.