Quick wins: Managing power supply

10th May 2012


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Voltage management can help to lower energy consumption and cut carbon if applied correctly. Sarah-Jayne Russell investigates

In the past decade, voltage management has gone from an unknown quantity to a burgeoning part of the energy-efficiency market, with firms offering technologies to “reduce”, “regulate”, “stabilise”, “condition” and “optimise” electricity input. But what do these terms mean and how does the technology behind them cut energy use?

Back to basics

While most energy-efficiency measures take effect at the point of demand, through light-emitting diode (LED) lighting, for example, voltage management is about controlling the electricity supply before it reaches electrical equipment.

Electricity is billed in kilowatt hours (kWh) – power (kW) × time (h) = energy (kWh). In this equation, power represents the amount of electricity being supplied, or the current. Voltage refers to how the current is supplied.

To use a common analogy: if the electrical circuit were a series of pipes, the current would be the amount of water in the pipes and the voltage is the pressure pushing the water through the pipes.

Basically, voltage management technologies are transformers lowering the voltage of the electricity supplied to a building. This reduces the amount of energy being consumed because much of the electrical equipment used in the UK can operate at a lower voltage than it is being supplied with.

Under EU legislation introduced in 1995, member states must supply electricity through their national grids at 230 volts (V), give or take 10%. Historically, however, the UK required the supply to be 240V (+/–6%) and the voltage remains much higher than in other EU countries. So, while counterparts on the Continent are receiving electricity at 220–230V, in the UK the average rate is 242V.

Manufacturers, therefore, design their products to operate when supplied with 10V or 20V less than they receive in the UK. Furthermore, most equipment does not use this extra energy to operate, but gets rid of it through heat or vibration.

A variety of options

Installation of voltage management technologies is relatively simple. They are units installed where the mains power supply enters a building, before the distribution board. For large properties, such as hospitals, there can be more than one point of supply and units need to be installed at each.

The building’s size and the amount of electricity being supplied also impact on the complexity of the unit; however, once built it generally takes two or three days to set up a unit, with the electricity switched off for no more than a couple of hours. For organisations with critical demand needs, such as medical equipment, generators can be brought in to cover the installation period.

There are a number of technologies on the market, falling into three levels of sophistication. At the most basic level are voltage reduction units. These units cut the voltage of supply at a specified level, for example 20V.

This is fine if your mains supply remains constant, but electricity from the grid often fluctuates. If, for example, the mains supply drops to 210V it will cut supply to the building to 190V, which could leave equipment struggling to operate if the unit cannot be bypassed.

More sophisticated “stabilisation” and “regulation” technologies counteract this problem by monitoring the incoming mains power and automatically bypassing the unit if the voltage drops below a certain level. This technology can also smooth out any sudden spikes and drops in supply (or transience).

Jeremy Dodge, head of marketing and technical services at cable trunking manufacturer and energy management firm Marshall Tufflex, explains: “Our main manufacturing plant is full of machines that are very sensitive to changes in power supply. When a supermarket was built between us and the mains supply, we were getting power dips that would knock out our machines.

“After installing our Voltis units, we don’t have the same problem. The units detect if there’s a voltage dip or spike and will switch between mains power or voltage saving mode. They connect with one supply before disconnecting with the other, allowing a seamless switchover, so our machines don’t react.”

The most sophisticated technologies “condition” the supply as well as reducing the voltage and smoothing out peaks and troughs. Electricity is delivered on a sine wave, which can be distorted as it is transported along the grid. Conditioning technologies help to suppress the distortion or “harmonics”.

Angus Robertson, chief executive of powerPerfector, explains: “If you don’t have a clean sine wave, it’s a bit like putting dirty petrol in your car; your equipment doesn’t work as efficiently and uses more power.”

For big electricity users such as hospitals, supermarkets and manufacturers, voltage management offers a quick way of reducing electricity use.

Robertson confirms: “The more power you use the more benefit you will get. Tesco, for example, is saving £16 million a year. That’s a huge financial and CO2 saving.” However, he advises: “Unless an organisation is really committed to investing in the technology for CO2 reduction, the returns on investment start coming in at £20,000.”

While payback times vary depending on the type of building and the amount of electricity consumed, installers can achieve a 33% return on investment, according to Robertson. With users’ electricity bills cut by 10% on average, supermarkets can see payback in as little as 18 months, with other large commercial buildings achieving payback in three to four years.

Know your load

The cost and CO2 savings voltage management offers are dependent on the type of electronic equipment installed. For example, while buildings with incandescent lighting will see a marked difference in the electricity consumed, the same is not true of those with LED lights, which have the same power demand regardless of the voltage supplied.

It’s a similar story with electric motors, with savings not possible from those with variable speed drives. With many IT technologies too, the savings can be negligible.

For any firm considering voltage management it is important to analyse the technology being used in the building and electricity consumption patterns. An analysis of half-hourly data, from at least the previous year, should be undertaken and for those without an in-house expert it is best to get independent advice on the savings to be expected.

Reputable voltage management firms will analyse your load and estimate the savings possible, with some offering performance guarantees. However, you should have an agreed measurement verification protocol in place to ensure the proposed savings are statistically sound.

Another important consideration is your firm’s wider energy-efficiency plans. If, for example, you are considering replacing incandescent lighting with LEDs, then that will impact the savings possible through voltage management.

To avoid creating a situation where you are robbing Peter to pay Paul, it is important to understand the interaction between all of the energy control measures you are putting in place.

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