Voltage Optimisation: Avoiding Common Pitfalls
With the CRC Energy Efficiency Scheme now in effect, voltage optimisation has become increasingly popular as a simple and practical energy management strategy. But there are several key considerations for making the most out of the investment, as Jim McIlfatrick of Claude Lyons, supplier to the MoD and Hilton Hotels, explains.
A
properly planned voltage optimisation strategy can deliver energy savings of up to 25% by reducing and regulating the
voltage electrical equipment receives from the national grid. It is not only cost- effective – it cuts electricity bills in addition to emissions – it is measurable, making it easy to assess carbon credit requirements under CRC. But amidst a burgeoning marketplace of products touting their emissions-saving potential, the wrong approach to voltage optimisation can limit effectiveness and even put a site at risk.
Voltage optimisation is not one-size-fits all – get a full site survey The installation of voltage optimisation equipment should begin with a comprehensive analysis of a site’s power conditions. Each site is different, with its unique infrastructure and specific load requirements, so there is no one-size-fits- all strategy – it should be tailored to ensure that savings are maximised.
A product can promise “up to X%” of savings on the tin, but the site’s particular conditions may only make a fraction of that savings possible. A site survey – with an equipment assessment, power supply analysis and electrical logging – will determine the actual energy saving potential.
Three phase logging is crucial for safe use and maximum ROI The electrical logging component of the site survey should involve three phase rather than single phase logging. Three phase electricity logging measures average voltage, current, power factor and wattage, as well as maximum
current. Voltage readings are taken at the furthest point or longest cable runs from the main incoming supply, recording phase to neutral voltages and time so as to provide a reference for the logged data and to identify the site’s worst case drop. Each metric should be analysed over at least a seven day period, recording each phase at five minute intervals. This will identify many power quality issues, such as significant mains voltage dips, sags or harmonic disturbances.
Although it can be tempting to use a single phase logger, it is a risky shortcut to take. Measuring just one phase at just one point does not accurately reflect a site’s full situation – it neglects key issues such as voltage imbalance and volt drops. It also makes for a very large margin of error in assessing equipment requirements, which can lead to catastrophic problems after installation and create issues in the event of future site expansion.
Ensure the equipment provides true, dynamic voltage optimisation There is more than one type of equipment that bills itself as ‘voltage optimisation’ technology, but in most cases this is a misnomer. Most products on the market are simply voltage reduction devices – essentially fixed-ratio transformers that reduce the supply voltage by a fixed percentage. These devices can achieve useful levels of savings if the site’s voltage is stable and the phases are always balanced, but for the vast majority of sites this is not the case, and equipment often ends up receiving too much or too little voltage. This results in inefficient equipment
operation, reducing equipment life. Most sites require true, dynamic voltage optimisation to maximise energy savings and carbon reduction. This breed of equipment has a so-called ‘regulator’ or ‘stabiliser’ function that continuously and automatically adjusts the amount by which the voltage is reduced – just as you use a thermostat to maintain room temperature at a desired level rather than having a heater on at all times. Regulator technology facilitates a controlled environment similar to that achieved with air conditioning or a compressed air system. It ensures that electrical equipment never receives more or less than the required minimum voltage for correct operation – important during the power dips and surges that can occur regularly. It also constantly balances the three output voltages, providing more efficient operation of three phase loads. With this technology, savings are greater than with a simple fixed-ratio transformer, and equipment lifetimes are maximised. As a result, equipment operates as efficiently as possible at all times, and running costs and carbon emissions are minimised.
‘Fit-and-forget’ can be dangerous – get an annual check-up Voltage optimisation technology operates in the background, with no effect on an organisation’s day-to-day operations. However, as with cars or boilers, the equipment should have an annual inspection to ensure that it remains appropriate given any changes to the site’s conditions. Most insurance will have some sort of requirement in this regard. A ‘fit-and-forget’ approach to voltage optimisation can mean that potential housekeeping hazards go unnoticed and potential savings aren’t achieved. New or ageing electrical equipment on the premises, or undetected variations to the power supply, can affect energy usage, so an MOT ensures that the technology continues to operate at maximum efficiency.
www.powersavetechnology.co.uk. Building & Facilities Management – August 2010 energy solutions 15
Energy Management Systems
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