Dave Mellor, Director of Cyntech Components advises ‘buyer beware’
A power supply’s efficiency relates to how much of the power going into it is wasted as heat, due to electrical losses, and how much power can be extracted from it. For example, a power supply that takes 10 Watts of power from the mains when delivering only 9 Watts to the load (perhaps a computer or television) is losing 1 Watt in heat. It’s said to be 90% efficient because 90% of the power drawn from the mains is used for its intended purpose. Power supplies are actually quite efficient when they are working near their maximum power output. However, when the load is switched off, the power supply still consumes some energy if it’s connected to the mains, perhaps a fraction of a Watt to a few Watts. It is this ‘no-load’ efficiency that has increasingly concerned regulators in recent years so energy efficiency regulations stipulate requirements for both full-load and no-load conditions.
According to the US Environmental Protection Agency (EPA), compliance with current external power supply efficiency regulations could save the US 32 billion kilowatts of energy every year – equivalent to about 7 power stations. Similar studies in Europe have concluded that improvements in power conversion losses and so-called ‘no-load consumption’ (the power consumed by an external power supply when the equipment it’s connected to is switched off) could, by 2020, save some 9 terawatt hours of electricity. The power supplies may be small but the big picture reveals that total power consumption is huge, as is the level of CO2 emissions resulting from it.
How can a buyer tell if a power supply conforms to regulatory requirements for energy efficiency?
There’s an established protocol for labelling power supplies to indicate the efficiency standards that they meet. Roman numerals identify the standards, from Level I through to Level V – the most recent, and most stringent. Until April this year, regulations in both the US and Europe only required external power supplies to meet Level IV efficiency, despite the fact that some power supplies now meet Level V standards. The efficiency requirement varies depending on the rating of the power supply, both in terms of its maximum power capability and its output voltage rating. Various formulae are used for the calculation but, as an example, an external power supply rated at over 49 Watts must have 87% efficiency to meet Level V, but only 85% efficiency for Level IV. The difference might seem small, but it takes a lot of engineering effort to achieve the improvement, sometimes involving more advanced and expensive components within the design of the power supply.
The Commission of the European Communities Directive 2005/32/EC was implemented in April 2009. It required external power supplies used in the European Union to meet Level IV efficiency by April 2010 and to meet Level V efficiency by April 2011. This two-phased approach was agreed in order that manufacturers had sufficient time to re-design their products. As a result of these more stringent regulations in Europe, products that meet US requirements may now not be suitable for use in Europe. Section 301 of the Energy Industry and Security Action (EISA) was passed by Congress in 2007 and stipulates that external power supplies manufactured after July 1, 2008 meet minimum efficiency requirements that are the same as those defined in Level IV. Although most new external power supplies are likely to meet Level V by the end of 2011, there is not mandatory requirement in the US that they do so, and no timeline is established for when this could be mandated. The US Energy Star programme for external power supplies was phased out on December 31st, 2010, but the EISA Level IV regulations remain in force.
If European buyers purchase power supplies designed for the US market, or from US suppliers who may not be aware of the latest European regulations, they risk end equipment failing to achieve its CE mark. This can lead to a costly and time-consuming re-qualification process. There are a few exceptions to the regulations in Europe. External power supplies for medical devices do not have to meet Level V efficiency standards. However, these are subject to other regulations to ensure that patients connected to medical devices are not electrocuted. Battery chargers are exempt, as are power supplies for some servicing equipment. Finally, low voltage external power supplies, defined as those with a nameplate output voltage of less than 6 volts and a nameplate output current greater than or equal to 550mA, are exempt too. It is complicated.
The safest and most economical way forward is for buyers to consult expert European suppliers who understand local regulations and can advise on the most suitable power supply for each specific application.
Dave Mellor, Director, Cyntech Components Tel: 01908 821811
Email: email@example.com Web: http://www.cyntech.co.uk