Time To Rectify Low Voltage DC! (An Inverted View By Blane Judd)

Blane Judd, EngTechNow
Blane Judd, EngTechNow
As the battery begins to fade on my smart phone my thoughts turn to recharging it. Unfortunately I've left the rather bulky transformer rectifier at home. The three pin styling albeit slim-line charger does not sit neatly in my suit pocket. As I search around for the correct model to work with my phone I'm left wondering if we had known about semi-conductors would all of the socket outlets supply 240V a.c.? The battle of the currents was lost some years ago but in today's digital world did the right winner emerge?
Take a look around any office and you'll see a significant number of low efficiency d.c. power supplies. Each one contributing to localised heating of the working space through I2R losses, not to mention the embedded carbon and semi-precious metals.  It seems that every manufacture selects a unique output, thereby increasing the number of devices. It is not a lot different in the home with TVs, phones, digi-boxes and computers needing the supply from the socket outlet to be rectified for use. 

The emergence of photovoltaics and other micro-generation devices with d.c. output means we are now inverting before rectifying neither process being a loss-less activity. d.c. power distribution has meant that consideration of LED lighting as a viable low energy alternative to incandescent lamps but we still have localised rectification in the domestic environment. Worse still the recent introduction of USB socket outlets which still rely on local rectification do little more than hide the transformer rectifier unit behind a face plate. With the development of international standards, from the IEEE’s Power over Ethernet, to those under development by the EMerge Alliance, will the UK be bypassed altogether?

Thankfully IET Standards have taken the step of producing the Code of Practice for Low and Extra Low Voltage Direct Current Power Distribution in Buildings. This document has been scoped and developed with an expert panel drawn from industry, academia and government, with the aim of helping to dispel many of the myths that have emerged about using d.c. power distribution (for both LV and ELV applications). It considers d.c. installations using telecommunications cabling, d.c. wiring or existing a.c. wiring infrastructure, including standardised solutions (such as PoE) as well as proprietary approaches for d.c. power distribution.
My hope is that single rectification solutions begin to become the standard in commercial and domestic buildings in the near future so that all I would need to charge my fading smart phone is a short cable.
For further information on the Code of Practice for Low and Extra Low Voltage Direct Current Power Distribution in Buildings, due for publication in May 2015, please visit: www.theiet.org/dc-cop
For information on the launch event – Low Voltage Direct Current: Powering energy demands in our digital world – which will be held on 18th June 2015 in London, please visit: www.theiet.org/lvdc
Blane Judd
Posted by Hannah Uzor on Mar 30, 2015 11:08 AM Europe/London


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