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Direct Current in the home

PeterRT

With more and more in the home being powered off DC (Direct Current) supplies, e.g. Battery & Solar Panels, then wouldn't it be more economical to consider extending the regulations to cover DC in the home avoiding the need for transformers?

For example, this is particularly appropriate now that lighting is dominated by LED.

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    SMPS are certainly lighter weight and more efficient than a conventional transformer plus linear regulator combo, as well as being more forgiving of mains variations - the mark-space ratio of the ultrasonic chopping waveform can be varied to alter the transformation ratio - by the same mechanism they can be made to draw current at intermediate voltages up and down the sides of a sinewave - while a 50Hz rectifier into a smoothing cap only draws current in a short burst near the crests when the input exceeds the reservoir, so with a bit of careful control, it is also possible to improve power factor/waveform quality this way. 

    However, they are not really more efficient than a well designed 50Hz transformer driving a resistive load like a lamp filament, so long as you are not trying to regulate. (magnetizing current is not loss, as it is at 90 degrees to the voltage.) Even so the fact that it is smaller and lighter and cheaper to make, usually wins the day.

    Mike

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    I don't think DC distribution in the public network is being considered at present (never say never, though, <snip>)

    Never say never indeed -  I am aware of an experiment in London, and there may be other high demand areas trying the same thing, where a DC bus of about 800v is linked between 2 substations each having a high power and reversible inverter, so that an under-loaded substation can prop up one or more of the phases on whichever substation is feeling most overloaded. Similar experiments  but  complicated by the addition of a DC car charge point or two to the DC bus instead are either underway or in the offing.

    Western Power's ‘DC share’ is a related idea for car charging.

    DC Share is a network equalisation solution designed to share system capacity across AC secondary substations with different load profiles. The available power will then be distributed to vehicle charge points via a new high capacity DC cable network to enable EV rapid charging, without traditional reinforcement.

    Still early days, but interesting reading

    Mike.

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    Sounds like the interconnectors albeit on a smaller scale!

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