Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • Replies 56 replies
  • Subscribers 43 subscribers
  • Views 10014 views
  • Users 0 members are here
Options
You may also be interested in

Plug-in Solar supposedly going to be 'easier'?

Steve Nixon76

Hi all, new to the forum.

I've been reading (various media outlets are running with the story) that the government is planning to make it easier (no mention of safety) for consumers to connect solar PV panel inverter directly to the mains using a 3 pin plug and socket arrangement.

Considering all of the current guidance regarding the connection of a solar PV inverter to the mains (dedicated circuit, own RCD, no 3 pin plug), how is this all of a sudden going to be 'safe'?

The argument that 'Balcony Solar' is all the rage on the continent surely doesn't negate the potential risks all of a sudden. Surely the IET is in discussions with government and arguing that the dangers cannot simply be swept under the carpet?

Parents

  • https://www.cef.co.uk/catalogue/products/1698557-outdoor-ip55-power-enclosure-with-4-gang-13a-socket-strip

    I have an image in my head of a plastic box on a house wall with a multi gang socket strip supplied from an existing socket outlet and a EV granny charger plugged into the socket strip along with one or more balcony PV sets.

  • in reply to Sparkingchip

    well, someone is bound to try it - and I'm not sure that it will be anymore dangerous than plugging in a flymo and using it, it is just that we are used to a very safe electrical approach, and rowing back on that is uncomfortable. I suggest its not much more risky than EV charging from PME, or many other things we do not worry about.
    Mike.

    edited for typo that reversed the meaning of the last sentence  . Apologies for any confusion caused.

  • in reply to mapj1
    mapj1 said:
    I suggest its more risky than EV charging from PME, or many things we do worry about.

    Is or is not? Slip of the pen/fat thumbs?

    If these things only work when plugged into the grid, and the grid supply is PME, how could the risk be reduced?

    What could work quite nicely is charging an EV on DC direct from the 'balcony' panels.

Reply
  • in reply to mapj1
    mapj1 said:
    I suggest its more risky than EV charging from PME, or many things we do worry about.

    Is or is not? Slip of the pen/fat thumbs?

    If these things only work when plugged into the grid, and the grid supply is PME, how could the risk be reduced?

    What could work quite nicely is charging an EV on DC direct from the 'balcony' panels.

Children
  • in reply to Chris Pearson
    Chris Pearson said:
    What could work quite nicely is charging an EV on DC direct from the 'balcony' panels.

    That may be difficult to achieve as most EVs use a 400V architecture*.  They aren't likely to be impressed at being offered less than 1kW either.

    *Some are now 800V but accept 400V charging for backwards compatibility.

  • in reply to Simon Barker

    I hope that I haven't got my decimal point in the wrong place, but a very modest (by modern standards) 100 kW is 400 V x 250 A, but perhaps the motor runs at an even higher voltage?

    Is there any reason why solar could not supply 400 V DC?

  • in reply to Chris Pearson

    I guess the motor must run on something like 400V, because stepping it down would only make the currents higher.  But the motor doesn't actually run on DC anyway.

    My Renault has a 100kW motor (so your figures are about right).  The motor Renault chose uses a 3-phase AC stator and a DC electromagnet for the rotor.  Others use permanent magnets instead.  I can only assume that there's a VFD hidden under the bonnet controlling all that.

    If you're using standard rooftop type solar panels, you'd need a good number of them for 400V.  My rooftop system has two strings of 9 panels, with each string running at approximately 300V.  The voltage isn't constant. and varies with insolation. So the charger will need sonething to regulate the voltage.  It will also need to handle black clouds drifting across the sky mid charge. Maybe a small buffer battery to keep the power going while the charger tells the car to slow down its charge.

    I think the complexity of direct DC charging is why most householders wouldn't bother. Easier to use an off-the-shelf solar inverter to generate 230V AC, then rely on the car's own charger to convert that back to DC again.

  • in reply to Chris Pearson

    not much more risky than,,, is what i meant to type. But didnt.Now corrected.

  • in reply to Simon Barker

    Indeed - the motors on most electric cars are in effect stepper motors, and the battery DC is gated onto each set windings in turn, cycling the effective polarity, to pull the magnet around one 'click' at a time at speeds of few Hz up to ~low kHz..

    Battery voltages seem to vary quite considerably between makers, - yes 350-400V is one standard, but so is 250-300 for small vehicles, and then 700-800V and even 800-900 for larger sportier cars. This is all about keeping the currents and wire sizes manageable.
    The actual Li-ion cells are between 3v (flat) and 4.1V (full charge) but are wired in complex series and parallel combinations to get the desired current capacity and voltage,
    To have an external  DC charger is not as convenient as it might seem, except when  the cell configuration for the specific vehicle is known, & even then the charger has to modulate its output voltage during the charge cycle to stay within a voltage-dependant safe current envelope as the cells charge.

    So using the on-vehicle charger that is carefully matched to the battery, and supplying it with a mains-like inverter-derived waveform, is generally still the most effective and certainly the lowest risk (and future proof for any new vehicle battery configuration).

    Mike.

Community Rules & Guidelines