Re: Renewables in power cuts

John Beardmore said:

> In message
> <pan.2005.09.30.22.41.45.350600@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Andy
> Baxter <news4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> writes
>>mogga said:
>
>>I've been volunteering at a place in lancashire who have been running
>>without any mains electricity for years - they have enough power to run a
>>house and another building (including a TV and computer), and only run out
>>of energy 4-5 times a year.
>
> Quite. This will be using normal inverters though. These cannot be
> connected to the mains, and frequently have square wave output.

Yes, they use a 240V modified square wave inverter with 240-600V
transformers at either end to transfer the current down the hill from the
windmill to where they live. The windmill is connected to a big battery
bank, which stores enough energy for several days use.

> A mains connected inverter must match the frequency and phase of the
> mains supply to deliver energy and avoid damage, i.e. it must be a
> synchronous inverter. Further, to meet UK specifications, it must
> shutdown if the grid fails, if only to avoid scenarios like putting
> power out onto a line when it has been shut down for maintenance. The
> specifications G57, G77 or G83 as above etc, are pretty much cast in
> stone. The inverter manufacture has little scope for whimsy or
> innovation.

Yes, but it would be technically possible to have the inverter disconnect
from the grid, but continue to supply current to the house from a battery
bank (maybe with a very short break when the grid came up again while it
resynchronised with the grid phase). Effectively what these
manufacturers have chosen to do is use the grid as the battery bank, and
count on the fact that in most places it's pretty rare to have a 100%
power cut. I.e. they've gone for a simpler spec to make the whole thing
cheaper, which is what I meant - the reasons are more economic and
regulatory than technical. (Unless the setup I've described is explicitly
forbidden by the specs, in which case I take your point).


--
http://www.niftybits.ukfsn.org/

remove 'n-u-l-l' to email me. html mail or attachments will go in the spam
bin unless notified with [html] or [attachment] in the subject line.

.

Relevant Pages

  • Re: Renewables in power cuts
    ... > connected to the mains, and frequently have square wave output. ... > A mains connected inverter must match the frequency and phase of the ... > power out onto a line when it has been shut down for maintenance. ... power into or out of the grid from the battery bank. ...
    (uk.environment)
  • Re: How to grid-locked/tied synchronous inverters work in alternative energy setups?
    ... >>pushing amps in in phase with the mains. ... > locally generated power thrown away. ... For example, don't feed the grid at 0-20V, and don't turn on your inverter ...
    (sci.electronics.design)
  • Re: Why do my freeview boxes keep crashing?!
    ... These do generate sinewave output, ... than that directly available from the mains supply. ... The cheaper BackUPS range from APC and similarly cheap UPSes from other ... inverter, or a stepped square wave (the latter, I think, in the BackUPS ...
    (uk.tech.digital-tv)
  • Re: Renewables in power cuts
    ... Further, to meet UK specifications, it must shutdown if the grid fails, if only to avoid scenarios like putting power out onto a line when it has been shut down for maintenance. ... The inverter manufacture has little scope for whimsy or innovation. ... There are huge advantages to eliminating the use of batteries. ...
    (uk.environment)
  • Re: 12v accessory sockets
    ... A hell of a lot of the equipment that people want to use in a car will ... charge and run from the 5v supply on a USB port - phones, satnavs, games ... The other very useful car-powered device is a 240V mains inverter. ...
    (uk.rec.driving)