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Reducing the mains voltage to save energy
- Thread starter John D v2.0
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Leaving aside the EU diktats (which I detest) for the moment, actually battery power can be really good.
Several weeks ago, we bought a new Dyson V11 which has proved to be a much improved model compared with our old V6 which wasn't that bad to be honest. This new model (though expensive - actually, Argos are currently selling them for £100 off!) is very powerful indeed and, I believe, compares favourably with many mains-powered upright models. Also, it is a damned sight easier to push around than our (even older) upright model and because of its careful design can go where uprights cannot venture, like under the settee.
The point is that battery power, at least in a domestic setting, can be not only acceptable but a distinct improvement.
Advances in battery technology have certainly made some big differences, but from my personal point-of-view there remain too major issues with most 'cordless' things.
Firstly, although this is improving all the time, run-time is limited, which is a particular problem for those like me with a very large house and very large garden. That can be partially addressed by having multiple batteries (maybe even multiple chargers), but that can be a very expensive approach.
Secondly, and worse, the batteries have limited life, and when they come to need replacements, they can be difficult/impossible to find and/or prohibitively expensive. For example, in my cellar I have a great stash of power tools which would work fine if only I could find (at all, or cost-effectively) batteries for them. That includes a couple of old B&D 'Dustbusters' - for which replacement batteries are still available (at least, when I last looked!), but at a price appreciably greater than that of a brand new product (with battery and charger).
Kind Regards, John
Your cellar is too big.
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Well, f it were smaller, I would probably have had to chuck them out - but it seems crazy to have to throw out perfectly good items just because their batteries have died.
I have sometimes replaced the cells in the battery packs, but it is usually neither a particularly straightforward nor a particularly cheap exercise - but I suppose I'm keeping them "just in case" I decide to try to rejuvenate some more of them one day!
Kind Regards, John
I give my old cordless to my BiL, he has a couple of boats and uses them on a wander-lead or sockets, off the battery. He has 12v and 24v circuits and says things can cope with "wrong" voltages.
One of the boats he fitted out had huge batts as used in forklift trucks.
One of the boats he fitted out had huge batts as used in forklift trucks.
Yes, that's one way one can partially salvage the situation, but it's of limited applicability. I have leads connected to a couple of my 'dead battery' ones, but very rarely use them, because of matters of convenience/practicality.
If only these things (or, at least, a substantial proportion of them) used 'generic' batteries, the situation would change dramatically, becoming much less annoying and 'planet unfriendly'!
Kind Regards, John
Yes, run time is limited of course. However, I have found that even using the motorised brush head on a carpet (the most power-hungry arrangement) I get about 25 minutes use time. Changing the setting to 'Eco' can extend this to well over 35 minutes, and using a non-motorised head extends it much longer still. Having said that, I have never approached anything like the stated times... and I have two cats to clear up after.
Our particular model has a two-year warranty, including battery replacement if necessary. Beyond that period it is possible to have the battery replaced at a service centre, though I am confident that they will last far longer than the two-year warranty period. Our previous, older model is still going strong after five or six years. I suppose it depends upon how long you use the things, though.
If, like you, you live in a palace and the battery runs out, you could always do some vacuuming until the battery is low, then have a break while it recharges and then do the rest. Of course, I don't bother to vacuum the garden!
Regarding battery replacement in general, I have an old DeWalt cordless drill of which both batteries have become unusable. Not wishing to shell out for the manufacturer's originals, a few months ago I bought replacements on Amazon Marketplace from a third-party seller (Chinese!) at a much cheaper price, which are still going strong and showing no signs of failing.
Yes, it is annoying when manufacturers charge so much for replacement batteries which is more than you'd pay for a completely new model.
If I were you, I'd put my stash (of tools in your cellar) on Ebay!
Yes, run times have definitely been improving.
Maybe in the case of the 'very expensive' ones (Dyson, DeWalt etc.) but I would not usually expect the battery of a cheap cordless power tool to last more than about 2 years.
The problem with 'the palace' is that it is the consequence of history and, particularly as I get older and older, is far more of a problem/liability than something to boast about! In theory, we should have 'downsized' donkey's years ago, but the extent of ouyr 'accumulated possessions' (including stashes of dead cordless tools!) makes that almost unthinkable - although the day may well come when I have no choice!If, like you, you live in a palace and the battery runs out, you could always do some vacuuming until the battery is low, then have a break while it recharges and then do the rest. Of course, I don't bother to vacuum the garden!
I don't vacuum my garden, eiether (
) but things like cordless hedge trimmers, strimmers etc. (let alone mowers) would probably not have enough run-time to be particularly appropriate for me.My personal experienced of 'cheap equivalents' are rather mixed and, of course, they are often not even available for the cheaper items.
It does seem a bit ridiculous, particularly in the case of expensive items
Yes, I have considered doing that - but it doesn't make me any happier that there is a 'need'!
Kind Regards, John
I'm the same, to be honest. I refuse to throw things away, despite Marge regularly nagging me to do so.
Back to the original post ...
ENW have been doing trials on reducing the voltage - including round here. At the time it was being touted as a means of offering short term demand reduction when needed to balance the system or cope with faults - as an alternative to disconnections. As pointed out in various threads, anything with SM PSU will still pull the same power, and anything with a thermostat (or any form of regulated output demand) will simply alter it's duty cycle.
But in the short term, lowering the voltage will lower power demand.
In general, I suspect that non-dimmable LED bulbs will reduce output, dimmable ones (which have a form of SM PSU in them) won't - but they are quite low power. Things like TVs etc won't change power consumption at all. Large loads like immersion heaters, kettles, cookers will be on for longer.
Once past that short term, it could potentially increase overall power demand since the additional current will result in significantly increased losses in the distribution network - AIUI that's why they normally try and keep the voltage as high as they can. Cutting the voltage from 240 to 230V means a 4.2% decrease in voltage, and hence a 4.3% increase in current -> 8.9% increase in I²R losses. The corresponding decrease in load power (for non-comples loads) would be about 8.2% - but as already mentioned, for the bulk of domestic loads, the duty cycle will alter to negate and reduction.
EDIT: Ah, a quick search found what I had in mind :
https://www.enwl.co.uk/zero-carbon/our-key-innovation-projects/class/
That was quite clear (to my reading) that it was about short term control of demand and system frequency, with a view to reducing/deferring investment in upgrades.
Ah, and then I find that it then rolled over into their Smart Street project :
https://www.enwl.co.uk/zero-carbon/our-key-innovation-projects/smart-street/
And the PR piece the Grauniad is quoting from :
https://www.enwl.co.uk/about-us/new...e-electricity-bills-cut-by-up-to-60-per-year/
But, I don't see how they got from the CLASS trials and Smart Streets to the statements in that PR piece. Because in this report, it's clear to me that they are talking about regulating the voltage - stopping it dropping below minimum under high load or going above maximum under maximum embedded generation (ie sunny day in an area with loads of Solar PV panels). I do know that in some places, they've had to turn the voltage down (manually change taps) to avoid over-voltage on sunny days. The knock on from that is that at other times (nights, EVs chanrging, electric heating going), the voltage can drop significantly.
Ie "optimum voltage" is about avoiding fridge compressors running inefficiently on low voltages and stuff like that.
And cost savings coming from reductions in capex on ENW infrastructure - eg re-inforcement of the network to reduce the effective supply impedance in order to reduce the voltage change.
Not mentioned in the PR, but it's in the reports, are low and high voltage capacitors. If there are sharp peaks in supply (eg strong gust of wind), then these can be switched in the create reactive load on the network, increase currents, and use the network cables to "dump" excess power. I believe they can achieve a similar effect by altering taps on parallel feeds and hence circulate currents round the network.
ENW have been doing trials on reducing the voltage - including round here. At the time it was being touted as a means of offering short term demand reduction when needed to balance the system or cope with faults - as an alternative to disconnections. As pointed out in various threads, anything with SM PSU will still pull the same power, and anything with a thermostat (or any form of regulated output demand) will simply alter it's duty cycle.
But in the short term, lowering the voltage will lower power demand.
In general, I suspect that non-dimmable LED bulbs will reduce output, dimmable ones (which have a form of SM PSU in them) won't - but they are quite low power. Things like TVs etc won't change power consumption at all. Large loads like immersion heaters, kettles, cookers will be on for longer.
Once past that short term, it could potentially increase overall power demand since the additional current will result in significantly increased losses in the distribution network - AIUI that's why they normally try and keep the voltage as high as they can. Cutting the voltage from 240 to 230V means a 4.2% decrease in voltage, and hence a 4.3% increase in current -> 8.9% increase in I²R losses. The corresponding decrease in load power (for non-comples loads) would be about 8.2% - but as already mentioned, for the bulk of domestic loads, the duty cycle will alter to negate and reduction.
EDIT: Ah, a quick search found what I had in mind :
https://www.enwl.co.uk/zero-carbon/our-key-innovation-projects/class/
That was quite clear (to my reading) that it was about short term control of demand and system frequency, with a view to reducing/deferring investment in upgrades.
Ah, and then I find that it then rolled over into their Smart Street project :
https://www.enwl.co.uk/zero-carbon/our-key-innovation-projects/smart-street/
And the PR piece the Grauniad is quoting from :
https://www.enwl.co.uk/about-us/new...e-electricity-bills-cut-by-up-to-60-per-year/
But, I don't see how they got from the CLASS trials and Smart Streets to the statements in that PR piece. Because in this report, it's clear to me that they are talking about regulating the voltage - stopping it dropping below minimum under high load or going above maximum under maximum embedded generation (ie sunny day in an area with loads of Solar PV panels). I do know that in some places, they've had to turn the voltage down (manually change taps) to avoid over-voltage on sunny days. The knock on from that is that at other times (nights, EVs chanrging, electric heating going), the voltage can drop significantly.
Ie "optimum voltage" is about avoiding fridge compressors running inefficiently on low voltages and stuff like that.
And cost savings coming from reductions in capex on ENW infrastructure - eg re-inforcement of the network to reduce the effective supply impedance in order to reduce the voltage change.
Not mentioned in the PR, but it's in the reports, are low and high voltage capacitors. If there are sharp peaks in supply (eg strong gust of wind), then these can be switched in the create reactive load on the network, increase currents, and use the network cables to "dump" excess power. I believe they can achieve a similar effect by altering taps on parallel feeds and hence circulate currents round the network.
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How does that work in terms of their regulated and contracted obligations? Does that perhaps mean that they would have to modify their distribution network so that no consumers were normally receiving anything like as low as 216.2V (so that they could, if/when they wished, temporarily reduce supply voltage without some consumers going below the 'minimum permitted'?
As I think is probably the implication of all that you go on to say, I've not convinced that it would have any appreciable beneficial effects (and, as you point out, it could actually have detrimental ones), even in the relatively short-term. The 'compensatory' effect of SMPSUs and thermostatic etc. control would be essentially immediate.
Kind Regards, John
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Not sure on that, old system if ball cock leaked the water would dribble outside and one would be aware of the fault, so quickly corrected, now over flows down the bowl so easy to miss, also if the syphon failed it would not flush, so you got it fixed, now if seal fails again water goes down the bowl often unnoticed, basic old style failed safe, new style can waste water for months before you even know anything is wrong.
As to power used with reduced voltage, on the Falklands I had as part of my job, to look after 4 x 250 kW generators, the generators had a over load cut out so if one generator failed in the main it would over load remaining and they would trip, however every so often the revs would drop before the over load tripped and as the revs dropped so did the volts so I would arrive at the generator shed to see exhaust manifold glowing red hot and running at around 35 Hz with around 160 volt per phase. Clearly as the volts dropped so load dropped so over load would not trip.
I would have to shed load as could not sync in more generators until back to 50 Hz, remember getting into trouble as I switched off the supply to offices and their computers and they claimed they had not saved work, I said if they could not realise there was a problem and had not saved work then time they were retrained which did not go down well, all fluorescent lights had failed, so that would have reduced load, but dropping from 400 kVA to 200 kVA is a massive reduction.
However other than fault conditions we have a lower limit, and micro generation to ensure under fault conditions it fails safe, has both a upper and lower voltage limit, the idea is should a neutral be lost, then the micro generators will all switch off. So if the voltage is allowed to either drop below or rise above the limits then the load to grid will increase.
AIUI they normally try to supply 240V, but they've been having to turn it down in some places to avoid over-voltage on sunny days. A reasonable margin there for dropping the voltage.
But by being able to control the voltage, they can change the taps and so keep the voltage up higher - turning it down if it looks like going too high on sunny days. That gives them more scope than they would have without it.
SMPSUs yes, thermostatic control no. Think about things like immersion heaters - the stats on those work on periods of minutes or tens of minutes. Similarly room stats. Dropping the voltage on these loads will probably give you a few minutes before the loads start recovering to normal (combined effects of many stat controlled loads).
DOL motors will similarly lower load. Industrial devices will run slightly slower (higher slip frequency in induction motors), and things like fridges will run slightly longer at a time - but that's another "timescale measured in minutes" load reduction.
Air conditioning system now are all inverter driven (I vaguely recall it being a required spec), and I imagine heat pump systems will be the same. They will not change load - just increase current - if voltage drops.
And finally, I would imagine EV charges are likely to reduce load as they'll be controlling max current draw from the supply for at least part of the charge cycle.
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