I think I'm gonna build me a windfarm.

What it does is help with one of the big drawbacks of wind power – intermittent supply and also reduces peak demand so reduces the amount of generation needed in total

We got rather sidetracked to argueing about minutiae of this and a long way from the orginal point. Where the OP had a basically fallacy – the reason that the windfarms were paid to not produce was the failure of the interconnect

I’ve got them in my home but the street lights outside are providing much less yellow light from many more watts

Small point, but those orange street lights are actually insanely efficient. Much more so than typical LED lamps.

LED street lights illuminate better and consume less than a third compared with sodium

Those are high pressure lamps. The traditional low pressure ones are more efficeint.

But this is off topic.

Low pressure sodium are better than high pressure but not as good as LED

High pressure sodium are what are in our street lights at present so if we are going to replace then LED lights are the obvious replacement.

Most are not high pressure ime. Only in some areas like town centres.

But anyway, not important 🙂

TJ – peak demand will be reduced by making people pay more for electricity at peak times. It will not come, in this country, from giving over our hot water tanks to the man.
Distributed generation and storage has many problems that have yet to be overcome at a practical level. Storage is not yet there. 2 way flow of electricity needs a lot more monitoring and controls and failsafes as well, so taking a ‘1 way grid’ and turning it into a ‘2 way grid’ is a lot to do.

I have no idea what sort of sodium lights are outside your house, Molgrips, but as you seem to have given up claiming they light as well as a lower rated LED light would I won’t insist on you climbing the lampost to find out. 💡

Edit: and it is important. Even if we assume that all the street lighting is currently low-pressure sodium we could cut electricity demand for street lighting in half by changing to LEDs. If we make a more realistic asumption based on the current mix of filament, neon, halogen, and high/low pressure sodium then a 70% saving is realistic.

Apologies if this has been mentioned, I can’t be bothered reading the whole thread.

Some respondees may be interested to know Sloy Hydro scheme is about to be converted to pumped storage, and two more schemes are proposed west of the Great Glen.

Further info can be found here.

P.S. I am currently reading up on all this for a dissertation. No way am I joining in here – far too many partially informed pedants 😉

Tootall – why not given it works in NZ, USA and RSA?

Its not a two way solution this – its just a way of smoothing peaks and troughs in demand by heating your water when there is surpus ‘leccy

We do have a two way grid tho – if you have PV or a turbine on your house you can feed back into the grid.

What it does is help with one of the big drawbacks of wind power – intermittent supply and also reduces peak demand so reduces the amount of generation needed in total

If by “help” you mean it’s better than it would be without, then yes. However if you mean (as you imply) that it solves the problem in any significant way, then no.

The trouble is, the wavelength of the variation in power supply by wind is a lot longer than the variation in demand. It doesn’t do a lot of good heating up water with excess wind energy when you want a bath in 3 days time (no implication about the frequency with which wind power advocates have baths intended 😉 )

The original work cited in that Guardian article seems to have disappeared from the internet but if you read some of the other work by the same guy what he seems to advocate to even the load, in order of preference, is:

1) Export the spare electricity to somewhere it’s needed
2) Store it as electricity (pumped storage, batteries etc)
3) As a last resort, store it as heat.

So the original author’s not quite as barking as he comes across, its just that he’s been Guardianised (if you tell them what they want to hear they won’t engage their critical faculties). On the other hand some of his other ideas about wearing different clothing so that we can sit comfortably in our houses at 15.8C may be a bit more on the fanciful side.

Rio – I mentioned it as one part of a solution and as is the way on here we all get sidetracked into minuiae. Its one part of the solution – there is no one mega solution – its a multifactorial solution that is required. Its just a neat idea – low tech and cheap

If you are reading up for a dissertation you are completely out of your depth here, Waderider. Come back in 20 years time. 😉

Every little bit helps, Aracer. Rather than dismissing or dissing TJ’s idea of managing people’s hot water tanks as a means of storing energy why not accept the idea as possible if electricity companies and consumers are willing.

The biggest obstacles are consumer and political attitudes. Some people can’t afford to invest in energy saving and those that can usually want a bigger, flasher car/Hi-Fi/Tv/etc. rather than a better insulated home with more efficient lighting and appliances.

Low pressure sodium are better than high pressure but not as good as LED

I searched that link, and couldn’t find any mention of LED, Edu – could you point out to me where in that article it proves what you claim?

In fact if you actually read the figures in that article (and compare with the figures in your other article, along with what us LED experimenters know about LED efficiency) you’d see the opposite is the case. The article claims 200lm/W for low pressure sodium, and the examples give 168lm/W and 140lm/W real efficiency including ballast. That’s opposed to the 90 or 110lm/W claimed in the other article (doubtless without any allowance for driver).

I think the problem starts with your first article – I mean the second one shows a real 92lm/W for high pressure sodium. Hmm, let’s check the URL – couldn’t possibly be any suggestion of bias from http://www.newledlight.com.cn could there? Fundamental flaw seems to be using a couple of photographs (not even both taken from the same point!) to “prove” the relative illumination of LED and sodium. You see as much as they might bluster about CRI (I’m not really that interested in telling what colour things are at night) the lumen is a really clever unit which incorporates the eye’s response – more lumens is brighter.

Rather than dismissing or dissing TJ’s idea of managing people’s hot water tanks as a means of storing energy why not accept the idea as possible if electricity companies and consumers are willing

I’ve said several times it’s a decent (if limited) idea – but are you suggesting it’s going to go any significant way to solving the energy crisis?

The biggest obstacles are consumer and political attitudes

Indeed – you need to concentrate your efforts on that rather than on insignificant technological advances.

So, 3kW immersion heaters.
19M homes.
60GW.

How hot does your water get from a 3kW heater?

At 4.2kJ/kgK, if your hot water tank holds 200litres of water (=200kg) then, each hour it will rise in temperature by 12C.

If ambient is around 18C, and you don’t want your hot water temperature to go above 40C (to avoid scalding) then you can go for just about 2 hours before the whole nation has to switch off.

So, there’s a nice strong storm in the middle of the night. It gives up just before dawn. The nation’s hot water tanks cool down just before everyone gets out of bed to have a shower, and all they get is cold water poured on them.

EDIT: if you get one of those long icy windless cold spells in the middle of winter then it’s completely useless – you still need all your gas/coal power ready and able to supply power. Only now your £2Bn gas power station spends lots of time standing around idle, not earning any money.

OK, so it’s a nice idea, and would be kind of neat, but I’d quite like to know how much modeling has gone into it prior to the press release.

(But separately, I wonder how large a flywheel would have to be before it could start being used to store significant amounts of energy?)

So they’re going to heat my hot water tank for less than it costs me to do it by gas are they? Cause if they’re not then they can keep their mitts off my immersion heater.

The original work cited in that Guardian article seems to have disappeared from the internet but if you read some of the other work by the same guy what he seems to advocate to even the load, in order of preference, is:

1) Export the spare electricity to somewhere it’s needed
2) Store it as electricity (pumped storage, batteries etc)
3) As a last resort, store it as heat.

Isn’t that what gonefishin said?

Isn’t that what gonefishin said?

Looking back and piecing together what’s been said you’re probably right. Maybe gonefishin = Mark Barratt?? 🙂

The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain. Perceived lighting levels depend on colour. Anyone that’s used a variety of bicycle lights knows that white 3W LED lights appear brighter than theoretically more more luminous but yellower halogen.

Colour also produces an emotional response and sodium light is not liked:

Conversely, very white (and consequently very cold) strong light, like a bright sky, has an energising effect, while strong red or yellow light is disturbing, for instance when you are in a tunnel illuminated with sodium lamps..

old and past it -the temp range is 45 – 65 C – so you never have no hot water. Its a system that is already in use so its proven. It takes a long time to cool down if properly insulated. So in your first scenario it will be very useful – thats similar to economy 7 water heating which has been in use for years. Still hot enough for a shower in the evening. I the second it will not be so useful

(But separately, I wonder how large a flywheel would have to be before it could start being used to store significant amounts of energy?)

I love this idea. Anyone want to work out how big and fast in needs to be? Would gyroscopic effects as the earth turns be an issue?

The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain. Perceived lighting levels depend on colour.

Let me edukate you
http://en.wikipedia.org/wiki/Lumen_(unit)
“The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the power of light perceived by the human eye”

Anyone that’s used a variety of bicycle lights knows that white 3W LED lights appear brighter than theoretically more more luminous but yellower halogen.

Do they? I think you’re getting confused by 3W LEDs producing more lumens than higher powered halogen – I’ve certainly comments from people who prefer halogen over harsher LED – ironically enough, the CRI of halogen is actually better!

Colour also produces an emotional response and sodium light is not liked

I thought we were bothered about saving energy, not people’s emotional state?

Which is colour dependant. You need to dig deeper, Aracer.

The colour sensation of a given light mixture may vary with absolute luminosity

Looking back and piecing together what’s been said you’re probably right. Maybe gonefishin = Mark Barratt??

Glad it wasn’t just me. And given that, we can assume this from TJ:

I mentioned it as one part of a solution and as is the way on here we all get sidetracked into minuiae. Its one part of the solution – there is no one mega solution – its a multifactorial solution that is required. Its just a neat idea – low tech and cheap

is that apology gonefishin was after.

The colour sensation of a given light mixture may vary with absolute luminosity

But as I mentioned before, we’re not interested in how pleasing the light is, or what colours things are, just how bright it is. Perceived colour doesn’t change the luminosity curve.

“The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain” is fundamentally wrong.

We are worried about people’s emotional state. What we want is people to be happy with the level of lighting. They want a level that makes them feel safe and confident they can see where they are going. White light does that better than yellow light so people perceive the need for less of it.

My quote is fundamentally right, Aracer. You’d have to go back over a century to find a definition of the lumen which was based on the human eye. The lumen is defined in terms of the candela which is:

Unité légale d’intensité lumineuse (symbole cd) – Intensité lumineuse d’une source qui émet un rayonnement monochromatique de fréquence 540×1012 hertz et dont l’intensité énergétique est de 1/683 watt par stéradian.

I’ll accept your statement that low-pressure sodium lights produce more lumens per watt than even the best LEDS. Where we disagree is how many watts you need to provide an acceptable level of lighting using the different colours. The French were glad to see the back of their yellow headlights for example.

We are worried about people’s emotional state

No we’re not.

They want a level that makes them feel safe and confident they can see where they are going

Yes they do. There’s a wonderful scientific measure of how well a light source helps people to see stuff. I think I might have already mentioned it.

White light does that better than yellow light so people perceive the need for less of it

For the same number of lumens, no it doesn’t.

I’m arguing hard science, you’re arguing hand wavy emotional fluffy stuff. Do you have any proper evidence to support your argument (which doesn’t come from a site with “LED” in it’s URL)? I’m kind of surprised at you, Edu, as I’d always seen you as a hard facts man, and don’t think I’ve previously disputed your science.

Are you prepared to admit to being wrong about “The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain”?

Edit: clearly not. If you’re not prepared to accept you’re wrong about a fundamental scientific truth like that then there’s no point continuing this discussion any further. You’re wrong, I’m right, end of. Does this help better than my previous link?
http://fr.wikipedia.org/wiki/Lumen_(unit%C3%A9)
“Le lumen est une unité subjective dépendant de l’être humain. Elle quantifie la quantité de lumière perçue par un être humain “moyen” en présence d’une source de rayonnement électromagnétique”

i would expect to see in the future the reintroduction of economy 7 type tariffs encouraging usage at non peak times eg dishwashers washing machines spin dryers after midhight ( all simple to do via timed sockets) and if the tariff was circa a third of normal daytime most people i assume would jump on the bandwagon

in the long term its not the wind or the waves or the nuclear energy businesses that will have to make the biggest changes its the consumer..

The lumen is defined in terms of the candela which is:

Unité légale d’intensité lumineuse (symbole cd) – Intensité lumineuse d’une source qui émet un rayonnement monochromatique de fréquence 540×1012 hertz et dont l’intensité énergétique est de 1/683 watt par stéradian
Indeed – the candela “sert à mesurer l’éclat perçu par l’œil humain d’une source lumineuse”, hence why the lumen is defined in terms of it. If it was otherwise, why do you think they quote the frequency of the light source? You really should try the English language Wikipedia sometime though – it might not only help with making yourself understood on an English language forum (assuming your intention isn’t to obfuscate), there’s also often additional useful information, like the luminosity function curves in http://en.wikipedia.org/wiki/Candela which make the dependency of the candela on human eye response rather obvious.

I’ll accept your statement that low-pressure sodium lights produce more lumens per watt than even the best LEDS. Where we disagree is how many watts you need to provide an acceptable level of lighting using the different colours.

Well done. The disagreement is because I’m using hard science and a unit designed to measure the level of lighting people perceive, you’re using hand waving.

The French were glad to see the back of their yellow headlights for example.

If that’s the best argument you can come up with you’re clearly struggling. The yellow headlights were formed with a yellow tinted lens which reduced the total light output from the headlights, resulting in fewer lumens. Based on some dubious argument about reducing glare, not the advantage of one colour of light over another given equal perceived brightness. Not at all surprised they prefer white.

I’ll stick with my definition of the lumen based on light energy in watts at a given frequency on a surface area, Aracer.

It’s time for bed so I’m not going to hunt for the equivalent of this in English but diagrams should be self explanatory. Ech colour of the spectrum has its own “efficacity lumineuse”

Ech colour of the spectrum has its own “efficacity lumineuse”

<sigh> indeed it does, and the lumen is a unit which cleverly accounts for that (by incorporating the luminosity curve), such that 1 lumen of yellow light appears just as bright as 1 lumen of green light or 1 lumen of red light.

You do realise that article you’ve just linked neatly supports my point (and shoots down your previous one – though I note you do at least now acknowledge the importance of frequency to the lumen)?

I’m still waiting for the admission that “The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain” is wrong – maybe we can move on when that comes.

captjon – just repeating what I said in my early posts.

TandemJeremy – Member

Oh – and there are plenty of proposals for things to deal with this – my favourite is local heat storage – basically ever house gets a hot water cylinder that when there is surplus eleccy is heated up – so you get free hot water. when it windy

What’s the sigh for, Aracer? Same graphs, same history of science, what is the problem with the SI definition of the lumen? We’re linking the same sites on light which is all well and good but it’s not getting us very far. If you don’t want to agree that people’s perception of lighting depends on the colour of the light source used we simply won’t agree however much you go on about lumens being the same for all colours (which is true).

White light reveals things yellow light can’t: other colours for example. White light contains all the colours so any colour will show up. Take a yellow light, shine it on a yellow suface and it’ll show up as a nice bright yellow, now what happens if you shine it on a purple surface? The light source is still the same number of lumens and your perception? It’s not teh same is it, because the light is not reflected.

That’s our problem isn’t it? You’re talking about the light source and I’m talking about how that light source illuminates. When we look at things illuminated with a sodium light they look poorly lit because of the absorbtion of the yellow light by anything other than yellow or white surfaces.

We’ve got a rippler unit on our hot water cyl. Most NZ houses have hwc as mains gas is mainly restricted to main cities and even in them not all areas have access to it. Therefore i would expect most houses have a alrge hot water cylinder. When you put one in you have to put it onto a separate feed from the rippler, this is what is controlled upstream and puts power into your hwc at times of non-peak load. I’ve got solar on mine as well and a timer so almost all the time it’s working purely on solar and then at night it will use the immerser. NZ power is flat rate btw – no tariff based incentives to use it at night. We also have a mainly coal fired backups to hydro and wind and a lot of contention on the peak times as many/most houses are single glazed, wooden framed, badly insulated if they are insulated at all, non-centrally heated boxes. Therefore most power use at peak is for heating.

Tootall – why not given it works in NZ, USA and RSA?

As mentioned by the NZ resident – the gasification of the UK means we have far more gas water heating and NZ has more electric, so the conversion would be a tad expensive. They also have a smaller population with a relatively more modern (overall) grid. It works in part of the USA – not ‘USA’.

The end of that gas will be interesting, with the mass electrification of all our heating requirements placing a huge increased burden upon the grid. Put electric cars in there too and you really make a big problem.

Most solar PV goes straight into the grid using an inverter. You don’t consume it at home – all you do is feed the grid and the sums are done after the event.

Useful flywheels start at about 50kg and the size, including the casing, of a suitcase but a bit thicker. When I say useful, I mean with the ability to store a few kW of energy for a few hours.

Looking back and piecing together what’s been said you’re probably right. Maybe gonefishin = Mark Barratt??

Err no I’m afraid. To be honest it’s the sort of conclusion that anyone with working knowledge of thermodynamics is likely to come to. That or something very similar.

is that apology gonefishin was after.

I think that’s as close as I’m likely to get. 😉

I’m still waiting for the admission that “The definition of the lumen is based on light energy on a surface not the electrical signal generated by the retina and sent to the brain” is wrong – maybe we can move on when that comes.

(the sigh was because of your first sentence, repeating your wrong definition)