Is the grid a waste of time?

[martin]

Having spent a lot of time meeting and chatting to a lot of "hard core" greenies at the BGG, I was at first surprised at their animosity towards "grid tie", but the more I think about it, the more I feel they may have a valid point - what's the point of generating electricity, then shovellling it into a system that may well waste 70-80% of that power in losses?
Discuss!

[chaso]

So the grid waste 70-80%, how is this done. I feel before everyone starts going oo-er we need to have some facts.

Just a thought, if you set-up a wind generator on batteries where this starts off as AC then goes through a regulator and comes out as DC then charges your batteries which then goes through an inverterand comes out as AC again to run your house. How much electricity loss happens here.

[wyleu]

The advantages of the grid are primarily that although the system is wasteful it still represents a better storage mechanism than many of those on offer, and if I've come to one conclusion over my fairly amateurish scrabblings arround the RE debate it is that producing energy ain't that hard; it's storing it that is the real problem. The 'quality' of the grid is another aspect that should be applauded. Can you gaurentee that your home inverter will produce precisely 24 hours worth of cycle in a day? Can you ensure that your home supply has a clearly defined impedence that allows you to make voltage drop calculations for devices like motors et al?

CAT's battery room is an excellent reminder of quite how much electricity you do need to store and if the grid is available to save me the heartache of hydrometer then I for one would continue to remain connected. Mind you I would like a 'cheap' system to allow me to continue to use local power if it is within a pre specified specification if I generate it when the grid fails cos another of my home won opinions is that the rate of service interuption or whatever euphamism will be used in the future for the industry or domestic dilema the Power generators will increasingly face will mean that the number of disconnected hours will increase considerably.
This is one of the main reason I am so keen to measure EVERYTHING. If our contracts with Powergen or whoever says the reliability is so many percent then we need to establish community network to keep them honest with supportable evidence to back ourselves up. They may deny one mad electrical engineer by a community network of results would be far harder to reject.

[martin]

I think the objections from the green lobby are for several reasons, not just the efficiency, or lack of it of the grid - to them it perpetuates the idea of centralised power generation, and are keen to put that back into the hands of the users, or local communities!
To try to work out actual losses is incredibly difficult - the electricity companies mutter about 8% as transformer losses, but I suspect it is considerably higher than that! - logically, if you live on a remote farm, with probably a pretty minimalistic power connection, I can foresee them being rather large! I'd welcome some true and accurate figures - I heard 70-80% being referrred to as "fact"  -illumination would help!

[wyleu]

The supply companies are a rule unto themselves. On a recent house rewire I complained that the inlet head had visible exposed mains terminals ( 100 Amp three phase!) and was told, as I already knew, 16th edition does not apply to DNO. IP4X be damned I could have got my finger onto live terminals very easily, such was the state of the device. They relented when I told them the household had an incontinent dog with a certified stud value. Mind you they still haven't provided a date for a changeover.

[Sigma Nova]

This is my understanding. Constructive correction welcome!

The efficiency with which a fossil-fuel-powered power station converts fuel energy to electricity is of order 22%. Old coal-fired stations are worse, modern combined cycle stations are significantly better. I believe state-of-the-art is of order 35%.
Of the electricity generated, some 10% is dissipated as heat in the grid, resulting in an overall efficiency of 20% - 29%. Some would argue that grid losses are higher but the principle remains; the main inefficiency is in the conversion of fuel energy to electrical energy. (This is why converting electricity to low-grade heat is simply balmy)

A significant portion of the grid loss is due to the highly concentrated nature of our current electricity generation infrastructure ie
comparatively few very large power stations.

If our ecologically aware vision of the future is in distributed micro-generation as mine is, then using the grid to share the generation of and demand for electricity is by far the best option we have to optimise its efficiency. The alternative - localised storage in batteries- is far less efficient.

[marktime]

Speaking from the armchair rather than practical experience off-grid at first glance seems to be the domain of true RE enthusiasts who can manage without the convenience of the grid.

Grid-tie would have the advantage that it could appeal to the ordinary man (or woman but there don't seem to be very many of them here) in the street. From what I have read getting credit for any surplus you put into the grid is a red herring but just knowing that you have the best of both worlds is a bonus. i.e. You are reducing your own consumption from the grid with whatever your source of RE is and you know that the grid will supply you needs if your RE is off the air.

Mark

[wyleu]

Your reaction to the standing charge might alter if you hadn't actually taken any juice from the grid over a considerable time.

[martin]

as part of this whole question - something that gets "forgotten" is that the G83 inverter standard means that if there's a failure of the grid, the inverter "switches off" to prevent shock to anyone working on the lines. In the real word, if you're a farmer and have your own grid tie sytem, you're not going to be very chuffed if the grid crashes, leaving you with a parlour full of cows needing to be milked! For these sort of installations, should we not be looking at "belt and braces" - perhaps a small battery bank system running alongside the grid tie?

[marktime]

Your reaction to the standing charge might alter if you hadn't actually taken any juice from the grid over a considerable time.

Valid point but unlikley to affect small scale 'doing by little bit' 'ordinary man in the street' type installation, if your RE had been consistanlty and reliably meeting all your own needs you would clearly want to step away from the grid.

I cannot recall the last time we had a power cut at home so that would not feature on 'my' list of reasons to do RE. The farmer on the other hand would be at much greater risk of a power cut and would be a very different case for many reasons, and speaking out of my well padded backside in it's comfy armchair I would imagine that an off-grid installation that would sustain a dairy farm through a 2-3 hour power cut would have to be pretty substantial.


Just a point of view.....Mark.......open to correction.

[wyleu]

Since we follow the Americans on most issues, their recent publicised problems with electricity supply will probably be showing up here with that peculiar British slant. My own house has semi rural pretentions and we have phases (sic)  of outages. Nothing longer than four hours but it tends to happen more at weekends. Mix in the reliability of broadband access, and the much vaunted always connected starts to look like something we would do well to generate figures for. The dear old telephone has the advantage of coming with it's own built in power supply but with the use of wireless phones even they fail in a power cut. All in all as utility provision becomes a scarcer resourse the companies will tend to favour the business users over the domestic if only cos business tends to be able to shout louder, and if it really does get to over demand situations they won't mind pulling the breaker on us to tide them over bad periods. Air condiioners were big sellers this year and you can bet that all those bought this year will be being pressed into service as soon as next year starts to get warm.

G83 certainly requires very sensible protection measures for the man at the sub station, but perhaps it might be beneficial to consider  'primary' and 'secondary' distribution boards for such situations where certain items can be taken off load in high load circumstances. I for one would prefer my freezer,computers, broadband and telephone to keep running and manage without TV,cooker and toaster for the duration of a power cut.
 Mucho computer intelligence, control, political willingness and motivation to make it all happen but I place great faith in the control mechanisms to intellegently control my domestic requirements. I am gradually re-wiring with X-10 control systems, which allow me to issue mesiainic commands like run all the lights at 80% full brightness and turn of room lights when nobody has moved in the room for 10 minutes. Every little helps, and I woul have my doubts about how X-10 might fair in a locally generated situation but can't yet put it to the test yet.

[chaso]

Ok I'm in Ireland and do get a few power cuts, but I use a generator as our backup supply as the power cuts rarely last more than an hour. (Ivan has some nice diesel generators just for this reason)

I might be wrong but would like to think that If most people did grid tie this would hopefully help reduce fossil fuel. If you needed a backup then

[chaso]

oops If you need a backup then all you need do is get a diesel generator and use bio-diesel.

[jncg]

Just about every dairy farmer I know has a tractor (PTO) driven generator to allow milking parlours and milk refrigeration units to run during power cuts.  Generally a changeover for the whole farm, often including the domestic supply makes the farm self sufficient for power during power cuts.

What saddens me and dissillusions people on the periphery of RE I speak to about it is that the rhetoric spouted at government level is just not substanciated, unless you're a foriegn investor planning a multimegawatt wind farm.  One of my dairy farmer friends/ client has an 18kw generator on his farm able to run on biogas supplied by his anaerobic digester yet so many barriers appear and the costs escalate so readily as we look at exporting his surplus power that he has not persued it, choosing to run the genny when on farm demand is high and effectively shutting it down at other times.  This is energy from a waste product produced at source but for a cash strapped family business that has to look at the economics of this sort of thing, we still have a way to go before 'normal' people come onside.

How does grid-tie work in Germany/ Austria etc?  I hear of a lot more success with energy crops there.

[djmc]

I purchaced a book pdf form called dont buy electricty make it for about 30 euro over the internet
It gives a detailed info but a short version is
Use a generator for about 2 to 3 hours a day with a 4kw inverter with a built in 120 amp charger at 24 or 48 volts to charge a battery bank
the batterys then should then run your house for the next 22 hours or so
Some inverters can start and shut off the generator automaticly when it sences low voltage
reading the book it makes sence but then again maybe paper dosent refuse ink