Hydro calculations

[guydewdney]

Try pipeflow wizard / advisor which can give accurate water flow predictions, but only for single pipes. That will then give you the flow to the T junction, then with that figure, do the same for each branch. Be mean with the figures (ie choose rough pipes, 90 degree bend where its a sweep etc). Back it up with the empirical measurement.

Ill crunch the figures if you provide me the site details.

[noah]

Guy
I can do that, I`ve got reams of things like pipeflow  tables going back years but if possible I`m trying not to play along with Ofgem and advance bogus information to satisfy box ticking bureaucracy.
In the end I`ll probably have to make a calculation and have an engineer with a letterhead rubber stamp it but I`d rather get Ofgem to acknowledge that their policies are unrealistic.
They are quite happy to accredit installations based on nothing other than the word of the applicant (I`ve had two accepted which, for all they know, might not even exist) but for some obscure reason decreasing an output requires much more evidence, including 3rd party evidence.

[Heinz]

...but if possible I`m trying not to play along with Ofgem and advance bogus information to satisfy box ticking bureaucracy.
In the end I`ll probably have to make a calculation and have an engineer with a letterhead rubber stamp it but I`d rather get Ofgem to acknowledge that their policies are unrealistic.

Seems to me that although you're probably right, you're just making life difficult for yourself.
I can see your point but you're trying to convert a bunch of paper shufflers...
What is the more important goal for you? Improving Ofgem or getting your hydro system working?

H

[noah]

Heinz
Being right is always my goal.
Like most of us I am usually forced to accept expedience.
`answer not a fool according to his folly lest thou be liken to him`

[Heinz]

Heinz
Being right is always my goal.
Like most of us I am usually forced to accept expedience.
`answer not a fool according to his folly lest thou be liken to him`

OK, we confirm that you are right    I'm not sure if the folly is at the Ofgem end or yours though....  It's like the completion certificate for my house. I had an external durgo valve fitted, designed for the job, to the correct BS standard for external use, fitted according to the regs. But the bloke from building control didn't like it. I could have taken two courses of action.
A/ Fight because I knew I was right, p*ss them off, waste my time and money. Probably win eventually, sometime, maybe, perhaps...
B/ Replace the valve with a conventional vent pipe and get my certificate two days later from a happy building standards man.
I chose option B 
Good luck.

H

[noah]

I`ll take option B as a last resort.

[smegal]

Smegal,
one of the conditions of derating is that it has to be `robust` ie not something that could be easily reversed by me. without actually rewinding a generator I don`t see how it would be possible. Even so I could replace the 5.5kw generator with a 4.5  and change the output fuse and reprogram the software in about an hour. They would not see this as a `robust` alternative.
Of course the stupid thing is that the whole process is unnecessary: the actual output is already limited to <15kw and cant be increased beyond this without major engineering.
The problem is that Ofgem seem to have a ruling that empirical evidence is not adequate and all claims must be backed up with measurement and calculations. Anyone who knows anything about waterpower will be familiar with the difficulties of estimating exact outputs when dealing with turbulent flows in less than pristine environments.
Its quite likely that in the end I or someone else will have to just fudge the figures to make it work. I don`t necessarily consider myself a paragon of honesty but I don`t like that sort of thing.

I do not understand hoiw replacing the generator is anything less than a robust alternative. It works with PV and it works with wind power.

I have spoken to numerous manufacturers mwho will de-rate an 850 kW wind turbine to 750 kW in order to sneek an install to a lower FIT boundry.

[noah]

Smegal
I think you`re right that replacing the genny would be seen as `robust` but its not a good option for me.
If this were a new install then asking the manufacturer to derate the generator/s would be easy. But a derating after an installation is commissioned requires a greater degree of proof. After all, original accreditations were based totally on my personal affirmations: for all Ofgem knew they could have been V8 powered or not even exist at all.
To relace the 5.5kw waterwheel genny with the next size down (4kw , just checked with manufacturer) would cost around £750 (not outrageous but worth avoiding) and take 3 months (motor/gen is rewound for 240v delta).
However the strength of this system is flexibility. The WW is rated at 5.5kw and will work efficiently from 1kw upwards. The turbine is 10.5kw but starts to be  inefficient below 6kw. So with the existing system I can make good use of flow from 10% to 100%.
With a 4kw wheel there would be a 2kw gap in possible generation and, as medium flow is more common than extreme flows then I might be hitting that gap a fair bit of the time.
Its also quite fun to see the Ofgem people slowly realising that I am not trying to snow them when I say that their accepted methods are not adequate for some situations.

[smegal]

Smegal
I think you`re right that replacing the genny would be seen as `robust` but its not a good option for me.
If this were a new install then asking the manufacturer to derate the generator/s would be easy. But a derating after an installation is commissioned requires a greater degree of proof. After all, original accreditations were based totally on my personal affirmations: for all Ofgem knew they could have been V8 powered or not even exist at all.
To relace the 5.5kw waterwheel genny with the next size down (4kw , just checked with manufacturer) would cost around £750 (not outrageous but worth avoiding) and take 3 months (motor/gen is rewound for 240v delta).
However the strength of this system is flexibility. The WW is rated at 5.5kw and will work efficiently from 1kw upwards. The turbine is 10.5kw but starts to be  inefficient below 6kw. So with the existing system I can make good use of flow from 10% to 100%.
With a 4kw wheel there would be a 2kw gap in possible generation and, as medium flow is more common than extreme flows then I might be hitting that gap a fair bit of the time.
Its also quite fun to see the Ofgem people slowly realising that I am not trying to snow them when I say that their accepted methods are not adequate for some situations.

In  that case it may be a good idea to get a consultant to analyse your system and write a report on how it won't exceed the 15 kW limit. This option would probably cost more than the £750 for a generator though.

Personally, I'd get fudging.

[noah]

Fudging must always be a last resort. How will the ignorant ever learn if we pander to their lack of understanding?

[Angus]

Just a point I thought I'd raise for thought....the FIT scale is based on the maximum installed capacity. For a wind turbine this is the turbine as a whole - not where you put it and the wind it is therefore exposed to. For a PV panel this is based on the panel itself and not the orientation, % shading, location within the country. Therefore for a hydro system it should be based on the data plate on the side of the unit (not the water resource available) So I see your only option to change the rating on the hydro plant itself.

Probably not the answer you were looking for but it makes sense to me! 

[noah]

Yes its normally the TIC (total installed capacity) that counts. This is a slightly special case:
(a) Ofgem knows, though won`t as yet admit officially, that they are at least partly responsable for the TIC being just over the 15kw limit. Without their misleading advice the installation would have been made at 15kw in the first place.
(b) the hydrostatic setup which produces the problem which leads to a 1kw drop in max measured output can only be overcome by an amount of work which is far greater than that needed to replace one of the gennys- which is in effect what Ofgem usually requires so the existing systems limitation on ouput is already as `robust` as it could be.

Ofgem have now accepted this and have said that they will accept my empirical proof based on actual output levels. But probably not in time for next FITs meter reading so wont get paid until Mid/end July 2012- almost 30 months from commissioning.

[dimengineer]

Guy
I can do that, I`ve got reams of things like pipeflow  tables going back years but if possible I`m trying not to play along with Ofgem and advance bogus information to satisfy box ticking bureaucracy.
In the end I`ll probably have to make a calculation and have an engineer with a letterhead rubber stamp it but I`d rather get Ofgem to acknowledge that their policies are unrealistic.
They are quite happy to accredit installations based on nothing other than the word of the applicant (I`ve had two accepted which, for all they know, might not even exist) but for some obscure reason decreasing an output requires much more evidence, including 3rd party evidence.

If the calculations were kosher, and it should be a pretty straightforward exercise, I'd be happy to countersign them. I am a Fellow of the Institue of Chemical Engineers. Its a very standard type chemical engineering calculation

Tim

[noah]

Thanks Tim for the offer.
I have got Ofgem to accept my empirical proof as long as it`s backed up by an independent expert. Dr Nigel Smith, who is a pretty well recognised expert in the hydro field, has volunteered to put his name to it on an expenses only basis.
I dont see how any calculation can be considered accurate enough for a window of +-6% when the inputs cannot be guaranteed better than 90%. One can always hope that the inaccuracies will cancel each other out but that has to be a hope. Mind you I`m always surprised when maths can seemingly tease out a result from arbitrary beginnings.

Is there any way of cheating on the GIGO rule?