I posted this earlier on the Navitron forum.
Warning: if you overgenerate for even a second Ofgem can change your TIC and push you into a lower FITs band!!
My 15kw hydro had been running at max during last summer (the wettest for 100 years). Ofgem came to monitor the output and reported overgeneration of 2.5% for 1 hour. On this basis they will be downgrading. (my average over two years is 12.2kw)
When I asked them what the margin of error was they replied `zero`.
I asked them to clarify and they confirmed that if the overgeneration is measurable then you are in breach of the rules.
As far as I can see this is not only a bit unfair (whine) but it is not physically possible to build a system- even solar- which can achieve its TIC without ever breaching this limit by as little as `what can be measured` (a femtowatt? or even a generous 10 watt/seconds)
Its certainly impossible with wind or hydro when you consider the effects of hysteresis.
My case is even more ludicrous than it seems: when the TIC of my system was agreed, Ofgem would not allow me to rely on electronics to sense when TIC limit was getting close. They insisted that the only form of control acceptable would be the inherent mechanical and hydraulic properties of the system (ie that 15kw was the limit at which the millpond began to overflow).
I pointed out at the time that this could only be accurate to within a few percent: this they ignored (probably, like me, thought `we`re not going to get a persistent 3 month period of rain that coincides with higher than normal mains voltage and not a single breakdown`)
Anyway enough of my vicissitudes.
This recent post
http://www.navitron.org.uk/forum/index.php/topic,19884.msg229238/topicse...
shows that overgeneration is not a rare occurence.
I call on all members (especially those of a technical bent) to email Ofgem
Daniel Murray [Daniel.Murray@ofgem.gov.uk]
if they agree with me that it is impossible to comply with this `zero tolerance` position on overgeneration.
Re: Ofgem will downgrade your installation!
Ofgem have now backtracked a bit and said that their `zero tolerance` policy will not be used but each installation will be judged on an individual basis. I am waiting for an explanation of the parameters that they will use to judge cases.
Re: Ofgem will downgrade your installation!
I wonder what the reaction would be if you asked them to produce the calibration certificates for their measuring equipment, to support their (implied) claim that it too had zero error?
Re: Ofgem will downgrade your installation!
I Would say ofgem are on very dodgy ground. As Robert pointed out they would need to prove in a court that the equipment they are using had absolute accuracy to assert a zero tolerance and no measuring device has that. Talk to your solicitor I think you have them by the short and curlies, after all even police radar has a percentage tolerance that gives you a few MPH leeway.