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Author Topic: overgeneration  (Read 2833 times)
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« on: December 20, 2013, 01:25:07 PM »

An email I sent today to Ofgem and a few in the biz:

"My hydro system, previously FITs rated at 0-15kw, has, after an observed period of overgeneration been `downrated` to 15.3kw by Ofgem - with subsequent loss of income.
  On examining the reasoning behind this I realised that there is an issue here for hydro and wind generators which could adversely affect anyone with a Total Installed Capacity [TIC] which is close to a FIT tariff change point.
  It is well known that all mechanical systems suffer from hysteresis - the inability to stop, start or change speed immediately without overshooting.
  The larger and heavier the system, the more it will tend to overshoot and the longer it will take to stabilise at a particular point.
  Low head hydro systems are particularly prone to this problem: the size and weight of machinery is in inverse proportion to the head available - the lower the head, the more massive the machinery - the slower the response. There may also be a problem with imbalances: my waterwheel, though balanced well enough to be turnable by hand, can still show an output of +- 5% during one rotation (12 secs).
  Therefore limiting the output of a generating system to a particular value has to take into account the virtual impossibility of ever hitting the exact  spot- there will always be some sloppiness in the system.
  My hydro system was observed generating 103% of its official capacity for 1 hour and this was sufficient for Ofgem to downrate it.
  When I asked Ofgem what the allowable margins of error might be their immediate reply was that there were no margins (!).
  When I queried this I was told that there were margins but I could not be told the parameters and each situation was treated individually.
  This I believe is unacceptable: How can a manufacturer supply the correct machinery without knowing the allowable parameters? How can a consumer be confident that their installation may not fall foul of Ofgem`s rulings?
  I think that Ofgem must as soon as possible open a debate with the interested parties and set some realistic and transparent parameters.
  I hope that all parties receiving this email will agree that there is a problem to be dealt with and that they will forward this email to anyone whom they think may have an interest or an influence.
  My personal feeling is that a 5% margin would probably suffice and it would be the simplest course of action for Ofgem to implement this ASAP. The problem, though large for the individuals concerned, is not a big deal in comparison to the entire FITs concern and does not deserve to become a long running saga.
  I will appreciate any feedback on this matter."
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« Reply #1 on: December 20, 2013, 04:23:03 PM »

Unfortunately this is just another example of OFGEM (re)writing the rules to suit themselves regarding TIC.

The entire area of exactly how TIC is defined - for each FIT technology - really needs a root-and-branch re-write from a technical/engineering perspective.

Of course OFGEM are just a bunch of bureaucrats who are mostly focussed on the 0.1% of systems that might 'game' the system for financial benefit and so this is unlikely to happen.

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