Select Committee on Science and Technology Appendices to the Minutes of Evidence


Memorandum submitted by Dr Stan Jones

  The practical problems pertaining to any non-controllable, unpredictable electricity source has to be clearly understood in terms of the reliability and integrity of the supply to the end user. Wave and tidal electricity sources are subject to uncontrollable energy input, hence electrical output. Statistically the maximum and minimum generation can be predicted under various circumstances. Only the minimum guaranteed output can be used in any calculation of the integrating of supply to the consumer. The excess actual generation over this minimum will be effective in climate terms in displacing conventional fuel consumed and therefore unwanted gas release, but will not reduce the need for totally controllable generating plant or stored energy to be available to make up the difference.

  This means that for every KW of nominal power installed of wave or tidal electrical generation (1-min) KW of storage or backup plant has to be installed. Since the accepted requirement would be to meet the maximum demand on a still winter's day, this backup generation/storage would, for the most time, be idle, or at best cover for breakdown of conventional plant at other times.

  The installed cost of wave and tidal power therefore has to include the cost of this necessary backup generation or storage. The short term excess of generating capacity today will mitigate against this requirement, but as this excess capacity is progressively de-commissioned, as too costly or aged, the true cost of the necessary backup will become apparent. Clearly the larger the fraction of electrical generation which is of this "unreliable" nature, the more this backup will be apparent with ultimately a large amount of conventional generators lying idle for long periods.

  The higher the statistical minimum can be pushed, the more pumped storage and other storage techniques can be utilised and the more demand/generation can be averaged by geographic dispersion (eg Link to France) the less generation backup will be needed.

  As wave and tidal power is comparatively very expensive in its own right, the addition of allocating backup to this cost will considerably widen the difference.

  The above describes the "steady state" problem of integrating non-guaranteed electricity generation to the system. There are a number of dynamic problems which I presume will be covered by others.

  R&D into improving the reliability of output over a wide range of input energy, cost-effective storage and cost effective backup (such as very low capital cost coppiced wood burning generators where fuel storage and continuous running could be a problem—making them suitable for peak looping backup), would clearly improve the situation.

7 February 2001

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