Select Committee on Environmental Audit Memoranda




  There is confusion in Government documents over the carbon savings which will be realised if the 10 per cent target for electricity from renewable energy sources is met. Table 1, below, shows the various estimates in recent DETR and DTI consultation documents. The latest estimates are only one-third of the initial levels.

  It is vital that these savings are accurately quantified, as it will affect the value of any carbon credits traded in the future. As the carbon savings ascribed to renewable sources now seem to be extremely low, any monetary credits derived from renewable energy sources in the UK may have an artificially high value.

Table 1


Savings MtC/yr
DETR:UK climate change programme: consultation paper, October 1998
"in addition to those expected to be realised from NFFO arrangements already in train"
DTI: New and renewable energy, March 99
3.5 to 5.4
"above that from existing programmes"
DTI: New and renewable energy: conclusions, January 2000
2.6 to 3.0
"an additional 2.6 to 3 MtC"
DETR : Climate change: UK programme.

  As the reference date for carbon emissions under the Kyoto protocol is 1990, it makes sense to refer all data to this starting point. The first DETR consultation paper did so and suggested that the "arrangements already in train" would account for 2 million tonnes of carbon (MtC). So the total savings from the 10 per cent renewable target would be (5.4+2), i.e. 7.4 MtC. In the latest DETR document that this has been scaled down to 2.5 MtC, without any explanation.


  The emissions of greenhouse gases saved by switching electricity generation to renewables depend on which fossil fuel is displaced. In the day-to-day running of the UK power system it is coal plant which is taken off load when additional "base load" plant such as nuclear or renewables start to generate. All the nuclear and most of the gas plant has baseload status, and so their operation is unaffected by the introduction of renewables. This point is clearly demonstrated in data published by The National Grid Company which describes the make-up of plant on the system at various times[11]. The nuclear and CCGT plant operates continuously throughout the day and the output of the coal plant is changed to meet changes in demand.

  In the medium-term, there is another issue to consider: whether the introduction of new renewable plant will inhibit the construction of new gas plant or force the closure of nuclear plant. Both scenarios are highly unlikely. The nuclear closure programme has already been announced and the closures are likely to be delayed rather than brought forward. It is also extremely unlikely that construction of any gas plant will be delayed, as the government found it necessary to introduce the stricter consent regime (just lifted). It follows that the introduction of any new plant, including renewables will accelerate the closure of old coal plant. This reasoning is reflected in the latest DTI estimates of emissions from power generation.[12]

  A report to the House of Commons Energy Committee in 1988 used similar reasoning[13]. The CEGB suggested carbon dioxide savings from renewables would lie between 867 and 1000g/kWh by 2005. The corresponding emissions per unit of electricity, based on the average plant mix, were 620g/kWh. The important point is that emissions based on the average plant mix were not used to derive the savings attributable to renewables. A 1994 DTI fact sheet used similar reasoning. Emission savings elsewhere in Europe (and in America) are calculated in the same way, unless oil, rather than coal, is the displaced fuel.


  A 10 per cent contribution from renewable energy to electricity supplies corresponds to 38 TWh/yr in 2010, given the expected rise of electricity consumption. As the UK's large Hydro plant was operating in 1990 (the baseline year for carbon emissions), its output must be subtracted. Average output over the last nine years has been 4.5 TWh, so 10 per cent of renewables will save emissions corresponding to (38-4.5) = 33.5 TWh of electricity .

  Each kWh of renewable energy displaces electricity generated by coal-fired plant and the corresponding emissions are 862[14] grams of CO2, or 235 grams of carbon. So the carbon savings associated with 10 per cent of renewable energy are simply 33.5 TWh multiplied by the savings per unit, which gives about 7.9 million tons of carbon (MtC). The figure in a recent House of Lords report[15] is slightly lower at 7.6 MtC, but these estimates are broadly consistent with the figure of 7.4 MtC in the first DETR document.


  The Government response to the House of Lords Report[16] did not seek to justify the DTI figures on carbon savings, but simply argued "it is a complex subject in which there are no definitive answers". It did, however, reiterate that the upper bound of carbon savings for 10 per cent RE (above savings from 5 per cent RE) was 5.4 MtC. As recently as December 1999, therefore, there was still implicit confirmation that the upper bound was still 7.4 MtC of savings, relative to 1990 levels.

  The DTI/DETR position does not appear to be explained further. The supporting analysis[17] to the DTI Renewable Energy consultation document of 1999 proposed three scenarios for assessing the range of carbon savings:

    —  "Renewables displace combined cycle gas turbines;"

    —  "Renewables displace modern coal plant"; and

    —  "Renewables displace the current generating mix".

  The analysis suggested that the first scenario was unlikely in practice, but did not comment on the scenarios further. Nor were the underlying calculations of the carbon savings provided. An additional anomaly appeared in the Draft Climate Change document, which suggests nuclear saves 12 to 24 MtC per year. This is inconsistent with the renewable savings, as it suggests carbon savings from nuclear—per unit of electricity—may be over three times those of renewables. It is difficult to envisage a technical basis for this difference.


  All the available evidence (including information from government sources) points to the carbon savings from delivering the 10 per cent renewable energy target being in the range 7.4 to 7.9 MtC/yr. The latest DETR figures (which comes with no proper explanation or qualifications) of 2.5 MtC/yr are far too low.

24 January 2001

11   National Grid Company plc. 1999 Seven Year Statement. Back

12   DTI, 2000. Energy projections for the UK. Energy Paper 68. Back

13   House of Commons Energy Committee, 1988. Energy Policy and the Greenhouse Effect. Memorandum submitted by the CEGB. Back

14   This figure has been derived from National Power's Environmental Performance Review for 1999. It is a weighted average, taking data from all the coal plant. Back

15   House of Lords: Select Committee on the European Communities, 1999. Electricity from Renewables. HL78-1. Back

16   House of Lords: Select Committee on the European Communities. Electricity from Renewables: further documents. HL Paper 18, December 1999. Back

17   New and renewable energy: Prospects for the 21st century; supporting analysis. Back

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