RENEWABLE ENERGY

( File 3)

A pragmatic review of the likely reductions on 1990 CO2 emissions that the UK electricity generating industry may be able to achieve by 2020 / 2030

Most media and government attention when considering reductions in CO2 emissions over the past few years has focussed on the electricity generating industry, but there is a limit to what can be achieved in this sector. To assess what the upper limit for reductions is likely to be we should measure the potential future CO2 output of the industry assuming the most favourable trends in current and future factors helping to reduce CO2 production.

In this way we can identify what will be the upper limit to the reductions that the electricity generating industry can make and this figure can then be reliably used in an overall assessment for total UK CO2 emissions.

Accordingly the following assumptions are made for generation mix predictions that will be most favourable to achieving further ongoing reductions in total CO2 output from UK electricity generation.

1) Gas fired generation is limited to a maximum of 50% of average generation in the interests of security of supply. If other generation does not meet targets, particularly nuclear and offshore wind, then gas fired generation and coal firing will have to increase which will increase CO2 production.

2) Wind powered generation will achieve 10% ( 4 GW ) of average generation ( 40GW ) by 2010, this is unlikely now as only 9 years remain to 2010. It is also assumed that wind powered generation reaches 20% ( 8 GW ) of total generation by 2020.

3) Nuclear generating capacity reduces gradually to only Sizewell B ( 1 GW ) by 2020.
This may happen more quickly than planned due to plant failure and so increase CO2 production for a few years as gas or coal generation has to fill the gap until offshore wind power catches up.

4) For arithmetic simplicity it has been assumed that the ratio of CO2 per unit of electricity generated using coal to the CO2 per unit of electricity generated using gas is 2, this is to enable the impact of the switch from coal to gas to be quantified.

Only the later CCGT gas plant achieves the much publicised high energy conversion of 65% whereas earlier CCGT plant and open-cycle plant used for peak lopping is less efficient. The best coal fired plant in use in 1990 and still in use today achieves 35 to 38 % efficiency. Comparing the gas fired plant with coal gives a ratio of say 60 to 35 = 1.71 and so a ratio of 2 allows for the higher carbon content of coal.
5) We will assume that growth in demand for electricity will be offset by increased efficiency of use of electricity, i.e. the average UK demand remains constant at 40 GW.

This will not be achieved unless the cost of energy generally rises to take up the increase in disposable income that increased efficiency would otherwise release because increased disposable income leads to increased energy consumption. Also if these efficiency gains do not materialise then CO2 emissions will rise as more gas and coal generation is required.

6) It is assumed that coal-fired plant is retained at a viable load factor to provide full generating backup for wind-powered plant at periods of peak demand during periods of calm weather affecting the whole country. Without this, significant wind-powered plant cannot be considered, peak demand has to be met regardless of CO2 output.

7) It is assumed that by 2020 the full potential of all economic UK small renewables, i.e. hydro, sewage and landfill gas, have been developed and energy from crops is 2GW which will require 2000 square miles ( 4% of land area of England) At present photo-voltaics, PV, are still a bit of an unknown and so have not been included other than within the small renewables total. But if PV succeeds then it will help reduce CO2.

8) It is also assumed that by 2020 the cross Channel connector to France is no longer available, but even now in 2001 it is probably importing subsidised coal-fired electricity so represents CO2 output in France.

On the basis of the above assumptions we can predict the future generation mix starting with the mix of generating plant operational today. We can then compare year by year the amount of CO2 that would be produced expressed as a percentage of the CO2 produced in 1990.

The following notes apply to the different means of electricity generation included in the following table that will be available to us.

1) Coal At present there is about 25 GW of modern efficient coal fired plant available in the UK. It is run profitably at a low annual load factor of about 35% mainly in the winter to meet peak demand. Currently peak demand is nearly 53 GW and we only have about 20 GW of gas plant and 11 GW of nuclear giving a reliable total of 31 GW which is 22 GW short of peak demand! To bridge the gap we have 1 GW pumped storage for a few hours, approximately 1 GW of renewables and 2 GW from France if it is available, so as you can see we remain and will continue to remain very dependent on coal.

As a guide to capacity, the big coal fired power stations in Nottinghamshire and Yorkshire have a capacity of 2 GW each and could burn 7 million tons of coal per year each.

2) Nuclear. Nuclear is now past its peak which was at over 12 GW last year ( 2000 ) and will continue to decline as the Magnox and then the AGR stations reach the end of their economic lives. Only Sizewell B will remain after 2020 which has a capacity of about 0.85 GW. There are now no designs or plans for new stations in the UK. If nuclear was to be considered it would be starting from scratch, there is nothing on offer to discuss at present so we will have to see what is presented in due course.

3) Small Renewables. These are very important and should be developed to their full potential in the UK. They include energy from waste, landfill and sewage, traditional large-hydro and new mini-hydro on rivers. Altogether when their full UK potential is developed they will add up to about 4 or 5 GW of very reliable, economic and predictable generating capacity.

In due course energy from crops will contribute 1 GW per 1000 square miles of farmland used ( England has a total area of 50,000 square miles ) and PV will become important. But they are not in the same league as UK offshore wind power which has 100's of GW potential capacity, nor the world wide potential of PV in desert areas.

The Severn Barrage is often mentioned but it does not have the capacity it might appear to have. It would generate over 5GW at peak output twice a day but it also has zero output twice a day so the average output would only be 2 GW and because the peak and zero output move through the day with the tides on a 28 day cycle the useful capacity of the barrage to the National Grid is only about 1GW.

As the Severn Barrage would cost £10Billion and take ten years to build before generating electricity it is the most expensive of the possible renewable energy projects.

4) Gas Natural gas Methane, CH4, is the fuel of the age and will dominate for the next ten years but after that all bets are off because all predictions rely on private company decisions and investments and no one knows for sure what will happen. For this reason wise governments will limit their country's dependence on gas and the UK should do likewise

5) French Imports This refers to electricity coming via the cross Channel interconnector which has the capacity to supply 2GW either from France to England or vice versa.

6) Wind Power For the UK windpower is in a league of its own offering 100's of GW of potential capacity on land and offshore. Typical turbines for offshore development are currently of 2MW output giving an average output of 0.7 MW per turbine. This means that the number of turbines per GW is 1000 / 0.7 = 1430.

So to supply 10 % ( i.e.4 GW ) of UK electricity requires 4 x 1430 = 5720 turbines.

At the present time the predicted cost of offshore wind turbines installed in the Southern North Sea is less than £1 Million per MW which gives a capital cost of about £3 Million per MW of annual average generation to allow for the varying output.

7) Efficiency Improvements. The potential for improved energy efficiency is enormous, especially for improving the energy performance of buildings by improving insulation and the management of solar heating. In the transport sector the fuel consumption of cars could be improved by a factor of 5 or more. By using less energy less CO2 will be produced.

Proposed Generation Mix in GW
and Emission of CO2 expressed as a % of 1990 CO2

From the above table it can be seen that the reduced output of CO2 for 2000 is 75% of the emissions from electricity generation in 1990, in 2010 it becomes 71%, in 2020 it is still 71% and in 2030 begins to fall again to 67% of the 1990 emission.

What this illustrates is that for the past 10 years CO2 reductions have been achieved by the "dash for gas", for the next 20 years the reductions in CO2 emissions due to expanding renewables will be cancelled by the decline in nuclear generation, after 2020 a downwards trend is established as renewables continue to expand. Coal and gas generation remain static at 27GW while nuclear is eclipsed by renewables, especially offshore wind power backed up by coal on calm days.

These figures are all projections based on a pragmatic extension of our current experience. The assumptions and projections are designed to give the most favourable conditions for reducing CO2 which are in fact unlikely to be met. Therefore it is unlikely that any practical scenario starting from where we are now will achieve a reduction in CO2 to less than 67% of the 1990 emission from electricity generation.

As electricity generation contributed 1 / 3 of the total 1990 CO2, then the reduction on total 1990 CO2 will be 33% of 1 / 3 = 10%. Therefore the remaining 50% reductions to give the 60% reduction recommended by the Royal Commission on Climate Change has to come from other the other two sectors, i.e. transport and heat. The values in the tables can be illustrated as pie charts as follows:

The above pie charts and table all relate to average generation which for a given mix of generation determines the annual production of CO2. Average generation is assumed to remain constant at 40GW by vigorously pursuing improvements in the efficiency of use of electricity to offset increasing demand.

Of equal importance is the need to meet peak demand which can now be 53GW. For details on meeting peak demand see File 4 Maintaining the capacity to meet the peak demand for electricity from an integrated energy system incorporating significant variable renewable energy sources, while at the same time reducing average annual CO2 emissions. The continuing importance of coal

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