RENEWABLE ENERGY

( 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.

This is the difficult bit that is invariably ignored in proposals by individual vested interest groups promoting their particular technology. The reason for this is that meeting peak demand requires extra generating capacity and reduces the average load factor at which generating plant will operate. Advocates of competing technologies usually base their costings on a 100% load factor because this gives the lowest cost per unit of electricity generated and makes the technology they are promoting look more economically attractive. But if a system is generating electricity at a period of low demand that electricity may be of zero value and if the system cannot generate to meet it's scheduled commitment to generate then some other generator has to fill the gap immediately or there will be a voltage reduction (a "brownout" as they call it in the USA) or a disconnection, an old fashioned powercut not seen since the miners strike in 1974

Everyone is guilty of this. Wind generators don't explain what happens on calm days that can last for weeks, PV proponents don't mention zero or low output on dark winter days and at night, the nuclear lobby doesn't mention that they have always had "first right to run" in the UK ( this immensely lucrative concession to nuclear power is about to end) The "dash for gas" is justified on base load running costs and someone else (super flexible coal running at a load factor below 40%) is still responsible for meeting the peak winter demand.

To give credit where it is due the following sources of zero CO2 generation do not have the problem of periods of zero output

1) Energy from crops (vehicle fuels and electricity and heating)

2) Energy from waste, landfill and sewage gas (vehicle fuel and electricity)

3) Large and mini hydro, although output is reduced in periods of low rainfall.

4) Tidal barrage and tidal streams, although they do have the disadvantage that peak output varies in accordance with the lunar cycle which means there are periods every month when peak generation will be in the middle of the night producing electricity no one wants and at times of peak demand the generation will be zero at least once every 4 weeks!

The Severn Barrage is a good example of this problem. Although it would have a peak generation of over 5 GW at some changing time during the day the average daily output would be 2GW and it's usefulness for scheduled electricity supplies would be about 1GW. At a capital cost of £10 Billion, i.e. £10,000 per kW and a 10 year construction period the Severn Barrage is the most expensive of the proposed UK renewable energy sources.

5) Nuclear power if we ignore fossil fuelled processes in the whole fuel and waste cycle (these should be quantified). However apart from public anxiety about accidents and waste, nuclear power suffers from excessive capital costs which means it is only economic for base load running, it must have the "first right to run", that is why this concession was extended to British Energy when the AGR stations were privatised and only now is this concession being ended. First right to run meant that nuclear generated electricity was always taken first by the National Grid which meant that nuclear power stations could run at full capacity through the night and so in effect half their capital cost.

Because of the high capital cost and long construction period nuclear power has missed the boat for now. By not getting stations built in the 1980's ( because they were too expensive, took too long to build and were considered dangerous and created an unsolved waste problem) the base load market has gone to cheap gas and it will only be when this base load generation is replaced that nuclear will get another market opportunity. However by that time alternatives will be a lot cheaper and well established and different grid operating systems will result in nuclear not getting the "first right to run" concession without which it cannot compete economically.

However nuclear power could eventually make a come back in 20 years time in combined plants generating electricity, desalinating sea water and making hydrogen fuel for transport.

Meeting Peak Demand in the UK up to 2010 / 2020

As explained above, peak demand for electricity must be met or we will have voltage reductions and powercuts. Currently peak demand is 51GW in December / January. The requirement to meet peak demand is of the same importance as the need to reduce CO2 emissions and a mix of generation has to be developed that achieves both at the most economic cost.

The Government's policy is that electricity generation should be economic, sustainable and secure so the generating mix has to meet these requirements also.

Average generation will determine the mix, or market share, of the different generators used, i.e. how much gas, coal or renewables and nuclear, while it lasts, is used over a year. This will determine the total CO2 emissions for the year. During the year CO2 emissions will vary, peaking with more burning of coal in the winter.

Peak generation will determine the total required capacity of all the available generating plant which must always be sufficient to meet peak demand. ( Government policy requires security ) This is a problem for wind generation and will be a problem for PV when it gets established, both will have to be backed up by conventional fossil-fuelled generating plants.

In the UK it is coal fired plant that is best placed to provide this back up because we have large coal reserves of our own and coal can be imported and stored and we don't want to become too dependent on imported foreign gas. Over 20 GW of coal fired plant currently exists in the UK, new plant is cheap and relatively quick to build and fuel cost is pro-rata related to generation and coal is cheap, plentiful and can be stockpiled for up to a year without serious energy losses. These factors mean that coal fired plant is economic to run at low load factors.

The gap between average generation ( 40 GW ) and peak demand ( 51 GW ) is 11 GW and could be maintained at this level if increased electricity demand is met by increased efficiency of electricity use.

The plan outlined here anticipates wind powered generation being 4 and 8 GW in 2010 and 2020 and the back up required from coal fired plant will have to be of a similar capacity. So in 2010 coal-fired plant required to cover peak demand on calm days will have to be 11 + 4 + 7 = 22 GW in 2010.

2020 and 2030 are too far away to make reliable predictions like this but 2010 is now only 9 years away and we have to plan now with what we have today and for back up for wind power and to meet peak demand the cheapest option is coal. The required plant already exists, in fact it is this plant built before the "dash for gas" that is keeping the lights on in winter even now. If we don't maintain or replace this plant we will not be able to meet peak demand in years to come, especially as more wind powered generation comes on stream.
( but see below ) This 22 GW of coal fired plant will run at an annual load factor of 7 / 22 = 32% which is acceptable for coal fired plant.

After 2010 the problems described here will still exist but there will be more options for dealing with them as a larger integrated energy system develops.

If wind power is expanded to produce hydrogen fuel for transport then the impact of calm days affecting all of the wind farms around the country at the same time will be less significant and sufficient generation will be easier to maintain. Also some electricity will start to be generated from new domestic combined heat and power systems so the proportion of wind power generation committed to the National Grid will reduce. If these developments are planned for, then 22 GW of coal fired capacity will continue to be adequate to cover peak demand at all times and we won't run out of coal.

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