Control of The National Grid - Power Generation and Transmission Statistics

Power Generation and Transmission Statistics

• Total generating capacity is about 70 GW, supplied roughly equally by nuclear, coal fired and gas fired power stations.

• In the UK, the peak winter demand is 57 GW. N.B: This peak would be much higher if it were not suppressed by various mechanisms such as maximum demand tariffs, and the system of triad warnings and charges.

• Annual energy used in the UK is around 360 TWh (1.3 EJ). N.B: The average load factor is then 3.6×1011/(8,760 × 57×106) = 72%

• There is generally about 1.5 GW of so-called spinning reserve—this is typically a large power station paid to produce at less than full output.

• NG pays to have up to 8.5 GW of additional capacity available to start immediately but not running, referred to as warming or hot standby

• At any one time a large number of power stations are unavailable due to regular maintenance, being off-line due to a fault becoming apparent, or because of sudden breakdown. Other stations are mothballed or deep-mothballed which means they cannot be readily called upon; even in an emergency it may take several months to de-mothball. In Summer 2006, Fawley Power Station near Southampton was de-mothballed to cope with anticipated power capacity shortages for winter 2006/07.

• 500–550 MW of instantaneous load reduction. Effectively capacity can be supplied by the Frequency Response participants mentioned below: steel works, cold stores, etc.

• Approx. 750 MW of Standing Reserve diesel generators (as offered by many other uses of small diesels such as factories, water companies, distribution centres and so on), small gas turbines (e.g., 22 MW operated by First Energy) which as we shall see augment the Frequency Service arrangements.

• 2 GW fast response plant such as large open cycle gas turbines (OCGTs). OCGTs are gas turbines that are in the range 25–100 MW, and which can start in a few minutes (slower to start than diesel engines and marginally less reliable upon start up). Normally, these are not used for power generation since their low operating efficiency means that the cost per kWh supplied is prohibitively expensive. However, they have low capital cost, as demonstrated by the 100 MW unit at White City, London.

• The pumped storage schemes at Dinorwig and Ffestiniog can offer up to 2 GW of power within 15 seconds (incidentally, at the time Dinorwig was built, which was solely to cope with the inflexibility of nuclear power and the inherent unreliability/indeterminacy of large power stations, a further similar station was planned on Exmoor but was never built, so presumably it could still be built if the need arose).

• A cross channel HVDC power line can bring in up to 2 GW of power from France, though this tends to be unreliable.