Nuclear helps offset dip in UK coal generation, 2015 data show

Figures released today by the Department of Energy and Climate Change (DECC) show that electricity generation in the UK fell by half a percent last year to 337.7 TWh, from 338.9 TWh a year earlier. The change reflected a large fall in generation from coal that was offset by increases from renewables and nuclear, according to DECC's Energy Trends report for March 2016.

The document is published in June, September, December and March. The March editions cover the fourth quarter of the previous year and also the previous year as a whole.

The increased share of nuclear generation, "at the expense of the less thermally efficient coal", has meant fuel use fell by more than generation in 2015, DECC said.

Nuclear's share of output at 21%

Of electricity generated in 2015, gas accounted for 30% (broadly unchanged compared to 2014) and coal 23% (a fall of 7 percentage points on 2014). Nuclear's share increased by 2 percentage points on 2014 to 21% of the total. Renewables' share of generation increased by 6 percentage points on 2014 to a record 25%.

Of electricity generated in Q4 2015, gas accounted for 30%, whilst nuclear and coal accounted for 21% and 20%, respectively. Low carbon electricity's share of generation increased from 37.5% in the fourth quarter of 2014 to a record high of 48.1% in Q4 2015, with increased generation from renewables and nuclear.

Primary electricity output rose by 14.3% between 2014 and 2015, due to increased nuclear output following outages towards the end of 2014, and strong capacity growth in wind generation in 2015.

Consumption of coal fell by 32% on an unadjusted basis in Q4 2015 compared to a year earlier, however nuclear consumption rose by 33%. These changes in consumption levels reflect the switch from coal to other fuels, including nuclear and renewables, as the main sources of electricity generation in 2015, according to DECC.

Among data for indigenous production of primary fuels in million tonnes of oil equivalent, the figure for nuclear power dipped from 15.6 in 2011, to 15.2 in 2012 and then retraced to 15.4 in 2013. It then dipped to 13.9 in 2014, while it rose last year to 15.3. In Q4 2014, the figure for nuclear was 3.1, which rose to 4.1 in the same quarter of last year.

The demand for coal by electricity generators in 2015, was 29.3 million tonnes - a new record low, DECC said. This was 24%, or 9.1 million tonnes, lower than demand in 2014, due to increased availability of nuclear and wind generation, an increase in the carbon price floor (from April 2015), and reduced coal capacity overall. The demand for coal in Q4 2015 was 35%, or 3.6 million tonnes, lower than Q4 2014.

Net imports of electricity, at a record high level at 20.9 TWh, made up 5.8% of electricity supplied in 2015 and were up 2.1% from 20.5 TWh in 2014.

Final consumption of electricity in 2015 was 0.2% higher than in 2014. Domestic consumption fell slightly by 0.1%, despite a slight fall in temperature.

Q4 2015 electricity generated in Q4 2015 fell by 2.0% from 90.0 TWh a year earlier to 88.2 TWh.

Gas' quarterly share of generation increased from 29.1% to 29.7%, while coal's quarterly share fell from 30.9% to 19.9%. Nuclear's share increased from 15.6% to 21.2%. Renewables' share of electricity generation increased from 21.8% in Q4 2014 to a record 26.9% in Q4 2015 due to increased solar and wind capacity. In December, generation from wind was at a record high 4.60 TWh, with generation from offshore wind at a record high 2.45 TWh. Again, this was due to increased capacity along with an average wind speed increase of 3.0 knots compared to December 2014.

Final consumption in Q4 2015 fell by 1.3% on a year earlier, and domestic sales fell by 2.2%, as a result of the warmer weather, including the warmest December on record.

In 2015, coal fired generation fell by 24% from 100.7 TWh in 2014 to 76.3 TWh, its lowest level in the time series, as a result of reduced capacity due to the conversion of a unit at Drax from coal to biomass and the temporary closure of some plants due to market conditions, in addition to an increase in the carbon price floor. Nuclear generation rose 10.3% from 63.7 TWh to 70.3 TWh. Gas fired generation fell 1.2% from 100.9 TWh to 99.7 TWh.

In 2015, wind and solar PV generation rose 33% from 36.1 TWh to 48.0 TWh, mainly due to increased capacity compared to 2014. Hydro generation rose 7.4% from 5.9 TWh to 6.3 TWh, with average rainfall in 2015 17.5% higher than a year earlier.

The share of generation from coal decreased from 29.7% in 2014 to 22.6% in 2015. The share from nuclear increased from 18.8% to 20.8% in 2015, while the share from gas fell from 29.8% to 29.5%.

The share of generation from renewables (hydro, wind and bioenergy) increased from 19.1% to a record 24.7%, mainly due to increased wind, solar and bioenergy generation capacity.

In Q4 2015, coal fired generation fell by 37% from 27.8 TWh in 2014 Q4 to 17.6 TWh. Gas fired generation remained constant at 26.2 TWh. Nuclear generation rose 3.3% from 14.1 TWh to 18.7 TWh due to increased availability after outages in Q4 2014. Wind and solar PV generation rose 23% from 11.2 TWh to 13.9 TWh. Hydro generation increased 2.6% from 1.7 TWh to 1.8 TWh.

Electricity supply in the UK

In the UK a variety of fuels are used to generate electricity. Primary electricity is obtained from natural sources such as wind, solar pv, hydro and tidal. Secondary electricity is produced from the heat of nuclear fission and by burning combustible fuels such as coal, gas and biofuels.

In 2010, gas and coal together accounted for around 75% of the electricity generated in the UK, with a range of other sources used. In 2015 this combined percentage had fallen to around 52%. For gas and coal the energy content of the fuel entering the power station to be transformed into electricity is measured.

The electricity produced by the transformation process (turbines) and sent to the National Grid is subsequently measured. This process involves losses, as not all the energy produced from combustion can be converted to electricity. Typically the thermal efficiency of coal plants is around 36%, whilst gas plants in the UK operate at around 48% thermal efficiency. Data on thermal efficiency are published each year in table 5.9 of DUKES, the Digest of UK Energy Statistics.

Nuclear energy accounted for around 16% of generation in 2010, but increased to around 21% in 2015. For nuclear, the heat from nuclear fission is measured as the input to electricity generation, with the output of electricity also recorded. For the last few years the thermal efficiencies of the nuclear fleet has been just under 40%.

Researched and written
by World Nuclear News