Slightly misleading

I read this short piece in the Western Mail today:

Wales falls behind in green energy

Wales is lagging behind the rest of the UK in increasing the amount of electricity it generates from renewable sources, a report has shown.

While the country scores well for its capacity to generate green energy, with projects rated as capable of producing 753.3 megawatts of electricity an hour, more than any of the English regions and Northern Ireland.

Wales’ capacity grew by 31% from 2008 to 2009, but the amount of electricity it produced fell by 1% to 1,609.9 gigawatts, putting it behind the east, north-west and south-east of England.

Scotland with its considerable hydro resources outpaces all of the UK on green electricity.

Western Mail, 1 October 2010

Perhaps it's unfair to single out the Western Mail, because many reporters elsewhere don't have the first clue what they're writing about, either. But generating capacity is measured in watts (or megawatts or gigawatts), not watts per hour; and the amount of electricity produced is measured not in watts, but in watts per hour.

It doesn't take too much research to find out which report is being referred to. It's contained in DECC's Energy Trends for September in the section starting on page 25. But for comparisons with previous years we need the spreadsheets downloadable from this page.

Our 31% increase in renewable capacity from 574.4 MW to 753.3 MW compares well with increases of 13.9% in Scotland and 17.5% in England, but is behind NI's 44.9% increase.

However it is remarkable that the total of renewable electricity generated in Wales has gone down, albeit only very slightly. The reason is mainly to do with when the increased capacity became available. The capacity figures are for the end of 2008 and 2009, but the generation figures are for the whole of each year. Most of the increase in Wales' capacity was the 90 MW offshore windfarm at Rhyl Flats, opened in December 2009. So the figures are slightly misleading and, for the same reason, the capacity factor for windpower in Wales is also lower than it actually is, because it's simply one figure divided by the other.

But on top of that, it's completely wrong for the Western Mail to say that the 2009 generation figures "put us behind" the east and north west of England, since we were also behind them in 2008 and in the years before. Because of large populations, these regions generate a lot of electricity from landfill gas, as does south east England.

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Just for fun, I've put together this table showing how much renewable energy was generated per person in 2009. It's not perfect because the population figures are from different years, but it gives a fairly good overall picture:

Wales ... 0.54 MWh/person
Scotland ... 2.07 MWh/person
Northern Ireland ... 0.47 MWh/person
England ... 0.23 MWh/person

East Midlands ... 0.38 MWh/person
East ... 0.40 MWh/person
North East ... 0.32 MWh/person
North West ... 0.29 MWh/person
London ... 0.05 MWh/person
South East ... 0.24 MWh/person
South West ... 0.13 MWh/person
West Midlands ... 0.18 MWh/person
Yorks & Humber ... 0.30 MWh/person

UK ... 0.42 MWh/person

Scotland is streets ahead, of course, but this is certainly not only because of hydro electricity. In 2009 Scotland produced almost as much from wind and wave (4.56 TWh) as it did from hydro (4.88 TWh) and wind will probably edge ahead this year. Wales is comfortably second. Northern Ireland is surprisingly (at least to me) but encouragingly high.

To put these figures into a wider perspective, total electricity consumption in the UK is about 6.2 MWh/person, according to this international table.