Without coal how do we keep the lights on?

Without coal how do we keep the lights on?

by Paul Spare
article from Saturday 20, January, 2018

THERE HAVE BEEN several announcements in the last two years on the BBC and in press releases by Renewables UK noting that the proportion of electricity generated by renewables has reached record levels.  They deduce that there is an inexorable change in the generation mix that will see the replacement of conventional large-scale generation by renewables.  The press releases are extremely confident but they have a great weakness.  They are exclusively confined to the days when conditions were favourable to the selected power sources. 

Such an approach may be justifiable in public relations ethics but with electricity supply, dispassionate, objective, auditable data is required that also examines unfavourable events and plausible fault conditions.  This could be a power station transformer failure or loss of the cross-Channel interconnector. The continuity of mains electricity supply is so crucial to the wellbeing of society that the complete spectrum of conditions has to be addressed.

Electricity is generally produced with about a 99.98 per cent continuity of supply… something like a loss for one hour per year.  Can higher renewables penetration achieve this level of reliability?  Data collected from the Gridwatch or MyGrid websites over the last five years shows that such a future would be fraught with danger.   

Every winter we have several days in succession when wind output falls to only a per cent of grid demand. On 10-11 January 2018, all the thousands of wind turbines combined were producing only 1-1.5 per cent of what we needed. At the end of the early morning demand peak 9.30 am on January 11th, the wind contribution had declined to 0.6 per cent.  Fortunately we could call upon about 9,000 MW of coal plants to make up the shortfall and prevent blackouts plus 7,500 MW of baseload nuclear – thanks to the planning of the now defunct Central Electricity Generating Board in the 1960s. 

For several days in mid-December last year, similar conditions prevailed.  For example 10.50 am, 12 December, total demand was 46,000MW with wind power only about 3 Per cent.  Fortunately coal station output was increased to almost 10,000MW – 20.7 per cent of grid-connected generation.  

The same pattern was seen almost exactly five years before over a period of five days, but apparently this warning was not to be instructive.  From early morning of 13 January 2013 to early evening of 17 January 2013 wind power varied between 0.5 and 3 per cent. Varying continuously on 13th and 14th around 0.5 per cent.

Despite the clearest evidence that our coal stations are preventing power cuts, when gas-fired power plants are already working at maximum output, there are siren voices demanding that coal be phased out by 2025.

The following conclusions can be drawn from the Gridwatch data.

1. On many days of the year, wind power can fall to very low levels. The low output can persist at less than 1 per cent for many days at a time;

2. The low levels can occur at any time of day and in any month of the year;

3. Wind power can be reducing at times when demand from the consumers is increasing, necessitating a greater than normal rise in conventional generation;

4. In a typical year wind output falls to less than 2 per cent of demand for about 25 days; and,

5. This pattern of negligible wind generation is repeated year after year.

The misery is further aggravated by huge sums that have to be paid to wind farms as ‘constraint payments’ when their output cannot be used in times of low demand.  Such costs and the costs incurred by National Grid constructing additional HV power lines to connect distant wind farms to demand centres are loaded on to consumer bills in an orgy of waste.  There is more potential expense to come, if large battery storage facilities have to be constructed to accommodate massive variations in renewables output.  Such parasitic costs are not needed in the operation of conventional thermal plants.

Even the claims that renewable power will be a vital element in the evolution of the low-carbon economy are fallacious.  One has only look across the Channel to see how propaganda has overcome reason and logic.  The prodigious effort to expand renewable power in Germany has seen emissions stagnate and in 2017 increase.  Their emissions per capita are almost twice those in France, Sweden and Switzerland that rely on a mixture of nuclear and hydro.

A technologically advanced society cannot rely on the proliferation of wind farms and must invest in secure supplies from conventional generators.

Paul Spare CEng, FEI FIMechE

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