Readers letters
Blaise Kelly rightly notes that Reliables, generators whose fuel supplies we can assure, achieve load factors much lower than 100%. But they clearly doesn’t understand the dynamics of public electricity supply.
The combined 2012 Power demand of our millions of customers varied between 59,105 MW at 1700 h in winter, and 21,421MW at 0400 on a summer dawn, up and down every day in a regular pattern. So generation overall is under-loaded all of the time.
Generators are effectively ranked in Merit Order, the cheapest down to the dearest – excluding WTs, wind turbines. System Control, by government decree, must accept every watt-hour WTs offer, although it is the most expensive electricity we have.
For any commodity, the fixed costs of owning the means of production, (power station) continue unchanged, whether it produces much or nothing. But the variable costs, for fuel, materials, waste disposal, vary with the amount (kWh) produced.
The House of Lords found that for fossil fuels, those variable costs accounted for 70p in the £ of the retail kWh price. For nuclear, it was 10p, of which 1.5p was for imported uranium, 8.5p for the processing we do here.
So as load diminishes from peak, fossil power is shut down, not nuclear – that accounts for most of the difference in fossil/nuclear load factors. Further, the system must always be under-loaded, to ride through a breakdown of any major generator, or transmission circuit.
Further still, power stations need routine maintenance and statutory safety inspections, as does your car. When a power station is shut down, its output must be replaced by one that is necessarily further down in the Merit Order, more expensive. In winter, that means going further down in the Merit Order than in summer. So obligatory shutdowns for high Merit plant are scheduled for summer time.
It is necessary to shut down a number of power stations every year, but it is done at a time of our choosing.
We can’t choose when Renewables shut down – wind doesn’t just bloweth where it listeth, but when it listeth. Anticyclones impair the output of all our WTs, and wave machines, and they are not mutually supportive. Reliables are.
I’d be pleased to hear her comments on the under-performance of wind in the fortnight ending today, particularly the 0.45% achieved on 2nd March.
Bill Hyde, Offham, Kent
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