On Saturday 23 May at about 8.30 pm the electricity interconnectors that link us to grids across the Channel were humming. France was supplying us with 152 MW and the Netherlands were supplying 466 MW. Meanwhile, however, the UK was supplying Belgium with 688 MW.
The cables across the English Channel can only use direct current (DC), and the grids on both sides of the water use alternating current (AC). So the 600-odd megawatts of electricity coming from France and the Netherlands had to be converted from AC to DC and then back again. A somewhat larger supply of power was, at the same time, sent to the Belgian interconnector, where it was converted to DC for its journey back across the water. At the other side it was converted back to AC for injection into the Belgian grid.
But each step along the way involves energy losses. For electricity that does the full trip, from the Netherlands to the UK to Belgium, the conversion process is only 90% efficient. So 60 MW of electricity is simply being converted to heat and lost; at the windspeeds prevailing that weekend, this is the equivalent of the output of 150 onshore wind turbines.
And who pays for those losses? Why of course we, the electricity consumers, do.
Mike Travers CEng, MIMechE, FIET is a retired electrical engineer, having worked in the Royal Engineers, the hydroelectric sector, and in manufacturing industry.