There’s nothing that renewables advocates like to discuss more than building power lines, lots of them. And a favourite subject is to build very expensive power lines between the UK and Scandinavia so that we, like the Danes, can balance variable wind generation off their controllable hydro. Every country in Europe wants to do this.
The UK of course has its own suite of hydro dams with 1.7 GW capacity, most of it in Scotland. And so you would think that before we begin to dream about balancing our wind power off Scandinavian Hydro we would start by utilising our own hydro to maximum effect before hand (Figure 1). Nothing could be further from the truth.
Figure 1 If UK hydro were being used to balance wind, a negative correlation between the two would be expected since hydro generation should be turned down or switched off altogether when the wind blows. If anything there is a positive correlation suggesting that UK hydro is not being used to balance wind power at all. Data points are 5 minute intervals for the whole of 2012. Data sources BM reports from Gridwatch.
Another way to look at the data is of course as time series as shown for January 2012 in Figure 2. From this it is perfectly evident that UK hydro is not turned down or off when the wind blows nor is it turned up when the wind doesn’t blow. It is more or less kept running the whole time with minor fluctuations made to meet diurnal demand pattern.
Figure 2 Click chart for very large readable version. The x-axis is at 5 minute intervals for the month of January 2012, the labels are spaced on a daily basis. There is precious little evidence from this that UK hydro is being used to balance variable wind. Data sources BM reports from Gridwatch.
The picture for January 2014 is pretty much the same although there is a hint that hydro may be run a little harder during windless spells (Figure 3). It is never turned off and it never gets close to generating 1.7 GW the supposed name plate capacity.
Figure 3 Click chart for very large readable version. The axis is as described for Figure 2. In January 2014, hydro is still producing all the time and does not get much above 1 GW output. The diurnal variance that helps meet peak daily demand is still evident. The scale of wind variability has grown to dwarf hydro output.
Most of UK hydro is owned by utility Scottish and Southern Energy (SSE). They presumably are running their assets according to engineering and economic prerogatives. The positive correlation shown in Figure 1 most likely shows that both hydro and wind production are higher during wet and windy periods that occur mainly in winter months. The small diurnal variations in hydro are down to SSE selling some of their power into high priced, peak demand periods.
So why is the UK not using indigenous hydro to balance wind choosing instead to make curtailment payments to wind producers when the wind blows too much? I don’t know the answer. I suspect that turning hydro off would cause our rivers to run dry and producing flat out would produce floods. It must also be noted that wind is now producing over 6 GW of variable range in output (Figure 3) that dwarfs the maximum output of our hydro suite. Hydro balancing wind in the UK seems to be yet another empty Green promise.