Matching Supply and Demand In A Low Carbon World
By Paul Homewood
There is one very interesting chart I have come across in the working papers for the CCC’s Fifth Carbon Budget:
The CCC notes explain it:
Figure 3.4 shows hourly demand data in hypothetical 2030 scenario reaching 100 gCO2/kWh sorted high to low against nuclear, wind and solar PV output in that hour.
In other words, this is what the demand/supply balance could look like under a typical 2030 scenario, with the sort of high deployment of nuclear/wind/solar required to meet carbon targets.
Two things stand out.
1) There are times when low carbon sources cannot supply all of demand.
This will come as little surprise! But what may be revealing is that this is not simply an issue for a few days in winter. Or, for that matter, just a shortfall of a couple of GW or so, that we can fill with diesel engines and DSR.
Instead it would appear that there could be large shortfalls for 30% of the year.
Even the CCC recognise that CCGT will need to supply something like a quarter of our electricity in the Fifth Carbon Budget period of 2028-32.
But nobody seems to have any plan at all of what we are supposed to do in the years after, as decarbonisation targets become progressively tighter.
2) Just as significant though is the other end of the graph.
There are times during the year, maybe as much as half, when supply far exceeds demand.
If the answer to (1) is to build more low carbon generation, this will simply exacerbate the problem.
Of course, there is always going to be spare capacity, particularly in summer months, with any generation set up. But with conventional technology this can be easily planned for, for instance using downtime for planned maintenance.
With a lot of renewable energy in the mix, this is not possible.
But the other big problem with renewables is their variability. Because of this, you need much more capacity to produce a given output.
The CCC, for instance, offer some scenarios below for a 2030 Scenario:
Given the big problems experienced with Hinkley and the unlikelihood of CCS becoming commercially viable anytime soon, the most likely scenario is High Renewables.
Because of the inefficiency of wind and solar generation, the CCC reckon we will need 103GW capacity of low carbon capacity. (This is in addition to back up capacity).
Consequently, when it’s windy in summer, there is going to be an awful amount of excess generation.
Which raises the question, who will pay for this?