According to the National Grid figures wind will form the main source for electricity generation in years to come. The current figures show a very significant increase in maximum power - up to over 4 times the current power (depending on the scenario) - as shown in this graph.
However, the use of wind power presents what are probably the most challenging problems for electricity supply.
With a growing number of wind turbines in the UK, the problem of intermittency is presenting an increasing problem.
When planning the use of nuclear power sources it is possible to predict how much electricity will be generated with a high level of confidence. Gas is a controllable source and - subject to a maximum power which is dependent on the capacity of the gas generating facilities - it is possible to control the amount of energy being generated.
However, when dealing with wind it is not possible to predict how much energy can be generated over a certain period of time - or even at a point of time - in the future.
It is also not possible to control the amount of energy being generated, as it is not possible to control how much wind is blowing.
The amount of energy being produced is subject to extreme variations. Consider the following two charts that show the proportion of electricity being produced by major sources at two points in time.
In the first example wind is the most significant source, generating 47% of the electricity being produced:
In the second example wind plays a very minor role, and it is necessary to control other sources - notably gas and even coal - to produce enough electricity to meet demand.
The key issues are:
- We need enough "base load" to ensure a steady basic supply. Wind turbines cannot guarantee a base load, although they can provide a carbon-free contribution to the base load when it is windy.
- We need to be able to react to varying demand, so we need variable and controllable sources. We cannot predict when the strength of the wind will change, and we certainly cannot control the strength of the wind.
See what happens in an extended wind lull.
Wind Power Growth
In the last two years the growth in the total maximum power for wind generation in the UK has been significantly slowing. However, the current figures (see graph above) shows an even sharper rise in that total maximum power.
In the case of offshore wind this has been encouraged by the recently announced Sector Deal, which "could deliver 30GW of offshore wind power by 2030".
For onshore wind the total maximum power is expected to approximately double by 2030, and then to almost double again by 2050.
Overall the expectation is for the total maximum power for wind to more than quadruple by 2050.
In the case of onshore wind there is relatively little construction and commissioning in progress at the time of writing this. It is not clear how the rate of commissioning new onshore wind power will return to - and in fact exceed - earlier rates.
The pro-wind group RenewableUK have expressed their concern about the situation, specifically in relation to onshore wind.
Given the current situation, it will be interesting to see how well the wind power figures match the forecast over the next year or two.
(For more details and explanation of the National Grid forecast and outlook for wind power, see Chapter 5 of their main FES 2019 document.)
The Sector Deal includes indications of where the next generations of offshore wind farms are to be developed. You can see a map of consented and planned installations in this document.
However, in the case of onshore wind it is hard to see where the additional wind generation will be located as so little onshore wind generation is being proposed or implemented at present.
Where will all of these new onshore wind turbines be located, and how will they get planning permission?
It is well known that there is a general perceived reluctance to accept wind turbines - particularly onshore ones - nearby. This has led to a near stoppage of the commissioning of new onshore facilities. It is hard to see how this will be overcome.
The general lifespan for a wind turbine that is used for planning purposes is in the range 20 - 25 years. Since the first turbines for "production use" were installed in the late 1990s, the first of those are now approaching their end of life. In fact, the 2 turbine wind farm offshore at Blyth in Northumberland has already been decommissioned after being in operation for a little under 20 years.
The National Grid figures assume that all current wind turbines will continue to operate indefinitely. This therefore assumes in turn that wind turbines are repowered or replaced at their end of life.
However, there is no specific protocol or regulation related to this. We have approached companies that are responsible for operational wind turbines and so far they have all told us that repowering or replacement plans are not yet in place.
Even the pro-wind RenewableUK has published a report in which they express their concern about this.
Will all current wind turbines be repowered or replaced at their end of life? The National Grid assumption is that sites will generally repower (subject to any planning permissions) either as like for like capacity or with a larger capacity if the grid connection allows.
Who is responsible for making this happen? What is the impact on the National Grid figures if turbines are not repowered?
A number of scientific studies of the decline in performance of wind turbines have been performed, including this one.
Results vary, but there is a general agreement that there is a decline in performance over time. The level is typically of the order of 1.5% per annum. This means that in 20 years a wind turbine will lose about one third of its performance.
There is no evidence that this is factored into the National Grid's figures.
Most planning related to both onshore and offshore turbines is done on the basis of a life expectancy of 20 - 25 years.
So far it has not been possible to validate this as most turbines that are operational in the UK are considerably younger than 20 years.
However, evidence is appearing that life expectancy may - at least in some cases - have been overestimated.