Renewables In U.K. Show Inability To Power The Grid
“Another weekend with no solar power (cloudy days) and little wind, forced the grid to call on coal and more natural gas. Yet, politicians drive forward in electrifying the country with no guarantee the power will be there.”
The goal of decarbonizing our economies and running them totally on electricity struggles with the reality that wind and solar are intermittent power sources, which complicates managing the electricity grid. When electricity grids were powered entirely by fossil fuels, their operators were only stressed to ensure that the power plants operated 100% of the time and the output could be adjusted to meet fluctuating electricity needs throughout the day.
Confronting the reality of renewables intermittency requires adopting different operating strategies. In the case of solar, everyone knows it isn’t produced at night since the sun doesn’t shine. That daily timeframe can be planned around by using other power sources not impacted by the time of day. The problem for solar comes when cloud cover develops – intermittently when clouds drift across the landscape blocking the sun temporarily, or on cloudy days when sunlight is blocked all day or for multiple days. Improvements in weather forecasting allow grid operators to plan power source switches to counter the loss of solar power due to clouds. There is little that can be done to offset the power lost from drifting clouds, but hopefully the time and magnitude are minimal.
Managing wind intermittency presents different challenges. Meteorological knowledge enables us to anticipate when the wind will be blowing and likely how strong it will be. People often don’t appreciate that wind turbines can work at low wind speeds, but above certain speeds, they must be shut down to prevent them from being damaged. Again, weather forecasters can usually predict when those times may happen. The problem is when the wind stops blowing unexpectedly. The uneven warming and cooling of land can make onshore wind much more variable than offshore wind. Offshore wind is not only more stable, but it also tends to be stronger, allowing the harvesting of greater amounts of power.
Despite all the operational and forecasting improvements, depending on renewables remains a challenge. The problems of wind and solar in the United Kingdom were noted in a blog from Paul Homewood. As a retired accountant, Mr. Homewood is fascinated with numbers and adept at extracting data from massive government databases. As a result, he often posts government or energy industry charts that highlight problems with renewables that their proponents often overlook or minimize. His latest blog highlighted what happened to the electric grid in the U.K. during the weekend of December 5-6. He published a chart showing electricity supplied to the U.K. grid, by source, during half-hour increments. The data came from the BMRS system for the Balancing and Settlement Code overseen by Elexon Ltd. The company compares how much electricity generators and suppliers say they will produce or consume with actual volumes. Elexon works out a price for the difference and manages the payments. This process involves taking 1.25-million-meter readings every day.
That chart highlighted the loss of wind power, which can be seen by tracking the large dark blue section of the columns from the early morning hours of December 6, as they shrank during the day. The second chart showed the solar power output, which was impacted by it being a cloudy day. At peak generation of 1.68 gigawatts (GW) during the noon to 1:00 pm time-period, solar power’s contribution to meeting overall power needs was approximately 4.3%. At this point in the day, solar should be contributing at its maximum. For the second quarter of 2020, solar generating capacity accounted for 27.7% of total renewables capacity, or 13.4 GW. The peak solar output this day was 12.5% of total solar generating capacity. Interestingly, a 2020 European Union energy publication, based on 2018 data, showed that the U.K. had the third largest solar generating capacity among the 28 nations.
Exhibit 8. Wind Disappears During December 5, 2020 SOURCE: Paul Homewood
Exhibit 9. Solar’s Weak Contribution To Power Grid SOURCE: Paul Homewood
We went to the Elexon web site and collected the data for December 6 through part of December 7 (Exhibit 10, next page). This allowed us to extract the actual amounts of electricity produced by fuel source during each half-hour segment. As can be seen by the dark blue sections of each column, wind was present in the early morning hours of December 6 but virtually disappeared by late afternoon. Wind subsequently returned stronger in the mid- to late-afternoon of December 7, as shown by the larger dark blue sections.
Exhibit 10. Electricity By Source and Fuel During Two Days SOURCE: Elexon
We focused on the first half-hour (12:00 - 0:30 am) and the 35th half-hour (5:00 - 5:30 pm) to see how the power supply changed. We know from the columns that wind power, which was evident in the early morning, had largely disappeared by the late afternoon. In fact, wind power went from 1,564 megawatts (MW) to only 381 MW. As a percentage of total energy produced, wind’s share fell from 5.5% to only 0.9%. What can be seen in the afternoon time period is the emergence of coal power (black at the bottom of the columns).
Coal was not needed in the early morning hours, largely because total power needed was only 28,574 MW. In the afternoon, total power increased to 43,820 MW, a 53.4% increase. The mix of power supplies was also interesting. The amount of power imported from abroad (Belgium, the Netherlands and France) along with “Other” power sources increased by 9% between night and day. Imported power’s share of total power fell from 14.6% to 10.3%.
The fact that the U.K. relies on imported power for roughly 10% of its power needs is often overlooked by people when suggesting how the country can power itself just with renewables.
While the wind power contribution in the afternoon represented about a quarter of what it contributed at night, hydropower nearly doubled its contribution, and pumped storage contributed 3.9% of total power needs in the afternoon versus none at night. Nuclear power’s contribution was steady all day, while biomass increased by nearly 27% its contribution during the afternoon. The key power contributor in both time segments was natural gas, which contributed 47% of the power at night, and then increased its output by 80%, to contribute 55.3% of total power needs in the afternoon. You will notice that solar’s contribution was so small it failed to register.
To further note the intermittency of wind, we compared the amount of electricity produced from wind at specific time periods on December 6 and December 7. One can see how strong the wind was blowing during the early morning hours of December 6, but how that rapidly fell off by afternoon. The low wind during the afternoon of December 6 continued through the night and into the early morning hours of December 7. In contrast to the prior day, instead of declining further, wind’s contribution picked up significantly by the afternoon of December 7. If grid operators are unprepared for such variability, they would be left scrambling to secure other power sources. Alternatively, they might decide that power users need to be cut back. In those cases when there is too much wind, the grid operators are forced to pay the wind providers to avoid having to take their output. Through the first half of 2020, National Grid, the operator of the U.K. electricity grid, had paid wind developers over $1.3 (£1.0) billion not to supply their wind electricity to the grid. That is a cost that electricity customers are forced to pay.
Exhibit 11. How The Wind Blows And Doesn’t Blow SOURCE: Elexon, PPHB
The U.K. government’s plan to convert its economy to electricity and to decarbonize its power grid will need to overcome the realities of the intermittency of renewables. Battery storage and a restructured electricity pricing structure to encourage more off-peak electricity usage will help. In the United States, one electricity company has just received approval from its regulator to introduce hourly pricing to enable them to attempt to convince customers to shift their power needs. Neither battery nor variable power pricing are capable of handling renewables intermittency adequately, which is why power usage mandates will be relied upon until hydrogen power becomes a viable fuel supply option. It is more likely that the grand scheme for decarbonizing the U.K. economy will be pushed out beyond the currently hyped near-term targets.