accommodate such uncertainty the choices are to: 1) increase grid costs and infrastructure, 2) limit the operational flexibility of the grid , 3) increase generation costs through backup generation resources or 4) live with increased risks and degraded reliability. Likely all four are and will continue to occur to some extent as the penetration of intermittent resources increases.…
(W)hen intermittent resources only make up a small percentage of total system generation, the adverse impacts are masked by the margin and robustness built into the system… As penetration levels rise and renewables replace non-intermittent conventional units, they will have major impacts upon grid costs and reliability.
The next year in January of 2016 I elaborated on those points in a piece entitled Renewables and grid reliability. It’s worth a full read, but I will reference the key points here:
■ There has been a high value placed on having an extremely reliable bulk grid as the costs and consequences of bulk grid outages are severe
■ The bulk grid supports and is supported by conventional rotating generators (Coal, natural gas, hydro, nuclear, biomass) which provide “Essential Reliability Services” (ERSs)
■ Wind and solar provide increased reliability risks because they are new changing technologies, they are intermittent and they do not as readily provide ERSs
■ Current high levels of reliability depend upon experience gained over time through the gradual adoption of new technologies
■ Wind and solar can be made to provide approximations of ERSs, but that requires significant increased costs and reduced generation output
■ Because of the complexity of impacting factors and the high level of reliability maintained for the US grids, systemic degradation of the reliability of the grid is hard to detect and measure
■ The amount of renewable penetration that can be accommodated will vary from area to area and power system to power system –There is not a single answer
■ Because conventional resources produce an abundance
of ERSs, accommodation of low levels of renewables may be accomplished with negligible risks
■ Because current renewables do not provide adequate ERSs high penetration levels provide significant risks
■ Between the above two levels there is a gap of (wicked?) uncertainty.
■ For assessing grid reliability, the maximum penetration of wind and solar during times of stress is the key number not the “average” contribution of wind and solar
■ Increased penetration of such asynchronous resources, all else equal, will likely adversely impact bulk grid reliability
■ As the penetration level of asynchronous generation increases this will either increase cost, limit operational flexibility, degrade reliability or most likely result in a combination of all three factor
A decade ago, major power systems were still sufficiently robust, so the risks from emerging problems were minimal at the time. The above statements warned that such concerns would eventually arise if trends continued. At low levels of penetration, the additional risks were small, but as penetration increased, the risks grew exponentially. By the time of this posting, Wind and Solar Can’t support the Grid in December of 2024 the existing risks had become clear:
Unlike conventional rotating generation, wind and solar do not readily supply inertia and other essential reliability services. As penetration of wind and solar resources increase, grid reliability decreases. The challenges of increasing wind and solar increase exponentially as you increase their share of generation. Policy makers, academics and others seeking to increase wind and solar are focusing on the wrong problems (intermittency) and failing to study the real operational problems inherent in inverter based generation from wind and solar.
On February 19 of this year in this post Unraveling the Narrative
Supporting a Green Energy Transition, I outlined the major issues by addressing the misleading and false claims of the “green energy narrative” through bullet-point rebuttals. The points about inverter-based generation are particularly worth reviewing for those seeking more detail. After considering these factors and analyzing reviews of grid outages, it became
mentioned earlier, a thorough review will provide data that can be shaped into narratives to deflect attention from the root causes.
An expert from Madrid argues that the triggering event wasn’t an N-1 event (where the system loses its single most impactful element) but an N-2 event (a double contingency). He does not blame inertia, as the system isn’t required to have enough inertia to survive an N-2 event. He suspects one of the events was caused by RoCoF relays, which interrupt generation when frequency changes rapidly. Note that frequency problems tied to low inertia caused the loss of solar facilities and the system collapse.
I may not have heard his best arguments fully and correctly and they may be refined further. He likely knows more about the technical specifics of the occurrence than I do, but I suspect our differences are more philosophical then technical. He seems to be saying that: 1) the system performed outside the bounds of study protocols, 2) the causes of the two events leading to the double contingency are unclear (though RoCoF variations may have caused one), and 3) since the event was outside study criteria, low inertia isn’t to blame.
I counter that system planning was insufficient. Systems should remain stable across many N-2 events, as many double contingencies have less severe consequences than the worst N-1 event. This N-2 event doesn’t seem particularly severe compared to potential N-1 events. Moreover, both RoCoF issues and large frequency deviations are worsened by low inertia and mitigated by higher inertia. This blackout has the fingerprints of low inertia everywhere.
How Should We Define the Cause of Blackouts?
Consider the Suzuki Samurai, a popular automobile in the 1980s with a stability problem: it frequently tipped over. Proponents of these vehicles pointed out that rollovers were often accompanied by sharp turns, adverse conditions, road grading, unanticipated obstacles, or the behavior of other vehicles. Despite these complicating factors, Samurais were much more likely to tip over than other cars due to their tall, narrow body, high center of gravity, and short wheelbase. These characteristics made the car nimbler in off-road situations, particularly at slower speeds. Proponents could argue that if other cars drove more slowly and were equally nimble, Samurais wouldn’t need to swerve as much, reducing rollovers. Sweeping changes to
Conclusions
Proponents have long dismissed predictions that increased wind and solar use will raise costs and reduce reliability. Despite calculations on paper suggesting that large-scale integration of wind and solar is cheaper, realworld evidence shows they increase costs. Despite claims about reliability, previous outages have demonstrated the potential for wind and solar to heighten blackout risks. Pressure has been applied too frequently to distract from the real issues and real-world impacts.
It cannot be emphasized enough: the grid must be robust enough to survive major contingencies in an imperfect world. We must stop listening to those who, after an outage or blackout, insist the problem was unexpected events on the grid rather than the fact that grid reliability has been degraded by increased penetration of inverter-based generation.
Similarly, those who claim that wind, solar, and batteries can be made to support the grid more effectively must be challenged to acknowledge their current real-world capabilities and set reasonable expectations for future performance. Making inverter-based generation perform well enough to support a grid is a complex and extremely challenging problem.
Reuters’ suggestion to “not blame renewables, but rather the management of renewables” is particularly infuriating. Grid managers, tasked with maintaining stability, have been ignored for far too long. Grid and generation decisions are often driven by political rather than engineering