Implication of Assessment of Extreme Renewable Resource Lulls – Watts Up With That?

Roger Caiazza

Francis Menton (here) and I (here and here) have previously written about the magical dispatchable emissions-free resource (DEFR) technology that New York State agencies are using to describe the resource needed during periods of extended low wind and solar resource availability for an electric system that relies on wind, solar, and energy storage.  This post describes another flaw in the magical DEFR solution that advocates ignore.

David Truver writing at the Eigen Values Substack wrote an overview article about the Royal Society Large Scale Electricity Storage report that predicts how much large-scale hydrogen storage (fulfilling the DEFR role) will be needed for a British electric system dependent upon wind and solar.  A more recent Turver article follows up on his attempts to get the Climate Change Committee (CCC) to address the problems he identified.  Both of his articles are well worth reading on their own because he identifies weaknesses in the reports being used to establish targets into law that I think are common problems wherever net-zero transition plans are in place.

Quantifying the Renewable Resource Gap

In Turver’s first article he hinted that the CCC had made an error in its calculations about how much storage is needed to keep the lights on with a grid powered mostly by intermittent renewables. He explained that the Royal Society (RS) Large Scale Electricity Storage report authored by Professor Chris Llewellyn-Smith claims that Great Britain can meet its demand for electricity with wind and solar, supported by large-scale hydrogen storage.  Large-scale hydrogen storage is the placeholder DEFR technology in New York’s plan, so this is directly applicable to New York.

Turver argues that the RS report is deeply flawed and makes extraordinary claims that are not backed up. Among his concerns are the following:

They begin by assuming that electricity demand will be 570TWh in 2050 which represents roughly halving the energy demand across residential, transport and industrial and commercial categories. The evidence from Our World in Data shows that rich economies require high energy consumption to thrive. There are no rich countries with low energy consumption and those countries that have reduced energy consumption have grown more slowly, or even shrunk. The first extraordinary claim of low energy consumption fails because the evidence shows that if we allow that to happen, we will be much poorer.

The report then goes on to assume that the profile of electricity demand will be the same as today. However, as we move from gas to electricity to heat our homes and offices, the winter surge in electricity demand will be further exaggerated. Moreover, demand will change from year to year such as during the cold winter in 2010 that also coincided with a calm period when we would have generated much less renewable electricity. These variations in demand profile will lead to more generation capacity and an even bigger energy store than RS assumes, pushing up costs.

He goes on to argue that there are other flaws.  The report assumes unrealistic load factors for both onshore and offshore wind. It underestimates the amount of offshore wind needed and goes on to assume efficiencies and costs for hydrogen electrolyzers, storage, and generation that do not stand up to scrutiny.  He also points out that the economic assumptions are flawed. 

I was interested in the “main positive aspect of the report”:

The thing that stands out most is the painstaking analysis that has been conducted to understand the very significant changes in the weather that occur on yearly and decadal timescales. They analysed wind and solar records over 37 years to estimate the level of variation we might expect from wind power.

I have commented numerous times in New York proceedings that a similar analysis is necessary. The analysis of 37 years is longer than anything done to date for New York.  He also points out an aspect of DEFR that relies on hydrogen storage that I had not considered previously.  It is not just the annual worst-case episode but there can be multi-year issues:

They found that we can sometimes have several consecutive years where the wind speed is lower than average. This means that if we are to have a grid powered solely by wind, solar and storage, then we need to build up massive stores of energy in the windy years to be used in the calmer years. They conclude that to consistently deliver their 570TWh of electricity each year, we would need 123TWh of hydrogen storage. Some of that hydrogen may have to be stored for a decade or more before it is used.

He also points out that the requirement for decadal storage is another flaw for any DEFR backup resource that I think is applicable to all DEFR technology viability:

This has important implications for the economics of storage and effectively rules out batteries as the storage medium. Who would want to spend millions on building a battery or hydrogen storage cavern, even more to fill it and maintain it, yet not see any revenue from it for years after it was completed?

DEFR Backup Reliability Risk

Turver’s article raises what I think is the ultimate reliability risk for any weather-dependent electric system.  Today’s electric system resource planners for a conventional system base the amount of capacity that they determine will be needed based on decades of observations of the fallibility of power plants.  The result is that they have a good understanding about the probability there will be a shortage of available capacity to meet load when the installed reserve system capacity margin is a fixed percentage of the expected load.  In New York State the installed reserve margin to meet the accepted probability of a loss of load expectation of an outage no more than once in ten years reliability metric is around 20%.

A fundamental observation of that approach is that there is no expectation that the failure of conventional power plants will be correlated.  We do not expect that many will fail at the same time for similar reasons.  That in turn means that even if we decided to set the reliability metric using a longer period there would not be much of an increase in the installed reserve margin needed.

That all changes when the electric system transitions to one dependent upon correlated wind and solar weather-dependent resources.  We know that solar energy is zero and night and much lower in the winter.  Similarly, we know that wind energy is much lower in a high-pressure system, and that those systems are huge and cover all Great Britain and much of western Europe or eastern North America at the same time.  Exacerbating the problem is the fact that those conditions are associated with the hottest and coldest episodes with the greatest expected electric loads.

This impacts the amount of DEFR expected to be needed.  For example, the Independent System Operator of New England (ISO-NE) Operational Impact of Extreme Weather Events  completed an analysis that addresses the DEFR requirement needed in New England.  The study evaluated 1-, 5-, and 21-day extreme cold and hot events using a database covering 1950 to 2021. The results found that the system risk or “the aggregated unavailable supply plus the exceptional demand” during an event increased as the lookback period increased.  If the resource adequacy planning for New England only looked at the last ten years, then the system risk would be 8,714 MW, but over the whole period of record, the worst system risk was 9,160 MW which represents a resource increase of 5.1%. 

Turver’s post explains that the CCC did not even use the worst identified in the Royal Society report: “They used 1987 as a 1-in-20 year stress test, when they admit that 2010 was a 1-in-50 year event”.  His requests to address that problem and others identified have been ignored and concludes that if an “incompetent and damaging” analysis is used to set the law that the results would be impractical.

I believe his analysis raises the point that the DEFR gap is an insurmountable problem.  We know that if an even longer record of weather observations is used to identify the gap that there would very likely be an even worse event.  Instead of the confidence in the current planning process that increasing the lookback period will not markedly change the resources needed for the worst case, relying on weather-dependent resources means that it will increase substantially.  Inevitably there will be a period of extreme weather that exceeds the planning criteria chosen and the expected resources deployed based on the chosen criteria.  The costs to provide DEFR backup support will be extraordinary and building excess capacity for a very rare event will significantly add to those costs.  Providing even larger capacity for an even rarer event is untenable.  This trade-off means that eventually there will be a catastrophic blackout when the load exceeds DEFR capacity.

Conclusion

Turver’s articles are further evidence of the DEFR “gap” problems for any electric system that relies upon weather-dependent renewable resources.  The first problem is that you must determine how much DEFR capacity is needed which is limited by the amount of available data.  The second problem is that there is no commercially available DEFR technology that is available to deploy for the aspirational 2050 net-zero targets.  Thirdly, until a DEFR strategy is proposed we have no idea how much this will all cost so any claims that the 2050 net-zero transition will be “affordable” are incomplete.  Finally, there is the insurmountable weather-related probability that eventually there will be a unusual set of weather conditions coupled with extreme load requirements that exceed the DEFR resources deployed. 

To sum up: we know that a new resource will be needed, we don’t know how much, what it will be, how much it will cost, and that whatever we do some day it won’t be enough.  People will eventually die in a catastrophic blackout when electricity is unavailable when it is needed the most.  This is insanity.

Roger Caiazza blogs on New York energy and environmental issues at Pragmatic Environmentalist of New York.  The opinions expressed in this post do not reflect the position of any of his previous employers or any other organization he has been associated with.