IEEE Power & Energy Magazine - November/December 2021 - 36

Principle 6: Reliability Criteria Should
be Transparent and Economic
RA and system planning need to include the economic or
financial aspect of reliability. The costs of achieving 100%
RA would be extreme, and senseless for most consumers
when the same money could be spent on other reliability
mitigations. A single RA criterion, absent economic considerations,
is therefore unjustified. Grid planners and regulators
should have a clear understanding of the costs associated
with achieving different reliability targets. For example,
regulators should know the additional costs incurred by ratepayers
associated with increased reliability so that proper
value judgments can be made, and economic resources can
be selected. This consideration can also be used to ensure
that the value provided to the customer is worth the cost of
additional investment and that customers are not being asked
to pay more for reliability than it is worth.
Looking Forward
If the rolling blackout events in ERCOT and CAISO teach
us anything, it is that we-as an industry-cannot continue
to approach RA as we have in the past. These were not failures
of the evolving resource mix, but rather failures of planning.
Existing methods that have served well historically
require further insight as to the resource mix changes to
VRE, energy storage, and demand response, and experience
increased correlation of generator outages due to weather.
Today we are paying the price of limited planning and analytical
shortcuts that do not capture chronological operations
and correlated events.
Many of the metrics currently used, such as the traditional
planning reserve margin, are not adequate for modern power
system planning. The industry needs new options. In the short
term, there is no shortcut. As electricity system stakeholders,
we need to roll up our sleeves and do the hard analytical work.
What we will learn may help us develop heuristics and new
rules to make RA analysis easier and less costly to conduct
and simple to understand. But for now, we must rely on indepth
analysis of real systems.
While considerable work is needed to fully define what
robust RA looks like, some basic first steps can lead to improved
RA analysis. These steps include:
1) Consider how the first principles of RA should be applied
to the system being examined.
2) Make your RA analysis public and easily accessible
so that stakeholders can benefit from seeing a diverse
set of case studies from regions around the world with
different resource mixes, load profiles, and characteristics
of system risk.
3) Collect as much chronological and correlated hourly
historical weather and load data as possible, then consider
whether the available historical data are sufficiently
representative of possible future events, including
consequences of climate variability and change.
36
ieee power & energy magazine
4) Report a broader set of RA metrics such as:
* hourly EUE and normalized EUE (unserved energy
as a percentage of load)
* information beyond expected values, providing distributions
of capacity shortfall events rather than the
averages across many thousands of replications
* statistics on the shortfall events themselves, better characterizations
of the size, frequency, and duration events
so that mitigation measures can be properly sized.
Consistency in RA analysis and reporting will provide the
necessary data and better insight on what shortfall events look
like across many systems. This will help better understand
how the RA risk shifts with changes in the underlying resource
mix of increased VRE, energy storage, and load flexibility.
In time, these comparative analyses will allow for simplifications,
new summary metrics, and alternative planning
reserve margin methods. But for now, we need to roll up our
sleeves and do the hard work.
For Further Reading
California ISO. " Final root cause analysis, mid-August 2020
heat storm, " Jan. 13, 2021.
E. Gimon, " Why climate advocates should be interested
in resource adequacy, " Energy Innovation, Apr. 2020.
Gridworks. " Resource adequacy, reliability through the
clean energy transition, " Mar. 2021.
North American Electric Reliability Corp. " Probabilistic
adequacy and measures, Tech. Reference Rep., "
July 2018.
Schlag et al., Capacity and Reliability Planning in the
Era of Decarbonization. Energy and Environmental Economics,
Aug. 2020.
Biographies
Derek Stenclik is with Telos Energy, Saratoga Springs, New
York, 12309, USA.
Aaron Bloom is with NextEra Analytics, St. Paul, Minnesota,
55107, USA.
Wesley Cole is with the National Renewable Energy Laboratory,
Denver, Colorado, 80401, USA.
Gord Stephen is with the National Renewable Energy
Laboratory, Denver, Colorado, 80401, USA, and the University
of Washington, Seattle, Washington, 98195, USA.
Armand Figueroa Acevedo is with Black & Veatch,
Overland Park, Kansas, 66211, USA.
Rob Gramlich is with Grid Strategies, Bethesda, Maryland,
20817, USA.
Chris Dent is with the University of Edinburgh, Edinburgh,
Scotland, EH8 9YL U.K.
Nick Schlag is with E3, San Francisco, California,
94104, USA.
Michael Milligan is at Broomfield, Colorado, 80020, USA.
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