Illinois can address its resource adequacy shortfall by replacing the US state’s retiring fossil fuel plants with 2,972MW of energy storage, and without significant transmission upgrades.
That’s according to a recent study prepared for the US environmental advocacy group Natural Resources Defence Council (NRDC) by Alabama-based advisory firm Astrape Consulting, in response to a 2022 report issued by PJM Interconnection which raised concerns surrounding grid reliability following the passing of Illinois’s landmark Climate and Equitable Jobs Act (CEJA) in 2021.
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US$2 billion in regional transmission upgrades
The legislation requires the retirement of all Illinois coal-fired power plants, with the exception of Dallman Unit 4 and Prairie State Generating Station, by 2030 and all methane (natural) gas-fired plants to be retired or switched to burning green hydrogen by 2045.
The 2022 PJM report found that Illinois’s fossil-fuel phase-out would result in the state needing to import a “substantial amount of remote replacement power” to address the estimated loss in dispatchable power between 2030-2045 across Illinois in both PJM and MISO regions.
Calculations from PJM estimated the increase in electricity imports to cost an approximate US$700 million in transmission upgrades by 2030 and an additional US$1.3 billion by 2045.
Potential for extended fossil fuel plant operation
Despite PJM acknowledging that “new generation resources at the same points where units are retiring, or in similarly favourable locations, could decrease the transmission cost estimates,” it did not evaluate the impact of new energy storage resources within Illinois.
Conversely, PJM concluded it might “need to request that certain units operate beyond their desired deactivation dates”, referring to the continued operation of the state’s polluting fossil fuel plants, which the legislation was brought in to stop.
The recent NRDC report built on the 2022 PJM study by performing a resource adequacy assessment on the addition of BESS facilities at fossil-fuel plants set to be retired by 2030 in MISO Zone 4 and PJM’s ComEd service territory – referred to as the “Illinois Zone”.
In order to determine whether reusing interconnection capabilities of retired fossil-fuel plants would be a feasible strategy, the analysis carried out in the NRDC report limited new storage capacity to not exceed that of the retiring plants.
Resource adequacy simulation for four scenarios
The recent report prepared for the NRDC simulated four resource adequacy scenarios for the Illinois Zone, with each of the cases building on the previous one. This was measured against an industry standard 0.1 loss of load expectation (LOLE) target – equating to electricity demand outstripping supply no more than one day across a 10-year period.
The four cases were as follows:
- Base case: existing installed capacity in Illinois (as of March 2024).
- Post-CEJA: Base Case minus fossil-fuel retirement capacity as mandated by CEJA by 2030 (estimated 11,588MW reduction).
- CEJA plus queue: post-CEJA case plus expected additions from the Generator Interconnection Queue (GIQ) (estimated 7,727MW addition).
- CEJA plus storage – CEJA plus queue plus required storage to meet LOLE target.
3GW of BESS to address shortfall
The analysis (displayed in the following graph below) found that although the Base Case exhibited a 4,971MW surplus, both Post-CEJA and CEJA plus queue scenarios presented shortfalls, at 5,065MW and 2,213MW, respectively.
In order to meet the 0.1 LOLE target in the CEJA plus storage scenario, the report concluded that 2,972MW worth of 4-hour duration batteries would be needed.
Astrape Consulting carried out a separate sensitivity study to determine the required capacity of 8-hour durations batteries to meet the LOLE target.
It concluded that a lower 2,243MW worth of batteries would be required, drawing attention to the importance of longer-duration storage systems, which the California Energy Commission (CEC) also highlighted in a recent study covered by Energy-Storage.news Premium.
Difference in study assumptions and metrics
Although the PJM and NRDC reports both utilised the same methodology for estimating GIQ additions, there was a very large discrepancy between the two figures – with the PJM report estimating 1,723MW of additional GIQ capacity, and the more recent report for the NRDC estimating a much larger 5,605MW.
Astrape Consulting addressed this difference within its recent report citing the use of more updated GIQ data. However, this discrepancy is still worth pointing out.
The NRDC report didn’t quantify the costs associated with the deployment of 3GW worth of BESS, which would likely be substantial, although it stated that this “could be an area of future development”.
It’s also worth noting that, unlike the PM study which looked all the way until 2045, the analysis carried out by Astrape Consulting only took place until 2030.
The full report with all of its findings can be found here.
Illinois ‘Coal to Solar Energy Storage’ grant programme
The Illinois Department of Commerce & Economic Opportunity has created several programmes since instating CEJA to assist in decarbonising its grid, including the “Coal to Solar Energy Storage” initiative which saw funding be issued to the developers of five energy storage projects located at the site of closing or soon to be closed coal-fired plants.
Fortune 500 company Vistra Energy was the recipient of three of these grants in 2022 that will see the developer receive US$40.7 million for each project over a ten-year period, covered in Energy-Storage.News.
The three projects, located at the site of the developer’s Edwards, Havana and Joppa generation stations, will each provide the MISO region within Illinois with 37MW of storage capacity, scheduled to come online next year.
