Iowa Utilities Board issues generating certificates for Coggon, Duane Arnold solar projects

Certificates required to begin construction of facilities in Linn County

The Iowa Utilities Board (IUB) has issued certificates of public convenience, use and necessity for the Coggon Solar and Duane Arnold Solar electric generating facilities in Linn County.

The Coggon Solar project comprises a 100-megawatt solar generation facility to be located approximately 2.75 miles west of Coggon. Duane Arnold Solar I comprises a 50-megawatt solar generating facility near Palo, while Duane Arnold Solar II comprises a 150-megawatt solar generating facility and a 75-megawatt , 300-megawatt hour battery energy storage system, also near Palo.

Generating certificates are required under Iowa Code before construction can begin on a solar energy generation project. The generating certificates for the solar projects were issued by the IUB Nov. 9 and become effective Nov. 23.

Coggon Solar filed its application with the IUB on March 31, 2021, and the IUB approved the application on October 22, 2021, providing that Coggon Solar obtain all necessary zoning approvals and other permits. The Linn County Board of Supervisors issued a final zoning decision approving Coggon Solar’s request Jan. 25.

Applications were filed for both Duane Arnold solar projects on November 2, 2021. The IUB approved the applications July 26, but the projects had not received county zoning approval for the proposed projects at that time, so the IUB withheld the certificates to NextEra Energy Resources and Interstate Power and Light Company (IPL), the companies developing the projects, to ensure construction did not begin until after Linn County had issued a final zoning decision under the county’s utility-scale solar installation ordinance. The Linn County Board of Supervisors approved the companies’ rezoning requests Sept. 6.

The Coggon Solar and Duane Arnold Solar projects are both facing lawsuits filed by neighboring property owners, alleging flaws in the county’s approval process. Trial in the Coggon Solar lawsuit against the Central Iowa Power Cooperative has been set for Sept. 26, 2023.

In a separate ruling Nov. 9, the IUB denied Interstate Power and Light’s application for advance ratemaking principles filed Nov. 2, 2021, by IPL regarding the Duane Arnold Solar projects. The IUB found that IPL relied on a 2020 analysis in support of its decision to construct the Duane Arnold Solar projects, but it should have considered other sources of electric supply as required by Iowa Code and therefore could not proceed with the advance ratemaking principles application.

Requests for advance ratemaking principles enable utilities to establish regulatory treatment for certain aspects of electric generation facilities in advance of construction, but such cases do not immediately impact customers’ electrical base rates. If the utility proceeds with construction, a contested rate case must still be filed with the IUB once the new generation source is placed into service.

The IUB’s order indicates that IPL did not demonstrate that the Duane Arnold Solar projects “are reasonable when compared to other feasible alternative sources of electric supply as required by Iowa Code.” According to the order, IPL did not fully consider other sources of electric generation and did not update its analysis for changes in costs. The IUB also found that the federal Inflation Reduction Act (IRA) “presents IPL with other potential sources of electric supply.”

In the order, the IUB said that its decision does not indicate that IPL should not go forward with the Duane Arnold Solar projects, or that the projects are not reasonable, but that IPL needs to do additional analysis as required by Iowa Code before requesting advance ratemaking principles, or IPL can request cost recovery in a general rate case.