Clean Energy Portfolio Replacement at Tennessee Valley Authority
In early 2022, the Sierra Club retained Synapse to model the Tennessee Valley Authority's (TVA) system and examine the resource options available to TVA to replace retiring coal-fired generators. Synapse used state-of-the-art electric simulation software to determine the cost to ratepayers of replacing coal generators with new gas-fired resources relative to scenarios that forgo new gas builds in favor of resource portfolios with increased volumes of renewables, storage, and energy efficiency.
We modeled three resource portfolios:
Business-As-Usual (BAU), in which retiring coal is replaced largely with new gas-fired capacity;
Solar/Storage Replacement, in which retiring coal is replaced with new solar and battery storage resources; and
Clean Portfolio Replacement, in which retiring coal is replaced with a portfolio of energy efficiency, wind, solar, and storage resources.
Synapse modeling found that replacement portfolios that rely on renewables and storage will achieve the same levels of reliability as more fossil-intensive portfolios while lowering greenhouse gas emissions and costs to customers.
In late 2022, TVA released its Cumberland Fossil Plant Retirement – Final Environmental Impact Statement (EIS) which includes Appendix Q, a report by Concentric Energy Advisors (Concentric), responding to Synapse’s initial 2022 report. Following the EIS release, the Sierra Club retained Synapse to author a comment letter responding to the critiques in the Concentric report and to discuss the implications of the Inflation Reduction Act for TVA. In the comment letter, Synapse encouraged TVA's Board of Directors to make prudent decisions and recommended TVA move away from investing in costly replacements for its coal fleet.