Long-duration energy storage : A technoeconomic comparative analysis with case studies in Mexico

Abstract: While the interest in energy storage has grown in recent years, attention has been largely focused on short-duration systems with lithium-ion batteries. Long-duration (4-24 h) technologies, their business cases, and their potential to contribute to the energy transition have remained largely unexplored. Drawing from both academic and industry publications, this thesis presents the state of the art of energy storage technologies suitable for long-duration applications and performs a technoeconomic analysis of two technologies (lithium-ion and flow battery) applied to two case studies in Mexico.  This report presents the most relevant energy storage technologies that can provide long duration storage. It also briefly explores the general use cases for storage and the business models typically employed. Two case studies for PV+storage systems in Mexico are also developed, one for a behind-the-meter industrial user in 2021 and another for an independent power producer in 2025. Two storage technologies, a lithium iron phosphate (LFP) and a vanadium redox flow (VRF) battery, are chosen for both cases, based on the appropriateness and maturity of the technology and the availability of data. The technoeconomic performance of these technologies is evaluated using purpose-built models and varying system size and duration, as well as PV plant size. Additional revenues from Clean Energy Certificates are included. Sensitivity to key parameters is also assessed. The resulting indicators are compared.  The case studies suggest that PV+storage is attractive in Mexico only when large levels of self-sufficiency and/or clean energy are valued, although the electricity market and rates may change significantly in the coming years. LFP is found to be competitive against VRF for mid-range levels of self-sufficiency, whereas VRF is more competitive in the last 15-30% of self-sufficiency. To meet the last portion of demand and reach complete self-sufficiency, another source (such as a fuel genset) would likely be more economical to avoid drastic oversizing of the PV plant. VRF and LFP systems with fast charging may be significantly more competitive than the base cases, but more research is required to verify the assumptions. Business recommendations for PV+storage projects in Mexico are offered, considering findings from both the technologies and the country’s energy sector.