[Objective] Driven by the dual carbon goals

the high-penetration integration of renewable energy and the large-scale retirement of coal-fired power plants present significant challenges to grid stability. In this context

retrofitting decommissioned thermal power units into Carnot battery energy storage systems has emerged as a promising solution. This technology offers a pathway to repurpose existing infrastructure assets

provide essential large-scale

long-duration energy storage

and support the transition to a cleaner power system. Therefore

a comprehensive investigation into its technical feasibility

the supporting national and local policy frameworks

and the potential electricity market mechanisms is both timely and necessary for its future deployment. [Progress] This work begins by summarizing the current developmental status of new energy storage technologies in China and elucidating the fundamental operational principles of Carnot Batteries. A comparative analysis is then performed to assess the technical characteristics of mainstream energy storage technologies and to position the competitive environment for Carnot Batteries. Subsequently

a review of relevant domestic and international research concerning the Carnot Battery retrofit of decommissioned thermal power units is presented. The investigation extends to an examination of policies at both the national and local levels pertaining to thermal power plant retrofitting and the broader field of new energy storage. Furthermore

based on the current state of the electricity market and existing profit models for standalone energy storage systems

an analysis of potential market mechanisms for the retrofitted units is conducted. [Conclusion] The research findings indicate that the retrofit technology

which involves replacing the original boiler with a molten salt heat pump system

possesses tangible potential for practical implementation. The sequentially introduced policies that support the conversion of retired thermal power plants into energy storage facilities and foster long-duration energy storage development has created favorable conditions for this technological application. The retrofitted thermal energy storage system can generate revenue through participation in multiple market segments

including the energy market

compensated ancillary services

capacity compensation schemes

and capacity leasing arrangements. However

several significant obstacles currently hinder progress. These include the relatively low energy efficiency of high-temperature heat pumps

the detrimental impact of frequent start-stop cycles on system longevity

incomplete policy frameworks and technical standards

and market mechanisms that are not yet fully aligned with the technology's value proposition. With anticipated advancements in technology and continued innovation in electricity market design

the Carnot Battery retrofit of decommissioned thermal power units holds considerable promise. It is positioned to become a crucial supporting element for enhancing power system flexibility and facilitating the ongoing energy transition.