With the continuous increase of installed capacity of new energy generation in power grid

thermal power units have to undertake more peak shaving. However

the flexibility and peak shaving capacity of current thermal power units are generally insufficient. A subcritical 300 MW coal-fired unit is retrofitted for molten salt energy storage. Six heat storage strategies and two heat release strategies are proposed and investigated. The influence of heat storage and release process on the peak shaving capacity and thermal performance of the unit under three working conditions is analyzed

the technical and economic analysis is performed in terms of the net present value.The results show the feasibility of extracting reheated steam for heat storage is higher

with a peak shaving depth of 58.9%. However

the coal consumption would increase at the same time. During the releasing heat stage

the maximum increment of power generation up to 11.3% of the rated power generation is achieved by heating the water supply to generate steam

while the higher temperature of the molten salt is required. Using high-temperature molten salt instead of low-pressure heater to preheat water supply is proved to have more advantages

while the power generation increment is relatively small. During the whole process of heat storage and release

the maximum circulating electricity efficiency can reach 0.987. The economic analysis of heat storage transformation is conducted.The dynamic investment payback period is 11.65 years

and the net present value is 49.118 million yuan. Therefore

the renovation scheme is feasible.