20 - Storing energy using molten salts

Abstract

This chapter gives an overview on the history, experience, and lessons learnt with molten salts as storage media. It reviews the lessons learnt in the various demonstration pilots and presents the upscale from those pilots to utility scale and commercial implementation. It shows the various utility scale commercial use cases of such molten salt storage systems first in solar thermal electric parabolic trough and later in molten salt solar tower plants. The precipitous fall of utility scale solar PV's global weighted average levelized cost of electricity in the decade 2010–19 led then to the concept of hybrid solar thermal electric and solar PV projects with molten salt. Developments to improve charge/discharge molten salt storage efficiency with the use of high temperature heat pumps are presented. The potential of retrofitting molten salt storage to existing retiring coal plants is discussed. Salt mining, availability, and environmental sustainability are analyzed. The detailed characteristics of molten salt as heat transfer and storage medium are summarized. The equipment components as tanks, pumps, piping, trace heating, and insulation of a commercial utility scale molten salt storage system are presented.