Various classifications of electrochemical energy storage can be found in the literature. Active storage uses sensible heat, latent heat (stores using phase-change materials) and thermochemical reactions. On the other hand, passive warehouses refer to structural elements of the. . Broadly, storage solutions fall into four major categories: electrochemical, mechanical, thermal, and hydrogen (chemical). This article explains how each works, typical applications, advantages and limitations, performance characteristics, and how to choose the right type for a project.