A thermal energy storage apparatus is disclosed. The thermal energy storage apparatus has a phase change medium. The thermal energy storage apparatus also has an inner manifold area having at least one inner feed port. The thermal energy storage apparatus also has an outer manifold area having at least one outer feed port and fluidically coupled to the inner manifold area. The inner manifold area and the outer manifold area are configured to be substantially immersed in the phase change medium. Methods of constructing and controlling embodiments of related thermal energy storage apparati are also disclosed, as well as embodiments of related heat exchangers.