Dynamic Modeling and Control of a Two-Reactor Metal Hydride Energy Storage System

TL;DR

This paper develops a nonlinear dynamic model and a predictive control strategy for a two-reactor metal hydride energy storage system, enabling precise heat transfer management despite variable conditions.

Contribution

It introduces a novel integrated nonlinear model and model predictive control approach for two-reactor metal hydride systems, enhancing energy storage and heat transfer control.

Findings

Controller accurately tracks desired heat transfer rates

System maintains performance under variable inlet temperatures

Enables effective energy storage and heat pump integration

Abstract

Metal hydrides have been studied for use in energy storage, hydrogen storage, and air-conditioning (A/C) systems. A common architecture for A/C and energy storage systems is two metal hydride reactors connected to each other so that hydrogen can flow between them, allowing for cyclic use of the hydrogen. This paper presents a nonlinear dynamic model and multivariate control strategy of such a system. Each reactor is modelled as a shell-and-tube heat exchanger connected to a circulating fluid, and a compressor drives hydrogen flow between the reactors. We further develop a linear state-space version of this model integrated with a model predictive controller to determine the fluid mass flow rates and compressor pressure difference required to achieve desired heat transfer rates between the metal hydride and the fluid. A series of case studies demonstrates that this controller can track desired heat transfer rates in each reactor, even in the presence of time-varying circulating fluid inlet temperatures, thereby enabling the use of a two-reactor system for energy storage or integration with a heat pump.