# A Metal Hydride Compressor Concept using Hydrogen as a Heat Transfer Fluid

## TL;DR

A new metal hydride hydrogen compressor uses hydrogen as a heat transfer fluid, improving efficiency and productivity compared to traditional designs.

## Contribution

Using hydrogen as a direct heat transfer fluid in metal hydride compressors to enhance productivity and efficiency.

## Key findings

- An integrated compressor design using hydrogen as a heat transfer fluid was demonstrated.
- Simulations showed specific productivities of 300 Ln h⁻¹ kg⁻¹ with isothermal efficiencies over 75%.
- The design avoids limitations from pressure-bearing walls in conventional systems.

## Abstract

Metal hydride hydrogen compressors have been explored as an alternative to mechanical hydrogen compressors since the first patents were filed in the 1970s. As heat engines, their productivity notably depends on the achievable heat transfer rate, which is limited by the pressure-bearing walls separating the heat transfer fluid from the reactive metal hydride beds and their effective thermal conductivity. Here we present and analyze an alternative metal hydride compressor system that uses hydrogen as a heat transfer fluid in direct convective contact with the metal hydride material. Following this principle, we demonstrate how an integrated compressor can be designed and how it behaves at both system and metal hydride bed levels. Simulations of a system operating at 10 – 90 °C indicate that specific productivities of 300 Ln h⁻¹ kg⁻¹ can be achieved at low electrical energy demand, with isothermal efficiencies surpassing the ~75 % typically attained by mechanical piston compressors.

Lukas Fleming and colleagues propose a metal hydride hydrogen compressor that uses hydrogen itself as the heat transfer fluid. The resulting convective heat transfer avoids solid-wall limitations of conventional designs and increases compressor productivity.