Abstract

Critical materials are essential to the global economy but face supply risks from geopolitical, environmental, and market pressures. The European Union identifies 34 critical materials, ranging from lithium, cobalt, and nickel for batteries to rare earth elements for magnets, and high‑strength alloy metals such as chromium and tungsten. Even abundant metals like copper and aluminium can become critical when demand outpaces sustainable supply.

Eco‑design offers strategies to mitigate this dependency by extending product lifespan, enabling component disassembly for recycling, and seeking viable material substitutions. In modular construction — especially container‑based self‑sufficient modules — such measures can improve both resource efficiency and sustainability.

Although these modules are increasingly used in remote and off‑grid contexts, little scientific work has quantified the criticality of their materials. This study addresses that gap by applying thermodynamic rarity indicators to a case study: the ZEROENERGYMOD project module, built to PassivHaus standards and integrating renewable generation with dual energy storage (lithium batteries and green hydrogen).

The research focuses on identifying subsystems with the highest critical material contribution, assessing trade‑offs between energy storage options, and proposing design measures to reduce criticality without compromising function. The structural frame and internal partitions contributed 72 % of total thermodynamic rarity, largely due to nickel in stainless steel. Photovoltaic modules and hydrogen systems, though lighter in mass, showed elevated rarity from tellurium, platinum, and iridium. Hydrogen storage offered higher energy density (MJ/kWh) than lithium iron phosphate batteries under the studied conditions.

Replacing stainless steel with coated carbon steel where feasible, favouring wind over photovoltaics in suitable contexts, and developing alternative photovoltaic technologies can reduce critical material use without compromising function. These strategies demonstrate how thermodynamic rarity metrics can be integrated into sustainable module design to address multiple Sustainable Development Goals.