As the world grapples with the urgent need to mitigate climate change, the role of pumped thermal storage (PHES) in reducing carbon emissions has come to the fore. Essentially a large rechargeable thermal battery, this innovative technology has the potential to revolutionize the way we store and use energy, with significant implications for our carbon footprint. PHES works by converting excess electricity from renewable sources into thermal energy, which can be stored and then converted back into electricity when needed. The process is highly efficient, with a return efficiency of up to 75 %. This means that for every four units of electricity put into the system, three can be recovered. This high efficiency is a major advantage over other forms of energy storage, such as batteries, which typically have a return efficiency of around 80–90 %, but degrade over time and require expensive materials. (