In a future energy system, the large share of volatile renewable energy will increase flexibility needs to resolve the temporal mismatch between demand and supply. A central enabler for this flexibility needs is energy storage. While short duration storage applications recently are getting widely adopted, in a renewable based future energy system there will be an increasing need for Long Duration Energy storage. Stand-alone long duration energy storage technologies, however, face economic challenges due to their high capital costs and limited revenue streams. To overcome these challenges, hybrid energy storage systems (HESS) that combine long duration storage with short duration storage have gained significant attention in scientific literature.