Optimal co-planning of hybrid energy hubs and integrated electricity-hydrogen transmission infrastructure

Clusters of large-scale renewable energy projects, also known as renewable energy zones (REZs), are essential elements in the transition to net zero. Hybrid energy hubs (HEHs), which incorporate other energy vectors such as green hydrogen (H 2 ) into REZs, can further leverage economies of scale and diversity in electricity and H 2 production and demand to reduce the required capacity of connection assets and decrease overall operational and capital costs. This paper introduces a general, optimization-based framework for the co-planning of HEHs and integrated electricity and H 2 systems (IEHS), aiming to find the least-cost designs of HEHs, along with the electricity and H 2 transmission infrastructure required to connect them to the main grid. This framework features a modular HEH model that enables flexible technology selection and sizing without a predefined hub configuration, while minimizing the capacity of shared connection assets. Comprehensive case studies on the Australian National Electricity Market (NEM) that integrate HEH and system-level planning compare investment strategies between independent connection configurations and shared connection configurations within HEHs. The findings show that integrating HEHs with optimized shared connection assets into IEHS planning can not only displace investments in both electricity and H 2 transmission infrastructure, but also reduce renewable energy curtailment and enhance the utilization of existing and new assets. Moreover, although including H 2 transmission development can reduce system costs, HEHs with shared connection assets alone may provide greater cost reductions as an alternative investment strategy, enough to avoid all the uncertainty associated with building a new H 2 pipeline network.