  Power-to-X (P2X) needs to scale up rapidly to provide the fuels required in
the hard-to-decarbonize industrial and heavy transport sector. Only recently,
the European Commission proposed requirements for \textit{renewable} fuels. P2X
energy hubs enable efficient synergies between energy infrastructures,
production facilities, and storage options. In this study, we explore the
optimal operation of an energy hub by leveraging the flexibility of P2X
including hydrogen, methanol, and ammonia synthesizers, and analyze potential
revenue streams such as the day-ahead and ancillary service markets. We propose
EnerHub2X, a mixed-integer linear program that maximizes the hub's profit based
on current market prices, considering technical constraints of P2X such as unit
commitment and non-linear efficiencies. We model a representative Danish energy
hub and find that without price incentives, it mainly produces liquid hydrogen
and sells renewable electricity. Only by adding a price premium of about 50\%
(0.16 \euro{}/kg) to the conventional fuel prices, sufficient amounts of
renewable ammonia and methanol are produced. To utilize production efficiently,
on-site renewable capacity and P2X must be carefully aligned. We show that
renewable power purchase agreements can provide flexibility while complying
with the rules set by the European Commission.

Physics and Society