  The intermittent nature of renewable energy resources such as wind and solar
causes the energy supply to be less predictable leading to possible mismatches
in the power network. To this end, hydrogen production and storage can provide
a solution by increasing flexibility within the system. Stored hydrogen can
either be converted back to electricity or it can be used as feed-stock for
industry, heating for built environment, and as fuel for vehicles. This
research examines the optimal strategies for operating integrated energy
systems consisting of renewable energy production and hydrogen storage. Using
Markov decision process theory, we construct optimal policies for day-to-day
decisions on how much energy to store as hydrogen, or buy from or sell to the
electricity market, and on how much hydrogen to sell for use as gas. We pay
special emphasis to practical settings, such as contractually binding power
purchase agreements, varying electricity prices, different distribution
channels, green hydrogen offtake agreements, and hydrogen market price
uncertainties. Extensive experiments and analysis are performed in the context
of Northern Netherlands where Europe's first Hydrogen Valley is being formed.
Results show that substantial gains in operational revenues of up to 51\% are
possible by introducing hydrogen storage units and competitive hydrogen
market-prices. This amounts to a \euro 126,000 increase in revenues per turbine
per year for a 4.5 MW wind turbine. Moreover, our results indicate that
hydrogen offtake agreements will be crucial in keeping the energy transition on
track.
