Optimal scheduling of a P2G plant in dynamic Power Heat and Gas markets

This paper presents a techno-economic optimization study of the operation of a Power-to-Gas (PtG) process. PtG is one option for long-term energy storage in solar and wind dominated energy systems, but provides also short term dynamic opportunities that could be utilized in existing power markets to enhance PtG profitability. The scheduling feasibility and profitability is dependent on PtG process characteristics as well as the dynamic markets for wholesale power, regulating power, gases and heat. Market characteristics, such as power bid structures and timings, differ clearly for different market types, areas and countries, as well as local grid conditions and dynamic demands on produced gases and waste heat. We show shortly the differing market situations in some representative EU countries. Completely deregulated wholesale and control power markets reflect the power balance situation for several time horizons and real need for additional balancing capacity. In this market environment, the schedule when to provide regulating power, operate in primary frequency control and when to only schedule pure gas production could be determined beforehand from cost-efficient bidding in each market. Other market models result in different PtG operation and balancing power availability. We assess a sample of representative 24 hour periods in two countries with very differing wholesale and control power markets characteristics. In the assessment, the operation optimization is applied on a future example PtG process consisting of commercially available large alkaline electrolysers, H2- and O2- compression and storages, O2 consumer like pulp industry, and methanation with feed into the gas grid. Operation schedule dynamics are validated with a detailed dynamic process simulation model of the process. In the assessment examples, differing operational profitability are shown for the largely differing energy market operation conditions. Also, sensitivities to CO2-allowance price and selling "green" synthetic natural gas (SNG) to the mobility sector are shown.