(439d) Optimal Co-Production of Market-Based Power Grid Support and Renewable Fuels or Chemicals

This paper addresses the operational profitability and benefits of co-production and dynamics in renewable Power-to-fuel or Power-to-Chemical processes, when utilized to stabilize the power grid.

To reach climate neutrality, the transport sector must switch to climate-neutral or climate-positive fuels or power. This can be done by a proper mix of electric vehicles, where the power is based on renewable electricity, hydrogen vehicles, where the hydrogen is based on side-product hydrogen or renewable power based processes, or to use in existing vehicle fleet renewable biofuels instead of fossil fuels. For hydrogen-based or hydrocarbon-based chemical industry, similar change needs are obvious.

Today, renewable fuels can be produced with biomass based plants or in bio-refineries. If biomass cannot be utilized, new so called Power-to-X plants could produce renewable fuels or chemicals of non-biomass origin. Examples of such Power-to-X fuels and chemical processes are renewable hydrogen, SNG, Methanol or similar C¹-based Power-to-fuel or Power-to-Chemical processes. These processes are utilizing hydro, solar or wind power via electrolysis for production of the needed additional hydrogen fraction [1].

In a power system with high penetration of intermitted renewable power production, wholesale prices as well as grid balancing support and ancillary service prices tend to be more and more volatile and uncertain. We handle here this uncertainty with a robust optimization approach, where we solve the conflict between the need for stable unit process conditions versus the power consumption fast dynamics asked for by the power markets and needed grid ancillary services. The robust optimization requires knowledge on the amount and duration distributions of the needed ancillary services, which in this paper is handled by examples on required primary frequency control for some selected Transmission System Operators.

Optimized day- or week-ahead planning can increase considerably the value of the renewable Power-to-Fuel or Power-to-Chemical plant operation, which are shown using examples from data of existing wholesale and primary frequency control markets. Such optimal operation can enhance commercial viability of the Power-to-X plants, and in this way introduce these climate-positive mid-sized distributed units into a smart grid.

Finally, we show the value of the dynamics of key unit processes and intermediate storages, which can help to address future research and development efforts to most important parts of the process.

 [1] Gerda Gahleitner, Hydrogen from renewable electricity: An international review of power-to-gas pilot plants for stationary applications, International Journal of Hydrogen Energy, Volume 38, Issue 5, 19 February 2013, Pages 2039-2061, ISSN 0360-3199, http://dx.doi.org/10.1016/j.ijhydene.2012.12.010.