A dynamic model of a power conversion system with indirect thermal energy storage for a pulsed fusion tokamak for use in design optimisation

This work addresses the challenge of designing a power conversion system, which converts thermal energy into electrical energy, that can handle heat generation from a pulsed fusion tokamak. Large transients would be damaging for components such as turbomachinery and make grid integration difficult. Energy storage is considered as a solution to buffer the impact of the tokamak dynamics on power generation. A dynamic model is presented of a possible power conversion system design using sensible thermal energy storage, implemented in the Modelica modelling language. Novel lumped-parameter dynamic models, based on the logarithmic mean temperature difference, are developed for both one- and two-phase heat exchangers. The models are then used for two optimisation-based design problems: a single objective optimisation problem for steady state turbine power and a bi-objective optimisation problem that allows for reduced power generation during a tokamak dwell when no heat is being generated. The optimisation problems are solved using the Fresa.jl meta-heuristic plant propagation algorithm and a multi-agent system allowing for the cooperation of different fitness ranking methods. Both case studies show the dynamic models are robust and fast enough for use in this optimisation framework, and demonstrate the potential of simulation–optimisation in the design of prototype fusion power plants with pulsed operation. • Developed novel lumped-parameter dynamic heat exchanger models. • Dynamic model of power plant with one pulsed heat source is presented. • Thermal energy storage decouples power generation from pulsed heat. • Model is fast and reliable enough for use in optimisation. • Trade-off between storage system size and dwell power generation is considered.