Session: 30-02 Cycles

Paper Number: 152393

Multi-Objective Technoeconomic Optimisation of Closed Loop CO2 Power Cycle for Spherical Tokamak Fusion Reactor 

In the energy sector, fusion is an emerging clean energy source in the medium to long term. The UK Atomic Energy Authority is paving pathway for a commercial magnetically confined fusion power plant, namely Spherical Tokamak for Energy Production (STEP), with the ambition of building a STEP Prototypic Powerplant (SPP) by 2040.

The fusion power cycle has conflicting requirements [1], thus pushing the boundary of conventional cycles. For example, large plant parasitic load necessitates high power conversion efficiency, demanding high operating temperature of reactor, whilst the power cycle has to also integrate multiple heat grades from different reactor in-vessel components (IVC), including low temperature heat received from high surface heat flux plasma facing components. Similarly, the power cycle has to exhibit high operational flexibility whilst also achieving high reliability and plant life for intermittent pulse mode operation of SPP, during the initial phases.

Authors previous work has presented a steam Rankine cycle design for meeting the design requirements of SPP [2]. Closed-loop CO₂ power cycle show promise in realising high efficiency (>550 °C), efficient integration of low-grade heat by capitalising the enthalpy gap due to real gas effect of CO₂, and high-power density CO₂ turbine & compact heat exchangers signifying the potential of realising operational flexibility.

A multi-objective techno-economic optimisation of CO₂ power cycle integrating four heat sources from the STEP reactor is presented in this work. This paper applied a NSGA-II algorithm that maximises the efficiency whilst minimising the power block capital cost by optimising 10 process variables. This work also presents the challenges of integrating multiple heat sources from IVC with five novel CO₂ cycle configurations which are the derivatives of transcritical CO₂, supercritical recompression CO₂, and partial cooling CO₂ cycles with intercoolers using the multi-objective optimisation approach, demonstrating the feasibility of using such a power cycle design for SPP. The thermal physical property of CO₂ is estimated using REFPROP® equation of state and a verified in-house tool, developed in MATLAB®, is used to model and optimise different cycle configurations. The selected designs are benchmarked against the steam Rankine cycle design.

 

ACKNOWLEDGEMENTS: This work has been funded by STEP, a UKAEA programme to design and build a prototype fusion energy plant and a path to commercial fusion. To obtain further information on the data and models underlying this paper please contact PublicationsManager@ukaea.uk.

 

References:

[1]     J. Acres and C. Clements, "Fusion Energy and Future Fusion Power Plants," in ASME Turbo Expo 2024, London, UK, 2024.

[2]      D. Thanganadar and J. Acres, "Thermodynamic Design and Analysis of Steam Rankine Cycle for Nuclear Fusion Application," in ASME Turbo Expo 2024, London, United Kingdom, 2024.

Presenting Author: Dhinesh Thanganadar UK Atomic Energy Authority

Presenting Author Biography: Dhinesh Thanganadar Ph.D. is a Principal Engineer at the UK Atomic Energy Authority with over 15 years of experience in power generation industry, including coal-fired, combined cycle, first-of-its-kind CSP, and nuclear fusion power plants. He earned his PhD in 'Performance and Operational Analysis of the Supercritical CO2 Cycle' from Cranfield University, UK.

Authors:

Dhinesh Thanganadar UK Atomic Energy Authority
Jacob Connors UK Atomic Energy Authority
Jack Acres UK Atomic Energy Authority