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Abstract Supercritical CO2 (sCO2) power cycles have many promising characteristics for supporting the energy transition, including high efficiency, competitive costs, compact machinery, and enhanced flexibility with respect to competing systems. The EU-funded SOLARSCO2OL project aims to build a MW-scale sCO2 pilot facility for concentrated solar power (CSP) application. A transient model of the demonstration plant was previously developed to study the operational envelope of the cycle. In the present work, the model is upgraded to account for the effects of the crossflow sCO2-air cooler. The system must meet several constraints, such as compressor surge margin, turbomachinery inlet temperatures/pressures, and desired power output. The operational controls for these constraints were designed considering the responses of the system to variations in input variables, which include: 1) compressor rotational speed, 2) anti-surge valve fractional opening, mass flow rate of heat exchange fluid through the 3) cooler and 4) heaters, and 5) CO2 inventory for injection and extraction of working fluid. The control structure includes proportional-integral-derivative controllers (PIDs), feedforward action, and their combinations. The controllers are tuned using a mix of established methods, such as Cohen-Coon response-based tuning and combination with feedforward controls which take into account steady-state off-design simulations and the interactions between each controller and the other controlled variables. The final control setup is tested on various power ramps to assess the capability of the prototype cycle in load following and disturbance rejection, showing very good performance in set-point tracking.
Tucker et al. (2024) studied this question.