Preliminary experimental study of a supercriticalCO₂ power cycle test loop with a high-speedturbo-generator using R134a under similarity conditions

Abstract

Research on applying a supercritical carbon dioxide power cycle(S-CO₂) to concentrating solar power (CSP)instead of a steam Rankine cycle or an air Brayton cycle has beenrecently conducted. An S-CO₂ system is suitablefor CSP owing to its compactness, higher efficiency, and dry-coolingcapability. At the Korea Institute of Energy Research (KIER), to implementan S-CO₂ system, a 10 kWe class test loop witha turbine-alternator-compressor (TAC) using gas foil bearings wasdeveloped. A basic sub-kWe class test loop with a high-speed radialtype turbo-generator and a test loop with a capability of tens ofkWe with an axial type turbo-generator were then developed. To solvethe technical bottleneck of S-CO₂ turbomachinery,a partial admission nozzle and oil-lubrication bearings were usedin the turbo-generators. To experience the closed-power cycle anddevelop an operational strategy of S-CO₂ operatedat high pressure, an organic Rankine cycle (ORC) operating test usinga refrigerant as the working fluid was conducted owing to its operationalcapability at relatively low-pressure conditions of approximately30 to 40 bar. By operating the sub-kWe class test loop using R134aas the working fluid instead of CO₂, an averageturbine power of 400 W was obtained.

Keywords

supercritical CO₂ / power cycle / turbomachinery / compressor / turbine

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