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CSP-4: Small-Scale Positive Displacement ORC Expander

Solar Energy Research Center for India and the United States (SERIIUS)


Multiscale Concentrating Solar Power


Low-temperature organic Rankine cycle


To develop an advanced high-volume-ratio scroll expander suitable for an organic Rankine cycle (ORC) power block operating from a solar collector temperature source at 150°–250°C. The major design goal is to achieve an isentropic efficiency surpassing previously tested two-stage scroll expansion (70% isentropic), while simplifying the ORC and improving the delivery and control of power to the DC bus, using solar-thermal energy at >150°C.

C16: Thermo-mechanical modeling and optimization (12 months).

C17: Detailed CAD modeling and prototyping (30 months).

C18: Testing on ORC loop at Florida (36 months).

C19Prototyping in India with design adaptations (48 months).

C20: Testing on ORC loop in India and tuning of controls (60 months).

Task 1: Small-scale positive-displacement ORC expander

  • Massachusetts Institute of Technology (MIT)
  • MIT/STG International
  • University of South Florida (USF)
  • Indian Institute of Science (IISc)

Development of low-cost, high-efficiency scroll expanders for micro-CSP ORC units (~3–25 kW) suitable for off-grid power systems. A model–prototype–evaluate process will be followed to generate new insights regarding the geometric and thermo-mechanical variables influencing cost and performance. System- and component-level modeling will be collaborative between MIT and IISc, and include development of general positive displacement expander design tools. Prototype expanders and controls will be tested in a small 5-kWe CSP ORC plant in Florida. Engineering design tools and CAM processes will be transferred by STG to collaborators in India for scaled prototyping and evaluation on a CSP test loop in India.