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.


Thermo-mechanical modeling and optimization (12 months).


Detailed CAD modeling and prototyping (30 months).


Testing on ORC loop at Florida (36 months).


Prototyping in India with design adaptations (48 months).


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

Task 1: Small-scale positive-displacement ORC expander

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.