Title: Mini-ORC Turbogenerator for Renewable Energy Sources

Acronym: Solar mini-ORC

Time Period:


Financing: Bosch Corporate Research, Energy Storage and Conversion sector

Short description:

A small and highly efficient energy converter for external thermal sources opens up a new horizon for the deployment of the distributed energy scenario. The conversion of localized renewable energy sources like waste heat from processes and thermal engines, solar collection in inhabited areas, together with micro-cogeneration, could have an enormous impact in the solution of the global energy issue. Constraints on cost, reliability, materials, scalability, flexibility, and complexity have so far prevented the realization of a technology capable of exploiting these energy sources. The goal of the project is related to a possible solution to this problem: a small high-efficiency turbogenerator based on the Organic Rankine Cycle (ORC) principle, suitable for volume production. By leveraging on the results of previous scientific projects, the research group acquired the knowledge on working fluids, thermodynamics, and dense-gas fluid dynamics necessary in order to overcome the hurdles arising from the need of miniaturizing a machine based on the ORC principle. The main deliverable will therefore be an experimental test bench suitable for testing various configurations at system and component level, and all the characterizing measurements and related knowledge. In order to achieve this goal, the most advanced simulation techniques at system and component level developed by the research group will be further enhanced, and used in an innovative integrated way in order to design and verify the setup. Several working fluids, cycle and turbine configurations will be analyzed and tested. The very high Mach number and large expansion ratio occurring in supersonic flows of dense organic vapors are the most challenging aspects for the turbine. No measurements of such flows exist, and models might be affected by errors. Dedicated experiments on high‑Mach number nozzle expansions using the prototype’s balance‑of‑plant will be performed. Visualization and laser-based techniques will be applied to the supersonic flow of dense organic vapor through an optically accessible scaled-up nozzle. The proprietary zFlow CFD code will be validated by comparison with shock angles, pressure, temperature and mass flow measurements.

Website: Bosch Corporate Research, Energy Storage and Conversion sector