Development of Organic Rankine Cycle Prototype for Thermal Energy Conversion

Abstract

The conversion of low-grade thermal energy into electricity is a developing field with almost limitless potential. Low temperature (<150◦C) heat from solar, geothermal and industrial waste heat utilization plants is a promising source for Organic Rankine cycles (ORC) to recover the power. The falling price of ORC technology is renewing interest in the subject and increasing the viability of low-temperature ORC systems. A lack of experience in the design, fabrication and operation of compact ORCs, however, is hampering the continued development and utilization of this technology.
This Masters thesis presents an in-depth study of compact ORC prototype design and fabrication. An investigation of component selection and cycle configuration is carried out, followed by prototype development. Guidelines are developed for the safe charging, start-up and operation of the cycle with refrigerant R245fa. Comprehensive experimental testing is also carried out to capture the cycle characteristics under a wide range of operating conditions. The experimental ORC test bed is able to achieve a thermal efficiency of 8.7% at a stable base point.
Based on experimental characterization, component models are developed and integrated into a cycle model for advanced ORC design. Experimental parametric studies are carried out to aid in further understanding of complicated system dynamics. Of particular interest is the abnormal behavior of the ORC near the operating limits, where cycle-level thermal-fluid oscillations are recorded. System stalls are also investigated and deeply explored.
This thesis contributes to potential application of compact ORC technology to increase its accessibility and cost reduction for low-grade thermal energy conversion, including rural electrification and industrial waste heat recovery.

Date of Award	May 2014
Original language	American English
Supervisor	TJ Zhang (Supervisor)