Test and validation of a control system for a small-scale energy recovery system based on sliding-vane technology

A significant amount of the total waste thermal energy is dissipated at low temperature, from 30 °C to 200 °C. The most widely used solution to take advantage of these low-enthalpy thermal sources is the use of an Organic Rankine Cycle (ORC). This paper presents a fully automated ORC-based recovery system in recuperative configuration, equipped with sliding-vane rotary pump and expander, that exploits waste heat generated by large-scale air compressors to produce the net electric power of about 2.7 kW. The hot source is the water from the compressors cooling system. The working fluid employed is R1233zd. The expander generator and the pump motor are driven both by inverters in order to vary the rotational speed and guarantee the system flexibility. The control logic implemented in the system is presented in the paper. The approach for the start-up phase and the settings for the system damage prevention are described. In order to evaluate the thermodynamic conditions of every significant point of the cycle, temperature and pressure transducers are installed on the system.