Experimental Investigation of a Small-Scale ORC Power Plant Using a Positive Displacement Expander with and without a Regenerator

Abstract

While large-scale ORC power plants are a relatively mature technology, their application to small-scale power plants (i.e., below 10 kW) still encounters some technical challenges. Positive displacement expanders are mostly used for such small-scale applications. However, their built-in expansion ratios are often smaller than the expansion ratio required for the maximum utilisation of heat sources, leading to under expansion and consequently higher enthalpy at the outlet of the expander, and ultimately resulting in a lower thermal efficiency. In order to overcome this issue, one possible solution is to introduce an internal heat exchanger (i.e., the so-called regenerator) to recover the enthalpy exiting the expander and use it to pre-heat the liquid working fluid before it enters the evaporator. In this paper, a small-scale experimental rig (with 1-kW rated power) was designed and built that is capable of switching between regenerative and non-regenerative modes, using R245fa as the working fluid. It has been tested under various operating conditions, and the results reveal that the regenerative heat exchanger can recover a considerable amount of heat when under expansion occurs, increasing the cycle efficiency.

An Optimum Design for a Fast-Response Solenoid Valve: Application to a Limaçon Gas Expander

“…Moreover, the energy and power can be increased by increasing the input pressure, which further improves the efficiency. It should, however, be noted that the maximum isentropic efficiency achieved with the optimized valve is 56.67%, which is lower than popular positive displacement machines such as scroll (68.3%) [15] and screw (64%) [23]. This is because this study aims to optimize the speed of response of the inlet valve only and provides a snapshot of how this optimization affects the expander performance.…”

“…Positive displacement expanders have thus gained popularity recently for small-scale power generation and waste heat recovery applications based on ORC. Experimental investigations of ORC-based power plants using positive displacement expanders of various types such as scroll [15][16][17][18][19], rotary vane [20,21], swash-plate [22], and screw [23][24][25] have been realized of late. As the primary component of the thermal-to-power conversion process of the ORC, the expander plays a vital role in the overall performance of the ORC [26,27].…”

Fuels from Waste as Renewable Energy in Distributed Generation on the Example of the ORC System

“…Due to its compact build, the ORC might be a solution for places which are not easily available, and where there is not a developed heating network. These solutions can be installed in places where the demand for electricity and heating lasts throughout the year or in places where there is periodical demand for heating, and where they can generate cold in air-conditioning and ventilation systems out of season [19][20][21][22].…”

Comparative Analysis of Small-Scale Integrated Solar ORC-Absorption Based Cogeneration Systems

“…As the combined cooling, heating and power system can improve the solar energy utilization ratio and match solar energy supply and energy use, it has attracted the increasing research interests. While most of the present studies referred to large scale plants [21], which were relatively mature technologies [22], a few researches focused on small-scale CCHP systems, for example the small-scale ORC expander [23], the solar micro-CCHP based on dual-ORC [24], the small-scale concentrated solar combined heat and power system [25], the domestic scale solar-powered ORC and vapour compression cycle coupled system [26]. Small-scale systems were considered a relatively more suitable solution for building applications [27].…”