Small-scale, low-temperature ORC systems in time-varying operation: turbines or reciprocating-piston expanders?
File(s)
Submitted version
Author(s)
Type
Conference Paper
Abstract
Manufacturers of small-scale organic Rankine cycle (ORC) engines face a number of possible options for the expansion device, some of which are not yet commercially mature. The choice of this device can be influenced by a number of factors, including the heat source temperature and flow rate, the working fluid and corresponding cycle pressure and volume ratios, and requirements for off-design operation. A comparison is therefore made between radial-inflow turbines and reciprocating-piston expanders for a small-scale ORC engine, recovering low-grade (95 °C) heat from the jacket water circuit of a stationary internal combustion engine. The heat available varies between 350 kW and 850 kW, such that high-efficiency operation at off-design conditions is key to a cost-effective ORC engine installation. Detailed component models for the turbine and reciprocating-piston expander are used first to identify optimal designs for each, and then to generate off-design performance maps. In the selected low temperature and, therefore, low pressure-ratio (~ 2) application, the design-point isentropic efficiencies are found to be 82.6% and 69.8% for the turbine and piston machine, respectively. The net power output and specific investment costs of corresponding ORC systems at their design conditions are 37.5 kW and 10,500 £/kW with a turbine, and 32.0 kW and 11,000 £/kW with a piston expander. Examination of part-load performance indicates that the advantage held by the turbine over the piston expander persists across the range of low-temperature heat-source conditions analysed in this work.
Date Issued
2019-06-23
Date Acceptance
2019-05-17
Citation
Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems International Conference. 32nd 2019. (ECOS 2019), 2019, pp.1725-1736
ISBN
9781713803294
Publisher
Silesian University of Technology, Department of Thermal Engineering
Start Page
1725
End Page
1736
Journal / Book Title
Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems International Conference. 32nd 2019. (ECOS 2019)
Copyright Statement
Copyright© (2019) by Silesian University of Technology - Institute of Thermal Technology All rights reserved.
Source
32nd International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2019)
Publication Status
Published
Start Date
2019-06-23
Finish Date
2019-06-28
Coverage Spatial
Wroclaw, Poland