Imperial College London


Faculty of EngineeringDepartment of Chemical Engineering

Professor of Clean Energy Technologies



+44 (0)20 7594 1601c.markides Website




404ACE ExtensionSouth Kensington Campus






BibTex format

author = {Oyewunmi, OA and Kirmse, CJW and Pantaleo, AM and Markides, CN},
doi = {10.1016/j.enconman.2017.05.078},
journal = {Energy Conversion and Management},
pages = {1508--1524},
title = {Performance of working-fluid mixtures in ORC-CHP systems for different heat-demand segments and heat-recovery temperature levels},
url = {},
volume = {148},
year = {2017}

RIS format (EndNote, RefMan)

AB - In this paper, we investigate the adoption of working-fluid mixtures in ORC systems operating in combined heat and power (CHP) mode, with a power output provided by the expanding working fluid in the ORC turbine and a thermal energy output provided by the cooling water exiting (as a hot-water supply) the ORC condenser. We present a methodology for selecting optimal working-fluids in ORC systems with optimal CHP heat-to-electricity ratio and heat-supply temperature settings to match the seasonal variation in heat demand (temperature and intermittency of the load) of different end-users. A number of representative industrial waste-heat sources are considered by varying the ORC heat-source temperature over the range 150–330 °C. It is found that, a higher hot-water outlet temperature increases the exergy of the heat-sink stream but decreases the power output of the expander. Conversely, a low outlet temperature (~30 °C) allows for a high power-output, but a low cooling-stream exergy and hence a low potential to heat buildings or to cover other industrial thermal-energy demands. The results demonstrate that the optimal ORC shaft-power outputs vary considerably, from 9 MW up to 26 MW, while up to 10 MW of heating exergy is provided, with fuel savings in excess of 10%. It also emerges that single-component working fluids such as n-pentane appear to be optimal for fulfilling low-temperature heat demands, while working-fluid mixtures become optimal at higher heat-demand temperatures. In particular, the working-fluid mixture of 70% n-octane + 30% n-pentane results in an ORC-CHP system with the highest ORC exergy efficiency of 63% when utilizing 330 °C waste heat and delivering 90 °C hot water. The results of this research indicate that, when optimizing the global performance of ORC-CHP systems fed by industrial waste-heat sources, the temperature and load pattern of the cogenerated heat demand are crucial factors affecting the selection of the working fl
AU - Oyewunmi,OA
AU - Kirmse,CJW
AU - Pantaleo,AM
AU - Markides,CN
DO - 10.1016/j.enconman.2017.05.078
EP - 1524
PY - 2017///
SN - 0196-8904
SP - 1508
TI - Performance of working-fluid mixtures in ORC-CHP systems for different heat-demand segments and heat-recovery temperature levels
T2 - Energy Conversion and Management
UR -
UR -
VL - 148
ER -