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Session: Session 5: Supercritical ORC
Session starts: Monday 12 October, 14:40
Presentation starts: 15:20
Room: 1B Europe

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Tryfonas Roumpedakis (National Technical University of Athens)
Konstantinos Braimakis (National Technical University of Athens)
Sotirios Karellas (National Technical University of Athens)

Abstract:
In this work, the detailed investigation and the optimization of the operational parameters of an experimental, small scale trigeneration system encompassing a supercritical Organic Rankine Cycle (ORC) and a heat pump are presented. Both the ORC and the heat pump jointly operate with the same working fluid (R227ea). The heat input to the ORC is provided by a 75kWth biomass boiler. The electricity produced by the ORC, which has a nominal power output of 5 kWe, is used to power the heat pump, capable of covering a cooling load of 4 kWth, while any surplus electricity is exported to the grid. Meanwhile, the heat generated during the condensation of the working fluid (around 70 kWth) is utilized to produce hot water. The system has therefore the potential to produce combined cooling, heating and electricity, depending on the load requirements, by utilizing a renewable energy source with zero net CO2 emissions. The investigation carried out includes the selection process of the working fluid of the system through the comparison of its performance with that of other typical working fluids and by taking into account environmental and safety factors. Furthermore the study presents the optimization procedure for selecting the working temperatures and pressures in order to maximize the cycle’s efficiency, given the technological limits of the elements of this system (heat exchangers, scroll expanders etc.). In addition, a supercritical plate heat exchanger model, used for the design of the heat exchanger of the unit, is presented.