Abstract
In the present study, a subcritical and supercritical regenerative organic Rankine cycle (rORC) was designed. The designed rORCs assist a combined heat and power (CHP) engine, the fuel of which is biogas produced from anaerobic digestion of domestic wastes in Belgium. R245fa was selected as the working fluid for both the subcritical and supercritical rORC. During the parametric optimisation, the net power production, mass flow rate, exchanged heat in the regenerator, total pump power consumption, thermal and exergetic efficiencies of rORC were calculated for varying turbine inlet temperatures and pressures. After parametric optimisation of the rORC, the results were compared with the results of the previous study, in which only a simple ORC is analysed and parametrically optimised. Moreover, the effect of the regenerator was revealed by examining all results together. Finally, the exergetic analysis of the best performing subcritical and supercritical rORC was performed. Furthermore, the results of the present and previous studies were considered together and it is clearly seen that the subcritical rORC shows the best performance. Consequently, by using the subcritical rORC, the disadvantages of the using simple ORC (low performance) and supercritical cycle (safety, investment) can be eliminated and system performance can be improved.
Highlights
In recent decades, energy has become one of the key factors to be a powerful country for both developing and developed countries [1]
The subcritical regenerative organic Rankine cycle (rORC) is designed for a varying pressure from 4 bar to 30 bar and a temperature from 56 °C to 166 °C
This study aims to demonstrate the effect of the regenerator on the system performance as well reduces the turbine performance and decreases the performance of the rORC
Summary
Energy has become one of the key factors to be a powerful country for both developing and developed countries [1]. Some countries have their own natural energy sources, fossil fuels, which will be depleted in the near future. All countries, whether they have fossil fuel sources or not, strive to produce their energy from alternative energy sources [2,3,4]. Combined heat and power (CHP) engines widely use biogas as an energy source [20,21,22]. The remaining energy coming from the Energies 2019, 12, 575; doi:10.3390/en12040575 www.mdpi.com/journal/energies
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