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Optimization of a Partially Evaporating Organic Rankine Cycle with thermal non-equilibrium expansion.van Heule, Xander; Skiadopoulos, Tasos; Manolakos, Dimitris; De Paepe, Michel; Lecompte, StevenThe Trilateral Flash Cycle (TFC) is an alternative to the Organic Rankine Cycle (ORC). The TFC have been shown to have greater exergy efficiencies compared to the ORC in low-grade heat-to-power conversion. This is a result of the more efficient heat transfer from the heat carrier to the working fluid, even though the TFC has inherently a lower thermal efficiency. However, these results are based on cycle modeling assuming equilibrium conditions, but the actual two-phase expansion process is a nonequilibrium process. Thermal non-equilibrium between vapour and liquid occurs during the evaporation (or flashing) of the working fluid during the two-phase expansion process. The liquid phase has a temperature greater than the corresponding pressure’s saturation temperature and the equilibrium assumption overestimates the actual vapour quality. In a previous work, this non-equilibrium expansion was modeled and predicted based on the homogeneous relaxation model (HRM). In this work, the impact of the non-equilibrium process on the efficiency of the TFC is investigated and compared to the equilibrium model. The overall power recuperation is around 86% lower when including the thermal non-equilibrium nature of the expansion process. Therefore, the thermodynamic non-equilibrium losses should thus be incorporated when predicting the performance of a TFC.- Performance analysis of a 1.5 MW organic Rankine cycle in a Carnot battery system for grid balancing servicesTassenoy, Robin; Van De Velde, Hannes; Couvreur, Kenny; De Paepe, Michel; Lecompte, StevenDue to the increasing share of variable renewable energies in the energy mix, large-scale (>1 MW), long duration (>4 h) energy storage systems are becoming essential to ensure secure and stable energy supply. Carnot batteries, a combination of a power-to-heat, a thermal storage and a heat-to-power system, could provide a possible solution. Organic Rankine cycles have been considered as power-toheat technology for Carnot batteries. However, it is not clear which grid services these organic Rankine cycles could deliver. To answer this question, a 1.5 MW organic Rankine cycle, suitable for integration in a Carnot battery, was modelled dynamically in Modelica. Dynamic finite volume heat exchanger models were used, while the operation of the pump and turbine was considered quasi-steady state due to their low time constant compared to the heat exchangers. The storage tanks were assumed perfectly mixed and modelled by time-varying boundary conditions. Furthermore, a control strategy driven by the requirements of the electrical grid was proposed. The dynamic model simulates and evaluates the organic Rankine cycles’ response to the qualification test profiles for grid balancing services. It was found the organic Rankine cycle can deliver a 1 MW capacity for downward and upward secondary and tertiary reserve. Delivery of a 0.5 MW symmetric capacity for primary reserve is currently not possible due to the required full activation time. Nevertheless, the results indicate that the delivery of secondary and tertiary grid balancing services with the organic Rankine cycle could be an additional revenue stream to increase the financial feasibility of Carnot battery systems and it is thus worthwhile to investigate its potential financial benefits.
- Optimizing the performance of a hybrid Solar-Biomass micro-CHP system with a TFC engine as the prime mover for domestic applicationsSkiadopoulos, Anastasios; van Heule, Xander; Lecompte, Steven; De Paepe, Michel; Manolakos, Dimitriossolar energy and biomass with a Trilateral Flash Cycle (TFC) engine as the prime mover is simulated and optimized in this work. The system is sized to meet the Space Heating (SH) demand of a typical multi-family building in Athens, Greece. Particular attention is paid to the challenging two-phase expansion phenomenon, the factor mainly affecting the efficiency of the TFC, under off-design and partial load conditions. Under optimized operating conditions, the average annual CHP efficiency, TFC thermal efficiency, and solar energy conversion efficiency were estimated to be 89.2%, 8.4%, and 4.3%, respectively. The TFC can cover 18% of the building’s SH demand and 40% of its electricity demand, with the Levelized Cost of Electricity (LCOE) and Levelized Cost of Heat (LCOH) in the range of 0.21~0.28 €/kWhel, and 0.065~0.087 €/kWhth, respectively. Furthermore, PayBack Periods (PBP), between 15 and 25 years, can be anticipated, when current market energy prices are considered.
- ENHANCING KNOWLEDGE OF ENGINEERING STUDENTS AT ALL LEVELS ON ORGANIC RANKINE CYCLE SYSTEMS FOR THEIR APPLICATION IN THE BUILT ENVIRONMENTCioccolanti, Luca; Moradi, Ramin; Abdullah, Ermira; Saadon, Syamimi; Yusof Idroas, Mohamad; Yew Heng, Teoh; Kraitong, Kwanchai; Van Nieuwenhuyse, Jera; Skiadopoulos, Anastasios; Manolakos, Dimitris; Lecompte, Steven; De Paepe, MichelAccording to International Energy Agency (IEA), the global energy crisis is accelerating the use of renewable energy in the next five years. Furthermore, the building sector which accounts for about 30% of the final energy consumption, has a significant room for improvement in curbing its share of energy consumption and integrating renewable energy technologies. Hence, the ‘Skybelt’ project, co-funded by the EU under the framework of the Erasmus+ programme and coordinated by eCampus University - Italy, aims at enhancing the skills of engineering students at all levels for application of sustainable renewable energy solutions to be integrated into the built environment in several Asian and European universities. The market analyses conducted in the initial stage of the project have revealed that combined heating and power (CHP) and combined cooling, heating, and power (CCHP) are the most interesting applications of knowledge for future employees on renewable energy. Among the potential CHP and CCHP technologies, Organic Rankine cycle (ORC) systems are interesting for the building energy sector thanks to their capability to be combined with solar and biomass sources. Therefore, Universiti Putra Malaysia (UPM), Universiti Sains Malaysia (USM) and Naresuan University (NU) opted to be equipped with non-regenerative ORC test benches for training of engineering students at different levels. In particular, bachelor students at UPM will work on the development of different control approaches on small-scale ORC units within the modernised module of ‘Control System Analysis’, and students at USM and NU will be trained on the operating performance of these systems to be combined with different renewable energy sources. Hence, the project has given the opportunity to foster knowledge about the ORC systems for engineering students at all levels with the perspective of adopting them in buildings.
