References of "Dickes, Rémi"
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See detailCharge-sensitive modelling of organic Rankine cycle power systems for off-design performance simulation
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Guillaume, Ludovic ULiege et al

in Applied Energy (2018), 212

This paper focuses on a charge-sensitive model to characterize the off-design performance of low-capacity organic Rankine cycle (ORC) power systems. The goal is to develop a reliable steady-state model ... [more ▼]

This paper focuses on a charge-sensitive model to characterize the off-design performance of low-capacity organic Rankine cycle (ORC) power systems. The goal is to develop a reliable steady-state model that only uses the system boundary conditions (i.e. the supply heat source/heat sink conditions, the mechanical components rotational speeds, the ambient temperature and the total charge of working fluid) in order to predict the ORC performance. To this end, sub-models are developed to simulate each component and they are assembled to model the entire closed-loop system. A dedicated solver architecture is proposed to ensure high-robustness for charge-sensitive simulations. This work emphasizes the complexity of the heat exchangers modelling. It demonstrates how state-of-the-art correlations may be used to identify the convective heat transfer coefficients and how the modelling of the charge helps to assess their reliability. In order to compute the fluid density in two-phase conditions, five different void fraction models are investigated. A 2 kWe unit is used as case study and the charge-sensitive ORC model is validated by comparison to experimental measurements. Using this ORC model, the mean percent errors related to the thermal power predictions in the heat exchangers are lower than 2%. Regarding the mechanical powers in the pump/expander and the net thermal efficiency of the system, these errors are lower than 11.5% and 11.6%, respectively. [less ▲]

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See detailTechnical and economic optimization of subcritical, wet expansion and transcritical Organic Rankine Cycle (ORC) systems coupled with a biogas power plant
Dumont, Olivier ULiege; Dickes, Rémi ULiege; De Rosa, M. et al

in Energy Conversion and Management (2018), 157

Generally, >40% of the useful energy (cooling engine and exhaust gases) are wasted by a biogas power plant through the cooling radiator and the exhaust gases. An efficient way to convert this waste heat ... [more ▼]

Generally, >40% of the useful energy (cooling engine and exhaust gases) are wasted by a biogas power plant through the cooling radiator and the exhaust gases. An efficient way to convert this waste heat into work and eventually electricity is the use of an organic Rankine cycle (ORC) power system. Over the last few years, different architectures have been widely investigated (subcritical, wet expansion and trans-critical). Despite the promising performances, realistic economic and technical constraints, also related to the application, are required for a meaningful comparison between ORC technologies and architectures. Starting from the limited literature available, the aim of the present paper is to provide a methodology to compare sub-critical, trans-critical and wet expansion cycles and different types of expanders (both volumetric and turbomachinery) from both technical and economic point of view, which represent one of the main novel aspects of the present work. In particular, the paper focuses on the thermo-economic optimization of an ORC waste heat recovery unit for a 500 kWe biogas power plant located in a detailed regional market, which was not investigated yet. By means of a genetic algorithm, the adopted methodology optimizes a given economic criteria (Pay-Back Period, Net Present Value, Profitability Index and Internal Rate of Return) while respecting technical constraints (expander limitations) and thermodynamic constraints (positive pinch points in heat exchangers, etc.). The results show that optimal ORC solutions with a potential of energy savings up to 600 MWh a year and with a pay-back period lower than 3 years are achievable in the regional market analysed. © 2017 Elsevier Ltd [less ▲]

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See detailPerformance correlations for characterizing the optimal off-design operation of an ORC power system
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Quoilin, Sylvain ULiege et al

in Energy Procedia (2017), 129

The goal of this work is to develop a set of simple correlations in order to characterize the optimal off-design performance of an ORC power system. To this end, a 2kWe ORC test rig is investigated as ... [more ▼]

The goal of this work is to develop a set of simple correlations in order to characterize the optimal off-design performance of an ORC power system. To this end, a 2kWe ORC test rig is investigated as case study and a validated off-design model is used to assess the highest net power generation achievable by the system over its complete range of operating conditions. The off-design model employed is charge-sensitive (i.e. it imposes the total mass of refrigerant in the system) which permits to predict the ORC state (i.e. its pressures, temperatures, mass flow rates, subcooling, etc.) based on the system boundary conditions only. Since such modelling approach and optimization process are time-consuming, a set of simple analytical equations is developed so as to easily predict the optimal performance of the ORC systems. [less ▲]

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See detailEffects of void fraction and heat transfer correlations in a charge-sensitive ORC model – a comparison with experimental data
Dickes, Rémi ULiege; Guillaume, Ludovic ULiege; Dumont, Olivier ULiege et al

in Proceedings of ECOS 2017 (2017, July 02)

In order to properly evaluate the off-design performance of an ORC unit, it is important to use simulation tools that minimize the number of assumptions regarding the system state. To avoid imposing the ... [more ▼]

In order to properly evaluate the off-design performance of an ORC unit, it is important to use simulation tools that minimize the number of assumptions regarding the system state. To avoid imposing the condenser subcooling (or any other equivalent state variable), the ORC model should account for the mass repartition of working fluid through the unit in function of the operating conditions. Among the various components constituting ORC power systems, the proper modelling of the mass of working fluid enclosed in the heat exchangers is of primary importance. The goal of this work is to develop such a reliable charge-sensitive ORC model. To this end, a 2kWe recuperative ORC system is used as case study and experimental measurements are used as reference dataset. The ORC system features two brazed plate heat exchangers and one fin coil condenser. For these three heat exchangers, a large set of empirical correlations is investigated in order to evaluate both the fluids void fractions and their convective heat transfer coefficients. By comparing the models predictions with the experimental data, the study highlights the limitations of existing correlations and investigates three different correction methods to improve them. Ultimately, the analysis compares nine models of brazed plate heat exchangers, two models of condenser, three correction methods for improving the heat transfer correlations and four void fraction methods. Accounting for every combination possible, 288 different models of the ORC are compared for predicting both the heat exchangers thermal performance and the total mass enclosed in the ORC unit. Out of this study, the best modelling approach is identified and details of its charge inventory predictions are presented. [less ▲]

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See detailModelling of organic Rankine cycle power systems in off-design conditions: an experimentally-validated comparative study
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Daccord, Rémi et al

in Energy (2017), 123

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development ... [more ▼]

Because of environmental issues and the depletion of fossil fuels, the world energy sector is undergoing many changes toward increased sustainability. Among the many fields of research and development, power generation from low-grade heat sources is gaining interest and the organic Rankine cycle (ORC) is seen as one of the most promising technologies for such applications. In this paper, it is proposed to perform an experimentally-validated comparison of different modelling methods for the off-design simulation of ORC-based power systems. To this end, three types of modelling paradigms (namely a constant-efficiency method, a polynomial-based method and a semi-empirical method) are compared both in terms of their fitting and extrapolation capabilities. Post-processed measurements gathered on two experimental ORC facilities are used as reference for the models calibration and evaluation. The study is first applied at a component level (i.e. each component is analysed individually) and then extended to the characterization of the entire organic Rankine cycle power systems. Benefits and limi- tations of each modelling method are discussed. The results show that semi-empirical models are the most reliable for simulating the off-design working conditions of ORC systems, while constant-efficiency and polynomial-based models are both demonstrating lack of accuracy and/or robustness. [less ▲]

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See detailExperimental investigation of four volumetric expanders
Dumont, Olivier ULiege; Dickes, Rémi ULiege; Lemort, Vincent ULiege

in Energy Procedia (2017)

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See detailThermo-economic optimization during preliminary design phase of organic Rankine cycle systems for waste heat recovery from exhaust and recirculated gases of heavy duty trucks
Guillaume, Ludovic ULiege; Legros, Arnaud; Dickes, Rémi ULiege et al

in IMechE (Ed.) Vehicle Thermal Management Systems conference (2017)

Waste heat recovery (WHR) Organic Rankine Cycle (ORC) system is a very promising technology for reducing fuel consumption and consequently the CO2 emissions of future heavy-duty trucks (HDT). Nonetheless ... [more ▼]

Waste heat recovery (WHR) Organic Rankine Cycle (ORC) system is a very promising technology for reducing fuel consumption and consequently the CO2 emissions of future heavy-duty trucks (HDT). Nonetheless, the adoption of this technology in the automotive domain requires specific R&D activities going from the system definition to the on-board integration. This study focuses on the preliminary design phase of ORC systems recovering the heat wasted from two of the sources available on a HDT: the exhaust and recirculated gases. From these heat sources and their combinations, 6 possible architectures are identified. On the other hand, 4 volumetric expansion machine technologies are considered (scroll, screw, piston and vane Expanders). At the end, 24 topologies are therefore modelled considering the main components (Pump, Heat exchangers, Expansion machines). A three-step optimization method is proposed to identify the most promising system. First, the most suitable conditions are identified for the design of the ORC systems using a simple model of volumetric expansion machine. In a second step, the design phase, using more detailed models for the expansion machines, a thermos-economic optimization is performed. Finally, in a third step, the output power of the latter system models is maximized in off-design conditions, optimizing the evaporating pressure and the overheating degree. [less ▲]

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See detailChapter 16 - Solar thermal powered Organic Rankine Cycles
Orosz, Matthew; Dickes, Rémi ULiege

in Macchi, Ennio; Astolfi, Marco (Eds.) Organic Rankine Cycle (ORC) Power Systems: Technologies and Applications (2016)

Reference chapter about solar-based organic Rankine cycle power systems published in the book "Organic Rankine Cycle (ORC) Power Systems: Technologies and Applications"

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See detailORCmKit: an open-source library for organic Rankine cycle modelling and analysis
Dickes, Rémi ULiege; Ziviani, Davide; van den Broek, Martjin et al

in Proceedings of ECOS 2016 (2016, June 20)

As for many other technologies, modelling and simulation of organic Rankine cycles (ORCs) are crucial for design, optimization and control purposes. However, model development is often time consuming and ... [more ▼]

As for many other technologies, modelling and simulation of organic Rankine cycles (ORCs) are crucial for design, optimization and control purposes. However, model development is often time consuming and the scientific community lacks of open-access tools to study ORC systems. For these reasons, researchers from the universities of Liège and Ghent in Belgium gathered their knowledge and created “ORC modelling Kit” (ORCmKit), an open-source library dedicated to the steady-state simulation and analysis of organic Rankine cycles. Both component-level and cycle-level models are provided and different ORC architectures can be simulated. For each of the main component of ORC systems, different models are available with increasing complexity which allows a wide range of modelling possibilities. In order to remain general and accessible to as many people as possible, three widely used programming languages are covered within ORCmKit, i.e. Matlab, Python and EES (Engineering Equation Solver). Besides source codes, ORCmKit also includes calibration tools for empirical and semi-empirical models as well as a complete documentation for ease of use. [less ▲]

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See detailOrganic Rankine cycle modelling and the ORCmKit library: analysis of R1234ze(Z) as drop-in replacement of R245fa for low-grade waste heat recovery
Ziviani, Davide; Dickes, Rémi ULiege; Quoilin, Sylvain ULiege et al

in Proceedings of ECOS 2016 (2016, June 20)

Due to the wide interest in organic Rankine cycles (ORCs) as a sustainable technology and the importance of numerical analyses and optimization procedures while considering such systems, we created a ... [more ▼]

Due to the wide interest in organic Rankine cycles (ORCs) as a sustainable technology and the importance of numerical analyses and optimization procedures while considering such systems, we created a dedicated open-source library named “ORC modelling Kit” (ORCmKit). The comprehensive library includes single com-ponents and overall models for subcritical, transcritical and supercritical ORCs. Three main programming environments are currently supported: Matlab, Python and EES (Engineering Equation Solver). A detailed steady-state cycle model of a small-scale regenerative ORC with a single-screw expander is used to evalu-ate the performance influence of R1234ze(Z) as a drop-in replacement of R245fa currently used in the instal-lation. The ORC system is used to recover low-grade waste heat with a temperature range between 90°C and 120°C. A thermal oil heater is used to simulate the heat source. A parametric study is carried out to in-vestigate the performance of the system throughout the range of interest in order to optimize the ORC with R1234ze(Z). [less ▲]

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See detailSolar-based ORC systems
Dickes, Rémi ULiege

Conference (2016, May 20)

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See detailHot water tanks : how to select the optimal modelling approach?
Dumont, Olivier ULiege; Carmo, Carolina; Dickes, Rémi ULiege et al

Conference (2016)

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See detailImpact of model reduction on the dynamic simulation of a micro-scale concentrated solar power system integrated with a thermal storage
Dickes, Rémi ULiege; Wéber, Noé ULiege; Lemort, Vincent ULiege et al

in Proceedings of the ISES Solar World Congress 2015 (2015, November)

Because of the intermittent nature of solar irradiances, micro-scale solar thermal power systems almost never operate in nominal operating conditions. They are characterized by strong transients and ... [more ▼]

Because of the intermittent nature of solar irradiances, micro-scale solar thermal power systems almost never operate in nominal operating conditions. They are characterized by strong transients and require robust, fast and accurate dynamic simulation tools to permit a proper evaluation of their performance. Model reduction, i.e. the simplification of detailed models, is an attractive method to improve the computational efficiency while simulating such systems. In this context, a µCSP plant featuring a solar field of parabolic troughs, a thermocline storage and a 5kWe power unit is investigated. Both the solar field and the thermocline storage are modeled with complex and simplified methods. The whole power plant is simulated under identical operating condition and deviations between the simulation results are analyzed. Benefits and limitations of the current modeling approach are assessed. Improvements for the modeling of the thermocline storage are identified, implemented and validated. The Modelica language is used as simulation tool and the models developed in this work are integrated in the open-source ThermoCycle library. [less ▲]

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See detailAnalysis and comparison of different modeling approaches for the simulation of a micro-scale organic Rankine cycle power plant
Dickes, Rémi ULiege; Dumont, Olivier ULiege; Legros, Arnaud ULiege et al

in Proceedings of the 3rd International Seminar on ORC Power Systems (2015, October 12)

When simulating a system based on the organic Rankine cycle (ORC), different modeling methods can be used to predict its performance. Each method is characterized by advantages, limitations and a level of ... [more ▼]

When simulating a system based on the organic Rankine cycle (ORC), different modeling methods can be used to predict its performance. Each method is characterized by advantages, limitations and a level of complexity. This contribution aims to assess the impact of the modeling approach on the performance prediction of ORC systems. To this end, a 2.8 kWe ORC unit is investigated as case study. In this paper, the components of the test bench are modeled using different approaches of increasing complexity and each model is calibrated using experimental data from the test rig. The goodness of fit as well as the benefits and limitations of each modeling methods are analyzed and discussed. [less ▲]

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See detailModel reduction for simulating the dynamic behavior of parabolic troughs and a thermocline energy storage in a micro-solar power unit
Dickes, Rémi ULiege; Desideri, Adriano ULiege; Lemort, Vincent ULiege et al

in Proceedings of ECOS 2015 (2015, July)

Micro-scale concentrated solar power plants are characterized by strong transients and mostly operate in off-design working conditions. Both the sizing and the control of these systems are key challenges ... [more ▼]

Micro-scale concentrated solar power plants are characterized by strong transients and mostly operate in off-design working conditions. Both the sizing and the control of these systems are key challenges whose optimization requires powerful dynamic modeling tools. In this context, a system featuring a solar field of parabolic troughs, a thermocline thermal energy storage and a 5kWe organic Rankine cycle (ORC) power unit is modeled in the Modelica language. Model reduction methods applied to the solar field and the thermal storage are investigated and analyzed to improve the computational efficiency of the problem. Each model is described and integrated in the open-source ThermoCycle library. Results of simulation under identical operating conditions are compared and the benefits and limitations of model reduction are assessed. [less ▲]

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See detailSemi-empirical correlation to model heat losses along solar parabolic trough collectors
Dickes, Rémi ULiege; Lemort, Vincent ULiege; Quoilin, Sylvain ULiege

in Proceedings of ECOS 2015 (2015, July)

Solar thermal power plants convert sunshine energy into useful heat and electricity by means of solar collectors and a thermodynamic cycle. Among the different solar collector technologies, parabolic ... [more ▼]

Solar thermal power plants convert sunshine energy into useful heat and electricity by means of solar collectors and a thermodynamic cycle. Among the different solar collector technologies, parabolic troughs are nowadays the most widespread together with solar towers. In order to improve the computation speed required to simulate the temperature profile along solar parabolic trough collectors, a correlation estimating the effective heat losses of the receiver is an essential tool. However, the relations found in the literature lack accuracy and do not translate effectively the effects of the operating conditions in all cases. In this work, an alternative correlation is proposed and calibrated with the results of a deterministic model. Better fitting performance is demonstrated when compared to the prediction of the pre-existing correlations. The benefits and limitations of the new correlation are finally assessed. [less ▲]

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See detailDynamic modeling of thermal systems using a semi-empirical approach and the ThermoCycle Modelica Library
Altés Buch, Queralt ULiege; Dickes, Rémi ULiege; Desideri, Adriano ULiege et al

in Proceedings of the 28th International Conference on Efficiency, Costs, Optimization and Simulation of Energy Systems (2015, June)

This paper proposes an innovative approach for the dynamic modeling of heat exchangers without phase transitions. The proposed thermo-flow model is an alternative to the traditional 1D finite-volumes ... [more ▼]

This paper proposes an innovative approach for the dynamic modeling of heat exchangers without phase transitions. The proposed thermo-flow model is an alternative to the traditional 1D finite-volumes approach and relies on a lumped thermal mass approach to model transient responses. The heat transfer is modeled by the well-known Logarithmic Mean Temperature Difference approach, which is modified to ensure robustness during all possible transient conditions. The lumped parameter models are validated with references models and tested within a Concentrating Solar Power plant model. Results indicate that the developed lumped models are robust and computationally efficient, ensuring the convergence of the Newton Solver. They are significantly faster (~10-fold) than the traditional finite volume models, although a more extensive comparisons would be needed to confirm this figure. They are well suited to be integrated in larger system models, but are not appropriate for the simulation of detailed thermo-flow phenomena. [less ▲]

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