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See detailTHERMO-ECONOMIC OPTIMIZATION OF ORGANIC RANKINE CYCLE SYSTEMS FOR WASTE HEAT RECOVERY FROM EXHAUST AND RECIRCULATED GASES OF HEAVY DUTY TRUCKS
Guillaume, Ludovic ULg; Legros, Arnaud; Lemort, Vincent ULg

Conference (2016, September 14)

Waste heat recovery (WHR) ORC 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 ... [more ▼]

Waste heat recovery (WHR) ORC 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 modelled considering only 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 design conditions are identified using a simple model of expansion machine. In a second step, the design phase, using more detailed models for the expansion machines, a thermodynamic and economic optimizations are performed. Finally, in a third step, the output power of the latter system models is maximized in off-design conditions. [less ▲]

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See detailA general methodology for optimal load management with distributed renewable energy generation and storage in residential housing
Georges, Emeline ULg; Braun, James; Lemort, Vincent ULg

in Journal of Building Performance Simulation [=JBPS] (2016)

In the US, buildings represent around 40% of the primary energy consumption and 74% of the electrical energy consumption [U.S. Department of Energy (DOE). 2012. 2011 Buildings Energy Data Book. Energy ... [more ▼]

In the US, buildings represent around 40% of the primary energy consumption and 74% of the electrical energy consumption [U.S. Department of Energy (DOE). 2012. 2011 Buildings Energy Data Book. Energy Efficiency & Renewable Energy]. Incentives to promote the installation of on-site renewable energy sources have emerged in different states, including net metering programmes. The fast spread of such distributed power generation represents additional challenges for the management of the electricity grid and has led to increased interest in smart control of building loads and demand response programmes. This paper presents a general methodology for assessing opportunities associated with optimal load management in response to evolving utility incentives for residential buildings that employ renewable energy sources and energy storage. An optimal control problem is formulated for manipulating thermostatically controlled domestic loads and energy storage in response to the availability of renewable energy generation and utility net metering incentives. The methodology is demonstrated for a typical American house built in the 1990s and equipped with a single-speed air-to-air heat pump, an electric water heater and photovoltaic (PV) collectors. The additional potential associated with utilizing electrical batteries is also considered. Load matching performance for on-site renewable energy generation is characterized in terms of percentage of the electricity production consumed on-site and the proportion of the demand covered. For the purpose of assessing potential, simulations were performed assuming perfect predictions of the electrical load profiles. The method also allows determination of the optimal size of PV systems for a given net metering programme. Results of the case study showed significant benefits associated with control optimization including an increase of load matching between 3% and 28%, with the improvement dependent on the net metering tariff and available storage capacity. The estimated cost savings for the consumer ranged from 6.4% to 27.5% compared to no optimization with a unitary buy-back ratio, depending on the available storage capacity. Related reduction in CO2 emissions were between 11% and 46%. Optimal load management of the home thermal systems allowed an increase in the optimal size of the PV system in the range of 13–21%. [less ▲]

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See detailModelling of an automotive multi-evaporator air-conditioning system
Gillet, Thomas ULg; Lemort, Vincent ULg; Rullière, Romuald et al

Scientific conference (2016, July 13)

An automotive multi-evaporator air conditioning system, which is composed of two evaporators and a secondary fluid cooler, was modeled using the LMS Imagine.Lab Amesim® 1D software. The present study ... [more ▼]

An automotive multi-evaporator air conditioning system, which is composed of two evaporators and a secondary fluid cooler, was modeled using the LMS Imagine.Lab Amesim® 1D software. The present study focuses on understanding the dynamic coupling of the several loop components such as the three evaporators having different cooling capacities. This kind of multi-evaporator air-conditioning system has a number of technological barriers that must be overcome. Understanding the behavior of their respective expansion devices and the choice of these latter is also essential to control properly the transient phase and ensure an optimal operation of the air-conditioning system. In order to study the behavior of the loop, step disturbances were simulated on an operating point at medium and high load. The impact of these disturbances on the stability of the supplied cooled air temperature is analyzed for two types of expansion valve. Initial results show that the thermostatic expansion valves can cause instabilities. Furthermore, the electronic expansion valves have to be regulated with an advanced control in order to use their full potential and to try to achieve desired results. [less ▲]

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See detailExperimental results for hydrocarbon refrigerant vaporization in brazed plate heat exchangers at high pressure
Desideri, Adriano ULg; Rhyl Kaern, Martin; Ommen Schmidt, Torben et al

in Proceedings of the 16th International Refrigeration and Air Conditioning Conference at Purdue (2016, July 11)

In recent years the interest in small capacity organic Rankine cycle (ORC) power systems for harvesting low quality waste thermal energy from industrial processes has been steadily growing. Micro ORC ... [more ▼]

In recent years the interest in small capacity organic Rankine cycle (ORC) power systems for harvesting low quality waste thermal energy from industrial processes has been steadily growing. Micro ORC systems are normally equipped with brazed plate heat exchangers which allows for efficient heat transfer with a compact design. An accurate prediction of the heat transfer process characterizing these devices is required from the design phase to the development of model- based control strategies. The current literature is lacking experimental data and validated correlations for vaporization of organic fluids at typical working conditions of ORC systems for low temperature waste heat recovery (WHR) applications. Based on these premises, a novel test-rig has been recently designed and built at the Technical University of Denmark to simulate the evaporating condition occurring in a small capacity ORC power unit. In this contribution the preliminary experimental results obtained from the first experimental campaign carried out on the rig are reported. HFC-134a was selected as working fluid. The experiments were carried out at saturation temperature of 60, 70 and 80 ○C and inlet and outlet qualities ranging between 0.01-0.3 and 0.5-0.95 respectively. The heat flux ranged between 19.4 and 43.1 kWm−2. The results are presented in terms of refrigerant side heat transfer coefficient and pressure drop. The heat transfer coefficient showed significant sensitivity to the saturation temperature and was characterized by a decreasing trend with respect to the mean evaporator quality. The frictional pressure drop showed a linear dependence on the mean quality value and increased as the saturation temperature decreased. The experimental heat transfer coefficients were compared with a well-known correlation for nucleate boiling which is able to predict the results with an accuracy of around 20 %. [less ▲]

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See detailLoad modulation strategies of residential heat pumps for demand-response programs with different thermal storage options
Georges, Emeline ULg; Lemort, Vincent ULg

in Proceedings of the 4th International High Performance Buildings Conference at Purdue (2016, July)

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See detailORCmKit: an open-source library for organic Rankine cycle modelling and analysis
Dickes, Rémi ULg; 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 ULg; Quoilin, Sylvain ULg 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 detailSteady-state and dynamic modelling of a 1 MWel commercial waste heat recovery ORC power plant
Andritsos, George; Desideri, Adriano ULg; Gantiez, Clement et al

in Steady-state and dynamic modelling of a 1 MWel commercial waste heat recovery ORC power plant (2016, June 19)

ORC power systems have been proven to be a mature technology for low quality waste heat recovery applications. ORC units stand out for their simple structure, reliability and cost- effectiveness. The non ... [more ▼]

ORC power systems have been proven to be a mature technology for low quality waste heat recovery applications. ORC units stand out for their simple structure, reliability and cost- effectiveness. The non-constant nature of the energy source requires the ORC power unit to be flexible. Dynamic modelling can be adopted to evaluate and optimize the response time of a system in case of transient conditions, to develop and test control strategies, to support the tuning of the controller and to support maintenance. In this work the dynamic model of a 1 MWel commercial ORC unit is presented. The dynamic model is developed based on the ThermoCycle Modelica library. The different component model are validated in steady-state against 21 measurements points. The dynamic model of the whole power unit is then developed connecting the validated component models. Different modelling approaches of various complexity are implemented to model the heat exchangers of the power system. The performance of the developed heat exchanger (HX) models are tested by running different transient simulations. The results allow identifying benefits and limitations of the tested HX modelling approaches. [less ▲]

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See detailModélisation d'une climatisation automobile multi-évaporateurs
Gillet, Thomas ULg; Rullière, Romuald; Haberschill, Philippe et al

Poster (2016, June 02)

La modélisation d’une climatisation automobile multi-évaporateurs, composées de deux évaporateurs et d’un refroidisseur de fluide secondaire, a été réalisée à l’aide du logiciel LMS Imagine.Lab Amesim® 1D ... [more ▼]

La modélisation d’une climatisation automobile multi-évaporateurs, composées de deux évaporateurs et d’un refroidisseur de fluide secondaire, a été réalisée à l’aide du logiciel LMS Imagine.Lab Amesim® 1D. Dans le but d’étudier le comportement de la boucle, des perturbations sous la forme d’échelon ont été simulées sur un point de fonctionnement à moyenne et haute charge. L’impact de ces perturbations sur la stabilité de la température d’air soufflé est analysé pour deux types de détendeur. Les premiers résultats montrent que les détendeurs thermostatiques peuvent engendrer des instabilités. [less ▲]

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See detailPerformance evaluation of an Organic Rankine Cycle (ORC) connected to two-phase closed thermosyphons
Le, Van Long ULg; Declaye, Sébastien ULg; Dumas, Xavier et al

in PROCEEDINGS OF ECOS 2016 (2016, June)

This paper aims at evaluating the performance of a waste heat-to-power plant using an organic Rankine cycle (ORC) connected to two-phase closed thermosyphons (or gravity-assisted heat pipes or wickless ... [more ▼]

This paper aims at evaluating the performance of a waste heat-to-power plant using an organic Rankine cycle (ORC) connected to two-phase closed thermosyphons (or gravity-assisted heat pipes or wickless heat pipes). The heat exchanger, made up of two-phase closed thermosyphons, is used for transferring heat from exhaust stream to ORC working fluid. In practice, a hot oil loop or a pressurized hot water loop or a saturated steam loop or even a direct evaporator is often used to transfer heat from heat source to ORC system. However, installing a heat exchanger directly in the hot gas paths of ORC system evokes the concerns for the flammability and/or toxicity of organic working fluids especially when the heat source has a relative high temperature. Also the use of an intermediate heat carrier loop such as thermal oil or saturated steam or pressurized water loop is relatively expensive and involves installation of relatively heavy components. A priori, the use of two-phase closed thermosyphons for capturing and transferring heat from a waste heat source to organic working fluid is less expensive than the use of an intermediate heat transfer loop and eliminates safety concerns as in the case of direct installation of an ORC evaporator in the hot gas paths. [less ▲]

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See detailDirect control service from residential heat pump aggregation with specified payback
Georges, Emeline ULg; Cornélusse, Bertrand ULg; Ernst, Damien ULg et al

in Proceedings of the 19th Power Systems Computation Conference (PSCC) (2016, June)

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service is defined by a 15 minute power modulation, upward or ... [more ▼]

This paper addresses the problem of an aggregator controlling residential heat pumps to offer a direct control flexibility service. The service is defined by a 15 minute power modulation, upward or downward, followed by a payback of one hour and 15 minutes. The service modulation is relative to an optimized baseline that minimizes the energy costs. The potential amount of modulable power and the payback effect are computed by solving mixed integer linear problems. Within these problems, the building thermal behavior is modeled by an equivalent thermal network made of resistances and lumped capacitances whose parameters are identified from validated models. Simulations are performed on 100 freestanding houses. For an average 4.3 kW heat pump, results show a potential of 1.2 kW upward modulation with a payback of 600 Wh and 150 Wh of overconsumption. A downward modulation of 500 W per house can be achieved with a payback of 420 Wh and 120 Wh of overconsumption. [less ▲]

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See detailTowards nzeb goal for newly built office buildings in Europe using high temperature cooling.
Randaxhe, François ULg; Lemort, Vincent ULg; Lebrun, Jean ULg

Conference (2016, May 24)

In the design phase of a building, many HVAC systems options are available to satisfy the basic requirements related to its use. The design engineer is responsible for considering various systems and ... [more ▼]

In the design phase of a building, many HVAC systems options are available to satisfy the basic requirements related to its use. The design engineer is responsible for considering various systems and recommending a system that will meet the project goals and perform as desired. In addition, high efficiency requirements are imposed to the HVAC equipments through strong regional regulation such as the Energy Performance of Buildings Directive which requires minimum efficiency of HVAC equipments in the market. In reaction, major improvements have been made by manufacturers to improve the performance of their systems and meet all these criteria. With the nearly zero energy goal for all newly constructed buildings in Europe after 2020, it seems very likely that the design of the future building should rely on today’s technology to meet these targets. The integration of High Temperature Cooling in buildings can bring a fresh perspective in this context. The study presents the sensitivity analysis of a primary system to chilled water supply temperature for a water cooled chiller with a cooling tower and a free-chilling heat exchanger. It allows a proper assessment of the impact of the chilled water temperature on the primary system performance. [less ▲]

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See detailDescription of a Modelica-based thermal building model integrating multi-zone airflows calculation
Ransy, Frédéric ULg; Gendebien, Samuel ULg; Lemort, Vincent ULg

Conference (2016, May 23)

Nowadays, in newly built housings, energy losses due to the ventilation can represent up to 50 % of the total building energy consumption. As a result, heat recovery ventilation units are widely used in ... [more ▼]

Nowadays, in newly built housings, energy losses due to the ventilation can represent up to 50 % of the total building energy consumption. As a result, heat recovery ventilation units are widely used in order to save primary energy and different control strategies for ventilation systems are investigated. For instance, demand control ventilation sounds like a promising solution to decrease the energy impact of the ventilation system in the residential sector. An accurate building model integrating the influence of ventilation (so called thermo-aeraulic building model) is necessary in order to investigate the control and the impact of the ventilation system on a yearly basis. The aim of the present paper consists in a description of a combined multi-zone airflow network model and thermal building model implemented in the Modelica language. The thermal model is a simplified dynamic model using equivalent thermal resistance and capacity. The airflow network is based on the traditional electrical circuit analogy. The model can be used for ventilation systems design, infiltration rate calculation, inside air quality calculation, energy consumption calculation, etc. The first part of the paper details the multi-zone thermal building model. The results obtained from the model are compared to experimental in situ results collected in the typical single family house test facilities. Those experimental results have been obtained in the frame of the IEA-EBC Annex 58. The second part of the paper introduces the multi-zone airflow network building model. Obtained model results are compared with the results provided by a typical multizone airflow analysis software, for a simple three zones test case. The third part of the paper describes the coupling between both thermal and airflow models. The different numerical problems encountered are described and solutions are discussed. [less ▲]

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See detailAnalysis of the flexibility of Belgian residential buildings equipped with Heat Pumps and Thermal Energy Storages
Georges, Emeline ULg; Garsoux, Pierre; Masy, Gabrielle et al

in Proceedings of CLIMA2016 Conference (2016, May)

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See detailEnergy Reduction in Public Building Stock: Assessing the Impact of Control Strategy over Expected Energy Savings and Indoor Comfort Level
Ruiz Flores, Roberto ULg; D’Antoni, Matteo; Lemort, Vincent ULg

in CLIMA 2016 - proceedings of the 12th REHVA World Congress: volume 1. Aalborg: Aalborg University, Department of Civil Engineering. (2016, May)

In the framework of EU FP7 BRICKER project, the renovation of public owned nonresidential buildings is addressed through the installation of innovative passive and active technologies. The expected impact ... [more ▼]

In the framework of EU FP7 BRICKER project, the renovation of public owned nonresidential buildings is addressed through the installation of innovative passive and active technologies. The expected impact is a primary energy reduction of about 50% with respect to the existing scenario with a large replication potential under different European countries. In order to achieve such ambitious goal one issue that cannot be ignored is the effect of control strategy, not only over the resulting energy performance but also over the resulting indoor comfort conditions. In this paper, the actual control strategy implemented in the Belgian demo of Bricker project is introduced, compared against an ideal approach and accordingly optimized. The resulting proposed approach is then tested by means of numerical simulations over a base case scenario before renovation. The main conclusion of this work is the demonstration that control strategy of energy generation and distribution systems has to be revised whenever deep renovation of passive or active building technologies is undertaken. Contrarily to which, project renovation goals cannot be met. [less ▲]

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See detailIntroduction aux échangeurs de chaleur
Declaye, Sébastien ULg; Gendebien, Samuel ULg; Lemort, Vincent ULg

Conference (2016, April 14)

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See detailPerformance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application: An experimental comparison between R245fa and R1233zd
Guillaume, Ludovic ULg; Legros, Arnaud ULg; Desideri, Adriano ULg et al

in Applied Energy (2016)

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial ... [more ▼]

The goal of this study is to experimentally compare the performance of an Organic Rankine Cycle (ORC) system equipped with a radial-inflow turbine for two working fluids: R245fa and R1233zd. The radial- inflow turbine is a small-scale prototype designed to convert the waste heat from the exhaust gases of a truck combustion engine and was developed mainly using components of truck turbochargers. It is directly connected to a high-speed synchronous generator. The bearings system of the turbine and the generator have the innovative particularity to be respectively lubricated and cooled down by the working fluid so no additional lubricant or coolant is needed. The experimental comparison is carried out over a test-rig equipped with the radial turbine. The heat wasted by the truck through the exhaust gases is sim- ulated using an electric oil boiler coupled to the ORC loop. The electrical power supplied by the turbine, limited to a maximum of 3.5 kWel by the generator, is then dissipated in a load bank composed of truck fans while the condenser is cooled by a water loop. Measurements in steady-state are performed in order to evaluate the performance of the turbine-generator set when varying the pressure ratio, the rotational speed, the inlet temperature and the mass flow rate of the turbine and the lubrication flow rate of the bearings for various oil temperatures and mass flow rates. In order to identify the most suitable fluid for the Waste Heat Recovery (WHR) application, three comparison methods are proposed and discussed based on the measurements. Finally, because the turbine-generator set is the first oil-free prototype developed by the manufacturer, potential sources of improvements are discovered and discussed. [less ▲]

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See detailExperimental comparison of organic fluids for low temperature ORC (organic Rankine cycle) systems for waste heat recovery applications
Desideri, Adriano ULg; Gusev, Sergei; Van den Broek, Martijn et al

in Energy (2016), 97

This contribution experimentally evaluates and compares the performance of an ORC (organic Rankine cycle) system for stationary bottoming WHR (waste heat recovery) application operating with two different ... [more ▼]

This contribution experimentally evaluates and compares the performance of an ORC (organic Rankine cycle) system for stationary bottoming WHR (waste heat recovery) application operating with two different working fluids, SES36 and R245fa. The test rig is a regenerative cycle equipped with a single screw expander modified from a standard compressor characterized by a nominal shaft power of 11 kW. A total of 36 and 43 steady-state points are collected for SES36 and R245fa respectively, over a wide range of operating conditions by changing the expander rotational speed, the pump frequency and the cooling condenser flow rate. The performances of the ORC components are individually evaluated. A maximum expander isentropic efficiency of 60% is reached using SES36 at 3000 rpm, and a value of 52% is reached with R245fa at 3000 rpm. However, for a given pressure ratio the expander output power is higher with R245fa than with SES36. The overall performance of the ORC unit are investigated in terms of first and second law efficiencies and net output power for the two fluids. The results experimentally demonstrate the correlation between the working fluid critical temperature and the ORC unit working characteristics for low temperature waste heat recovery applications. Open experimental data are provided for both fluids. [less ▲]

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