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127
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Introduction
Additional affiliations
October 2007 - present
Position
- Professor (Full)
Description
- //Teaching: Heat transfer, Air-conditioning, Energy and buildings //Research: Thermal systems theory, Model predictive control, Parameter identification, Performance measurement
November 1998 - September 2007
Publications
Publications (127)
Heat flux meters are used for measuring the heat flux densities going through walls, usually at quasi-steady state. The limitations of heat flux meters under dynamic conditions are well documented in the literature; nonetheless there is a theoretical limitation which is mostly not considered and should be also taken into account. Since heat transfe...
Accurate and efficient prediction of electric water boiler (EWB) energy consumption is significant for energy management, effective demand response, cost minimisation, and robust control strategies. Adequate tracking and prediction of user behaviour can enhance renewable energy minigrid (REMD) management. Fulfilling these demands for predicting the...
This paper proposes the method pELECTRE Tri, a novel probabilistic Multi-Criteria Decision Making (MCDM) method using the traditional ELECTRE Tri, probability distribution, and Monte Carlo simulation to support informed decision-making in complex and uncertain decision environments. The proposed method is illustrated through a case study involving...
Decision-making in energy retrofit of existing buildings needs to consider the economic and technical criteria, as well as social and environmental ones. The main problems are to define and to aggregate these contradicting issues to support a measurable and verifiable decision process. The working hypothesis of this paper is that the ELECTRE Tri me...
Heating and cooling load calculation based on dynamic models is widely used in simulation software and it is the method recommended by ASHRAE and CEN. The principle is to make the heat balance for the air volume of a room space considered at uniform temperature and to calculate from this equation the load, i.e. the power needed to obtain the requir...
State-space representation is essential in the theory of dynamic systems. This paper introduces a methodology for obtaining state-space representation from the thermal models of elementary components of a building by the conjunction of two methods: 1) assembling of thermal circuits and 2) state-space extraction from thermal circuit. These methods a...
Psychrometric chart is a basic tool for analysis of processes in air-conditioning systems. While psychrometric calculators and numerical psychrometric charts are widely available, there is a lack of numerical algorithms for solving the sizing problem by using psychrometric analysis. After introducing a classification of modelling problems in direct...
The dynamic thermal behaviour of the buildings can be represented by thermal networks. These oriented weighted graphs are graphical representations of the set of equations of heat transfer by conduction, convection, radiation and advection. Techniques for linearizing the models, especially the radiative heat exchange, are shown. Being linear (or li...
Non-intrusive loading monitoring (NILM) provides a smart solution to the problem of electrical energy monitoring of households at the appliance level. In blind disaggregation, the power level of each appliance is not known a priori. In this paper, we propose an event-based blind disaggregation algorithm that uses Gaussian mixture models (GMM) for c...
To investigate and optimize a refrigeration system, the behavior at various operating conditions must be known or determined. The performance and improvement possibilities may then be inferred from measurement data and compared with corresponding performance key figures. These values are typically referred to normal conditions and it is usually unk...
The dynamic thermal behaviour of the buildings can be represented by thermal networks. These oriented weighted graphs are graphical representations of the set of equations of heat transfer by conduction, convection, radiation and advection. Techniques for linearizing the models, especially the radiative heat exchange, are shown. Being linear (or li...
Exergy analysis has been widely used to assess refrigeration systems by evaluating exergy losses or exergy efficiency. The latter is mostly used as an indicator to determine the system performance, which requires the comparison of the actual system with its idealized reversible version, but not the practical achievable efficiency. Therefore, a prac...
Overall heat transfer coefficient, also known as the intrinsic performance measurement of the building, determines the amount of heat lost by a building due to temperature difference between indoor and outdoor. QUB (Quick U-value of Buildings) is a short-term method for measuring the overall heat transfer coefficient of buildings. The test involves...
State-space representation is essential in dynamical systems theory. This paper introduces a methodology for obtaining state-space representation from the thermal models of elementary components of a building by the conjunction of two methods: 1) assembling of thermal circuits and 2) state-space extraction from thermal circuit. These methods are fu...
Exergy analysis allows us to determine the quality of energy sources and losses due to irreversibilities through a system. However, the quantification of possible improvements as compared with the state of the art in technology is complicated. Typically, it is referred to the thermodynamic ideal, which is not achievable in practice. Therefore, this...
The quick U-building (QUB) method is used to measure the overall heat loss coefficient of buildings during one to two nights by applying heating power and by measuring the indoor and the outdoor temperatures. In this paper, the numerical model of a real house, previously validated on experimental data, is used to conduct several numerical QUB exper...
Quick U-building (QUB) is a method for short time measurement of energy performance of buildings, typically one night. It uses the indoor air temperature response to the power delivered to the indoor air by electric heaters. This paper introduces a method for estimating the expected measurement error as a function of the amplitude and the time dura...
Experimental calibration of dynamic thermal models is required for model predictive control and characterization of building energy performance. In these applications, the uncertainty assessment of the parameter estimates is decisive; this is why a Bayesian calibration procedure (selection, calibration and validation) is presented. The calibration...
Dynamic behaviour of a system may be described by models with different forms: thermal (RC) networks, state-space representations, transfer functions, and ARX models. These models, which describe the same process, are used in the design, simulation, optimal predictive control, parameter identification, fault detection and diagnosis, and so on. Sinc...
Experimental identification of grey box model is the key of two social needs, the energy performance measurement and the energy management. Obtaining a reliable model may be time consuming and depends on the knowledge of building characteristics available. Furthermore, on-site measurements have to be collected before starting the identification pro...
Heat flux meters are used for measuring the heat flux densities going through walls, usually at quasi-steady state. The limitations of heat flux meters under dynamic conditions are well documented in the literature; nonetheless there is a theoretical limitation which is mostly not considered and should be also taken into account. Since heat transfe...
Heat transfer in solids may be dealt with the heat equation, which is a partial differential equation, from which different analytical solutions for the study of heat transfer throughout solids and at their surfaces may be found. This implies the resolution of a distributed parameter model. On the other hand, the possibility of considering the ther...
This study proposes new matrix relationships of the radiative interactions in enclosures along with their corresponding applications. By means of several transformations one establishes matrix formulae based on equations of radiative exchanges containing variables defined in a discrete analog form, and further on, by means of a multidisciplinary ap...
The air transformations are represented graphically on the psychrometric diagram, which is very non-linear. The sensible and latent heat may be decoupled, which allows the representation of air transformations by linear variations. The saturation curve may be also linearized in a point. If the mass flow rate and if the sensible and latent heat flow...
Autoregressive models with exogenous (ARX) are widely used for parameters identification of walls although their parameters do not have a direct physical interpretation. This paper uses measured data and an ARX model, obtained by deduction from a thermal network, for identifying the parameters with physical meaning of a wall tested under real weath...
Abstract Experimental identification of the dynamic models of heat transfer in walls is needed for optimal control and characterization of building energy performance. These models use the heat equation in time domain which can be put in matrix form and then, through state-space representation, transformed in a transfer function which is of infinit...
The typical air conditioning steady-state processes are graphically represented by straight or curve lines on the psychrometric chart. Neglecting the sensible heat of the moisture results in decoupling the sensible and the latent heat, that results in linear variation of the enthalpy on the psychrometric chart. The vapor saturation curve may also b...
Assessing controller performance in normal operation needs reproducible conditions and comparison with the best possible result. Tests in emulation are reproducible. Model Predictive Control (MPC) gives the best possible performance when the future inputs and the model of the process are known. When the benchmark is used for building energy managem...
Dynamic models are needed for automatic control and online fault detection and diagnosis of desiccant wheels used in solar cooling systems. The parameters of these models need to be experimentally identified during operation. A model based on the heat and mass transfer equations, given in state-space representation, is developed. Using this model,...
Heating and cooling load estimation is based on the
heat balance method. Although this method has
strong physical basis, it yields an acausal system
when the heat capacity of the indoor space is non-
negligible. New emergent problems in low energy
buildings require time steps significantly smaller than
1 hour, which is usually used by simulation so...
A Desiccant Air Unit (DAU) may provide complete control of temperature and humidity in air-conditioned spaces. The key element of the DAU is the desiccant wheel. Its control needs models adapted to the analysis and synthesis of control algorithms. Such models can be obtained by a gray-box approach in which the structure of a state-space model and s...
Thermal load calculation based on dynamic models is widely used in simulation software and it is the method recommended by ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning Engineers) and CEN (European Committee for Standardization, in French: Comité Européen de Normalisation). The principle is to make the heat balance for the...
Simulation based optimization may use parametric runs or optimization techniques. We propose a hydraulic schematic for a multifunction multi-source solar system (MFMSYS) and we consider the area of the solar collector and the volume of the thermal storage tank as the parameters to be optimally sized for minimizing the total cost. An additional cost...
This paper highlights the importance of the control in building simulation. The absence of the controller during building simulation leads to multiple prob-lems like non-physical evolution of the indoor tem-perature, different thermal peak loads when using different sampling times and wrong energy perform-ance assessments. By using optimal control...
Free-cooling by ventilation is one of the most energy efficient techniques for cooling. When ventilation is used for cooling, variable airflow rates should to be used in order to achieve comfortable room temperatures and to minimize the energy demand for mechanical ventilation. Thus, free-cooling, requires, obviously, the existence of a potential f...
An important performance in building thermal control is to ensure thermal comfort with minimal energy consumption. Model Predictive Control (MPC) is considered to be one of the most suited solutions for this due to its ability to use occupancy schedule and weather forecasts for optimal temperature control. MPC relies on a dynamical model of the bui...
The goal of optimal temperature control in buildings is usually to ensure thermal comfort with minimal energy consumption. In intermittently occupied buildings, this presumes the ability of the controller to recover in due time the building from setback. Model Predictive Control (MPC) is considered among the best candidates for this task due to its...
A building is permanently in thermodynamic non-equilibrium due to changing weather, free gains and indoor temperature set-point. Load calculation in dynamic conditions is an essential goal of building energy simulation. This paper demonstrates that the load calculation is a control problem. Supposing that the thermal model of the building is linear...
The present work is aimed to investigate the minimization criterion used in Model Predictive Control (MPC). The paper shows that minimization of currently used objective function in MPC does not minimize the consumed energy in the case of true bond graph models of the systems. Thus, it is proposed to use another criterion which removes this drawbac...
A l’heure où les bâtiments doivent être construits ou rénovés en leur assurant la meilleure étanchéité à l’air, il devenait de plus en plus impératif que les systèmes de ventilation naturelle ou hybride puissent être conçus, dimensionnés et mis en œuvre dans le respect de règles communes et puissent ainsi constituer une solution alternative à la ve...
The choice of the design solutions for low energy buildings requires the performance evaluation of the alternatives. In the present study, simple polynomial function is used to estimate the annual energy demand as a function of building envelope physical and geometric parameters. The coefficients of this function are obtained by regression from dyn...
A rational choice of solutions for low energy building requires a performance evaluation for a large number of parameter combinations. Currently, building thermal dynamic simulation is used to check design solutions but it gives little information on what and how much may be improved. Iterative parameter optimization is a solution but the methods u...
Real-time control of air conditioning needs dynamic models of temperature distribution and air velocity field in rooms. Complete models, based on computational fluid dynamics (CFD), give this information, but they are too time-consuming for real-time applications. Therefore, a reduced model is needed. In mixed convection, when the air temperature h...
Real-time control of comfort in indoor spaces needs models of temperature distribution and the air velocity field. Complete models, based on CFD, give this information but, because of processing time limitations, cannot be applied to real-time calculations. Therefore, a reduced model is needed. This study proposes to reduce the complexity of a CFD...
Usually, the airflow in rooms is fully turbulent. To treat the turbulence, Reynolds averaging may be used. Con-sequently, in equation (1), the effective diffusivity, eff a , can be split into a laminar term and a turbulent term: (2) where: λ: thermal conductivity, ν t : turbulent viscosity, � t : turbulent Prandtl number, here equal to 0.9. The vel...
Real-time control of comfort in indoor spaces needs models of temperature distribution and air-velocity ve- locity field. Currently, a one zone model is used assum - ing that the temperature is homogenous in the whole space. If the heterogeneity of air velocity field and the temperatures distribution is to be taken into account by the control syste...
The air-handling units (AHUs) provide complete control of temperature and humidity in air-conditioned spaces. The models of the AHU elements are nonlinear and the controlled variables, temperature and relative humidity, coupled. This paper demonstrates that in the case of sensible heat exchange without moisture removal if the outputs of the electri...
The use of water droplet evaporation in shower towers and passive downdraft evaporative cooling needs the estimation of the time needed to completely evaporate the drops. To solve this problem, a cellular approach is proposed in which the spray is considered as a pile of rigid spheres of equal size; each sphere has multiple layers and contains a dr...
Estimation of energy performance indexes, like the heating curve or the energy signature, requires robust regression of the heating losses on the outdoor temperature. The solution proposed in this paper is to use the range between the 1st and the 3rd quartile of the quantile–quantile (q–q) plot to check if the heating losses and the outdoor tempera...
The methods used to assess the energy performance of buildings are static or dynamic. A paradigm shift is to estimate the energy consumption by using a probabilistic approach and a single concept for the whole range of operation of the building (heating, ventilation and cooling) and to decouple the thermal behavior of the building, the thermal comf...
Natural ventilation is less effective in urban than in rural environment, especially in street canyons. Reduced wind velocity, urban heat island, noise and pollution, are considered to be important barriers to its application in urban environment. To quantify their effect on ventilation, wind, temperature, noise attenuation and outdoor–indoor pollu...
Natural ventilation is one of the most effective techniques for cooling. Its potential for cooling may be assessed by using a method based on the indoor–outdoor temperature difference of the free-running building, the adaptive comfort criteria and the outdoor temperature. It is demonstrated that the free-running temperature may be used instead of t...
This paper demonstrates that if the outputs of the heating and cooling coils and of the steam humidifier of an air handling unit (AHU) are considered to be the temperature difference and the humidity ratio difference between outlet and inlet, respectively, then the transfer function of the coils is of first order with variable gain and the transfer...
The parameter identification of the discrete-time models of the elements of the AHU is done in two steps: first, the ARX model of the sensor is obtained; then, this knowledge is introduced in the discrete model of the coil or humidifier written in space-state form. Thus, we determine the transfer function of the sensor, and then, the transfer funct...
Contrat EDF/LEPTIAB n° 8108 CAX 4300034809, rapport final
A discriminant analysis model using 1-day lagged ozone maximum concentration and the weather forecast of wind and temperature proves to correctly classify ozone episodes, if reasonable error ranges are accepted. Seven classes are defined around the ozone level of interest, each having a range of about 7.5–10% of the absolute value of the class. Thi...
The application of natural ventilation is more difficult in urban than in rural environment, especially in street canyons due to reduced wind velocity, urban heat island, noise and pollution, which are considered to be important barriers to the application of natural ventilation. The wind, temperature, noise attenuation and outdoor-indoor pollution...
The design of a building should provide the flow paths needed for natural ventilation. Therefore, the decision to apply natural ventilation should be taken early in the building design process, when little information is available for airflow estimation. To deal with this lack of data, a semi-qualitative method to assess the potential of an urban s...
The architectural decisions for building that use natural ventilation should be taken in the initial stages of design when little information is avail- able. A new approach is to compare the poten- tial natural ventilation of known buildings in a new site and to adapt the design of the known example. The potential of natural ventilation may be chan...
The design of a building should provide the flow paths needed for natural ventilation. Therefore, the decision to apply natural ventilation should be taken early in the building design process, when little information is available for airflow estimation. To deal with this lack of data, a semi-qualitative method to assess the potential of an urban s...