Joseph Virgone

Trade-off between environmental and economic objectives in the optimization of multi-energy systems

An increase in the energy and environmental performance of building system can be found in a design that allows the operators to choose between multiple energy sources. Such a system can be referred to as multi-energy system and recently a strong interest was put in this topic at both district and building levels. Since multi-energy systems use non conventional aggregation of energy sources, new energy converters, and unusual system layouts, it is of the foremost importance to provide modelling and optimization procedures for those systems. In this paper, some objective functions based on a set of economic and environmental criteria are defined and used to perform the system optimization. The relations between the outcomes of the optimizations are then analyzed on a case study as a function of the customer, the energy costs, and the pollutants emissions showing that there is generally a trade-off between environmental and economic objectives.

An Analysis of the Performance of Different Intermittent Heating Controllers and an Evaluation of Comfort and Energy Consumption

This article presents a new controller, based on fuzzy logic, to be used for the control of heating systems in intermittently occupied buildings. Its originality lies in the fact that it takes into account the thermal state of buildings, as well as the outside temperature. The TRNSYS simulation software was used to model a multizone building, its hot-water-radiator heating system, and a several types of thermal control. The controller was tested for different configurations of thermal inertia, excess plant capacity, internal loads, and set-point temperature for periods when unoccupied. Comparisons with classical control methods were used to demonstrate that the fuzzy controller gave superior results in terms of the control and optimization of the recovery time after setback. For each case, the differences in comfort and energy consumption between the different types of room were studied.

Modelling heat transfers in building by coupling reduced-order models

Abstract The components of the envelope models can be coupled by non-linear or by linear heat transfers laws, depending on the level of the expected accuracy. One way to obtain these models is to use a state representation approach for conduction heat transfer. The reduction technique used here consists in linear systems aggregation, which has been applied in several ways for large dynamical systems reduction. Different strategies of coupling these models are described and results are discussed. One of the major results of this paper is the important decrease of the computation time with no significant losses of accuracy.

Full-scale study of a building equipped with a multi-layer rack latent heat thermal energy storage system

Phase change material has been installed as a latent heat thermal energy storage system coupled with the ventilation system in an office building located in Lyon, France. The main purpose of this study is to determine if the phase change material system can guarantee the summer comfort of the occupants without energy-consuming cooling devices. Sensors have been set up, and the collected data are monitored to study the thermal behavior of the building and the phase change material. Numerical simulations complete the work to study and compare the building behavior without phase change material. The temperature charts in each office show that the thermal comfort of the workers is acceptable in winter and summer. Numerical results show a difference of temperature in offices due to the ventilation through the crawl space equipped with the phase change material multi-layer racks. The temperature in the crawl space varies between 12°C and 25°C (53.6°F and 77°F) all through the year. It is then possible to conclude that the new ventilation system is efficient for the precooling or preheating of air.

A presence-based control strategy solution for HVAC systems

This paper presents an energy-saving control solution which has been developed for existing public buildings by designing an intelligent ICT-based service system for monitoring and controlling the environmental conditions. The proposed control strategy addresses the required infrastructure and implements the design to properly balance energy savings and comfort issues. In this work, a combination of occupancy detection and daylight harvesting is presented as input to the control algorithm. The implemented results presented here utilize the hardware and software on a pilot campus and achieve an average energy saving of 71% for three sample days during summer times. Simulation results are also presented for annual period and complete test case building.

Commande floue et thermique du bâtiment. Proposition d'une loi de chauffe adaptée à la régulation des bâtiments de type tertiaire à occupation discontinue

Abstract Fuzzy control and thermal properties of buildings: proposition of a heating law fitting the regulation of tertiary buildings with intermittence. In this article, we start with a general presentation of thermal regulation in buildings and of fuzzy logic applied to the control. Then, thanks to the numerical simulation of a building, we show why regulators based on the use of a straight line heating law are not adapted to the practice of intermittence. The command law we propose is based on fuzzy control. It takes into account both the exterior temperature and the thermal state of the building we estimate by means of the same function whatever the building. Simulating the opening of a window, we show that the closing degree of the regulation loop is very weak. The inference system incorporates constraints upon the conclusions which allow to do an off-line learning from the second week (respect of the open-loop) without any risk of obtaining an aberrant power because of a non-learned rule. The regulation we obtain limits considerably the disfunctioning caused by the open-loop control with intermittent regime. We conclude upon the interest of fuzzy control as regards to the temperature regulation of complex dynamic systems.

Reducing the energy consumption of space heating in buildings: design of an optimal controller

Abstract The reduction of the energy consumption in buildings has become a priority in every developed country. Automatic control is one of the latest techniques introduced to this purpose. This paper describes the design of a new controller which controls the internal temperature of an individual dwelling by adjusting of the heating power. First, considering the intermittency the occupation, an optimal temperature trajectory in term of control cost has been computed. Second, introducing an augmented state representation, a state feedback law has been calculated. Third, since this law required an inaccessible state, a Kalman estimator has been introduced to estimate this state. Introducing a deconvolution problematic in its design, a “virtual feed forward” based on estimation has been introduced to balance the external disturbances. Fourth, in order to take into account the control saturation of the heating system, an anti-windup compensator has been introduced to the controller. Finally, the controller has been tested in simulation on an experimental building and the interest of the virtual feed forward has been illustrated.

Modélisation thermique de l'opération de formage à chaud de feuilles de verre

Abstract Thermal modelling of the hot forming of glass sheets. This work deals with the hot forming of a glass sheet between two metallic moulds. We have developed a 1-D calculation code simulating the thermal behaviour of the different parts - glass and moulds - during the whole operation. The glass is represented as a non-grey medium, the thermophysical properties of which may depend on temperature. We have used the PI method for the description of radiative transfer and the control volume method for the discretization of the coupled problem. The results are given in diagrams showing the evolution of the surface temperature of the moulds and glass, but also the temperature inside the glass sheet, at the end of the most important phases of the operation.

Experimental Study of an Air Distribution System for Operating Room Applications

Abstract An understanding of airflow patterns in operating rooms is required if the design of air distribution systems in such environments is to be improved and the risk of postoperative infection reduced. To assess a detailed description of contaminant distribution, the airflow patterns and the spread of contaminants in an operating room were analyzed using an experimental model. These experiments were carried out in a test cell, MINIBAT, equipped with an operating table, a medical lamp and a manikin representing the surgeon. A diagonal ventilation system was tested for two types of conditions: (i) isothermal, with the manikin and lamp switched off and (ii) non-isothermal, with the manikin and lamp switched on. Indoor air temperatures, air velocities and tracer gas concentrations were measured automatically at more than 700 points. The overall airflow patterns, due to ventilation, were very similar for the two experiments. However, in the zone between the lamp, the table and the manikin (which was the main area of interest), the tracer gas distribution was different. In the non-isothermal case, the thermal plume from the manikin induced better mixing, and had a beneficial effect on the evacuation of contaminants. The thermal energy emitted by the lamp had almost no impact on the airflow patterns.