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Hybrid ventilation control design and management.

Article Excerpt
INTRODUCTION

Background

Nowadays, there is a growing interest in taking ventilation systems into account at the early design stage of a building. Designers are interested in ventilation features as well as in indoor air quality, thermal comfort and energy consumption (Heiselberg 2000). In addition, several studies have shown that ventilation systems control have a great potential to improve occupant's productivity (Annex 35 2000). Indeed, large degree of control leads to better perceived productivity (CIBSE 1998). One way to reach these targets is to combine both natural and mechanical ventilation advantages into a hybrid system. The purpose of such ventilation system is to use both natural and mechanical driving forces to provide a good and healthy indoor environment at the lowest cost possible. Although there were projects and studies on natural ventilation like AIOLOS (Allard 1998) or NatVent (Aggerholm 1998), there remains a lack of knowledge concerning the implementation of hybrid ventilation systems, the use of such technologies and their suitable control strategies. The first studies concerning hybrid ventilation systems have been initiated by the IEA Annex 35 "Hybrid Ventilation in New and Retrofitted buildings" (Annex 35 2000). In addition, reliable design tools are needed to generate guidelines on control strategies. Examples of existing hybrid ventilation and control strategy systems in office and educational buildings (Agger-holm 2002) show that control strategies have to be carefully designed to take into account the building design, the ventilation system, the occupant behaviors and their indoor climate expectations.

The purpose of this paper is to describe part of the work done by the ENTPE/LASH laboratory in this field. The presented work has been initiated within the framework of IEA Annex 35 and developed thanks to academic and industrial partnership. The main objective of this work is to design and numerically and experimentally assess optimal control strategies for hybrid ventilation systems.

Methodology

Ventilation has a major impact on the global performance of buildings, in terms of energy consumption as well as regarding indoor climate: thermal comfort, indoor air quality, and acoustics. Thus a ventilation control strategy must be designed and evaluated within a systemic approach using simulations and experiments. Several constraints and parameters have to be taken into account as soon as possible in the design of the building: indoor air quality, noise, occupancy, physical phenomena, climate, ventilation configuration, maintenance, control parameters, sensors and actuators ... As shown in Figure 1, the design procedure of a controlled ventilation system must be a retroactive one. Hence, the stat of the art allows taking advantage of hardware and software technology and applying standards specifications. The ventilation design principles stage must take into account: Building type, building regulation, climate and local environment. Numerical modeling will be helpful to test the behavior of the system.

[FIGURE 1 OMITTED]

Control strategy procedure development must take into account thermal and ventilation demands, user preference. Several...

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