Optimisation du design préliminaire des systèmes CVCA

Abstract

HVAC (heating, ventilation and air conditioning) systems are recognized as one of the biggest energy consumers in commercial and institutional buildings. Generally, designers use common sense, historical data and subjective experience in designing these systems: such designs must take into account the way in which the zones served by the systems are grouped as well as the number of systems that serve each building. HVAC energy efficiency is not an easily calculable criterion to use when selecting such systems; usually, the lowest investment price becomes the primary selection criterion and not the life-cycle cost. The grouping of the zones served by the systems and the number of systems serving the building are the variables during the iterative optimization process. This thesis outlines a first optimization method for preliminary HVAC systems design using an evolutionary algorithm that uses reduction in energy consumption, as the optimization criterion. DOE-2 software was used to calculate the objective function, that is to say, HVAC energy consumption. The use of a calculation engine such as DOE-2 requires the involvement of a simulation expert in order to construct the building's model as well as to solve any problems encountered during simulation. As this problem is rather complex, we suggest to modify the first method by introducing a simplified model based on the zones' daily profile loads: essential data in the preliminary phase of design. A global load ratio (GLR), described as the ratio between the system's real load and its possible maximum load for a given period, is applied as objective function. The optimization variables are: (i) grouping of the zones served by the systems and (ii) number of systems serving the building. Constraints have been selected in order to ensure accurate representation of the variables' limits. The two optimizations methods are applied on a real building to see the impact on the energy consumption. The results we obtained during preliminary HVAC optimization design process could prove to be very useful for engineers during the preliminary design phase. The comparison between the reference building and the optimized building (under identical constraints) yielded significant energy savings for HVAC energy consumption. These savings are dependent upon the building's configuration, type of constraints imposed, types of HVAC systems it has, and the control strategies these systems employ.

Date	2 May 2012
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Stanislaw Kajl (Supervisor) & Louis Lamarche (Co-supervisor)