CASE STUDY OF ACTIVE FREE COOLING WITH THERMAL ENERGY STORAGE TECHNOLOGY

Abstract: May 25, 2011, Reuters’ headline read: "New York State is prepared for summerelectricity demand". The NY operator forecasts for next summer a peak of 33GW, close to therecord ever reached. With soaring cooling demands, the electricity peak load represents a substantialconcern to the energy system. In the goal of peak shaving, research on alternative solutions based onThermal Energy Storage (TES), for both cooling and heating applications, has been largely performed.This thesis addresses thermal comfort applications with use of active free cooling through implementationof latent heat based TES. Active free cooling is based on the use of the freshness of a source, the outsideair for example, to cool down buildings. This work conceptualizes the implementation of TES basedcooling system with use of Phase Change Material in an in-house-built model. The principle of PhaseChange Material, or Latent Heat TES (LHTES), lies on latent energy which is the energy required for thematerial to change phase. In order to properly size this cooling system, a multi-objective optimization isadopted. This optimization, based on minimization of multi-objective functions, led to optimal designconfigurations. In parallel, the electrical consumption of the system and the volume uptake of the systemwere also considered. Through the obtained optimization studies, we identified non-linearinterdependency between the two objective functions: the cost of the system and the acceptable remainingcooling needs. By remaining cooling needs, we mean the cooling needs that the system cannot meet. As amatter of fact, sizing the system according to these cooling needs would imply a very high cost. It wasfound that for a certain amount of remaining cooling needs, the PCM-based cooling system reveals to bean interesting solution compared to conventional air conditioning in terms of electrical consumption andoverall system cost.