Modeling of a solar-assisted HVAC system with thermal storage. M. Ortiz, H. Barsun, H. He, P. Vorobieff ∗ , A. Mammoli The University of New Mexico, Albuquerque, New Mexico 87131, USA Abstract A numerical model of the solar-thermal-assisted heating, ventilation and air conditioning system in a 7000 m 2 educational building, situated in a high-desert climate, is used to predict performance and optimize control parameters. Heating, cooling and shoulder seasons are considered in the study. It is found that the solar assist can account for over 90% of the total heating requirements if certain energy conservation strategies are adopted. The solar cooling assist can reduce the total external cooling energy requirement by between 33% and 43%, the latter result achieved, surprisingly, at lower solar array operating temperatures. In the shoulder season, it is possible to operate the building without any external contribution, by heating the building in the coldest hours of the day, and using any excess heat to produce chilled water, to be stored and used when required. Operation of the solar-assisted system within a much larger district energy system makes it possible to achieve maximum performance. Key words: solar thermal, building, absorption chiller, heating, cooling 1. Introduction In the developed world, a large fraction of the primary energy budget (40% to 50%) is consumed by buildings to run heating, ventilation, and air conditioning (HVAC), lighting, appliances and equipment [1]. The breakdown varies according to building type and geographic location, but the HVAC portion of the load is in all cases substantial and in many cases the largest [2]. Unlike most other energy-consuming entities, buildings offer an ideal platform for distributed solar energy harvesting, due to large surfaces exposed to solar radiation. Furthermore, because thermal conditioning accounts for a large fraction of the peak energy use [3]., thermal storage is an attractive and economical energy management resource, which could also provide an important contribution to alleviating one of the major problems associated with renewable energy, namely intermittency [4]. Only a small number of medium-sized buildings worldwide combine solar assisted heating and cooling with substantial thermal storage. Wildin [5] describes the design and operation of the building considered in this study (the UNM Mechanical Engineering building at the University of New Mexico) in its original configuration. ∗ Corresponding author. E-mail address: kalmoth@unm.edu Preprint submitted to Elsevier October 2, 2009