Performance Modeling of a Solar Thermal System for Cooling and Heating in Carnegie Mellon University’s Intelligent Workplace

The Robert L. Preger Intelligent Workplace (IW) is a 650 m² living laboratory of office space at Carnegie Mellon University (Pittsburgh, PA). The IW has received the first commercially available solar absorption system for air-conditioning with integrated controls as a donation from BROAD in August 2006. The IW is now testing this solar thermal system. A TRNSYS model has been developed and used to assist the design of the system, evaluate its performance throughout an entire year, and optimize its initial configuration. The components of the system are a 52 m² parabolic trough high temperature solar array, a 16 kW hot water and gas fired absorption chiller, and an overall control system. This model predicts the energy required to cool and heat the south part of the IW (around 10 MWh in winter, 15 MWh in summer) and the fraction of that energy that can be provided by solar energy. The effects of significant system parameters — orientation of the receivers, volume of hot/chilled water thermal storage and insulation thicknesses on the piping and tank — on the fraction of solar provided energy have been calculated by the model. This study emphasizes on two significant aspects: - the impact of system integration during the preliminary building design on the energy performance, - the importance of the energy modeling to assist and optimize the design of the system and its operation but also to reduce the investment and operation costs.