ANALYTICAL MODELLING AND DESIGN PARAMETER STUDIES OF SOLAR-POWERED ABSORPTION CYCLE HEAT PUMP SYSTEMS

The application of solar energy to power heat pumps based on the water-lithium bromide absorption refrigeration cycle is studied. Three solar-powered heat pump configurations with increasing operational flexibility are considered: (1) With absorption cycle machine directly coupled to a solar energy collector, (2) With an external thermal energy storage coupling collector to absorption cycle, and (3) With latent energy storage internal to the absorption cycle. A primary objective of this work is to evaluate the operational and economic advantages of the innovative internal latent energy storage concept.; Performance equation sets suitable to make computer simulations of the time behavior of the systems are developed in the first phase of the study. These system models include representations of solar collectors, energy storages, absorption cycle machines, and building load demands. Functional representations of the thermodynamic properties of refrigerant-absorbent mixtures and of hourly insolation and air temperatures are also developed.; The second phase of the study is a thorough analysis of the instantaneous operation of each of the three systems to develop operating algorithms that establish optimal operating points for each of the system components. Particular concern is taken also to develop operating algorithms to handle limit situations such as empty storage tanks and temperature constraints. In the final phase of the study, design parameter studies are carried out using the discrete time computer programs that simulate the hourly performance of each of the three systems for cooling mode operation over a specific weather sequence. Collector area and energy storage capacity are optimized with respect to a cost objective function.; This study establishes the operational viability and economic superiority of the internal latent energy storage concept relative to the more conventional systems. It is shown to justify 60% more collector area than the external thermal storage system while costing 32% less for the specific weather sequence. Further work on this solar-powered heat pump concept is recommended, specifically, the analysis of heating mode operation with ground-coupled evaporator and further design method development.