Comparative Analysis of Single- and Continuously Variable-Capacity Heat Pump Concepts

摘要

This work is an initial assessment of the potential benefits of continuous-capacity-modulation in electric-driven, air-to-air heat pumps for residential application. The purpose of the project was to provide a quantitative estimate of the possible annual performance gains of advanced continuously modulating heat pumps relative to single-speed designs at comparable levels of development. Previous analytical design work in this area at ORNL dealt with single-design-point, heating-mode optimization of single-speed heat pumps. For that work the ORNL Steady State Heat Pump Design Model was connected to a constrained numerical optimization code. The present work represents an extension of the earlier work in two directions. First, seasonal (heating and cooling) and annual performance factor (APF) analysis capability was added to allow direct evaluation of annual energy use from heat pump performance data generated by the ORNL heat pump model. Secondly, a modulating version of the heat pump model was developed to provide a means for simulating the steady state performance of continuously variable-speed (CVS) systems. With these tools, the APFs of both single- and continuously variable-capacity (CVC) concepts could be studied as basic heat pump design variables were varied. Based on this initial evaluation of CVS systems and considering the potential for electronics costs to further decrease as electricity prices rise, we see such advanced CVS systems as a strong future competitor to single-speed systems and as decidedly superior in energy conservation potential. To achieve this position, it seems especially important that such systems be computer optimized to take full advantage of the increased design flexibility available. Further, development of PM-ECMs or equivalent technology must continue to the point of providing speed controllers of: moderate to low cost, moderate to high performance, and high reliability. 16 refs., 12 figs. (ERA citation 10:033981)