Texas Field Experiment -
Interim Results
The U.S. Department of Energy's Weatherization Assistance Program has weatherized more than five million low income residences since its inception in 1976. Evaluations of the Program in hot climates had produced puzzling results concerning cooling savings. Despite numerous analyses showing the potential for cost-effective cooling energy savings in hot climates, studies conducted with the Princeton Scorekeeping Method (PRISM) had not found statistically significant cooling savings. The Texas Field Experiment (TFE) was initiated to provide a closer, more in-depth look at how electricity was actually being used in hot-climate Program homes. Obtaining detailed information on electric loads, with a more sensitive monitoring tool, was expected to shed light on unresolved hot climate issues.
The new more-sensitive tool selected for this study is the Single Point End-use Energy Disaggregation (SPEED) recorders and their accompanying computer server and software, which together comprise the Non-Intrusive Appliance Load Monitoring System (NIALMS). This system disaggregates electric loads by their electricity-use signatures. SPEED/NIALMS monitoring has made it possible to examine electric loads and occupant behaviors in Program homes in sufficient detail to understand why actual consumption is different from audit predictions, or why usage goes up or down during a monitoring period. Pre-weatherization SPEED/NIALMS monitoring allowed identification of house-specific factors that were determining levels of heating and cooling energy use.
While SPEED/NIALMS has proven to be a valuable tool, developing appliance models has proven to be more labor intensive than expected. ORNL found it necessary to closely monitor, customize and verify appliance models throughout the data analysis process. Although mastering SPEED/NIALMS took considerable effort, ORNL now can use this capability in a variety of research applications. Based on the TFE experience, ORNL has applied SPEED/NIALMS to studies of heat pump water heaters and heat pump window units.
Pre-weatherization monitoring revealed a striking diversity in energy use patterns, especially for space heating and cooling. Total annual electricity use varied by a factor of about 2.5 in the TFE single-family houses and by a factor of almost 3 in TFE mobile homes. Some of the TFE houses had consistently well-controlled indoor temperatures, but most were heated or cooled intermittently. Such intermittent usage patterns were even more typical of cooling behavior. About three fourths of the TFE homes lacked central heating and air conditioning systems. The houses without central systems typically heated or cooled only a few rooms and often used their heating or cooling equipment only when the occupant was in a specific room. A few houses used little or no energy for air conditioning. Several TFE house used very little energy for space heating. In one house the only source of heat was the oven. Some houses used only a few small portable electric heaters.
After the modeling and analysis of post-weatherization electric loads is completed in 2005, findings on house-by-house Program impacts will be available.
Contact: Mark Ternes
