Demonstration of Load Shifting and Peak Load Reduction with Control of Building Thermal Mass

J.E. Braun and T.M. Lawrence, Purdue University, Ray W. Herrick Laboratories
Curtis J. Klaassen and John M. House, Iowa Energy Center

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Abstract

In this paper, results of testing at the Iowa Energy Center are presented that demonstrate the potential for load shifting and peak load reduction through precooling of the building structure. This facility is used for performing research on building controls and diagnostics and is very well instrumented and maintained. Cooling loads for individual zones can be determined directly from measurements. A sequence of two week-long tests were performed using a conventional night setup and a simple precooling control strategy. The cumulative occupied load for the test zones was 23% less for the precooling strategy than for night setup control. The simple precooling strategy was not optimized to reduce peak loads since the room temperatures were held constant in the middle of the comfort region during the entire occupied period. Even so, the cumulative peak load of the test zones was reduced by about 9% with the simple precooling strategy. The east test rooms had the largest peak load reductions (15%) because the peaks occur earlier in the day when the thermal mass is cooler and therefore are more effective as a heat sink. The interior rooms also had a significant peak load reduction (12%), whereas the south and west zones had negliglible peak load reductions for the simple strategy that was employed. The building chosen for testing was not considered to be a particularly good candidate for use of building precooling. The results make a strong case for application of control strategies that take advantage of load shifting opportunities from building thermal mass.