Demand Shifting With Thermal Mass in Light and Heavy Mass Commercial Buildings

TitleDemand Shifting With Thermal Mass in Light and Heavy Mass Commercial Buildings
Publication TypeReport
LBNL Report NumberLBNL-61172
Year of Publication2006
AuthorsXu, Peng, and Leah Zagreus
Keywordsdemand response, demand shifting (pre-cooling), pre‐cooling, thermal mass
Abstract

The potential for utilizing building thermal mass for load shifting and peak demand reduction has been demonstrated in a number of simulation, laboratory, and field studies. This project studied the potential of pre‐cooling and demand limiting in a heavy mass and a light mass building in the Bay Area of California. The conclusion of the work to date is that pre‐cooling has the potential to improve the demand responsiveness of commercial buildings while maintaining acceptable comfort conditions. Results indicate that pre‐cooling increases the depth (kW) and duration (kWh) of the shed capacity of a given building, all other factors being equal. Pre‐cooling and demand shed strategies worked well in both the light and heavy mass buildings. A properly‐controlled exponential temperature set up strategy in the shed period discharged thermal mass smoothly in both buildings. The optimal strategy for avoiding rebound was an exponential temperature reset strategy. Pre‐cooling was very effective even in cool weather conditions in the heavy mass building. Night pre‐cooling had noticeable effects on the second day cooling load in the heavy mass building. Night pre‐cooling reduced both HVAC peak demand and energy consumption in cool weather in the heavy mass building. Due to the time necessary for pre‐cooling, it is only applicable to day‐ahead demand response programs. The effectiveness of night pre‐cooling under hot weather conditions has not been tested. Further work is required to quantify and demonstrate the effectiveness of pre‐cooling in different climates. Research is also needed on occupant response with advance notification of the pre‐cooling DR event. Further work is necessary to develop screening tools that can be used to select suitable buildings and customers, identify the most appropriate pre‐cooling strategies, and estimate the benefits to the customer and the utility.

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