Demand Shifting with Thermal Mass

Vision

The purpose of this Demand Response research is to investigate the methods and effects of shifting electrical energy usage in small and large commercial buildings using various pre-cooling strategies. "Pre-cooling" techniques reduce the building mass temperatures and interior temperatures in the early part of the day and reduce cooling electricity demand and electricity use in the afternoon.

Research Questions

• Which thermostat control strategies minimize peak electric demand while satisfying thermal comfort for building occupants?
• How much pre-cooling can be done without impacting occupant comfort?
• How might these techniques reduce building owners' operating costs?
• What are people's perceptions regarding the precooling strategies and market acceptance issues?

Methods

• Simulate building energy use resulting from different thermostat strategies.
• Host customer "focus group" discussions regarding pre-cooling buildings.
• Assess the practicality of implementing pre-cooling by interviewing building owners.
• Conduct pre-cooling field tests:
• Design, develop, fabricate and install computerized polling devices to determine occupant comfort in stores and banks.
• Develop a web-based comfort survey to poll occupants of large office buildings.
• Test pre-cooling strategies in small and large buildings.
• Analyze energy use and comfort issues.

Findings

• Field tests and simulations demonstrate the potential of large peak demand savings.
• Preliminary results indicate that occupant comfort is satisfactory when the temperature is varied between 70°F and 78°F.
• Preliminary building owner focus group results suggest that comfort is a factor when considering pre-cooling strategies.

The purpose of the "Demand Shifting with Thermal Mass" research project is to perform an initial evaluation of the viability of shifting the electric usage of buildings by making adjustments in thermostat set temperatures. By pre-cooling the building during off-peak hours and allowing the building temperatures to rise within the comfort range in the on-peak hours, there is a real potential for shifting the buildings electric energy usage. This project will involve an initial small-scale evaluation of both small and large commercial buildings to address technical potential and customer acceptance. This project's key aspects include:

• Evaluation of implementation requirements and obstacles to assess technology readiness,
• Use of field results and energy simulations to evaluate demand-shifting potential for a limited number of building types and locations selected to provide the best indication of the wider potential of the commercial building stock, and
• Use of limited customer focus groups and surveys to evaluate customer acceptance of the demand-response strategies.

Southern California Edison (SCE), Purdue University, and University of California at Berkeley (UCB) will utilize communicating thermostats; add required instrumentation and use simulation, experimentation, focus groups, and customer surveys in a number of small commercial buildings. Pacific Gas and Electric (PG&E) and Sacramento Municipal Utility District (SMUD) will collaborate with Lawrence Berkeley National Laboratory (LBNL) in the selection of large commercial buildings to be audited to assess their suitability for demand response. Additional field analysis and simulations in the Santa Rosa Federal Office Building, plus one other building selected through the audit, will evaluate zone conditions and occupant comfort.

If results in the areas of technology readiness, customer acceptance, or demand reduction potential are positive, this research program may proceed to subsequent phases leading to potential market implementation of demand shifting with thermal mass.

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