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Battle of the Walls: Peak Reduction

  • 1.  Battle of the Walls: Peak Reduction

    BPA Staff Member
    Posted 07-08-2022 10:52

    By Rob Hammon and Steve Vang

    In the cooling-dominated Southwest, it is crucial to reduce residential A/C, which also drives summer peak demand. The added electricity to meet this summer afternoon demand is drawn from peaker plants that are typically among the most expensive and polluting per kW generated. Reducing and/or shifting A/C to lower-demand periods of the day could eliminate summer peak demand, which would reduce the need for peaker plants, reduce energy costs and pollution, simplify grid management, and increase grid stability. A strategy to achieve these benefits is to flatten the peak load by both reducing cooling requirements and moving the mechanical A/C to night and morning hours, when demand is low and compressor-based A/C is most efficient. Employing this strategy has the potential to reduce both total kWh usage and peak kW demand.

    Working under the DOE Building America program, the ConSol-led Building Industry Research Alliance (BIRA) team assisted Clarum Homes in the design and construction of three homes with identical floor plans but different wall systems and mechanical systems in Borrego Springs, California. (The authors work for ConSol.) Clarum's main objective was to find the best solution to building comfortable, cost-effective, super-energy-efficient homes with 90% reduced cooling requirements in the hot-dry climate of the American Southwest. One of the Building America objectives was to determine the impact of the three different wall systems in these homes on summer peak demand.

    The three different wall systems in question were (1) 2 × 6, 16- inches OC, wood-framed walls, insulated with Icynene foam; (2) structural insulated panels (SIPs); and (3) insulated concrete mass walls. The homes all have exposed, slab-on-grade foundations. All the exposed concrete slabs were dyed and textured, but they were not covered with any flooring that would reduce their thermal mass. The homes also had different cooling systems. 

    The experiment involved precooling the homes to 72°F during night and morning off-peak hours, from midnight to noon, and then letting them coast through the peak hours of the afternoon when electricity is most expensive by setting up the thermostats to 80°F from noon to midnight. The "coast" period was the period from noon to the moment when the indoor temperature exceeded the 80°F set point. The 80°F set point was chosen as being a comfortable afternoon indoor temperature when outdoor temperatures exceed 100°F.

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    Macie Melendez
    Editor in Chief, Building Performance eJournal
    Building Performance Association
    Moon Township PA