| Jul 13, 2022 |
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(Nanowerk News) Set by default to turn on before dawn, smart thermostats unintentionally work in concert with other thermostats throughout neighborhoods and regions to prompt inadvertent, widespread energy-demand spikes on the grid.
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The smart thermostats are saving homeowners money, but they are also initiating peak demand throughout the network at a bad time of day, according to Cornell University engineers in a forthcoming paper in Applied Energy (“Unintended consequences of smart thermostats in the transition to electrified heating”).
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“Many homes have their smart thermostats turn down temperatures at night in the winter,” said Max Zhang, a professor at Cornell’s College of Engineering and faculty director at the Cornell Atkinson Center for Sustainability. “The temperature can be programmed to ramp up before you wake up – and you’ll have a warm house. That’s the smart thing to do. But if everyone keeps their default setting, let’s say 6 a.m., the electric grid suffers synchronized demand spikes and that’s not smart for the system. That’s the challenge.
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“As we electrify the heating sector to decarbonize the grid,” he said, “this so-called load synchronization will become a problem in the near future.”
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In 2021, about 40% of U.S. homes had smart thermostats, as utilities encourage adoption, according to the paper. Zhang, together with co-author and Ph.D. candidate Zachary Lee, examined wintertime smart thermostat data for more than 2,200 homes in New York state, noted for its cold winter climate and a mix of urban, suburban and rural communities.
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Homeowners purchasing a smart thermostat can opt to share their data anonymously with electric utilities for research purposes.
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Lee and Zhang investigated “setpoint behavior” and learned that most homeowners use the smart thermostat’s factory-default settings. Evidence showed that residents remain confused about how to operate their thermostats and are often unable to program it.
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In fact, their data indicates homeowners achieved energy savings of only 5% to 8%, far less than the devices’ potential of 25% to 30%, Lee said.
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If hundreds of homes have their smart thermostat set to turn on at 6 a.m., the electric grids see a peak at 6:05 a.m., which is about an hour before daylight during New York state winters.
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While the setpoint schedules are designed to achieve the energy-saving benefit, the peak demands are concentrated primarily when renewable energy is unavailable – aggravating the peak demand by nearly 50%, according to the paper.
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Without a tenable way to store energy from renewable sources like solar power, the electric utilities will be unable to supply this peak demand, which prompts fossil-fuel generators to satisfy the power load. “This can offset the greenhouse gas emissions benefit of electrification,” Lee said.
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Zhang noted ways to address the growing pressure on the grid, such as educating consumers on how to use smart thermostats and staggering the morning ramp-up times. “The problem is not straightforward, due to the security and privacy issues involved with homeowners,” Zhang said. “In the end, however, we have to make smart thermostats even smarter.”
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