An energy storage solution may already be in your basement
The much publicized Tesla Powerwall battery offers a way for homeowners with solar panels to store their energy for use at night as well as help utilities manage the grid.
Yet a decidedly less flashy piece of equipment residing in basements and closets of homeowners holds much greater potential as a residential battery – electric water heaters.
For the past 30 years Great River Energy (GRE) has deployed electric water heaters in homes to manage loads. Today more than 110,000 homes – around 20 percent of its to customer base – have water heaters that collectively, according to the utility, amount to a gigawatt of storage.
GRE’s approach is finally receiving broader recognition as the Community Storage Initiative (CSI), a new national effort, ramps up to push for greater use of water heaters and electric vehicles for storage.
The initiative has received support from Duke Energy, several Minnesota cooperatives and other co-ops in Wisconsin, Pennsylvania and other states. Organizations involved include several major national associations, the Edison Electric Institute (EEI), the Natural Resources Defense Council (NRDC), Peak Load Management Alliance (PLMA) and the Rocky Mountain Institute.
Chairing the initiative is Great River Energy member services director Gary Connett, a veteran of the co-op’s water heater storage program and evangelist for community storage.
Along with a push for more community storage, the CSI released a study by the Brattle Group which showed water heaters consume on average 15 percent of household energy use.
Consumers can save money and reduce carbon dioxide emissions by 30 percent by using water heaters as a “thermal battery.” The study also revealed that emissions drop to 50 percent by deploying heat pump water heaters.
Connett spoke to Midwest Energy News about the CSI and GRE’s long standing behind-the-meter program that offers members rebates and deals to buy water heaters.
Midwest Energy News: Why is community storage important?
Connett: There’s a renewed interest in the load side of the business. We didn’t pay much attention to the load in the past but today we need to. Everyone is searching for the magic battery, from academia to researchers to the (utility) industry itself. But one could consider the water heater in everyone’s home as a battery.
How so? It’s hard for me to get my head around the water heater as a big Duracell in my basement.
It’s not a battery in the sense of what we think of as a battery. But the grid sees water heaters as batteries because they absorb energy in the night time hours when energy is abundant because the demand curve has dipped. At night is when we charge water heaters.
How much energy do they store?
Each water heater absorbs 13 to 14 kilowatt hours (kWh) of energy every night. The next day that water heater is discharging energy in the form of hot water, not in the form of electricity. At Great River Energy we store a gigawatt of power every night in water heaters.
Are they typical water heaters?
No. The water heaters we use are large volume, large capacity, collective resistance water heaters. They’re going to be 85 to 100 gallons in size, which is far larger than a normal water heater in someone’s home. We have the storage capacity to get customers through a long period of time without any energy being applied to their water heaters.
How does that work?
We charge water heaters from 11 p.m. to 7 a.m. For the remaining 16 hours of the day they no longer receive energy. There’s enough hot water to get the homeowners through the next day. There are times during the night when energy on the grid is free, or negative in price. We can heat water at an extremely low cost.
What if a customer has natural gas?
They can’t participate in the program. But we’re finding in new homes that having a natural gas water heater is quite expensive. You need an exhaust vent and an intake vent. In some cases new homes are choosing electric (water heaters) because they require two less penetrations in the walls and roofs. It’s a simple installation for contractors.