Water heaters use large amounts of energy. The ability to them control remotely could save substantial amounts of power and money. Congress just passed a law permitting this to be done on a large-scale. Thus, on a hot day, the utility might cut power going to hot water heaters to enable that power to be used for air conditioning demand. Conversely, water heaters could be turned on if there is a temporary oversupply of power. All this happens very quickly in response to supply and demand. The switching back and forth can happen in seconds, or just a few minutes, not long enough to seriously impact available hot water since it only controls some of the power, as shown in the image.
It’s not just utilities that are using water heaters for capacity demand response which are celebrating. Hot water heaters are also increasingly being tested as grid-balancing assets. In Hawaii, water heaters are being tested for frequency regulation and contingency reserves, while in the Pacific Northwest they are being tested to balance wind resources in five-minute intervals.
Here’s how it works.
Grid-interactive water heaters add bidirectional control to electric resistance water heaters, allowing a utility or third-party aggregator to rapidly toggle them off and on. This functionality turns a fleet of water heaters into a flexible energy-storage medium, capable of increasing and decreasing the load on the grid on a second-by-second basis.
GIWHs can’t supply electricity, but they provide exactly the same functionality by reversing this equation: They can modulate the load in order to follow generation. In times of overgeneration, fleets of water heaters can be switched on to absorb excess power, and in times of undergeneration, they can be switched off to shed load and redistribute the existing electricity on the grid. Thus, aggregated GIWHs can act as virtual power plants to quickly and effectively control the amount of power on the grid. Moreover, these fleets are completely scalable and can perform this functionality within seconds.