This column has previously featured companies storing energy in innovative ways with lithium-ion, nickel-hydrogen, iron redox flow, and even gravity batteries, so my ears perked up when I heard about a German company marketing an innovative thermal battery and providing “Heat-as-a-Service” to industrial clients.
Around half of all energy use is spent on heating something, from melting steel to providing warm showers to drying agricultural crops, and the industrial sector is a particularly heavy spender. The concept of HaaS seemed so novel, but I could only imagine it applied to industrial processes.
Imagine my surprise upon discovering that I can buy and install a high-efficiency thermal battery for my home in the form of a heat pump water heater.
Residential HPWHs have been sold on the U.S. market for about fifteen years by large, well-known distributors through nationwide hardware store chains.
HPWHs works like your kitchen refrigerator but in reverse. Instead of pulling heat out of a cold space and releasing it outside, it pulls heat from the surrounding air and transfers it into the water in the tank.
Ambient warm air is drawn into the heat pump, where the warmth turns a refrigerant from a liquid to a gas. The refrigerant gas is then compressed, which heats it further, then pumped through condenser coils inside an insulated tank filled with water. The hot condenser coils warm the water, and the insulation keeps it warm until it’s needed.
In a legacy electric resistance water heater, 1 kW of electricity generates 1 kW of heat. In a HPWH, 1 kW of electricity generates around 2-4 kW of heat, significantly lowering household energy use while washing clothes, dishwashing, and showering.
Another great feature of HPWHs and thermal batteries in general is their ability to release the energy put into them with very little loss. Lithium-ion battery installations—which convert electrical energy into chemical energy and back again—have round-trip efficiencies around 90%, a few percentage points above most other battery chemistries.
Thermal batteries, in contrast, convert electrical energy into heat. If thermal energy can be used directly, as in the case of a water heater, their efficiency is 98-99%.
HPWHs are so efficient that local utilities offer rebates to homeowners who install them. Paying people to use HPWHs makes financial sense to grid operators because grid congestion can be so costly during peak use periods.
Leave it to an entrepreneur familiar with the costs of grid congestion to devise an innovation that materially improves upon the already very efficient HPWHs.
Cala Systems, cofounded and led by a seasoned grid modernization executive, Michael Rigney, has developed AI-powered HPWH controllers that coordinate with the grid via Wi-Fi to schedule water heating when electricity prices are lowest.
Cala’s systems, which will hit the market later this summer, are designed to superheat water in the tank when electricity is cheap, then store it until needed. When someone turns on the hot water in the shower or starts the dishwasher, a mixing valve adds cool water to the superheated store to provide the appropriate temperature for the application.
These smart water heaters also communicate with other devices behind the homeowner’s meter (such as solar panels and battery systems) to heat water most efficiently given the home’s energy mix.
Unlike conventional water heaters, Cala’s system monitors a household’s hot water usage patterns and feeds these data into a predictive control algorithm licensed to Cala by the National Renewable Energy Laboratory. This algorithm lowers energy usage by determining the best time and speed to heat water, only heating as much as is needed. Users can increase heating through the Cala app if guests are visiting or the household otherwise exceeds its typical usage.
These innovations allow for a very efficient product–a heat pump water heater–to become even more efficient.
Rigney knows, as I know, the importance of increasing energy efficiency, decreasing carbon footprints, and decongesting our groaning legacy electrical grid. Intelligent investors take note.