EVs get efficiency boost from new heat pump technology

In electric vehicles, how every electron is used matters.

That's especially important in heavy, aerodynamically challenged pickups and SUVs. One of the best examples is the 2024 Ford F-150 Lightning.

The version that just went on sale won't look much different from the 2023 model. But engineers made a big change that will enable the vehicle to use electricity more efficiently, especially in cold weather.

The Lightning has a heat pump system developed with supplier Denso that reduces energy consumption. Previous F-150 Lightnings have resistive heaters, which use electricity to produce heat — think of the coils in a toaster. That system guzzles electricity.

Ford would not say how much the switch to a heat pump would extend the 2024 Lightning's range in cold weather but acknowledged the move would improve efficiency. The vehicle's EPA range estimate is unchanged from 2023. In online forums and videos, Lightning owners have complained that the pickup loses 20 to 30 percent of its range in frigid temperatures.

Although most efforts to increase EV range and efficiency involve battery size and chemistry, power electronics, curb weight and aerodynamics, the heat pump plays a major role in EV efficiency as the temperature drops.
"The heat pump enables all the other systems to do their jobs better," said Rob Cardno, a director in Denso's Green Technology Engineering group.

Heat pumps are not new. They have heated and cooled buildings for more than a century. But its journey into the automobile is just starting.

With the first generation, engineers were just figuring out how to heat and cool a vehicle, said Mark Dawson, Valeo's customer chief engineer for thermal products.

Most major suppliers — including Valeo, Denso, Bosch, Highly Marelli and Hanon Systems — are working on second- or third-generation automotive heat pumps. Unlike most components, which tend to become smaller and less expensive with successive generations, heat pumps are expected to become larger and more complex as automakers use them to collect heat from a growing number of vehicle systems.

"We can take advantage of heat scavenging opportunities in the electric axle, and we can move that energy around" to preserve battery charge, Cardno said.

Heats pumps are responsible for cooling and heating the vehicle's interior, battery pack, power electronics and several other parts of an EV.

Keeping those components at the proper temperature is key to EV efficiency. In cold weather, the battery pack will enable longer driving ranges if it is pre-conditioned, or warmed, before the vehicle leaves the driveway. In hot weather, the batteries, power electronics and charger need to be cooled for efficiency and safety.

The major components of a heat pump include a compressor, condenser, evaporator, expansion valve and a refrigerant, either liquid or gas. In a nutshell, a heat pump removes and transfers heat from air or from components. The refrigerant inside the heat pump system is either heated or cooled. Air passing over the condenser changes temperature, heating or cooling the cabin.

In an internal combustion vehicle, the engine's coolant, when it warms up, is the source of heat for the interior, while the air conditioning system, in a separate circuit from the heater, relies on a compressor, condenser, evaporator and refrigerant to cool the interior.

Heat pumps share several of the same components as traditional heating, ventilating and air conditioning systems — and at least one trait: Whenever either system is in operation, the vehicle uses either more gasoline or more electricity. But engineers say there are plenty of areas where heat pump efficiency can be improved.

At Denso, engineers have taken a modular approach to improvements. For example, combining the valves that were spread throughout the vehicle into a single manifold reduced the number of hoses and connections and lessens the chances of leaks, Cardno said.

One of the most promising areas where efficiencies can be gained is the software that controls the heat pump.

"It comes down to how well you understand where the energy is going, when it is going to get there, what the physics are and the dynamics that are happening at that moment in time," Cardno said.

The next generation of Valeo's heat pump will likely weigh less, consume less energy and deliver heat faster, Dawson said. The more heat that can be captured from the EV's mechanical and electrical components, the less electricity is needed to produce heat.

Suppliers are looking at different liquids and gases, such as propane, in the heat pump system. Some heat pumps use the same refrigerant as air conditioning systems, while others use glycol, the coolant that is in a combustion vehicle's radiator.

Despite heat pumps using less electricity than resistive heaters, they are not likely to replace them because of cost and other factors. For a heat pump to work at top efficiency for the lowest cost, suppliers have to be involved in the vehicle's design when the car is being engineered.

For instance, an EV's computer system generates a lot of heat and can be cooled by a heat pump. But if the car is not engineered for the heat pump's plumbing to be safely routed to the computer, a retrofit might not be possible.

Resistive heaters are likely to remain in lower priced EVs because of cost, and in more expensive vehicles they could be paired with heat pumps to deliver heat faster in cold weather.

Regardless of how heat pumps evolve, suppliers are hoping that consumers' experiences with heat pumps mirror those of Connecticut graphic artist Blake Tovin. He doesn't notice the performance of the heater in cold weather or the air conditioner in the summer when he drives his Polestar 2, his first electric car. The system just works, he said.

And the drain on range in the winter when the car is cold was not a consideration when he leased the car in 2021. Tovin's 15-minute commute to work is comfortable in cold weather. He uses the heaters in the steering wheel and seat to stay comfortable as the car warms up.

If there is a gripe, Tovin said digging in the screens to find the right settings is bothersome, but not the performance of the heat pump.