Audi Electric SUVs Offer CO₂ Heat Pump to Boost Driving Range

German automaker Audi, a subsidiary of Volkswagen, has introduced electric vehicles that offer an optional heat pump with CO₂ (R744) technology that efficiently heats or cools the interior very quickly,  “especially on longer journeys.”

Unveiled on April 14, the vehicles – the Q4 e-tron and Q4 Sportback e-tron – are Audi’s first compact electric SUVs. These are among the first cars – electric or gasoline-powered – to offer CO₂-based thermal systems as an alternative to HFO-1234yf.

The optional CO₂ heat pump uses the waste heat from the vehicle’s high-voltage electric components and the ambient air to control the climate in the interior. “This makes another contribution to increasing efficiency, especially on longer drives,” said Audi in a statement. In particular, the heat pump can reduce the “loss of range that climate control causes,”especially in winter.

The heat pump uses “eco-friendly CO₂ as a refrigerant, which flows through the circuit at high pressure,” Audi added.

In heat pumps for electric vehicles, CO₂, with its thermodynamic properties,is considered to have advantages over other refrigerants, noted Armin Hafner, Professor in refrigeration at NTNU (Norwegian University of Science and Technology),, "The new focus of the automotive sector towards powertrains with alternative energy sources to enable these vehicles to drive over long distances must include energy-efficient heating concepts," he said in an interview in 2019. "As most of the new vehicles will not rely on burning fuel in the future, the amount of surplus heat is very limited. The energy management is even more advanced, since different parts need to be cooled or heated to enable a safe and efficient drive.

"Taking all these aspects and flammability/toxicity issues into consideration, the number of options for the active heating and cooling of both the passenger compartment and important parts are limited," he added. "CO₂ has proven to be the champion, as we will see soon when these new vehicle platforms are introduced by the remaining OEMs."

Drivers of the Q4 e-tron can control the pre-entry climate of the interior from their smartphones using the myAudi app. This includes a function to heat the seats, the exterior mirrors and the rear window, while setting the preferred  interior temperature. Pre-entry climate control works even if the car is not charging via the power grid, though the car’s driving range would then be lessened.

The Q4 e-tron models comprise three drive versions (125kW, 150kW and 220kW), all offering zero local driving emissions, and charging times of around 10 minutes for sufficient power to travel about 130 kilometers (80.8 miles) in ideal conditions. The rear-wheel drive Q4 40 e-tron achieves a range of up to 520 kilometers (323.1 miles).

The vehicles go on sale in Europe in June 2021, with prices starting at EUR41,900 (US$50,217) in Germany, where customers can claim a subsidy of EUR9,000 (US$10,784).

CO2 heat pump in VW electric cars

Last December, Audi parent company Volkswagen started offering a CO₂ heat pump to supply heat and air conditioning in electric vehicles, becoming one of the first car makers to do so.

"All models of the new ID [Intelligent Design] like ID.3 and ID.4 are equipped with an R744 AC and heat pump," said Christian Buhlmann, Head of Communications, Technology and Innovation, for the company. 

On April 15, the ID.4 EV was named to Autotrader’s list of 10 Best Electric Cars for 2021.

Another German automaker, Daimler, has been incoporating CO₂ air conditioning in some models of gasoline-powered Mercedes-Benz cars since 2017 as an alternative to R1234yf. These include the S 400 Coupé, all variants of the S-Class (Sedan, Coupé & Cabriolet) in the main volume carriers S 560 and S 400 d. Also in the E-Class, the CO₂ air conditioning system is available in some variants as part of the Thermotronic equipment.