Heat Pumps: Game-Changer in EV HVAC Systems
As far as vehicular systems go, a vehicle’s HVAC system is likely not going to win the “most interesting component” award with respect to the average person. To an EV technician however, the EV HVAC system represents a sophisticated balance between performance and efficiency.
Of course, not all HVAC systems are created equally; new systems utilizing heat pumps as a two-way system create some unique advantages. In this article, we’ll take a closer look at why HVAC systems play such an important role in a vehicle’s performance and how heat pumps, of all things, can boost range and performance in electric vehicles.
Why Heating and Cooling Systems are Important?
Traditional heating and cooling systems draw a fantastic amount of energy from the vehicle’s battery on start-up. Most people who live in temperate zones (i.e., places that experience four distinct seasons) will have noticed that starting a vehicle in extreme cold is very different from starting it in warm weather. Simply put, depending on environmental conditions, the power drawn from the battery can vary significantly throughout the year. It is therefore beneficial to any automaker selling vehicles in these zones to develop a heating and cooling system that can operate as efficiently as possible, in spite of external temperatures. While important, power draw considerations are not the most critical factor associated with a vehicle’s HVAC system.
So why are heating and cooling systems so important? Consider for a moment how much heat is generated by an engine. A typical combustion engine (that operates by burning gases) can easily reach temperatures ranging between 195 to 200 degrees Celsius. Left unchecked, this heat can cause serious and expensive damage to a vehicle’s engine. Dissipating heat is arguably the most important function of the HVAC system, so it is understandable that considerable research and resources are pooled into developing a better system. Some of the newer systems consist of advanced heat pumps coupled with new types of coolants that will vaporize much more quickly, which in turn allows heat to dissipate significantly faster.
While EV motor temperatures don’t reach anywhere near those temperatures, the performance and range of the vehicle is intrinsically tied to ensuring the batteries are heated/cooled to optimal temperatures.
How Does an EV’s HVAC System Work?
We’ve already seen that EV engines don’t get nearly as hot as a combustion engine, but that doesn’t mean the vehicle doesn’t “manufacture” heat. In fact, we see a remarkable similarity in the mechanism responsible for heating and cooling systems in electric vehicles as we do in traditional vehicles. It’s fair to say that the primary difference between the two lies in the power source of the compressor driving the heating and cooling system. In an ICE vehicle, this would be the crankshaft, whereas the power source driving the HVAC system in an EV will of course be the bank of high-powered batteries.
We’re beginning to see the introduction of heat pumps into more of the contemporary EVs rolling off the assembly line. An air-to-air heat pump is powered by a lithium-ion battery and can operate in both heating and cooling modes. Warm air produced by the heat pump is directed into the cabin. The process for cooling air is slightly more complex; air must travel through a condenser, humidifier, expansion valve, and evaporator before it is delivered at the desired temperature (more on that later). Interestingly, the method in which AC is delivered to the cabin in EV has been qualified as “simplistic” by conventional automakers that some manufacturers are looking to emulate the process in ICE vehicles. It’s believed that in doing so, ICE vehicles could reduce fuel consumption and in turn reduce each vehicle’s total carbon footprint.
We know that heat pumps derive their power from the vehicle’s battery banks, and that there are four principal pieces to the system – the compressor, condenser, expansion valve and humidifier – but let’s look a little deeper into how all of it works in either mode. The first piece, i.e., the compressor, is powered directly by the motor. During the condensing phase, heat is extracted from the refrigerant which in turn heats the air. Alternately, the evaporation phase allows heat to be transferred to the refrigerant, thus cooling the air. This is how the heat pump system can operate in either mode to deliver the required air temperature.
Advantages of Heat Pumps in an EV HVAC System
One of the main reasons why heat pumps have become so popular of late is because they have the ability to utilize “free” thermal energy from the air using condensers and evaporators. Tests have shown that this approach to heating and cooling requires less energy than a conventional HVAC system. In a vehicle, less energy to power one system generally translates to improvements in performance for the remaining systems. For a bit of context, when the system is tested at temperatures between zero and 10 degrees Celsius, the heat pump requires approximately 1 W of energy to operate. This translates to a power savings of at least 50%. When considering energy consumption relative to AC usage during hotter periods, the general rule of thumb is anywhere from 5-15% of a vehicle’s total energy output is required for environmental controls. In an EV, this can seriously reduce the range of the vehicle. If that wasn’t bad enough, this ratio can double during the winter months to nearly 30%. Fortunately, the use of heat pumps will not require nearly as much energy to achieve the same result and thus the vehicle’s range will not be reduced to such a drastic degree.
Heat Pumps Are an EV Performance Game Changer
Electric vehicles are built to be efficient, environmentally responsible alternatives to conventional vehicles. Having said that, EV manufacturers are consistently pushing the limits on what is possible. Heat pump technology is being leveraged to maintain comfort without negatively impacting the range of the vehicle. If you’re interested in a career as an EV Technician, reach out to a program coordinator at George Brown College today and explore the various certificate programs that we offer.