All of the air conditioning systems you’ve seen on our website recently are in vehicles with an internal combustion engine. However, practically everyone in the automobile business agrees that electric vehicles are the way of the future. Electric automobiles, like cars with internal combustion engines, feature air conditioners, but instead of utilizing an engine to power the compressor, they use electricity. As straightforward as that may appear, there are various aspects to consider while rethinking a typical air conditioning system.
Tesla is pushing the electric vehicle industry forward at breakneck pace. Tesla automobiles, in their own words, use a compressor “similar to that found in a residential refrigerator,” except it runs on 400 volts. It is positioned in the front of the car and receives electricity from the car’s battery pack, or Energy Storage System (ESS) in Tesla parlance. The compressor pushes the refrigerant through the chilling unit and cools the air before it reaches the AC vent, just like in your IC engine-powered car.
The heating system is a little trickier. The heating system in cars with IC engines gets its heat from the engine’s coolant. Around 30% of the heat produced during combustion is transmitted to the coolant, resulting in a ready source of heat. As it passes through a heater matrix (a miniature radiator) containing the hot engine coolant, the incoming air is heated. None of these components are present in an electric vehicle.
Tesla has substituted an electric heater for the heater matrix. They had to make careful, though, that the heater didn’t draw too much power from the ESS. They employed a heater with a positive temperature coefficient (PTC) for this. It’s a resistor that increases its electrical resistance as the temperature rises. This reduces the amount of energy it consumes while also ensuring that the cabin does not become excessively hot.
But that isn’t the case. Another issue with electric automobiles is keeping the battery pack at the right temperature for extended life and effective functioning. The ESS of a Tesla is equipped with its own cooling system, which includes a pump that circulates a water/glycol antifreeze mixture around it as well as an independent chilling unit. This also distributes heat within the battery pack, ensuring that temperature differences between cells are kept to a minimum.
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The heat from the coolant is used to heat the passenger compartment in vehicles with internal combustion engines. Air conditioning compressors and power steering pumps are also powered by the engine. Because an electric automobile has no engine, it relies only on the energy stored in its batteries for heating and cooling, as well as auxiliary systems such as power steering and brake boosters. The more efficient these technologies are, the greater the vehicle’s range.
To warm the passenger compartment, many electric cars use old-fashioned resistance heaters, which are the same technology used in electric baseboard heat in buildings. It works well, but it consumes a lot of electricity to do so. Heat pumps are used in other electric cars, which are more efficient but also more expensive. A motor still drives a rotating compressor in air conditioning.
A group of experts has received funds from the European Union to do research into more efficient climate control technologies. Horizon 2020 XERIC is the name of the project. This week, the researchers unveiled the invention of an entirely new technology that uses less energy to heat and cool than traditional systems. The fact that their new technology divides the process into three parts heating, cooling, and humidity management is a key aspect. After there, each of those components can be built to perform as efficiently as feasible.
“We demonstrated that, compared to present systems that rely on electric direct heating in the winter, the prototype can save more than 50% of the energy consumed for air heating, cooling, and dehumidification throughout the year.” Furthermore, under extreme summer conditions, it can save up to roughly 33% of the energy consumed for air conditioning and dehumidification,” explains project coordinator Gaeta Soccorso.
According to the Green Car Congress, the researchers developed a hybrid system that combines a liquid desiccant cycle for removing moisture from the air with a standard compressor for cooling. The researchers developed a three-fluid mixed membrane contactor to extract humidity. Because that’s a mouthful, it’s abbreviated as 3F-CMC. The membrane interface captures the humidity in the air, requiring very little power from the battery. The team created an electronic control system for the compressor that uses a variable frequency drive compressor and a brushless direct current motor that is up to 95% efficient.
Any form of transportation, including buses, trains, trucks, and boats, can use the XERIC system. It can even be utilized in automobiles with internal combustion engines to more efficiently offer climate-controlled air for passengers, saving fuel. The project could potentially lead to more efficient building climate control systems. Air conditioning is expected to require an increasing amount of available electrical energy as the planet heats.
The team already has functional prototypes available for potential clients to try out, and they’re looking at forming agreements with OEMs and tier one suppliers. As the electric vehicle revolution progresses, everything that helps improve the range of electric vehicles is excellent news.
How do electric cars keep their interiors cool?
Customers want efficient and powerful heating and cooling in their vehicles in areas where electric cars are or will be a substantial part of the transportation burden in the future. Engineers have to move away from the vehicle’s ability to exploit the significant quantity of extra heat produced by internal combustion engines to support system advancements presently occurring in completely electric vehicles. Temperature regulation in a battery vehicle is a challenging task since the power source degrades in predictable ways under normal settings but in unpredictable ways under extreme temperatures.
Heat pumps, vaporized coolant, and innovative coolant flow system designs by EV manufacturers are among the most recent technologies used to improve EV interior comfort. Resistive heating, in which power from the battery is converted to heat simply by running power via resistant wiring, is the most inefficient approach employed in the last decade, and it consumes a significant amount of battery capacity. Heat coefficients, gas exchange, heating/cooling transition, start-up delivery, and battery lifecycles all play a role in the viability of a dependable cabin HVAC system, as we’ll see. Costs will be an issue for manufacturers, as they always are.
Although it may seem self-evident that temperature is the most important factor in heating and cooling, we’re talking about seasonal outdoor temperatures and their impact on battery life and run time. The start-up of heating and cooling pumps/fans, like many other automobile systems, consumes an excessive amount of energy from the battery. In all temperatures, continuous running conditions are more steady, but starting up in the cold is significantly different from starting up in the heat.
Advanced heat pumps with innovative coolants that evaporate and condense faster are already being used by designers. Heat pumps with aluminum scroll compressors operate well at first, but under high pressure, they degrade quickly. (1) The utilization of electric vehicles in northern China during the coldest months of the year was investigated in this paper. The issue of compressors and low temperatures is addressed not only in terms of performance, but also in terms of initial and ongoing costs.
This experiment, which was recently completed in China to test coolant flow and vaporization, revealed that employing a rotary compressor and the proper coolant improves heating performance. The developers of this research put together equipment to keep a standard EV at 68 degrees Fahrenheit while the outside temperature was 14 degrees. Because compressors have a constant displacement but varying efficiency depending on motor speed, choosing the right coolant was crucial.
R134a, R407c, and R290 were used in the experiment. The efficiency of R407c pushed by rotary compression increased by 21 to 30%. Thermodynamic cycling with this coolant became less efficient as compressor speed increased. This is how the experiment with the compressor was set up:
- “Three heat exchangers were used in this system: an external heat exchanger, an inside condenser, and an inner evaporator.
- The on/off bypass valve and model air door of the HVAC were used to transition between cooling and heating modes.
- High-temperature, high-pressure refrigerants pass through the inner condenser with no heat exchange.
- The outer heat exchanger and inner evaporator were utilised as the entire system’s condenser and evaporator at the time.”
The development of stronger heat pumps is one of the keys to a more efficient system. Mitsubishi Heavy Industries (MHI) pushed a heat-pump water heating system through development by keeping an eye on prices, configuration, and response. (2) An sophisticated heat pump is combined with a “next-generation electric compressor” in this unit. Both innovations are integrated into an existing cabin unit seen in many electric vehicles today, according to MHI, and the system provides the same level of comfort as an electric system.
- In tests, new electric compressors increased efficiency by roughly 10%. It’s the tiniest compressor on the market for the job, and it maintains its efficiency rating across all RPM ranges.
- To have a tiny platform, water-cooling condensers use laminated plate heat exchange technology. “For the bed materials (refrigerants and coolants),” the plates “create a flow channel.”
- At 0C, a real-time equipment test in a fully functional EV revealed improved warm air flow. The temperature in the cabin increased more quickly, but the temperature of the incoming air at foot level stayed constant.
- MHI claims that combining a traditional water heating system with this type of system in the future could make supplementary heating even more efficient in extremely cold areas.
The HVAC system’s components aren’t the only ones being studied and modified. Compressors and motors are getting smaller, which helps batteries use less energy, but materials research is becoming more important in development at the molecular level.
A thin film coated with conductive carbon nanotubes creates resistive heat using an electric current and the collision of nanoparticles, according to a report (3) on ultra-thin coatings. While the idea of resistance heating is now applied in EVs, the copper wire embedded in silicone is more heavier and larger, according to researchers from the Fraunhofer Institute in Stuttgart. Hard interior surfaces, such as armrests and seat backs, can be covered with this film.
Carbon nanotubes are increasingly being used in a variety of automotive and aerospace applications. The film does not retain heat, but it distributes it uniformly and quickly reheats.” This film heater debuted in 2015 and is still being developed. “The material cools down almost as quickly when the driver turns off the heating. The user can adjust the desired heating output indefinitely. Isolated flaws have no effect on functionality. Even tiny metal breakage in wire-based heating systems, for example, can cause failure,” according to the paper.
Currently, the film is bonded to surfaces in strips. The chemical will then be turned into a spray. “This would make the manufacturing process much more cost-effective especially when compared to wire-based systems.”
Some manufacturers are looking into adding a tiny conventional gasoline tank to electric vehicles, believing that no matter how popular EVs become, fossil fuels will not go away anytime soon. The inexpensive expense of a heating system for this reason more than offsets the vehicle’s increased weight. Natural gas/propane appears to be the most common fuel source these days, as it is inexpensive, plentiful, and portable.
Propane cars are widespread in cold locations like as Scandinavia. This fuel has the advantage of providing a lot of lost heat while being at least 12 percent less polluting than diesel. Using an enclosed burner to trap heat in an electric car is much the same as trapping heat from a propane motor. The principles of induction and conversion are the same.
If a safe, efficient burning method can be installed, propane, or LPG, has a number of advantages (5): it is always liquid and never freezes; it is readily available and inexpensive; and it provides enough BTUs per tank to heat EV interiors for the duration of most battery charges, allowing for refills when the car needs to be charged. LPG has also been employed in medium and big vehicles due to its high safety record and ease of filling and use. Propane can be simply replaced for refilling, and if safety concerns are addressed, an extra can be carried.
Do electric vehicles require air conditioning?
Earlier types of electric automobiles, such as the Nissan Leaf, employed air cooling. As electric cars become more prevalent, safety concerns with exclusively air-cooled battery packs have arisen, particularly in hot climates. Other automakers, such as Tesla, believe that liquid cooling is the most secure option.
Are there cooling systems in electric cars?
The cooling system in an electric car regulates the temperature of the battery pack and part of the electronics. A cooling loop is used in most electric vehicles. Ethylene glycol is commonly used as a coolant in this loop. An electric pump circulates the coolant through the batteries and portions of the electronics.
Do electric cars get too hot?
Yes, electric motors can and do overheat, much as internal combustion engines. Despite the fact that electric automobiles use a different energy source, the engine still expels a large amount of energy, which includes heat as a consequence.
What method does an electric automobile use to defrost its windows?
In cold weather, windows can fog up, necessitating the usage of the front and rear defrosters.
When it comes to the windshield, I use maximum defrost.
Defrosters may use more battery capacity than conventional heat, depending on your electric vehicle, but they will clear your windshield quickly and effectively.
Over time, I’ve discovered that using this strategy allowed me to get in an extra 5 to 10 kilometers.
Resistance heating does, in fact, deplete battery capacity. However, not utilizing it during the winter will almost certainly result in a loss of passengers, as well as generating such a disincentive that you will not want to drive your electric car no matter how warm you are.
Many electric-car owners are unaware that turning on the heat after it has been turned off for a long time consumes more energy since the heater has to work harder to warm up the cabin.
I keep my heater on at 70 degrees and increase the fan speed a notch at a time if I need more warmth.
After preconditioning the interior, the automobile will not have to work as hard to maintain a comfortable cabin temperature.
With the heat on, how long can an electric car idle?
People were stranded on a Virginia roadway for up to 19 hours during a winter storm, according to recent accounts. People used their cars’ engines to stay warm, heating their cabins and preventing hypothermia. The gasoline indicator progressively approaches empty, giving occupants a decent number of hours of comfort until the situation becomes dangerous. While it is conceivable to run out of fuel in such a situation, traffic jams rarely remain long enough for fuel endurance to be a serious worry.
As the use of electric vehicles grows, so does the variety of climates and geographies in which they are driven. Electric vehicles are no longer limited to sunny California! Many people are aware of the measurable limitations of an electric vehicle’s range in cold weather (if not, check out our report on the truth about winter EV range loss). But what about an EV’s safety and endurance under adverse situations, such as a whiteout? What happens if an electric vehicle becomes caught in a winter storm, and can it keep its occupants warm for as long as a car with an internal combustion engine?
There are several misconceptions regarding how long you can survive in a stranded EV during a winter storm, with most time estimates being significantly overestimated. But fear not, we’ve got battery science on our side!
To begin, consider the following facts about gasoline cars when they idle in cold weather:
- If the car gets stranded in a snowbank, avalanche, or other air-restricted situation, carbon monoxide is produced, which can be fatal.
- Idling endurance is mostly governed by the amount of gas in the tank; refueling is feasible if you have spare gas or if someone donates a spare canister, but transporting gas in dangerous driving circumstances comes with its own set of dangers.
- You may be able to eke out 30+ hours of idling before running a tank from full to empty, depending on the car.
- If the automobile doesn’t need to move, gas cars heat their cabins with waste heat created by the engine’s moving parts, which is an inefficient technique.
In an electric vehicle, the first concern about idling in cold weather is moot. There are no tailpipe pollutants to be concerned about, and an electric car’s heater may operate properly even if fresh air ventilation is not available.
The second reason is that both gas and electric cars have a lot in common. The amount of time you may sit in your car with the heat on is controlled by the amount of fuel in your tank or the state of charge in your battery. However, unlike a gas automobile, charging an EV when stuck is not common or practicable. Mobile chargers and emergency batteries, on the other hand, will become increasingly desirable as electric vehicles become more ubiquitous.
Given the wide range of fuel efficiency and tank sizes available in gas cars, it’s difficult to pin down an exact figure for how long one can idle in cold weather. We’ll start with a 30-hour baseline, assuming a full tank of gas in a typical ICE vehicle.
Finally, whereas a gas vehicle’s cabin heat is generated in an inefficient manner, the same cannot be said for most electric vehicles. Because there is little waste heat in a stationary electric vehicle, cabin heat is generated via heating resistive elements, drive stators, or heated seats or steering wheels. This heat consumes energy, and determining how much it consumes influences how long an EV can keep its passengers warm.
By the Numbers
Let’s say we have an average EV in 2022, with a range of roughly 250 miles and a battery capacity of around 70 kilowatt-hours. In general order from most crucial to least significant, there are five elements that impact how long you can heat an EV while sitting:
- Battery size: Assuming the EV described above, a driver will have enough of energy to work with. You have more electricity at your disposal than the average American home uses in two days when fully charged (60kWh).
- Battery state of charge (percentage left): Assume you’re trapped in the same EV with 50% charge remaining. This leaves you with 35kWh of battery capacity, which is still a significant amount of power!
- Heater draw: This is where things get interesting, because EV heater efficiency varies greatly. Resistive heating is used in older EVs and some newer ones, such as the Rivian. This means that more electricity is drawn from the battery solely for the purpose of heating cabin air. This consumes a significant amount of energy. Other EVs, especially those that are relatively newer, use a heat pump to transport heat from the motor stators to the cabin. Even when the vehicle is inactive, transferring existing heat costs far less energy than generating new heat, yet additional heat may still be required. A heater may use between 1kW and 5kW of electricity, depending on the automobile and the size of the cabin, with more energy required to heat the cabin from cold than to maintain a warm inside. Tesla patented a method for transferring heat from motors even while they are not in use.
- Temperature of the outside air: The colder the outside air, the more heat is transmitted away from the car. As a result, it takes more energy to heat a vehicle’s cabin. In the 55-75 degree Fahrenheit range, EVs use the least amount of energy for heating and cooling. A vehicle idling in sub-zero temperatures will use more electricity to heat the interior than a vehicle idling in 32-degree temperatures.
- Accessory draw (onboard electronics, sound system, etc.): The amount of energy required to run onboard computers and other accessories in a car is maybe one of the least quantifiable aspects here. Depending on the car, this can range from 500 watts to more than a kilowatt, although several anecdotes and trials show that around 1 kW per hour is normal.
How does all of this work in practice? Consider an electric vehicle with a resistive heater, such as the Volkswagen e-Golf. It’s a little car with a tiny battery and a tiny cabin to heat. Due to its resistive heating elements, all heat provided for the cabin is the same price whether the vehicle is moving or not. In temperatures ranging from 35 to 15 degrees Fahrenheit, drivers report a heater pull of 1.5-2.5 kW. On a 15-35 degree day, a 50 percent charge on a 32kWh battery translates to 6.5-10.5 hours of heat; double that on a full charge.
But what about a more current electric vehicle with a larger battery and more heating options, such as heated seats?
The Tesla Model 3 is here. Tesla has shifted from resistive heating to a heat pump for 2021. When it comes to heating their vehicles, drivers report a significant increase in efficiency. In sub-freezing circumstances, one customer slept in his Model 3 and ran metrics on it overnight, finding that the battery consumed 1.36kW per hour on average. This means that on a full charge, a Tesla with an 80kWh battery could keep you warm for about 59 hours, or around 29 hours on a half charge.