While the sales of electric vehicles have risen sharply, electric vehicle owners dare not open hot air in winter and dare not open air conditioning in summer, so many car owners call electric vehicles electric daddies. The freedom of air conditioning seems to be a threshold that electric vehicles can't get over. The emergence of heat pumps makes heat no longer rely solely on battery heating, can greatly improve heating efficiency, and at the same time, under the blessing of a new generation of thermal management system, air conditioning freedom can be achieved. The question is who has such a perfect solution.
Wen 丨 wisdom driving network Shuoqi
Can heat pumps make electric vehicles air-conditioning free?
Theoretically, yes. But the implementation process is difficult.
Before answering this question, let's first understand why the low temperature in winter will cause the battery life of electric vehicles to be greatly attenuated.
Among them, the attenuation of the battery at low temperature conditions is the root cause, and the low temperature performance of the lithium-ion power battery is manifested as the temperature decreases, the impedance of the power battery increases, the discharge voltage platform decreases, and the terminal voltage of the battery drops rapidly, resulting in a great attenuation of its usable capacity and power.
From the technical point of view, in the low temperature environment, the diffusion motion ability of charged ions in the positive and negative electrode materials becomes worse, and it becomes more difficult to pass through the passivation film between the electrode and the electrolyte, and the transmission speed is reduced.
Even after the lithium ion reaches the negative electrode, the diffusion inside the material becomes not smooth, and even lithium condensation may be formed at the negative electrode, which is reflected in the short-term sharp reduction of battery capacity and a long-term reflection on the shortening of battery life.
But the winter electric vehicle endurance decline is not only the above one reason, electric vehicles through air conditioning heating, air conditioning will convert the battery's power into heat, energy consumption is very high, a large number of consumption of power battery power.
The above two reasons have led to a significant decline in the current endurance of pure electric vehicles in winter compared with the advertised endurance.
At present, in order to solve this problem, R & D personnel mainly improve from the low temperature performance and thermal management of the battery.
The first is the research and development of low-temperature batteries, the current improvement of battery performance, mainly rely on the progress of materials, but the progress of materials requires the accumulation of time, and the current improvement of the low-temperature performance of lithium batteries is still a hot spot and difficulty in current research.
At present, mainstream manufacturers have set their sights on the thermal management of vehicles, heating batteries by improving efficiency, and heating air conditioners to achieve the effect of improving the winter endurance of electric vehicles.
Unlike fuel vehicles, electric vehicles do not have engines, so the vehicle heat management system can only rely on the air conditioning system, the battery and motor heat dissipation through the air conditioning compressor, heating through the air conditioning heat pump and PTC control.
In the extremely low ambient temperature, how to ensure that the car maintains a suitable temperature at the same time, so that it can be quickly defrosted, the battery is heated rapidly, the air conditioner temperature regulation maintains linearity, and the automatic air conditioner can be maintained at a high level of comfort, all of which belong to the content of the vehicle thermal management calibration, and the further pursuit is to use the least amount of electricity to achieve the above content, to minimize the degree of mileage reduction caused by the opening of the air conditioner.
Therefore, thermal management is not simply heating and cooling, it is through a complex system to keep each part of the car at the optimal temperature, simply put, thermal management is similar to making the components in the car like people use fever after using fever stickers; and when the cold is unbearable, you can use warm babies. Either way, however, thermal management between components is expected to reduce heat loss and improve efficiency.
In the mass production car, each brand will make trade-offs according to the positioning and use characteristics of their own products, come up with the most cost-effective solution, and then combine the software algorithm to optimize, which also makes the electric vehicles on the market perform very differently in thermal management solutions.
It can be said that in the current situation where the performance of the power batteries of various brands is close, thermal management has become the most important system for the winter endurance of electric vehicles, and it is also the embodiment of the technical hard power of various manufacturers.
——01——
Principles of thermal management system transformation for electric vehicles
Different from traditional fuel vehicles, the development of new energy vehicles is a big change for the thermal management system of automobiles. The thermal management structure of traditional fuel vehicles mainly includes air conditioning system and powertrain thermal management system.
Due to the change in power source, the new three-electric system has been added to the new new energy vehicle, so it is necessary to reconstruct the thermal management of batteries, motors, and electronic controls. In addition, the air conditioning system of new energy vehicles has also undergone major changes due to the transformation of power mode, from compressor components to heating systems, which need to be upgraded with technology and replaced by products.
In general, from traditional fuel vehicles to new energy vehicles, the thermal management system of automobiles has become more complex, and the importance of the whole vehicle has increased.
We take Tesla, the first large-scale mass production of electric vehicles, as an example, and the iteration of thermal management technology for new and old models is like a brief history of the development of thermal management technology.
Through the above table, we can see that the thermal management of the new model is gradually converted from the whole vehicle PTC to the way of heat pump and heat recovery to improve efficiency.
Here we need to clarify two terms, PTC and heat pump.
PTC in the car is the car heater, the full name is "Positive Temperature Coefficient", in the pure electric vehicle, the principle of PTC and electric heating appliances are similar, like rice cookers, induction cookers, air conditioners, etc., PTC technology is to generate a lot of heat by energizing thermal materials such as resistance wires / ceramics to provide the heat required by the vehicle.
If one is not enough, then add another one, or increase the power.
The heat it produces Q= I R * T, when the current is stable, the greater the resistance value, the greater the power, which means that the heat generated per unit time is also greater; when the current is stable, the resistance value is also stable, then the longer the time, the more energy is consumed.
However, due to the fact that the energy density of the battery is really small compared to gasoline, the energy density of the latest mass-produced lithium battery is 260 kWh / m3, while the energy density of gasoline is 8600 kWh / m3 and diesel is 9600 kWh / m3.
Even if all the electrical energy is converted to heat energy, the overall heat in the car is much less efficient than that of the fuel vehicle.
At this point, the engineer introduced a heat pump.
The introduction of this technology has been called "one of the best engineering designs" by Musk.
In theory, as long as the surrounding air is above absolute zero, its heat can be collected through heat pump technology, which means that heat pump technology can allow electric vehicles to drive normally in any extremely cold place on the earth, and keep the normal temperature required by people in the car.
However, the heat pump is not a new invention, and its principle can be simply understood as "moving the hot and cold air out and in", that is, the cold and hot air "porter", so that the temperature in the car reaches the ideal temperature, and more power can be saved in the power consumption.
Such a principle is also common in the current high-end household appliances, and we often say that "air energy" water heaters and "air energy" air conditioners apply this principle.
According to estimates, the current mainstream heat pump efficiency can exceed 100% at common temperatures.
In the heat pump, because the heat pump refrigerant vaporization temperature is lower than -20 °C, it can be vaporized under any other conditions above -5 °C, higher than -5 °C other conditions do not need additional auxiliary heating, by compressing the vapor of the refrigerant, the same reason heat pump in the heating cycle process can produce 400% thermal efficiency, and below -5 °C only need a small amount of electric heating to complete high efficiency operation, in the case of -18 °C, the best thermal management system can still achieve more than 200% thermal efficiency.
Therefore, in the current advanced pure electric vehicles, heat pumps have almost become the standard.
At present, the models applying heat pump technology mainly include BMW i3, Jaguar I-Pace, Audi e-tron, etc., and there are Weilai ES6, Roewe Marvel X, Nezha S and so on.
However, the efficiency of different brands and heat pumps varies greatly, and the factors here depend more on the manufacturer's control of the details of each heat.
——02——
A good thermal management system can recycle the heat you breathe
Last week, Nezha S, which will be pre-sold in the second quarter, is equipped with the first domestic vehicle system-level intelligent thermal management strategy, which has just completed the winter extreme cold test in the extremely cold environment of Heihe-30 °C in Heilongjiang.
Let's take this new car as an example to see what efforts the new domestic forces have put into the details.
Nezha S system-level thermal management, known as the opening of the vehicle thermal management, it means that from the crew compartment, battery, electric drive to electronic components thermal management are all open, to achieve the physical part of all components centralized and component control part of the concentration, on the one hand to achieve a 40% reduction in the number of pipelines, reliability increased by 50%. At the same time, the entire system widely uses elastic algorithms for intelligent control, which can minimize energy consumption under the premise of ensuring cockpit and battery heating.
This highly integrated design is also used in the design of heat pumps, using nine-way valves instead of 2 3-way valves and 1 4-way valve in traditional heat pump solutions.
The nine-way valve opens and closes precisely proportionally, enabling stepless power regulation via the VCU.
From the flow control valve and water pump, to the air conditioning compressor, the cooling fan on the front-end cooling module can achieve fine control to ensure that the battery, air conditioner, and electric drive work at the most suitable temperature.
And this degree of refinement to achieve battery waste heat recovery, motor waste heat recovery, battery natural cooling, heat pump battery heating, heat pump crew compartment heating and other energy-saving working modes, so that heat may not be wasted to the greatest extent, the degree of control and quantity of details even better than Tesla's proud "8 claws" 8-way valve.
The traditional heat pump can not be started in the environment below -10 degrees, the colder the weather, the lower the efficiency of the heat pump air conditioning, the worse the heating effect, and the lower the PTC heating energy consumption at low temperatures, which has a great impact on the endurance; Nezha S through the fine management of each component to support the efficient software system, its heat pump through the electric drive waste heat recovery to achieve intelligent collaborative control of various components of thermal management, the overall energy efficiency is optimal.
In the outdoor ambient temperature of -18 °C when the external circulation working condition is opened, the outlet air temperature can reach 48 °C, at this time the COP of the entire system can reach more than 2.05, and a single heat pump can meet the heating needs of the passenger cabin.
Nezha S's thermal management system uses heat pump + refinement + high integration + intelligent adjustment + energy recovery and other ways, through the adaptive intelligent thermal management control strategy, a single charge saves about 2%; the battery pack self-heating; the use of battery constant temperature liquid cooling system, 15 °C ~ 45 °C constant temperature accounted for 95%; -20 °C low temperature soaking for 6 hours, the battery temperature ≥ 0 °C; the battery self-heating during the discharge process, mainly through intelligent driving heating, winter endurance increased by about 4%.
It can be said that whether it is hardware design or software optimization, the thermal management technology of the latest products of the new forces of mainland car manufacturing is not weaker than that of foreign competitors.
In addition, whether it is batteries, batteries, intelligent driving, intelligent networking and other core technologies, China is also making rapid progress, and the iterative progress of each component will bring about the improvement of vehicle endurance, safety performance and experience.
——03——
The market-led electric vehicle market ushered in an era when technology was king
On February 20, the National Development and Reform Commission, the Ministry of Industry and Information Technology, the Ministry of Finance and other 12 departments proposed to continue to implement new energy vehicle purchase subsidies, charging facilities awards, vehicle and vessel tax reduction and reduction preferential policies in 2022, but the subsidy rate was 30% lower than in 2021. At the same time, the relevant departments confirmed that the subsidy policy for the purchase of new energy vehicles will be officially terminated in 2022, and vehicles licensed after December 31 this year will no longer be subsidized.
The subsidy for new energy vehicles will be officially cancelled after 2022, indicating that the new energy automobile industry in the mainland will completely complete the transition from policy-driven to market-driven. The head players of domestic new energy enterprises have also built a relatively complete industrial layout and supply chain system.
This makes the competition of China's electric vehicle brands more focused on core technologies.
The emergence of the upcoming Nezha S can be said to reflect the confidence of the new forces of mainland car manufacturing, which is evolving from the stage of mass production, survival, multi-model, and sales, to the stage of fighting technology and quality, and the personalized characteristics that dare to express in its products are derived from the sufficient confidence of technology and design.
"3.9 seconds of acceleration, more efficient thermal management for mass production, radical and stylish design." These characteristics are attracting more and more young people.
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