北京时间3月17日,特斯来开启了Model Y的交付,尽管由于新冠病毒的影响,全球各地商业运营或多或少都遭受影响,但是特斯拉缺开启了Model Y的上市交付,此举对于新能源市场来说无疑不是大的提振。
从目前透漏出来的信息来看,Model Y相比于此前的Model S、Model X及Model 3来说提供了一些独特的解决方案那就是热泵系统的搭载。
那么什么是热泵系统呢?
根据特斯拉的用户手册如图1所示,热泵系统能最大化效率,位于左前轮左侧,且告知了用户在低温情况下当车辆进行加热或者快充的时候空调压缩机及前端风扇工作会产生噪音。
图1:特斯拉用户手册介绍
从图中我们只能看到空调压缩机,具体的热泵系统是怎样的目前所知信息甚少。据国外特斯拉的死忠粉youtube播主Andy Slye视频介绍,详细的科普了什么是热泵,以及热泵系统的基本原理以及Tesla应用热泵的原因。(原文如下,详细的介绍了什么是热泵,以及热泵的优劣,本人就不做翻译)
「The SECRET Model Y Feature That No Other Tesla Has!
One of the biggest problems with Tesla vehicles up to this point may have just been fixed with this new feature on the Model Y that Tesla decided to hide from us until now. Driving a Tesla can be somewhat scary because of 「range anxiety」 which means you’re worried about running out of battery before reaching your destination.
In cold winter conditions an electric vehicle can lose up to 40% or more of its estimated range. In February I was on a road trip in my Model 3 and lost a lot of my estimated range while driving highway speeds when it was around 30 degrees F.
Electric vehicles lose range in cold temperatures because: colder air which means more drag, energy loss from heating the battery, and the energy used to warm up the vehicle’s cabin. All Tesla vehicles (prior to Model Y) warm the cabin through a resistive heating system where electricity is sent through a resistive heating element, which creates heat that’s blown out of the air vents. .
This means for an EV (like my Model 3) to warm up the cabin, energy from the battery must be used which of course decreases the estimated range. Electric resistance heating is considered 100% energy efficient in the sense that all the incoming electric energy is converted to heat.
Well it doesn’t get any better than 100% efficiency, right? Actually there is something better. It’s called a heat pump, and the Model Y is the first Tesla to have one. In the manual it says 「Model Y uses a heat pump to maximize efficiency; therefore, your air conditioning compressor and external fan may run and make noise even when the outside temperature is cold and your vehicle is heating or Supercharging"
A heat pump can be thought of as an air conditioner that has the ability to work in reverse. An air conditioner works by using refrigerant to trap the heat inside of an area, then move it outside. A heat pump works in exactly the same way, only it has a reversing valve which allows it to reverse the flow of the refrigerant and heat an area when it's cold out.
Heat pumps help efficiency because they move heat rather than generate it. The electricity is used by the compressor to send refrigerant around the system and capture the heat from outside, then bring it inside. It can do this because the refrigerant has an extremely low boiling point. And the best part is a heat pump can typically produce around 3kW of thermal energy for every 1kW of electrical energy resulting in an 「efficiency」 of 300%.
So this 「300% efficiency」 sounds awesome, right? Well, heat pumps are usually not effective below a certain temperature range and typically don't work well in extremely cold temperatures. However, heat pump technology has recently improved, and in some cases can be rated for outdoor temperatures as low as -4°F.
Why is the Model Y’s heat pump so important? A heat pump should be able to heat the cabin while using less energy which should lead to longer battery range when driving in cold temperatures compared to all the other Tesla models. This is a huge advantage!
Why didn't Tesla implement this before the Model Y? Most likely it was because a heat pump adds cost, complexity, and weight. But for a Tesla, which already has an air conditioner, a heat pump seems like a no-brainer because the added complexity would be pretty minimal.
The biggest questions now are: where does the heat come from in the Model Y heat pump and does the Model Y always use a heat pump or does it alternate between heat pump and resistance heating? From the Model Y manual it looks like it could be taking excess heat from the motor and battery, which would probably make it efficient even in extremely cold temperatures which would be nice. Teslas already have the ability to use the motors to heat the battery, and if the heat pump is powerful enough it can potentially heat both the battery and the cabin.
Either way, I can’t wait to see how the Model Y handles driving in the winter. It sounds like it will be the best Tesla for that task. 」
针对特斯拉的热泵方案,我们可以进行几个方面的猜测。
猜测一:直接式热泵「三换」方案
如图2所示,Tesla的Model 3 制冷如传统车用空调系统,制热采用了一个7Kw的风暖PTC,这样的系统设计很简洁,相对而言零部件数量少、复杂程度低。根据目前主流的热泵方案我们大胆可以猜测,Model Y有可能采用图3类似的热泵系统,即其热泵系统是由HVAC内增加一个室内冷凝器做为热泵空调的热源向乘员舱加热。此种方案为目前主流方案NISSAN、比亚迪等都是类似这样的方案。
图2:Tesla空调系统HVAC
但是考虑到现行的热泵系统受制冷剂的限值,在及低温下加热情况不太理想,可能还需要辅热,结合现在特斯拉的设计可能辅一小功率的风PTC进行低温环境下的辅热。
图3:典型的直接式「热泵」三换系统
猜测二:四通阀热泵方案
通过四通换向阀改变制冷剂的流动通道,改变制冷剂流向,直接将室内外换热器功能进行切换,从而达到制冷及制热的功能。三花作为此前特斯拉制冷剂阀的供应商,在阀体技术上的积累是深厚的,因此开发成熟的四通阀进行流向切换或许可以成熟应用,通过四通阀来实现热泵的功能,减少了一个「三换」方案的室内冷凝器,相应的管路传感器等都会减少,并且在系列车型上对于HVAC变动及相应开发减少了很多工作量。
如下图所示为一种利用四通阀设计实现的热泵空调系统:
图4:一种四通阀设计的热泵系统
猜测三:补气增焓式热泵方案
补气增焓是指压缩机采用两级节流中间喷气技术,采用闪蒸器进行气液分离,实现增焓效果。它通过中低压时边压缩边喷气混合冷却,然后高压时正常压缩,提高压缩机排气量,达到低温环境下提升制热能力的目的。
补气增焓技术的压缩机多了一个吸气口,通过产生蒸汽来冷却主循环的制冷剂,蒸汽从第二个吸气口进入压缩机,其压缩过程被补气过程分割成两段,变为准二级压缩过程。补气降低排气温度,同时降低其排气过热度,减少冷凝器的气相换热区的长度,增加两相换热面积,提高冷凝器的换热效率,当蒸发温度和冷凝温度相差越大会产生越好的效果,所以在低温环境下效果更明显。
如下图5所示,为丰田普锐斯的补气增焓热泵系统示意,此种系统制冷剂管路较为复杂,整车前舱布置繁杂
图6:丰田补气增焓热泵系统
猜测四:间接式集成热泵方案
与直接式不一样的是,间接式热泵空调系统将空调箱内部冷凝器拿掉,将其布置在机舱内,我们称之为外部板式换热器。最典型的例子就是BMW I3,如下图所示
图6:BMW间接式热泵系统
如下图5所示,为一种集成式的热泵方案,在此种方案中去除了传统的气液换热的散热器冷凝器和蒸发器鸡儿采用了「液液换热」的板换代替,此种形式将极大的优化空调制冷剂系统的管理,更多是通过水管进行整车的热量交互。
图7:一种高度集成的间接式热泵系统
考虑到Tesla在Model 3上应用的Supper Bottle专利技术,这一技术很有可能在Model Y上进行延续,根据Tesla对热泵的描述,其热泵系统可以对乘员舱及电池包进行加热,进而应用高度集成式的热泵系统将能有效的将电机液冷回路及电池液冷回路连接起来进行综合管理。
近日,银轮股份公告说,子公司上海银轮热交换系统有限公司与特斯拉、特斯拉(上海)有限公司签订了产品零件或服务通用条款合同。特斯拉将向公司采购汽车换热模块产品。不知这其中是否涉及到」液液板换」(大家见到最多的当属电池Chiller,此种即为制冷剂路和冷却液路进行热量交换)相关
综上,本人认为第四种可能性较大,特斯拉作为新能源汽车的当之无愧技术前沿,其新的热泵技术是否能带来行业变革,我们拭目以待。