现代摩比斯的阿尔耶普卢格测试基地的最高平均温度为-7℃。基地内有一汪冰湖，占地160万平方米，是多种汽车性能的测试场所。

- By Sebastian Blanco

SAE《汽车工程》杂志记者也赶到这里，见证全新Nexo 燃料电池版、Kona电动版及现代自主研发的HVAC关键系统的冬季测试。

瑞典阿尔耶普卢格市距北极圈约57公里。数十年来，这座边远小城已成为了一个热闹的汽车工业中心。自从1973年的第一场冬季测试以来，这座城市已经成为了数十家整车企业和供应商的冬季驻地。这里的冬季平均最高温度约为19°F（-7℃），最低为3°F（-16℃）。每逢冬季，这座小城就成了工程师的天下。

当地居民将住宅出租给涌进的汽车大军，自己搬到别人家，或是和镇上的亲朋好友一起住露营车，这种临时生活方式是汽车动力绿色化进程必然导致的一个副效应。

在这些车企中，现代汽车（Hyundai）选择寒冷地带开展测试的动力尤为强烈。现代希望在2025前成为全球环保车辆市场的龙头企业，实现这一目标的关键是发展纯电动车和燃料电池车。而鉴于这两种车型在低温下的独特性能，保证HVAC（暖通空调）系统拥有卓越的低温性能就成为了现代的首要任务。

阿尔耶普卢格市也就这样成为了现代功能汽车研发部主管Gunther Frank的第二故乡。今年年初，《汽车工程》杂志受邀前往Frank团队的冬季驻地，当时他们正在筹备全新Nexo燃料电池版和Kona电动版的量产。

FATC研发

现代HVAC系统的基础研发主要是在韩国南阳技术研究中心的气候室内完成。然后车辆被运到瑞典，进行场地测试和现场调校。Frank表示，低温测试通常会持续一到两周，接着进行同样时长的高温测试。而常温测试的时间最长，可能需要三到四周，因为FATC（全自动温度控制）系统很难实现常温下的精确调整。

“不论是从制冷或制热的角度来看，还是就FATC的控制而言，常温情况都要复杂很多，”Frank表示，“当我们在一个小时内从海拔2500米（8202英尺）、气温很低的阿尔卑斯山区开到22-23℃（72-73°F）的山谷，控制器需要感知到温度的变化，并做出反应。”

现代希望将FATC用于旗下所有车型，无论其采用何种动力类型。其基本构想是，驾驶员设好温度、按下“自动调节”按钮后，再也无需考虑开暖气还是冷气的问题。

“这当然是最理想的情况，但是人和人之间的差别很大，”Frank说道，“你今天的心情和另一天的心情相比，差别也会很大，我们无法创造出一个适用于所有情况的控制算法。这是一个很好的性能，但是你要确保用户可以修改系统，因为最终一切取决于用户的要求。”

不过对于在阿尔耶普卢格的Frank团队而言，更重要的挑战在于，如何在没有传统内燃机车辆所产生余热的条件下，获得稳定的热能。现代的全新燃料电池车和纯电动车均使用了高压电子压缩机。和旧版压缩机不同，电子压缩机可以独立运转，无需靠发动机带动，在座舱温度稳定之后可以关闭，进而降低能耗、提升效率。

由于高压系统无需等暖机后再运转，因此，和内燃机车型相比，它的制热速度更快。“从HVAC的角度看，新型车的情况比过去好太多了，”Frank说道，“如果没有电子制热设备，发动机启动后，座舱制热要花很长的时间。有了高压系统，我们可以让座舱马上变暖。”

Nexo 燃料电池版制热系统

Nexo 是现代计划于2018年推出的第二代燃料电池车型，和上一代途胜燃料电池版相比，Nexo电池堆栈的效率和性能都有了提升，而且所有零部件都经过了重新研发。Nexo的燃料电池系统实现了60%的效率，途胜为55%。此外Nexo还扩大了储氢容量，目前配备三个储氢罐，每罐容量为6.3千克（13.9磅）。这使得Nexo的续航里程在NEDC城市工况下达到了800公里（497英里），在美标工况下超过了370英里（595公里）。

虽然这些数字都只是初步测试成果，但是Nexo高级工程师Sang Ho Yoon表示，Nexo的续航里程应该比途胜燃料电池版高35%左右，后者的美标测试结果为256英里（426公里）。

Nexo的驱动和制热都是靠同一种能源，因此研发出一个高效的HVAC系统成为了实现长续航的关键。电堆在冷却时也会产生一些余热供Nexo的HVAC系统使用，这一点和传统内燃机车有些相似，但就整体过程而言，两者的差别还是很大。好消息是这种差别并没有影响Nexo的HVAC系统性能。

Frank在一个室外温度只有-23℃（-9.4°F）的日子成功证明了Nexo的快速制热性能，这让他很高兴。在短短三分钟之后，一个与驾驶员胸部位置持平的温度感应器显示车内温度已经达到了15°C（59°F）。

“我们的内部目标是，当环境温度为-20℃（-4°F）时，座舱的平均温度可以在开车后20分钟内达到18℃（64°F），”Frank说道，“相信我，对小型内燃机车来说，要达到这个目标非常困难。而对我们的纯电动和燃料电池车型而言，这将轻而易举。”

Frank还说道，车内搭载的3.7 kW Air Side PTC（正温度系数）热敏电阻也是快速制热的一大功臣。早在90年代，人们就开始研究使用PTC热敏电阻作为车载加热器。有些汽油车也采用了PTC热敏电阻，例如一些三缸欧系车搭载的1Kw PTC单元。而在替代能源车辆上，PTC才真正有了用武之地。

他解释道，“要加热燃料电池车的座舱，第一步是加热电堆的冷却系统。然后，PTC就会开始为Nexo的座舱快速提供热量。电堆温度升高后，余热产生，PTC的功率下降。在瑞士，我们发现PTC功率可以一直降到零。”

 “当车辆状态稳定后，制热过程就和内燃机车很相似了。制热系统的运行不需要额外的电能，”Frank说道，“在稳定状态下，续航里程不会受到影响。”

现代为Nexo内部研发了一款全新的膜电组件和3D多孔流场。Yonn表示，“3D多孔流场是为Nexo电堆制定的全新概念，它可以提升能量密度，改善电堆性能。”他还说道，Nexo采用了全球最小的汽车供氢系统，因为Nexo摒弃了途胜燃料电池版的氢气循环泵，仅靠喷嘴为电池堆的电化学反应提供氢气。

此外，Nexo的全新热管理系统采用了一个双向阀门和一个四向阀门，从而改善了电堆制冷剂温度控制的响应性。Yoon表示，这是首次在电动汽车上使用四向阀门，它可以改善Nexo的冷启动性能。冷启动是燃料电池汽车的硬伤，但Nexo可以达到现代旗下所有内燃机车必须通过的标准，即在-30℃（-22°F）下启动。

而且这不是唯一Nexo可以和内燃机车相媲美的地方。据Yoon介绍，由于Nexo采用了一种全新的高度耐用膜、一种全新的电池堆铂金催化剂以及一项全新的操控技术，因此其动力总成的额定使用寿命和现代内燃机车一样，都是10年16万公里（10万英里）。

Nexo动力总成的最大输出功率为120kW、最大扭矩为395N·m。据称，这将使Nexo的最高时速在途胜燃料电池版的基础上提升10%，加速性能提升25%。

Kona电动版的制热系统

Kona电动版分为两款。第一款的电池容量为64 kWh，续航里程为470公里（292英里），（这里所有续航里程都只是基于WLTP“世界协调车辆排放试验规程”制定的目标数据。）功率为204hp，百公里加速7.6秒。第二款的电池容量为39kWh，续航里程为300公里（186英里），电机功率为135 hp，百公里加速9.3秒。两款的最大扭矩都是395N·m。如果使用100kW的快充器，第一款车可在不到一个小时内充满80%的电量，但如果使用7.2 kW Level 2充电器，充电时间将长达近10小时。

电动汽车面临的一大难题就是根据座舱温度调节电池温度。Kona 电动版采用了Ionia和起亚Soul电动款的气冷电池组，但加大了尺寸。Kona电池组的最高工作温度为40℃（104℉）。为防止过热，电动版采用了一个主动液冷系统和一个散热器。如果还不能满足要求，也可以使用座舱的空调系统来冷却电池组。

和Nexo一样，Kona 电动版也采用了Air Side PTC热敏电阻，功率为5kW，此外还有一个2.7kW的热泵。之所以采用比Nexo更强劲的PTC，是因为Kona电动版没有燃料电池堆的余热可供座舱制热。不过，Kona还是可以汲取电机等其它电子零部件的热能。

Frank说，“我们可以传递其它热能来加热座舱，这样的话，整体加热系统的效率都能得到提升。”

Kona热泵系统的理想工作温度为0℃（32℉）以上，使用空气中的热能来驱动AC。Frank表示，当环境温度为0℃（32℉）、座舱温度为23℃（73℉）时，“和关闭加热器相比，PTC系统的热能损失多了近40%，但由于热泵系统可以产生超过20%的额外能量，因此整体能效会更高。”

为了让新能源车型的用户满意，这些都是现代冬季测试工程师必须达成的目标。如果PTC、FATC等HVAC组成部件能在阿尔耶普卢格运作，那么其它地方就应该不是问题。要是不行，那就再回到这片严寒之中做更多的测试。

Kona纯电动和Nexo的冰湖趣味

一辆早期原型车的驾驶体验，往往只能帮助我们粗略猜想未来量产车的性能表现，但是在瑞典北部，开着全新的现代Nexo氢燃料电池版和Kona电动版在冰湖上疾驰，却向我们证明了一点——环保车的调校方式不止一种。

几乎可以肯定地说，Nexo的价格会高出Kona，这似乎是理所当然的。Nexo的悬挂更灵活，稳定控制系统更强，即使在现代的冰湖赛道上，也极少会失去抓地力。节气门和转向响应性虽然受到了极大的限制，但是系统可以进行迅速且强力的干预，这对于量产车型的安全性能来说是个良好的开端。车辆没有发生太多的过度转向，而至于转向不足的情况，在冰面上自然是会出现的。

相比之下，Kona电动版离量产还有更长的距离。在严寒极限下，车辆后部噪声十分明显。安全控制策略的调校也有所不同，车辆可以在冰面上适度漂移。因此，在广阔的冰面赛道的安全范围内，驾驶电动版更有意思，这也意味着两种车型中，电动版可能是更有乐趣的一款。

Kona电动版的重心低，驾驶稳定性好，这要感谢安装在底板下的电池组。在湿滑路面，很难测试电动版的最快加速度。但在冰面上，当车速达到100km/h （62mph）时，车辆的扭矩表现仍十分出色，不过一旦碰到湿滑路段，就算将油门踩到底，加速效果也十分微弱。

这两款零排放车型都采用了防滑轮胎，驾驶稳定性很好。Kona采用的是大陆215-55 R 17 V XL WinterContact TS 850P 轮胎，Nexo则选用了韩泰Winter I-cept Evo2 245/45R19 102V M+S轮胎。

AE goes way north for an inside look at Hyundai’s winter testing of the new Nexo FCV and Kona EV and their unique and critical HVAC systems.
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Arjeplog, Sweden sits around 35 miles (57 km) below the Arctic Circle, but this remote city has been a bustling hub for the automotive industry for decades. Since the first winter tests were conducted here in the 1973, the area has become a second home to a dozen OEMs and suppliers during the brutally cold winter months. Engineers take over the small town every winter when average high temperatures hover around 19°F (-7 C) and the average low is a brisk 3°F (-16 C).

To make room for the influx, residents rent out their homes to the auto industry, moving into guest rooms or in campers parked with relatives or friends in other parts of town. These temporary living situations are required as the automotive industry pushes forward to greener powertrains.

Hyundai has a particular impetus to test where it's cold. Battery EVs and fuel-cell vehicles (FCV) have unique cold-climate operating characteristics, and those propulsion types will play a major role in the company's aim to vie for the global eco-car sales lead by 2025. Ensuring optimum HVAC system cold-climate performance for EVs and FCVs is paramount.

Arjeplog, then, has become like a second home to engineer Gunther Frank, Hyundai’s head of Functional Vehicle Development. Automotive Engineering was invited to join Frank and his team in their winter lair in early 2018 as they prepared the new Nexo fuel cell vehicle and the Kona EV for production.

Developing FATC

Hyundai does most basic HVAC development work using a climate chamber at its Namyang Technology Research Center in Korea. Then the cars come to Sweden for on-site field tests and fine tuning. Frank said a car typically spends one to two weeks in cold weather testing, and the same amount of time in hot weather. It's the in-between climate that actually takes longer, maybe three or four weeks, because it's difficult to get the full automatic temperature control (FATC) system just right.

"Mild climate conditions are much, much more complex, not from the performance point of view in terms of cooling or heating, but from the control point of view of the FATC," Frank said. "In alpine regions, when we are at a height of 2,500 meters (8,202 feet) where it is quite cool, and we are driving within an hour down to the valley where we see temperatures of 22 or 23 °C (72-73°F), the controller has to be aware of the changing conditions and react."

FATC is Hyundai's end goal for all of its vehicles, no matter what powertrain they use. The basic idea is that the driver can set a temperature, push the "auto" button, and then never think of the heating or cooling settings again.

"This would be the ideal situation, having just the 'auto' button, but human beings are so different," Frank said. "The way you feel one day in comparison to the other is also so different and you are never going to be able to create a control algorithm which will fit all of them. It's a very nice feature, but you have to make sure that the customer has the possibility to overwrite the system, because finally it's up to them."

The more important challenge for Frank and his team in Arjeplog, though, is getting consistent heat without the waste heat from a traditional ICE. Both of Hyundai's new fuel cell and all-electric vehicles use high-voltage electronic compressors. Unlike older compressors, which needed to run off of engine RPM, the electronic compressors can be run independently. They can also be turned off when the cabin climate is stable, which then reduces the load on the energy source and thus leads to increased efficiency.

The high-voltage systems can also heat up the cabin faster than an ICE, since they don't need a warm engine to work. "From the HVAC point of view, it's a much, much better situation than in the olden days," Frank noted. "If you don't have an electronic heating device, when you start your engine, it takes a very long time until the cabin becomes warm. With our high-voltage systems, we have the possibility to immediately warm up the cabin."

Heating the Nexo FCV

The Nexo is the Hyundai's second-gen fuel-cell vehicle, arriving some time in 2018. It follows the Tucson FCV and has increased fuel cell stack efficiency and performance. All of its components are newly developed. In fact, the Nexo achieves 60% fuel cell system efficiency, compared to the Tucson's 55%. Based on this improvement, along with an increase in the hydrogen storage available on board (three tanks that each hold 6.3 kg (13.9 lb) of hydrogen, the Nexo's driving range could reach over 800 km (497 mi) in NEDC city mode, and over 370 miles on the U.S. test cycle.

These numbers are preliminary, but Nexo senior engineer Sang Ho Yoon said the driving range would be around a 35% increase over the Tucson fuel cell. That vehicle is rated at 265 miles in the U.S.

The same energy used to move the car is needed to heat it, so developing an efficient HVAC system is important to achieving long range. While there are similarities between the HVAC system in the Nexo and a standard ICE vehicle – there is some free heat energy available because the stack needs to be cooled down – the overall process is quite different. The good news is that different also works.

Frank happily proved the Nexo's rapid heating power on a day when the outside ambient temperature was -23°C (-9.4 F). After just three minutes in the prototype, a breast-level temperate sensor showed it was 15°C (59 F) in the car.

"We have an internal target that with an ambient temperature of -20 C (-4 F), the average cabin temperature should reach an average of 18°C (64 F) after 20 minutes of driving," Frank said. "Believe me, it's quite tough to fulfill that with low-capacity internal combustion engine cars. With our full EV cars or with our fuel cell car, we are able to reach that target much, much faster."

Part of that quick heat comes from a 3.7-kW Air Side positive temperature coefficient (PTC)  thermistor. The use of PTC thermistors as heaters in cars has been studied since at least the 1990s and they are used today in some gas cars, especially 1-kW units in 3-cylinder European vehicles. With alternative powertrain models, PTCs have really come into their own, Frank explained.

The first step to warming a fuel cell car's cabin, Frank explained, is to heat up the cooling system of the stack. While this happens, the PTC offers quick heat in the Nexo's cabin. Once the stack is warmed up and able to provide some excess heat, the PTC's power is reduced, even down to zero in the conditions we experienced in Sweden.

"When the car is in a stable condition, it's similar to internal combustion engine cars and we don't need additional electronic power to run the heating system," he said. "In stable conditions, there is no influence on driving range."

Hyundai developed a new membrane electrode assembly and 3D porous flow field in house for the Nexo. "The 3D porous flow field is a new concept for the Nexo stack," Yoon said. "It can improve the stack performance for power density." Yoon said the Nexo uses the world's smallest hydrogen supply system for automotive use because it does away with the hydrogen recirculating pump required in the Tucson fuel cell and only uses an ejector to supply hydrogen for the electrochemical reaction within the fuel cell stack.

A new thermal management system means improved response time to control the coolant temperature of the stack thanks to a two-way and a four-way valve. The four-way valve is a world's first for electric vehicles, Yoon said, and it improves the Nexo's cold-start ability. Cold starts are traditionally difficult for fuel cell vehicles, but the Nexo can start at ambient temperatures of -30°C (-22 F), the same threshold the company's ICE vehicles must pass.

That's not the only way the Nexo will function like an ICE. Thanks to a new, highly durable membrane, a new platinum catalyst in the stack, and a new operating control technology, Yoon said the durability rating for the new fuel cell powertrain warranty will cover 160,000 km (100,000 mi) and 10 years, just like the company's ICE vehicles.

The Nexo's powertrain has a maximum power output of 120 kW and 395 N·m. This will improve top speed by a claimed 10% and acceleration performance by 25%, compared to the Tucson FCEV.

Heating the Kona EV

The Kona EV will come in two flavors, a 64-kW·h model with up to 470 km (292 mi) of range (all range numbers here are just targets, and are based on WLTP homologation). This model offers 204 hp and a 0-100 km/h (0-62 mph) time of 7.6 seconds. The 39-kW·h model will get up to almost 300 km (186 mi) on a charge with a motor that generates 135 hp and hits 100 km/h in 9.3 seconds. Both powertrain versions deliver 395 N·m. On a 100-kW fast charger, the 64-kW·h battery can be charged to 80% in less than one hour. A 7.2-kW, Level 2 charger will take almost 10 hours to fully charge the larger pack.

One challenge with electric vehicles is that the battery temperature needs to be moderated along with the cabin. The Kona EV uses battery packs that are bigger than the ones used in Hyundai's Ioniq and Kia Soul EVs, which are air-cooled. The Kona's battery pack shouldn't get hotter than 40°C (104 F), which is why the battery in the Kona EV uses an active liquid cooling system in combination with a radiator to keep it from overheating. If this is not sufficient, the cabin's AC system can be used to cool down the battery as well.

Like the Nexo, the Kona EV prototype uses an AirSide PTC – this time a 5-kW unit – along with a 2.7-kW heat pump. A more powerful PTC is needed because there's no waste heat from a fuel cell stack to help warm the cabin. The Kona EV does manage to siphon some heat energy off of the electronic components, including the motor.

"We are able to transfer it and use that energy to warm up the cabin and to increase the efficiency of the overall heating system," Frank noted.

The heat pump system uses some heat energy from the air, ideally at ambient temperatures above 0°C (32 F), which then runs the AC drive cycle. At an ambient temperature of 0°C (32 F) and a cabin setting of 23°C (73F), "we are losing about 40% in comparison to heater off when we have a PTC system, but we are able to create 20% more energy with the heat pump system and therefore to increase the efficiency," Frank said.

Those are the numbers that Hyundai's winter test engineers have to crunch to keep drivers of their new powertrain vehicles happy. If the PTC and the FATC and all the rest can work in Arjeplog, chances are they will work in other parts of the world. If not, it's back to the cold for more testing.

Frozen-lake driving in a fuel cell car

Driving an early prototype gives only a hint of what the finished vehicle will act like, but spinning the upcoming Hyundai Nexo hydrogen fuel cell and the Kona EV around a frozen lake in northern Sweden prove there's more than one way to tune an eco car.

The Nexo, as seems appropriate for what will almost certainly be the more expensive of the two models, has a softer suspension and an aggressive stability control system that prevented the FCEV from ever really losing its footing, even when speeding around Hyundai's circular ice track. Throttle and steering response were dramatically limited and the system's interventions were early and substantial, which bodes well for the safety of the eventual production vehicle. There was not a lot of oversteer and there wasn't much to do about the understeer in the icy circumstances.

The Kona EV, on the other hand, felt further from production ready, with plenty of noise coming from the back when pushed to the frozen limits. The safety control strategy is also tuned different here, allowing us to mildly drift the car on the lake. This meant more fun on the safe confines of the expansive ice track, and it means the EV might be the more fun of the two models.

Thankfully, the Kona EV's floor-mounted battery creates a low center of gravity that helps keep the car firm locked onto the track. It was difficult to test out the EV's flat-our acceleration on the slippery surfaces, but the impressive torque got the tires spinning on the ice, even when we were already at 100 km/h (62 mph). Even so, pushing the accelerator pedal all the way to the floor didn't do much once the system detected slippery conditions and neutered our input.

Thanks in part to their grippy tires, both zero-emission vehicles kept their composure. The Kona rode on Continental 215-55 R 17 V XL WinterContact TS 850P tires, while the Next wore Hankook’s Winter I-cept Evo2 245/45R19 102V M+S.

Author: Sebastian Blanco
Source: SAE Automotive Engineering Magazine