Model produksi pertama kenderaan bersifat komersial ialah Ford model T yang diperkenalkan pada era 1900. Ketika itu ia langsung tidak dijangka menjadi antara penyumbang utama pencemaran alam sekitar. Kekaguman dunia terhadap industri automotif memuncak tanpa adanya kesedaran bahawa kemudahan yang kita kecapi hari ini penyebab kemusnahan dunia. Hakikat bahawa pencemaran oleh gas karbon monoksida hanya disedari 70 tahun selepas itu dengan negara maju mengambil inisiatif memperkenalkan alat catalytic converter, had pengeluaran asap dan jangka hayat kenderaan (Source: Kosmo).
Kini teknologi hybrid muncul bagi merancakkan lagi usaha ke arah menjadikan bumi lebih hijau. Antara gergasi automotif yang telah memperkenalkan teknologi hybrid mereka ialah Toyota (Hybrid Synergy Drive) melalui model Toyota Prius, Honda (Integrated Motor Assisstant) melalui model Honda Civic Hybrid, Ford (Fusion Hybrid) melalui model Ford Fusion Hybrid dan sebagainya dan tidak ketinggalan syarikat automotif tempatan, Proton (Lotus Range Extender) melalui model kereta konsep mereka, Proton EMAS.
Tulisan saya kali ini akan memaparkan secara ringkas bagaimana teknologi tersebut berfungsi.
First of all I think it’s best to define what a hybrid car is, and the various types of hybrid cars available on the market.
A hybrid vehicle essentially combines two or more power sources to move the vehicle. It commonly refers to hybrid electric vehicles, which combine a combustion engine with electric motors.
When you implement a hybrid system, there are a few ways to configure the combustion engine and electric motors. With the introduction of the Honda Civic Hybrid, we’ve been introduced to the concept of a mild power assist hybrid system, or a mild parallel hybrid system.
In a mild parallel hybrid system, the internal combustion engine is always used as the primary power. A electric motor is installed between the engine and the transmission. It is only used to assist the combustion engine whenever needed, hence Honda calling it an Integrated Motor Assist system. Because the motor steps in whenever the driver demands more power, a smaller and more fuel efficient combustion engine can be used. However with this configuration there is no such thing as a zero emissions full EV mode – the car cannot run solely on the electric motor.
And then you have series hybrid cars, where a combustion engine running at a constant most efficient RPM is used as an electricity generated to power an electric motor, which drives the wheels.
The THS Hybrid Synergy Drive system in the Toyota Prius is of the variant called a full hybrid, a power-split hybrid or a series-parallel hybrid. It offers the best of both world, can run on either the combustion engine only, electric motor only, or both, but is heavier as it has more parts, and more complicated in design.
THS consists of an internal combustion engine, two water-cooled motor-generators (electric motor with dynamo functions), a powersplit device, and a battery pack. The first motor-generator functions as a power generator, converting the internal combustion engine’s mechanical power to electric power, which recharges the battery and supplies electricity to power the second motor-generator. The second motor-generator is used to drive the vehicle. It is mounted on the driveshaft. It also serves as a dynamo during brake-energy regeneration.
Power from the internal combustion engine is split via the power split device and goes to either the front wheels or the first motor-generator. The Prius combustion engine revs independently of the vehicle speed much like how a car with a CVT transmission would, but there is no CVT transmission in a Prius! Some trickery between the power split device, motor-generators and the combustion engine play around with the engine revs that one would find confusing, but the bottom line is the end result is perceived to us as CVT-like. Toyota calls it an ECVT system.
But the best part of such a system is the EV mode where the car runs on the electric motor only. On one end really fast 0 to 100km/h acceleration times can put a smile on your face but I found out that the other end is also true! Complete silence from the car while you are creeping through a traffic jam or looking for parking in a parking lot can be strangely satisfying, it could be something to do with the fact that your car can do something that most likely no other car in that parking lot can do.
The internal combustion engine of the new Prius is the 2ZR-FXE, an Atkinson cycle engine with 1.8 liters of displacement. This is up by 0.3 liters from the previous 2nd gen Prius 1.5 liter engine. The new engine puts out 99 PS compared to 77 PS from the 1.5 liter engine, and 143Nm of torque at 4,000rpm. Now why does a 1.8 liter engine put out so little power you ask? It’s because of the Atkinson cycle – it’s more fuel efficient however has less power density. The engine is now beltless thanks to an electric water pump. The combined output of the motor-generators produce 60kW and 207Nm of torque.
The Prius continues to use a NiMH battery. Some competitors have talked about starting using lithium ion and Toyota says they also have a li-ion battery coming by the end of this year but according to Prius chief engineer Akihiko Otsuka, NiMH and Lithium Ion both have pros and cons. EVs might need the larger capacity of lithium ion batteries, and they can be larger because of the lack of a combustion engine and fuel tank, but in hybrids where the battery can be smaller and of less capacity, NiMH is more suitable as it can sustain a high power output over a shorter period of time. But for plug-in hybrids in the future, they can benefit from lithium ion technology.
Something interesting is an optional feature which is a solar panel on the roof. This panel doesn’t recharge the battery but it actually helps keep the car cool while it is parked under the sun. Unfortunately from what I hear, UMW Toyota specifications for the Prius in Malaysia will not carry this solar panel.
There were no city drives as part of the test drive session that I attended at the Tokachi International racetrack in Hokkaido. Instead, Toyota had designed a series of acceleration and braking patterns set by a pace car over a total of 10.2km on the racetrack that’s meant to emulate city driving. While this isn’t really an indicator of real life driving, CBT’s Thomas Huong and I managed to score a nice average 31.6km per liters fuel consumption, which was the most economical figures of the day.
We later repeated the same track run at full throttle and managed to score about 9km per liter, which is still pretty decent considering it was pedal to the metal for most of the track. I think the Prius would be able to score a decent 20km+ per liter in real life fuel consumption, which is impressive for largeish (you could call it European D segment) car with a 2,700mm wheelbase. The chassis is a common one called the MC platform shared with some Toyota cars such as the RAV4, Estima, Avensis and Auris.
Fuel efficiency and less pollution is all the rage these days with cars. Honda brings us their updated IMA (Integrated Motor Assist) system to the 2006 Civic Hybrid.
The Hybrid i-VTEC system provides three stages of valve timing which are the low-rpm, high-rpm and cylinder idle mode. The IMA system is an improved version over the previous version, with battery output increased by 30% while retaining the same size. The electric motor employs coils with high-density windings and high-performance magnets to attain that power. The battery is recharged using regenerative hydraulic braking.
Honda says the system will perform equivalent to a 1.8 liter pure gasoline engine. Impressive.
Modes of operation:
- Vehicle stationary – The engine is turned off and fuel consumption is zero.
- Startup and acceleration – The engine operates in low-speed valve timing mode with motor assist.
- Rapid acceleration – The engine operates in high-speed valve timing mode with motor assist.
- Low-speed cruising – The valves of all four of the engine’s cylinders can be closed and combustion halted, the electric motor alone can power the vehicle.
- Gentle acceleration and high-speed cruising – The engine operating in low-speed valve timing mode powers the vehicle.
- Deceleration – The valves of all four of the engine’s cylinders are closed and combustion halted. The motor recovers a significant portion of the energy normally lost during deceleration and stores it in the battery.
- Motor Assist – water-cooled inline 4 cylinder, 1,339cc. Max output – 95hp at 6000rpm, 119Nm torque at 4500rpm.
- Electric Motor – AC synchronous drive ultra-thin DC brushless motor rated at 158 volts. Max output is 20hp at 2000rpm, 140Nm torque at 0-1160rpm.
- Combined output – 115hp at 6000rpm, 183Nm torque at 2500rpm.
Let’s have a look at the very heart of the Proton EMAS Concept cars – the Lotus Range Extender Engine. There has been a lot of concerns from readers about the range which has been rated at 50km. First of all, the car is still a concept at this point of time, so these figures are generally quite meaningless unless the car gets closer to production.
Concept cars are generally done as a ‘what if’ exercise and to gauge public perception and interest before moving ahead with the production version. This is why the one big question put forth at the Proton Concepts microsite is “would you like this to be the future of Proton”. According to Datuk Syed Zainal, it may take another 2 years before we can see a production version of the Proton EMAS on the roads.
But in any case, one of the most common comparisons in the comments so far is between the EMAS and the Mitsubishi i-MiEV. After all, the i-MiEV is somewhat similar – raised floor, compact size, rear motor and rear wheel driven. But the key difference between the two cars is that the i-MiEV is a pure electric car while the Proton EMAS Concept is a series-hybrid. But what exactly does series-hybrid mean? Does it mean it is not an electric car thus is not as ‘clean’ as an i-MiEV?
A series hybrid is basically an electric car, as long as you have enough juice in the battery packs for the electric motor to function. The Proton EMAS Concept has a range of 50km, which is shorter than the i-MiEV’s 160km range. But note that it isn’t an apple to apple comparison – the i-MiEV’s 160km range is calculated based on the Japanese 10-15 urban mode driving cycle, while Proton’s 50km range is not specified. It might be a mixed mode range or a ‘best effort’ range.
The difference is range can be quite easily explained – it is simply because the i-MiEV has a larger battery. It needs to have a larger battery because the battery is its only source of energy. Once you’re out of juice, you’re a sitting duck. With the Lotus Range Extender system, you do not need to have such a large battery – only one that is large enough to complete most city trips. That means less weight and less cost in terms of battery costs. Let’s say your office is about 15km to 20km from your home. You’ll hopefully be able to complete a to and fro trip on a single charge. When you get home, you plug the EMAS into your wall socket again to fully charge it up (3 hours on our 240V voltage – longer in 120V countries), and repeat the cycle the next day.
What happens when you need to travel further than 50km? The internal combustion engine will turn on and run to generate power. Because it only generates power and does not drive the wheels, Lotus can optimize it to run only at certain RPM points, so there is no need for costly variable valve timing, or this or that. The engine is a very simple 1.2 liter 3 cylinder single cam engine with only 2 valves per cylinder and a 10.0:1 compression ratio. It does not have to be built to withstand high RPM speeds so it can be lighter and cheaper to manufacture. The Range Extender engine only runs at 2 points – 1,500rpm and a higher 3,500rpm when you need to generate power a little faster. Peak torque is 107Nm at 2,500rpm, while peak power is quoted at 51hp at 3,500rpm.
Thus the Proton EMAS is hybrid in the sense that the electricity that its electric motor requires can be obtained through 2 ways – either a wall socket, or by the range extender engine burning fuel to generate electricity. As long as you do not exhaust the 50km battery capacity, your EMAS is technically as good as an electric vehicle and there won’t be any exhaust gas coming out of your exhaust pipes. But we don’t know yet how the battery management system works so the range extender engine might kick in earlier to ensure the battery does not get too weak in order to preserve battery life.
Walaubagaimanapun buat masa ini teknologi hybrid masih lagi mahal. Harga sebuah Toyota Prius di Malaysia ialah RM 175 000, Honda Civic Hybrid RM 130 000 manakala Proton EMAS dijangka akan berada di jalan raya seawalnya 2012. Ketika mana dunia mengalami penyusutan bekalan petroleum, pengenalan dan penambahbaikan teknologi hybrid amatlah dialu-alukan. Jika sekarang sebuah kereta bersesaran 1600 cc yang menempuh kesesakan jalan raya selama 45 minit untuk ke tempat kerja berjarak 12 km (penghuni Pulau Pinang Pulau Mutiara lebih memahami) memerlukan 7.0 L petrol untuk perjalanan sejauh 100 km, maka dengan teknologi hybrid jumlahnya boleh dikurangkan kepada 3-4 L petrol sahaja. Jadi bayangkan penjimatan petrol dan wang yang ditawarkan selain pengurangan asap dan bahan pencemar lain ke atmosfera bumi.
Namun apa yang lebih utama ialah menjadikan teknologi hybrid sebagai teknologi mampu milik untuk segenap lapisan masyarakat dan juga untuk setiap jenis kenderaan. Kita telahpun melihat bas-bas di Putrajaya menggunakan NGV sebagai bahan bakar utama dan siapa tahu kita akan melihat bukan sahaja kereta hybrid bahkan juga motosikal hybrid, lori hybrid dan bas hybrid suatu hari nanti.
Selamat berusaha para jurutera automotif sekalian.
Usaha tangga kejayaan.