So what's the work-around?
Well, it comes from somewhere unexpected: cars driven by electric motors without a plug. In other words, a petrol (gasoline) motor drives a generator which in turn drives an electric engine which turns the wheels.
When I first heard this I thought it was insane. Why would you choose two energy conversion losses over one? As so often, the situation is more complex. The internal combustion engine (ICE) has a single number of revolutions where it is at its most efficient. But when it's the only engine, it must vary its revolutions per minute because of changing speed. Which reduces efficiency. Which is also why ICEs need gearboxes. An electric engine doesn't need a gearbox, and will run efficiently at a wide range of revs. Plus, with an electric engine you can have regenerative braking, where slowing down the car recharges the battery. And because the petrol/electric engine combo is more efficient, it can be smaller and lighter. As well as needing no gearbox.
When I first heard this I thought it was insane. Why would you choose two energy conversion losses over one? As so often, the situation is more complex. The internal combustion engine (ICE) has a single number of revolutions where it is at its most efficient. But when it's the only engine, it must vary its revolutions per minute because of changing speed. Which reduces efficiency. Which is also why ICEs need gearboxes. An electric engine doesn't need a gearbox, and will run efficiently at a wide range of revs. Plus, with an electric engine you can have regenerative braking, where slowing down the car recharges the battery. And because the petrol/electric engine combo is more efficient, it can be smaller and lighter. As well as needing no gearbox.
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| EV vs serial hybrid vs parallel hybrid Source:CarAdvice.com |
e-Power is the petrol-electric hybrid technology Nissan hopes will transition the world to EVs
Nissan Australia may be without a 'proper' passenger car in its current line-up but the Nissan Note e-POWER small car is gaining fans in Japan thanks to its flexible hybrid powertrain. Taking knowhow from the LEAF battery electric car and applying it in a series hybrid, the little Note e-POWER offers sprightly city car performance. Combining a battery, electric motor, 1.2-litre three-cylinder engine and decent-sized fuel tank, the Note has a theoretical range of around 1300km. Will this affordable transition technology be a successful bridge to the future?
While it may be Tesla that gets all the electric car plaudits, it is Japanese manufacturer Nissan that has the most runs on the board. In the past eight years, Nissan has sold over 300,000 battery-electric LEAF vehicles, with owners accumulating over 3.9 billion kilometres on pure electric power.
Building on that success, the second generation Nissan LEAF has just been confirmed for Australia and its longer range (expected to be around 240km of real world driving) is likely to extend its appeal to a broader group of buyers. Without widespread charging infrastructure and incentives, however, it may prove tough to convert mainstream buyers to a mid-$40,000 small car, regardless of its tech smarts and environmental credentials.
This is where Nissan's new e-POWER technology comes in. e-POWER is a petrol-electric hybrid system with no plug, which offers electric car performance and exceptional fuel economy with no compromise on long-range driving.
It reduces the need for a large battery, so it is more affordable too. Unlike other car manufacturers which have gone from internal combustion engines through hybrids to battery electric vehicles, Nissan's gone the other way around -- taking what it has learned from LEAF and applying it to the e-POWER system.
Simply, e-POWER system is a series hybrid which pairs a 40kW electric motor with a small 1.2-litre three-cylinder engine which acts as a generator for the 1.5kW battery.
Whereas a conventional parallel hybrid uses the engine to drive the wheels, the purpose of the e-POWER's engine is just to charge the battery -- the wheels are always electrically driven.
On start-up, the Note is silent and initial acceleration is instant thanks to the electric propulsion system.
At moderate throttle input, e-POWER draws charge from the battery but when needed, the engine-generator kicks in to charge up the battery. The combination makes a noticeable drone once it is activated. As the engine itself is a small three-cylinder unit that runs at constant rpm, it isn't a conventional engine noise and a bit monotone in its sound.
[Read more here]
The efficiency gains are astonishing. The Nissan Note e-Power gets 2.9 litres/100 km, or 81 MPG (in the old, and still US measurement) This compares with Toyota's Prius, which has a combined electric/petrol engine where both engines can directly drive the wheels (i.e., a parallel hybrid) , with a MPG of 54 (4.4 l/100km), with the average US MPG at 24.7 (9.5 l/100km) and Australia at 10.6 l/100 km (22.2 MPG). Wow. What's more, because it has such a small battery, it's relatively cheap. Carsales.com (the source of the review above) lists 2017 Nissan Notes at A$28,000 including 10% sales tax (US$19,600) The 2019 model will cost more, but the 2019 new Leaf will cost A$50,000 (including import duties and sales tax). 40% cheaper with no range anxiety.
From the consumers' POV, a serial hybrid is very like an old-fashioned ICE. You put petrol in it, it has about the same 'sticker price' as an 'ordinary' petrol-driven car, but on the other hand it is super efficient and cheap to run, just like an EV. You get some of the fun of driving an EV. You don't have range anxiety. In fact you never plug it in to an electrical socket. Parallel hybrids like the Prius are more expensive and not as efficient. And of course EVs are scary, and expensive to buy. From the car-makers' POV, building a serial hybrid is the way to learn all about making real EVs, plus you don't have to source lots of batteries in a world where battery demand greatly exceeds supply. From society's perspective, serial hybrids will reduce emissions from transport by more than 50%, without a huge up front cost.
I expect that the push to reduce emissions will lead to rapid growth in serial hybrid market share, until battery costs fall enough to make a petrol engine more expensive than larger batteries. And it's something the legacy car makers can do to get aboard the EV bandwaggon before it's too late. Most haven't set up substantial battery supply contracts or factories—they have little choice if they want to avoid bankruptcy/extinction.
I've been lamenting that ordinary folk won't be able to buy an EV for another 5 years. But if legacy car manufacturers get their act together (I admit, that may not happen) we may be able to buy cheap and efficient serial hybrids before that. And I surmise that as battery costs fall, Nissan and othe manufacturers will add a plug and a larger battery. For example, adding just 4 kWh capacity to the Note's existing 1.5 kWh battery would give an extra 40 kms (25 miles) of petrol-free range, so that overnight charging would provide most motorists with the day's commute.
Some more articles about it:
Nissan e-POWER technology explained:
Nissan Note e-POWER 2018 Review
Nissan e-power explained
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