In Defense of the Electric Car – Part 1

[Full disclosure: I own an electric car, and I think they are useful for city transportation. However, having owned one for a decade, I can say that it hasn’t been practical or cost-effective. John Hardy believes they are the future, I’ll let you, the reader, decide. – Anthony Watts]

By John Hardy – Re-Blogged From http://www.WattsUpWithThat.com

Preamble

In the West, almost all climate change activists consider Electric Vehicles (EVs) important because they are believed to emit less CO2 per mile. In contrast, many (but not all) climate sceptics consider them a waste of space because they regard them as a solution to a non-problem: they believe that all that EVs are good for is virtue signalling.

Actually, and quite regardless of “the environment”, EVs are poised to inflict the mother of all disruptions on the automotive industry. This can’t be explained (or dismissed) in a soundbite, so this is the first of three posts setting out why this might be so. This first post is mostly background. The second addresses the problem for the established automakers. The third addresses some misapprehensions about EVs.

The LA times reported in 2009 that the outgoing CEO of GM said that the biggest mistake he made was to kill the electric EV1 and throw away the technology lead that GM had acquired[1] , [2]. It isn’t just GM. The turgid response of all the big Western automakers leaves them at risk of being overtaken by agile Eastern competitors in the same way that the Swiss (mechanical) watch industry was overtaken in the 1980s by agile Eastern competitors making cheap accurate quartz watches[3]

What is so great about electric motors?

The internal combustion engine (ICE) is a complex beast which needs lots of air, lots of cooling and which generates large volumes of smelly exhaust. It has a high parts count, is a high maintenance device, and is plagued by noise and vibration. Worst of all it has an absurdly narrow torque band and won’t run at all below (typically) 500 r.p.m. or so. A lot of the complexity and expense in a modern ICE car is focused on minimizing these deficiencies.

By contrast, an electric motor is a model of flexibility and simplicity. Figure 1 shows the floor pan of the Tesla Model S.

Figure 1 Tesla Model S floor pan viewed from the rear. The two metal cans between the rear wheels are the electric motor (left) and the controller/inverter (right). Photograph from Wikimedia/Oleg Alexandrov

The entire drive train consists of two metal cans, sandwiching a fixed-ratio final drive. The motor revs to about 15,000 r.pm. It produces good torque at zero r.p.m. and (in some models) peaks at over 400HP. No clutch, torque converter or variable-ratio gearbox is needed. The motor is an ordinary AC induction motor. It has no brushes and (apart from the bearings) one moving part. It contains no rare earth magnets. The inverter is solid state. No exhaust system, turbocharger, oil pump, coil, distributer, intake air filter, complex vibration damping or heat shields; no pistons, valves, pushrods, camshafts, lifters, catalytic converters……….

The end result is smooth, seamless but ruthless acceleration and whisper-quiet cruising. Some models have a smaller drive train between the front wheels. The two together can accelerate a 4,000lb car at around 1G from standstill to 60 m.p.h. in under 3 seconds.

There is more. The inverter can adjust the motor torque in milliseconds so traction control is far more accurate than for a piston engine. (Elon Musk once Tweeted “Tesla dual motor cars are also all-wheel drive. Main goal of dual motor was actually insane traction on snow. Insane speed was a side effect” [4] ).

The motor can also act as a brake, which recovers energy (much of the energy used to climb a hill is put back into the battery rolling down the other side). The same characteristic makes it possible to drive on just one pedal; press to go, release to stop. It also saves on brake wear (one example was an electric taxi that did over 100,000 miles on the original brake pads).

Why now?

Electric drive dominated the early years of the automobile, and the electric motor has never ceased to be vastly better than a piston engine for driving a vehicle. There were however two big snags and one lesser one with electric drive. All three have been solved in recent years.

The first problem was energy storage. Piston engines may be inefficient, but motor fuel packs a huge amount of energy into a small volume. Once a distribution infrastructure is in place, the fuel is easily and quickly replenished which allowed essentially unconstrained travel. By contrast the lead acid batteries that dominated electric traction until recently were totally outclassed on both counts; too little energy and too much time to replenish.

Enter the lithium ion battery. Compared with lead-acid, this stores maybe three times the energy per unit of weight or volume (some a bit more, some a bit less). It has a far longer life than a lead-acid battery, is tolerant of partial charging, has no significant memory effect problems and (critically) can be charged very fast. 20 minutes for 80% charge is easily achievable with little effect on cycle life using modern batteries if you can suck power out of the wall fast enough [5]

The second big change has been the development of power electronics. Until the 1970s, electric motors were hard to control [6]. At worst they were either on or off. At best, control was lethargic. That all changed with so-called Vector Control. Inside a modern motor controller (sometimes called an “inverter” if the motor is AC) there are a number of huge transistors, capable of switching hundreds of amps. With cunning and some capacitors these can produce virtually infinitely variable output. A modern EV can be inched along at a creeping pace with far more precision than an ICE car equipped with a clutch, and with less effort: no clutch slipping needed.

The third, lesser, but still important change has been the growing capability of digital processors to do complex calculations in real time. Until quite recently, electric motoring has depended upon series (brushed) direct current (DC) motors. These work well at low speeds but they tend to run out of torque at high r.p.m. and are more difficult to cool. The advent of modern microprocessors has made it possible to synthesise three phase alternating current (AC) at the necessary power levels from a battery. This in turn allows the use of simple induction motors – no brushes to wear out and better cooling. An induction motor is essentially a hunk of iron on a stick inside a tube containing some electrical windings. Machines don’t come much simpler. [Some manufacturers prefer permanent magnet motors. They are smaller and lighter yet, but rely on rare earth magnets which creates supply issues. These motors can also terminate themselves in a sudden melt-down if they get too hot. I am not a fan.]

What remains to be done?

Several things need to happen before EVs become acceptable as a complete replacement for piston engine cars: broadly price, range and fast-charge

Firstly price. This is partly an issue of scale. If you make a million of the same model car, cost per car is a lot less than if you make 10,000. The financial services company UBS recently tore down and analysed a Chevy Bolt. Their conclusion? “total cost of consumer ownership can reach parity with combustion engines from 2018” [7]

Secondly range and thirdly fast charge. The average private car in the UK does about 21 miles a day. In the US, it is about 30. Most people do most of their driving either commuting or local driving. The problem is the half-dozen trips a year to visit granny or go on holiday. There is also a small percentage of users who do a high daily mileage as part of their work.

My personal opinion is that a 300 mile range should work fine for almost everyone, so long as fast charge to 80% capacity takes no more than about 20 minutes. This is just based on the idea that I wouldn’t want to drive more than 300 miles without a coffee and a potty stop.

Tesla’s high-end cars are well past 300 mile range. Even the (relatively) humble Renault Zoe which initially had a 130 mile range has (or soon will have) a 250 mile range option. Fast charge has some distance to go yet in practice, but there is no intrinsic problem in reaching a 20 minute charge.

Price, range and fast charge. EVs are a “whole system” problem that goes far beyond just making a better box for the punter to sit in.

Conclusion

This has been a quick run-through of the theory of EVs. If you are not convinced, go and drive one. Trickle along at three miles an hour listening to the birds sing then floor it. By the time you reach 30 you will be convinced.

Part 2 of this series looks at the problems this creates for the established Western automakers, and part 3 considers common misconceptions which lead some people to conclude that EVs will not be viable in the near future.

CONTINUE READING –>

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s