Electric Cars in their Time and Place

(originally published in Facebook, 2009-12-01)

Grid-powered electric cars are a short-sighted idea for general motorised personal transport. The concept doesn’t scale to fit a significant proportion of the motoring public.

It’s a simple matter of energy storage and transport. And the viability of such a scheme can be tested with a few simple calculations. Energy is energy.

Limits in Battery Technology

The energy density of safe, roadworthy batteries is simply too low with existing and foreseeable technologies. Electrochemical limits are the barrier. Physical limits of the real world. The energy needs for transport are too high when the vehicles have to meet the same standards for safety and comfort as “normal” cars.

The result is that electric cars will be city-bound; as the range is limited to about 100 km in practice; and will probably have no more than 2 seats. With such a short range, they will need frequent recharging and/or battery swaps if used for another purpose.

Battery Exchange

Battery exchange facilities would be getting between 3 to 5 times as many customer visits per day as a fuel filling station because of shorter vehicle range. For a busy exchange centre, that would mean around 10,000 exchanges per day. That takes a great deal of space because recharging a battery pack takes 50 times longer than refuelling a conventional car. The electricity supply grid isn’t capable of charging that many large batteries at a filling station. Each station would consume as much electricity as a suburb.

The “exchange fee” would have to be of the order of $10 to $20. With less than $5 in electricity stored in a “fully charged” one. Batteries will “wear” as they are discharged and again recharged; able to recover less and less of the initial energy put into the battery. The range of the vehicle becomes unpredictable as the battery is “suddenly empty”; with little warning possible.

Home Recharge

Charging at home also doesn’t scale. If one overlooks that garages are far from universal and a secure charging point is imagined viable, then it’s still a matter of putting the necessary energy into the car. And that amount of energy is 2 to 10 times the normal household’s electricity consumption for a daily commute.

Most commuter vehicles will need to be recharged during what are now off-peak hours for electricity; typically after 10 p.m. and before 5 a.m.. Off-peak electricity rates will shift to normal business hours as electricity providers will need to provide 3 times as much electricity in the dead of night, all night, as they do during the business day. That’s assuming that the electricity generation and distribution grid are upgraded substantially to match the demand for “domestic” traction power.

Viable Electric Cars

With battery technology having hit physical limits, we need to look elsewhere for ways of fueling electric vehicles. If you can’t get over the hurdle, sneak underneath or walk around it.

One option is to seek to produce chemical bonds in materials to produce a stable, synthetic compound; i.e. efficiently put the energy into a compound from a convenient, high-density energy source (e.g. nuclear). Then put that compound into the vehicle and collect the energy as the chemical bonds are released in a catalytically controlled reaction, as needed by the vehicle’s electrics.

The first part, that of producing a liquid electro-fuel, needs to do backwards what a fuel cell does forwards. Hydrogen is a small stepping stone, albeit in the wrong direction. It’s quite volatile with great expenses in distribution and storage; and is very energy-intensive to synthesize.

BMW announced early in December 2009, that the current fleet of hydrogen-fuelled vehicles would be the last in the foreseeable future. That followed VW’s earlier announcement that fuel cells were unsuited for volume deployment. (Article in the German Autogazette)

One of the “gotchas” with fuel cells that is not immediately obvious is that they develop a lot of “waste” heat. That heat must be rejected into the environment; which becomes more difficult in warmer climates and at higher altitudes. The amount of heat rejection is about the same as for a diesel-engined vehicle with similar engine output; so an active cooling system of about the same dimensions is essential.

Developing a liquid fuel with handling and storage characteristics like those of diesel fuel or gasoline would be a lucrative, commercial research field.

Finding CO2 not-guilty as accused of making the sky fall is probably a breakthrough as it makes carbon available for a heavily bonded synthetic fuel, which when run through a fuel cell, would produce nothing but harmless CO2, N2 and H2O.

The rest of the technology already exists to some degree. We “know” how to go about it.

Essential Internal Combustion

We can’t un-invent the internal combustion engine.

It’s gotten us where we are, and it’s doing so more efficiently and cleanly every year. The motor car provides unprecedented freedom of mobility, providing a large scope for choice of where we live, work and enjoy ourselves.

Remember those guilt-free Sunday drives?

Let’s not forget that internal combustion engines also move the raw material and products that we need to live. The even get us to a hospital in an emergency.

And we still need the internal combustion engine to provide a certain future. The necessary technologies for sustainable electic cars simply don’t all exist. Those technologies can be wished, but they also need to be invented before substantial money can be invested into making them commercially viable.

Footnote 2013-02-05:


Hybrid car pioneer and “father of the Prius” Takeshi Uchiyamada says the billions poured into developing battery electric vehicles have ultimately been in vain. “Because of its shortcomings–driving range, cost and recharging time–the electric vehicle is not a viable replacement for most conventional cars,” said Uchiyamada. “We need something entirely new.”

Addition 2013-12-03:

In response to a UWA Faculty of Engineering, Computing and Mathematics posting on Facebook pointing to an article at The Conversation: (With some links and fixes.)

Trailing-edge research.

$900,000 in R&D funds to tell us that nothing substantial has changed. EV are substantially hampered by the storage capacity of electrolytic cells and the distribution network of electrical power.

The full report mentions nothing of battery life; which is typically around 2000 cycles if the State of Charge (SoC), charge current and temperature are optimal. “Level 3” charging at 50kW of a 23kWh battery stresses the battery, shortening its life.

The City of Perth (CoP) Ford Focus had the longest trips totally about 27,000 km … in over 2100 trips. (~50km per day was the longest average for all by a wide margin. Trial average was less than 17km/day and less than 17 minutes per trip.) The battery in the CoP car would have used up about half of its life based on a partial charge per average trip. Deep charges following deep discharges shorten battery life significantly.

The cost of battery replacement per 100 km, given a 60,000 km notional life and $9000 for the parts, works out at $15/100km.

The electricity consumed (17% of which is reportedly lost during charging) is 16kWh/100km (the report is unclear if that was at the battery or at the charger outlet). A kWh of electricity costs about 30 cents, so that adds $4.80 to the battery-driven operational cost.

Add up the numbers and it’s about $20 per 100km.

For comparison, a modern turbo-diesel car of similar size (VW Golf) consumes up to 7 litres/100 km in urban traffic, which works out, at today’s heavily-taxed prices, to $11 per 100km. The diesel vehicle has a typical range well in excess of 700km and a “recharge” time of less than 6 minutes at a typical 5000kW (gross) outlet. [Units converted so that EE’s can understand the scale of power (and energy).]

Those are the sorts of cost and convenience metrics with which EV or any other vehicle technology has to compete. Still.

One has to keep in mind that EV were on the road for a decade before internal combustion engined cars. About 100 years ago. Their use over-lapped the first IC-engined cars for about 20 years. Liquid-fuelled, internal combustion engines won out for the majority of applications because of convenience (range) and costs.

Even with LiFePO chemistry, the temperature range of use (charge and discharge) is constrained and may not be possible in some exposed at certain times because the heat soak from the tarmac radiates directly onto the batteries which are, at the time, trying to lose heat. Battery life (and recoverable energy/range) is also significantly reduced when the vehicle is being driven “aggressively” on hot tarmac.

Additionally and especially given the recent Tesla eposode of where a battery pack, punctured by road debris ignited; the crash worthiness of such energy storage systems has to be considered. Directly at the front of the vehicle appears to be as smart as putting the petrol tank of a normal car in the front crumple zone.

As for the “Electric Highway”: It does not scale. Such concepts shouldn’t go past the back of the envelope jotting down the key numbers and the arithmetic that prove it to be unfeasible.

If EV are to “replace” conventionally powered cars, then there must be a plausible operational cycle not for a few thousand cars to serve a population of several million, but for a million cars to serve that population.

People buy and use cars to provide mobility. Independent mobility.

Addition 2013-12-17:

In response to a ABC Science posting on Facebook pointing to an article at Radio National where I found Monash Chancellor Dr Alan Finkel apparently spruiking for BMW’s i3 electric car:

The actual game-changing breakthrough is that the BMW i3 is available with an optional auxiliary power unit that converts it, when needed, from a pure electric car into a series hybrid electric car.

The breakthrough is a gen-set?

The intrinsic problems remain. Motive power requirements remain impractical to provide by “disconnected” electricity. The motive power requirements at the wheel are the same for all types of power source. Electricity is not amenable to the requisite storage density. Real people find that “filling up the tank” of electric vehicles is impractical.

While the i3’s gen-set provided a blindingly-obvious solution to being unable to store enough electricity to get around, it doesn’t stop the traction batteries from “wearing out”. Being smaller, they would be cheaper (for certain values of “cheap”) to replace, but would also cycle either more deeply or call on the gen-set more often. IIRC, 22kWh of replacement lithium batteries would cost about $9,000 at today’s prices.

In trying to be functionally acceptable, EV technologies consume a great deal of difficult to find and/or extract resources. It is doubtful if the EV’s will have resources available to meet the notional, long-term global requirement for personal motorised transport; of around 2,000million cars. (Maybe even 3,000million.)

There used to be a time when Mechanical Engineers could be impressed by blinkenlights. Now it seems that some EE’s can be entraced by the functionality of a simple generator driven by a de-tuned motorscooter engine. At least the gen-set’s 9-litre fuel tank can be refilled in a couple of minutes.

Without gen-set “range-extender” and at current electricity retail prices of around 30 c/kWh, the cost of “fuel” is $3.90. The 9 litres of fuel in the range-extender (gen-set) provide another 120 to 150 km. 7.5l/100km is not a good rate of fuel consumption for a small car built this decade. Even at 6 l/100km it’s off the game; especially when compared to a small turbo-diesel.

P.S. I remember that James May demonstrated the same transformational breakthrough in a self-constructed, electric car on Top Gear a couple of years ago.

1 Response to Electric Cars in their Time and Place

  1. DirkH says:

    I’d like to see a version of Mad Max II only with a huge battery transporter truck instead of a tanker. All the renegade vehicles would be EV’s as well. The chase scene would have to stop for a recharge every minute, and after a day of recharging their vehicles with solar panels they would drive a few meters until they run out of juice again.

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 )

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

This site uses Akismet to reduce spam. Learn how your comment data is processed.