Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Archive for the ‘electric vehicles’ Category

Thinking about Better Place’s EV infrastructure proposals.

with 2 comments

For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.
— Richard Feynman

Better Place has attracted a lot of publicity recently, including on the Today Show and in the New York Times, following their agreement with AGL Energy and Macquarie Capital Group to raise one billion Australian dollars (about USD $665 million) to build a network of electric-vehicle battery infrastructure across Australia.

Better Place’s model offers a network of battery stations, just like petrol stations, at which an attendant will swap out an electric vehicle’s discharged Li-ion battery for a newly recharged one.

Drivers belonging to a monthly subscription service gain unlimited access to Better Place stations and fully-charged batteries for their cars. While electric-car owners can still charge their cars at home, a series of stations gives them more flexibility to travel long distances despite a battery’s limited range.

These are the biggest challenges to electric vehicle adoption – even the very best electrochemical batteries give a relatively low limit to the maximum range, they take a long time to recharge, there’s no infrastructure for recharging on the go, the batteries have finite lifetimes, and they’re very expensive. There’s only so much energy you can store in a given amount of battery of any particular chemical composition, and there’s a limit to the rate at which you can pour energy back into the battery in practice – these barriers are not things you can easily get around with politics and marketing.

The Tesla Roadster, as an example of one of the few battery electric vehicles on the consumer market today for which plug-to-wheel energy consumption data is easy to find, consumes 199 Watt-hours per km. In February 2008, Tesla Motors reported that, after testing a Validation Prototype of the Tesla Roadster at an EPA-certified location, that those tests yielded a range of 220 miles (354 km) and a plug-to-wheel efficiency of 199 Wh/km. (Admittedly, the Tesla is probably sacrificing a little energy efficiency for the sake of performance, meaning that it could probably be possible to deliver better energy consumption in a vehicle designed with that consideration in mind.) I’ll use the Tesla Roadster as a specific example, mainly because such technical details of it are easy to find.

The battery in the Tesla takes 3.5 hours to charge from zero charge, and stores 53 kWh of energy. Efficiency of the charging electronics is 86%, so 62 kWh of electricity is needed for a single charge.

If you just plug in the vehicle to charge it, and it consumes 62 kWh to charge the battery, and charges in 3.5 hours, then the line power supply to the charger must supply 74 A at 240 V (AC RMS) or 144 A, on a 120 V grid. Those are very large currents, far in excess of the maximum capacity of 10 to 15 A or thereabout that we associate with standard domestic power circuits.

If you were to just plug in such a vehicle into a household electricity line socket to charge it, (at 10 A at 240 V), then a 12 hour charge would correspond to a range of 164 kilometers, or a round trip of 82 kilometers.

If you need to travel further than that in a day, then clearly “charging stations” like the Better Place model, or some kind of provision for high-current power supplies to charge the vehicles, needs to be available. In principle, at least, the Better Place business model sounds like a good idea.

The service also saves drivers time, according to the company, since Better Place attendants can swap out a battery in about three minutes, versus the few hours it takes to recharge a battery.

Keeping in mind that electricity is only as clean as its energy source, Better Place claim that their stations will purportedly recharge their stocks of batteries using electricity from renewable energy systems.

Better Place proudly proclaims that “We will build an electric vehicle network capable of supporting the switch of Australia’s 15 million gas cars to zero emission vehicles.” and that “AGL will provide all of the renewable energy—from wind and other sources—needed to power the electric vehicles and work with Better Place to optimize the network.”

The total ‘renewable’ electricity generation in Australia in 2007 was 20.964 TWh, almost all of which (14.722 TWh) is hydroelectricity.
[Source]

So, if all of Australia’s current renewable energy generation, across all energy utilities – which is already used, already traded for “carbon credit”, and sold to “green power” customers – was used to power Australia’s 15 million passenger cars, assuming that they were all replaced by battery electric vehicles, then there is only enough renewable electricity generation at present for each car to travel an average of 19.2 kilometers per day, assuming that only “renewable” energy, i.e. hydroelectricity, and solar, wind, tidal or biofuel generated electricity was used to power 15 million BEVs, and that every bit of electricity generated from these systems in this country was dedicated exclusively to this use.

In 1991, cars in Australia travelled an average of 14,600 km [source], or 40 km per day. If this level of car use was maintained today (unfortunately I cannot find any newer statistics), then total renewable energy generation would have to be multiplied 2.1 times from present levels – assuming all cars were replaced with BEVs and that all the renewable electricity generation was used exclusively for charging the BEVs, and no fossil-fuel-generated electricity was used. I don’t think I really need to convince anybody that any real expansion of hydroelectricity is not something that is at all foreseeable nor really practical in Australia.

Simply muttering the magic word “renewables” three times and clicking your heels, or something, isn’t grounds for conjuring up an arbitrarily large quantity of cleanly generated electrical energy – the infrastructure has actually got to be put in place to generate that corresponding quantity of energy.

The entrepreneur wasted no time comparing the east coast of Australia, where Better Place will build “electric highways” connecting Melbourne, Sydney and Brisbane, to the West Coast of the U.S. where Agassi would like to do the same between L.A., San Francisco and Seattle. The greater Melbourne-Sydney metro area will require 200,000 to 250,000 charging stations, Agassi said. Better Place plans on deploying some 500,000 charging points for the whole of Israel.

Under the plan, the three cities will each have a network of between 200,000 and 250,000 charge stations by 2012 where drivers can plug in and power up their electric cars.

If you have 250,000 charging stations (I’m not sure if they mean 250,000 total for the east coast, or 200,000 to 250,000 each in each of those three cities.) and 21 TWh per year of renewable energy, then that’s only enough for each charging station to be able to recharge three batteries per day, which is obviously completely insufficient. (1 day * (21 TWh per year) / (250,000 * 62 kWh) = 3.7)

In practice, burning one litre of petrol in an automotive engine results in emission of 2.32 kilograms of carbon dioxide per litre. Obviously, better fuel economy means better CO2 emissions economy per kilometer.

In Australia, the average GHG emissions intensity for electricity generation is 1000 gCO2/kWh. (In Victoria, it’s obscene, about 1300-1400 gCO2/kWh.) The Tesla Roadster has a plug-to-wheel efficiency of 199 Wh/km. Therefore, the equivalent CO2 emission for the Tesla Roadster is about 20 kg CO2/100 km.

So, if you can have a petrol-burning IC engine car with a fuel economy equal to 8.62 L per 100 km or better, then in terms of CO2 emissions, it is equally as good as, or better than, such an electric vehicle. In brown-coal-powered Victoria, the point of equivalence is about 11 to 12 litres per 100 km – which basically all cars surpass, at present.

8.62 L per 100 km is 27.3 miles per gallon – so that’s approximately equal to the old CAFE standard for cars in the USA, which I’m pretty sure was 27.5 MPG, and significantly worse than the newer standard of 35 miles per gallon. It is totally practical to build cars with such a degree of fuel economy.

Whilst in principle electric vehicles are a good idea particularly in the long term, we have to realise that right now, given the current state of electricity generation in Australia, the number one priority, in terms of mitigating excessive anthropogenic emissions of greenhouse gases, has got to be the replacement of fossil fuel based electricity generation with non-polluting systems.

While we’re implementing that, I also think that improving the fuel efficiency of ICE cars and vehicles is just as easy, probably more cost effective, and capable of delivering an equal degree of improvement in the environmental intensity of the transport sector, at least in the near term, until the coal-fired electricity generators start being replaced.

Robert Merkel over at Larvatus Prodeo posted a good post on the same topic recently.

I’ll leave you with a quote from Merkel – I couldn’t agree more with this:

If I were a government minister receiving a visit from Better Place and its partners for some kind of government incentive, I’d look very long and hard at the environmental benefits we’ll get for the dough they’re asking for.

Just like solar panels, I’d expect the answer to come back – lots of money for bugger-all environmental gains. And that should be the bottom line, not slick PR campaigns that suck in a gullible mainstream media.

Written by Luke Weston

October 29, 2008 at 8:31 am

Electric vehicles: A quantitative look.

with 4 comments

For argument’s sake, I’ll start with an assumption that the fuel economy of your average petrol-fuelled ICE passenger car is about 7 L per 100 km under conventional conditions.

7 L / 100 km corresponds to about 15.1 kg carbon dioxide emissions per 100 km.

(You can use the above expression in Google Calculator, and just substitute in any alternative figure for the fuel consumption for your particular car, if you like.)

(In the above calculation I’ve used the assumption that petrol is basically pure n-octane in chemistry terms, in terms of its density and carbon content.)

Obviously, better fuel economy means better CO2 emissions economy and vice versa.

(For readers in the US (or elsewhere) who would prefer the Imperial units, try this link instead. Fuel economy of 30 MPG will correspond to about 0.6 pounds of carbon dioxide per mile.

The Blade Runner Mk. II BEV, for example, (which you can buy in Australia now), requires a charge of 95 amp-hours at 240 V, and has a range of 120 km, corresponding to an electric power consumption of 190 Wh (Watt-hours) per km.

(Similarly, if we know the charger’s current draw, voltage, charge time, and the vehicle’s operating range for a single charge, then the electrical energy required to run the car for a given range is straightforwardly calculated for any EV.)

The tech specs for the Tesla Roadster claim that its electric power consumption is 110 Wh/km.

The specifications for the Mitsubishi i-MiEV correspond to about 154 Wh/km average.

In Australia, the average GHG emissions intensity for electricity generation is 1000 gCO2/kWh. (In Victoria, it’s obscene, about 1300-1400 gCO2/kWh.)

Therefore, the equivalent CO2 emission for the BladeRunner is 19 kg CO2 per 100 km, for the i-MiEV it’s about 15.4 kg / 100 km, and for the Tesla Roadster it’s about 11 kg CO2/100 km.

So, for electricity generation like Australia’s, the i-MiEV is about the same, in terms of its indirect greenhouse gas emissions intensity, as an average, reasonably fuel efficient, petrol-burning ICE car. The BladeRunner is significantly worse than an ordinary car, and the Tesla Roadster is significantly better – but I guess the Tesla represents what is essentially a top-of-the-line EV, with a price tag to match.

At the moment, in Australia, there is absolutely nothing to be gained at all, in terms of greenhouse gas emissions reduction, from electric vehicles. (Unless you get a Tesla). (In fact, choosing an EV over a new, relatively efficient petrol or LPG fuelled conventional ICE vehicle, which you could easily get for the same kind of budget, could very well represent a significantly worse choice, in terms of GHG emissions.) For that to change, what is required is a large reduction in the greenhouse gas intensity of electricity generation – replacing coal-fired generators with nuclear power or other clean electricity generation.

However, the greenhouse gas intensity of Australia’s electricity supply is very bad, by global standards. Ontario (in Canada) is an example of a place where extensive uptake of nuclear power, and extensive access to hydroelectricity, have almost completely displaced coal-fired generation, and provide electricity with extremely low greenhouse gas emissions intensity – about 200 gCO2/kWh, or 20% of the Australian average. In Sweden or France for example, you’ll see much the same.
In the US, for example, on the average, it is somewhere in between.

Thus, under these conditions, the BladeRunner has equivalent GHG emissions of about 3.8 kg CO2 per 100 km, 3.1 kg/100 km for the i-MiEV, and about 2.2 kg/100 km for the Tesla – all of which are far superior to any ICE vehicle.

Written by Luke Weston

August 10, 2008 at 4:37 am

Follow

Get every new post delivered to your Inbox.

Join 75 other followers