Been seeing and hearing a bit lately about electric cars. The latest is the hype in the latest NRMA Open Road.

I hear a lot that electric cars are "zero emission", and as an Electrical Engineer I can only say this is utter BS. They have left off the last bit - "zero emissions at the tailpipe but plenty at the power station"

Let's just think for a moment that every person in Sydney took their internal combustion cars to the scrap dealer and bought a full electric car. Wasted carbon aside, everyone would want to charge the cars at the same time. Picking a kW number to charge a car, as I don't know exactly what voltage they charge at or what current, let's say 5kW which is about 20A at 240V. A unit at Bayswater or Eraring power stations is 660MW. At 5kW per car that is 132,000 cars. So let's drop the charge kW and say 250,000 cars charging at about 2.64kW each ALL NIGHT needs a 660MW unit ALL NIGHT. So if we take 1 million cars off the road and replace them with electric cars, you need both Bayswater and Eraring running full tilt ALL NIGHT to charge the cars. So where does the power come from for normal operation of the rest of the State of NSW?

Then to get the power to Sydney, you also have to generate the energy loss in transformation and transmission.

To me it doesn't add up - we will need another at least 4 x power Stations the size of Eraring and Bayswater to keep up, yet we are losing Liddell soon and have already lost Vales Point and Munmorah. Solar cannot help, unless everyone charges their own cars with Solar, but you want to charge it at night when there is no sun?

From what I understand there are electric car Super Chargers that can charge a car in 30min, but run at 25kW up to as high as 130 odd kW. At 25kW that is only about 26,000 cars to a 660MW unit, minus the losses to get the power to the car.

So all the supposed savings in vehicle emissions we just shift to power stations?

The only way it can work is if solar panels charge the cars directly, so large volume solar panels are needed where high concentrations of cars park during the day, and the car batteries become the solar storage. Otherwise the economics don't add up.

It might a bit of an overstatement to say Hazelwood was the only reliable power supply, but it did constitute 25% of Victorian baseload capacity. I haven't seen any sensible replacement strategy yet, but I'm sure they'll be supplied by moonbeams and happy thoughts.

Something like the biggest fattest Tesla has a battery capacity in the order of 100kWhr, and a recharge efficiency around 90% so you'd need.to put 111kWhr back into a flat battery. From fully discharged, assuming a 12 hour recharge time you'd need 9.2kW which is 38.5A at 240V. Not everyone has a three phase mains connection, so a large proportion of houses would struggle to run a load that large with a single phase supply. ETSA in South Australia, for example, used to refuse to connect anything bigger than 5kW single phase due to supply balance and harmonics issues.
And that's ignoring the generation and capacity issues Byron raised.

Ever seen what a 111kWhr solar system looks like, or the battery system required to store it's output so you can charge your car at night?
Or the inconvenient fact that the real world lifetime for the car battery and the solar battery will be 6-7 years.

Not terribly practical just yet.

I suppose you could always run a "Bunnings special" generator all night to charge your car. That way you'd still look like a greenie during the day.

111kWh is what needs to go into a 100kWh battery to fully recharge it from a full dischrge. Add to that the charger efficiency and you have a mains supply draw of 123kWh.
Then the cost of ownership - a 7 year battery life to 40% capacity and depending on who you believe, a $40,000 full replacement cost.

Not cars, strictly speaking, but relevant to a previous topic.
The life for this system will be 7-10 years at best.


http://www.news.com.au/t...8e143cf3ae7f2cf53c67914d