Bazz: "You could charge batteries during the day and charge from them at night but the losses involved would make it a no goer."

Perhaps so - I don't know what the efficiency of the typical lead battery used in a house setup is. Certainly other battery chemistry's aren't so bad. This mob [1] claims their LiFePO4 batteries are 95% efficient, but people who have measured other brands of LiFePO4 seem to end up around the 90% figure.

However, there are other solutions - like getting paid to put your electricity into the grid, and then paying to charge from the grid where you park your car for the day. Or making the batteries part of the house system and rotating them through the car.

The point I was trying to make is that once you store the energy the unreliability of renewable energy becomes amenable to a lot of solutions and so is a lot less of an issue. The problem always was finding cost effective way to store the energy in the first place.

[1] http://www.edealsbargains.com.au/page1.php

rstuart,
A long, long time ago I attempted to measure charge/discharge
efficiency of lead acid batteries. I found it very difficult to do.
The specific gravity did not seem to track the electrical indications
too well. It was difficult to charge from a certain point and then
discharge to the same point. From memory I think I got figures between
50% and 80% before I gave up.
However the solar feedin and then charge at night would be pretty good.

Changing the batteries would be very cumbersome (and heavy).
Most electric cars I have seen distribute the batteries for and aft to
even out the load on the suspension and this would make battery
changing even more complicated.

No, solar cells feeding the grid during the day and charging from
the mains at night is the way to go.

Rstuart,

Your figure of 42% efficiency is possible using the latest hitech high temperature metals, using ideal coal (low ash top grade, not high ash or brown coal) which have only been possible to build in the last 10 years at great expense.

The reality is that the average efficiency world wide is 31% as quoted by:

http://www.euractiv.com/en/energy/analysis-efficiency-coal-fired-power-stations-evolution-prospects/article-154672

"Nowadays, with a world average efficiency of around 31%, coal-fired power stations is said to compare favorably with the upper range of any other power generation technology."

And considering that 31% is considered good, 42% is a bit fanciful.

Personally I drive a small car that get 6.5l/100km and our big car is a Renault 4x4 that gets 8.5 litres /km. The fact that Australians love their big cars with V8 engines would suggest that these cars use a little more that 20kW (cited by your hybrid car) and that using this figure is distorting the facts.

Secondly charging efficiencies on batteries including the charger losses (15%) are about 65% at best.

The figure I get is that the average car needs about 30kWhr per 100km (including battery losses delivering the power)

My reckoning is that a reasonably efficient family car (8.7l/100km) would generate 26.5kg CO2 and the Equivalent electric car would generate closer to 43kg of CO2.

While power generation is getting greener, it has to go a long way before the electric cars can claim to be greener.

Also the proposal to charge a spare battery during the day and changing batteries would be an extraordinary feat considering the size of batteries required for an electric only car.

Shadow Minister: "considering that 31% is considered good"

You sure chose the wrong link to illustrate your point - I wish I used it originally. Firstly 31% is the average for coal-fired power stations now. How can the average be considered good? The link said 31% was good compared other technologies, such as an internal combustion engine. Secondly the 42% figure I quoted was meant to show that we can expect improvements as time goes on. Compared to the conclusions in your link I was being conservative:

"Energie-Fakten considers it feasible to have 55% efficiency available for the necessary replacement and addition of coal-fired power capacity."

Shadow Minister: "30kWhr per 100km"

You and I will have to differ here. I will go with what the power meter on the Lexus says. The hybrid Lexus isn't a small or light car - its specs say the engines can deliver a combined total 360 KW. It has air-conditioning and every other gadget know to man, and they were all switched on. As I said, it the power meter showed it was drawing 25 KW and that is the figure I used in my calculations. This is more than the 20 KW figure often quoted as size of electrical motor required to push a vehicle at 100 Km/h, but the 25 KW is from a real, live family sedan going down a real live Queensland road at 100 Km/h, which is why I used it.

As for "battery losses" - as I said earlier, LiFePO4 has a cycle efficiency of 90%, or perhaps better. My calculations used 80%.

Democritus was simply wrong when he said electric cars produce "far more" CO2. "More" would of been defensible, on the understanding that it will become "less" or possibly even "far less" as electricity generation becomes greener. Call me pedantic, but I see take exception when I see crap like that come from someone that looks to have a strong technical background. I expect better from my peers - and thus the strong words.