Tracker wrote:and how could they charge excise for use of Home-Brew car fuel..???
Do you mean "how" from an ethical or practical viewpoint? From a practical viewpoint, you are requird to download the forms from the ATO web site, register as a producer of biodiesel and then start paying on a "declaration" basis. I would assume that electric cars and CNG, when "they" get wind of them, will fall under the same scheme! From an ethical viewpoint, it is no different to working for a week and then paying a large chunk in tax, or making an investment and paying CGT on the profits...!
Tracker wrote:The only question I am left with is what constitutes a FULL CNG tank and how far that will take you.
As you suggest, if the compressor output is 6.6L petrol equivalent/hour, and the time to fill a tank is 2.5 hours, then the tanks has a petrol equivalent of 16.5L - or about 165km of range in their "typical" car! Which is interesting because they say you can travel for 170km on $10 of "station" CNG - not without refueling you can't!!
Also, again as you suggest, 2.2kw for 2.5hours is about $2 in electricity, or >20c/litre petrol equivalent even at cheap rate. Natural gas, last time I looked, was about 2c/Mj, which equates to 76c/m^3 (at 38mj/m^3). The compressor specifications state 6m^3 = 6.6l petrol equivalent, so
(6m^3 x 76c/m^3) / 6.6 = 69c/litre petrol equivalent.
Add the 20c for electricity and you get 89c/litre.
I'm rushing because I have to cook dinner for the kids, but that doesn't equate to the 27c/litre petrol equivalent that they state....
It would appear that 1L of petrol has much the same energy a 1^m3 of natural gas (35mj for petrol, 38mj for natural gas) so the 6.6m^3 = 6.6L petrol does hold true. And if 2c/mj is the correct price for natural gas, then the price in the advertising blurb of 27c/litre petrol equivalent would indeed seems a gross understatement, even disregarding the electricity to run the compressor!