Punx0r said:
Ok, so 10min uphill trip at ~3MW = 500kWh.
We know that for a regen system energy recovered on the trip back down would be less than that, hence required battery capacity would be less, but would need to support or 6C charge rate, or be larger to reduce the C-rate.
IIRC A123 AMP20 cells will do 10C charge. But would weigh (500kWh/0.13kWh) 3850kg for bare cells alone and cost ($1/Wh) $500,000 retail.
There again, the truck weighs 360,000kg empty and the diesel engines are probably close to $500k each...
I see I got the numbers completely wrong.
Charging would be the big thing. Strip away the massive generators, and stick in a few megawatts of batteries. The big ones retail at about $5,000,000 another million wouldn't matter that much.
The Fuel Consumption
The fuel figure on Wikipedia is
198 g/kWh per generator. We'll go with the three megawatt figure for convenience and divide it in two for best scenario.
594 kg of diesel are consumed per hour.
According to another article they are refuelled every 12 hours. Let's say they can work up to 22 hours a day.
13,068kg of diesel are burned every day.
The Fuel Costs
A US gallon of diesel costs
$2.45 of thereabouts. Knock a best case scenario of 20 per cent off the price for bulk purchases and we'll call it
$2 a gallon. That's $8,115 wasted burning diesel every day. Run her 360 day of the year to allow some maintenance and tyre replacements and its now
$2,921,465.
Let's say you only run one of the generators and cut the consumption in half that is
$1,460,732 In reality the figure would probably be 75 per cent rather than 50 per cent.
Electric Haul Truck Consumption
Now to compare the same charges for electricity but we will try to error towards the worst case. Our all electric requires
66 megawatt hours of electricity per day - which works out at
23.760 gigawatt hours per year. Looking at the wholesale prices the average price per megawatt seems to be between
$35 and
$50 - that's according to the U.S. Energy Information Agency.
The all-electric haul truck works out at
$831,600 at $35 and
$1,118,000. A saving of between
$300,000 and
$600,000 per year.
German Fuel Prices?
I wonder what rates do countries like Germany pay per litre? If you knock 20 per off the price of a litre of diesel in Germany the fuel for the same haul truck above costs
$5.523 million and that's treating the euro as being on par with the dollar. Even if you half that figure again that still a lot more than American companies pay.
In Germany electric haul trucks make much better economic returns than in the U.S. Electricity is much cheaper the day ahead base price per megawatt hour is €32.9 for 2014 and the peak was only €36.24. You'd save €4.471 million per year in the best case scenario (if those fuel prices for diesel are correct.)
Our Hypothetical Battery
For the all electric dump truck, assuming
90 per cent efficiency compared to
50 per cent for the diesel generator you would need
18.3 megawatt hours of battery, plus a nice buffer - make it
25 megawatt hours for a like-for-like replacement -
11 hour shift.
That's a battery pack that weighs
192 tonnes if you go with
A123,
312 tonnes if you go with
lithium titanate and
100 tonnes if you go with
Tesla's Panasonic NCA for just the raw cells plus add on another
20 to 30 per cent for the structure to protect them, the BMS and the wiring.
We'll say that
A123 could do the battery for
$500 per KW/hr that's
$12.5 million for the cells for
A123, Toshiba could probably do the
SCIB for
$900 per KW/hr -
$22.5 million and
Panasonic could probably do the raw cells for
$190 (they charge Tesla $160) per
KW/hr - $4.66 million. Add another half a million for the wiring, cooling and BMS and you probably get the figure - though you might save that amount by not having the generators.
The Reality of The Electric Task
Fast charging seems to be the key. Irrespective of the chemistry if you could charge them at 2C up to 90 per cent and cut the run time down to every five and a half hours by charging for just 20 minutes the battery weight and costs are dropped in half. If you're going for longevity titanate is the only player but it is so expensive and way too heavy.
Liquid-cooled Panasonic cells are really the only viable option and the next-gen cells would reduce the weight from 50 tonnes to 40 when the 300 watt-hour per kg cells eventually are manufactured.
In terms of cycles with the
two shifts a day scenario that's
7,200 partial cycles over a ten year period.
Four shifts a day sees that figure jump to
14,400 cycles.
Anyway, I spent far too long on this.
Edit: Added some structure and highlights to the wall of text.
Anyway the final totals are correct as I used the proper figures.
