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Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 8:23 am
by aardvark_admin
This column is archived at: https://aardvark.co.nz/daily/2019/0509.shtml

Could it be that, with battery technology seemingly stalled for now, fuel cells may be making a come-back as the energy source for EVs?

With some of the earlier problems seemingly being solved, who wouldn't opt for the simplicity of liquid or gas refueling over lengthy recharging and the benefits that come from saving hundreds of Kg of weight by dispensing with all those thousands of 18650 Li-Ion cells in the floor-pan?

Might it be that although your next car could be a battery-powered EV, the one after that could be fuel-cell-based?

Re: Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 9:56 am
by namartinnz
Personally, I still like the idea of having a battery powered car and "topping it up" at home - whether by power from the grid or a future solar/battery setup. Unless there's a cheap and simple home solution to refill your hydrogen at home, you'll still be needing to rely on a 'gas station' to fill up. And seeing as most commutes are less than 30 or 40km, battery still looks good, even if they eventually lose part of their charging capacity. Risks aside with the occasional fire (and ICE vehicles don't catch fire..) I can live with that...And as for solid state batteries, they're not far away, probably along the same lines as fusion reactors...

Re: Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 10:20 am
by paulw
Hydrogen fuel cell vehicles sounds like a good idea but if you have to fill up at a gas station then you're still at the mercy of the the oil companies who will most likely own them and will be priced high. Also you have make hydrogen and store it. Can't see that happening at home.

Re: Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 10:23 am
by ffirman
These are the advantages for Hydrgoen Fuel Car cars. I can't comment on other fuels for the fuel cell, like methane.

Fast refill - 5-10mins
Long Range - 500-700km

And the Cons
Expensive to buy the fuel cell system - though that might change if more are made - economies of scale all that.
The hydrogen is also expensive - Where places actually have filling stations the cost to travel the 500-700km is similar to the cost with petrol.
It takes a lot of energy to create and store the hydrogen. The estimated source to wheels is about 30%. 1kg of Hydrogen = 40KWH. Electrolysis uses 50-55 to get 1 kg of hydrogen (80%). Compressing to 350bar takes 1KWH, fuel cell efficiency 40-60%, then it goes in to a battery (99% efficient) - out of battery (95%) and to the inverter (90%) then to the electric motor. (95%)
So total efficiency = 0.8*0.98*0.5*0.99*0.95*0.9*0.95 = 31.5%

For a battery car the efficiency is 0.99*0.95*.9*.95 = 80%

The life of the expensive fuel cell is thought to be around 2000-4000 hours in a car, with a continuously running one good for 40,000 hours. Average car speed is likely to only be in the order of 40km/hr, so that provides a range of 80,000 to 160,000km. Batteries are already lasting way longer than that (if not a Nissan Leaf battery). Estimated life down to 80% for a 64kWh battery (Hyundai Kona) is about 1,500 charge cycles. Each charge cycle in that car = about 400km. This gives a 600,000km life on the battery and it will still hold around 51KwH which if not good enough for the car would make an awesome solar house battery.

I have not been able to find any information on how long the carbon fiber tanks last for, or if they have to be tested like what used to happen for CNG tanks (every 5 years I think). Even standard LPG tanks only have a 10 year life, and these carbon tanks are buried inside the body of the car, so not something that is easy to drop out for testing or replacement.

For large vehicles, I can see that the extra energy density of the hydrogen will out way the extra costs - think Trucks, planes, boats etc. Though to make the storage of the fuel easier, as hydrogen really isn't, using methane might be a better option.

So for small vehicles, I see batteries being sufficient and a better option. For large vehicles where the amount of energy wanted is GwH+ then the fuel cell system sounds better. That being said there is a battery powered car ferry being run in Swedon/Norway and it has been so successful they are going to get more. This one only has enough storage (Still lots) to do one trip, and while the cars are unloaded/loaded they charge the batteries up.

As for the Range - that is not becoming that much of an issue. The latest cars / suvs are providing 400-500km or 6-8 hours of driving before requiring to be charged.
And the charging time is also not becoming that much of an issue either. After 6-8 hours, a 30 min top up of food, drink while the car gets a 80% charge isn't that much of an issue. And as an example BMW/Porsche showed a charger topping up a car from 10% to 80% in 15mins of a 90KwH battery. It was running at 900 volts and 500 amps, or 450KW.


Full disclosure - We own a Leaf and a Hyundai Ioniq electric. Also have a Toyota car, 3 motorbikes and a sail boat with an annoying diesel. (old)


Fran.

Re: Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 10:48 am
by phill
all are probably far more environmental ( sustainable ) than crude oil derived
but if i had a wish
ethanol would be the fuel of choice ( expect a huge backlash from the oil industry, electricity generators and the tax department )
the idea of a practical home manufacturing plant for ethanol by using starch containing plants and food scraps and then solar distilling is in the dream come true bracket
( current tec solar water heaters can get to slightly over 80C .. ethanol boils at 78.4C )
https://en.wikipedia.org/wiki/Direct-ethanol_fuel_cell

Re: Forget EV batteries (9 May, 2019)

PostPosted: Thu May 09, 2019 10:50 am
by aardvark_admin
Excellent information Fran!

Re: Forget EV batteries (9 May, 2019)

PostPosted: Tue May 14, 2019 8:59 am
by RoddyAxn
Fran
What a wonderful write up. Your comments are both qualitatively athorituve and quantitatively informative.

Think thorium power with hydrogen

The loss of heat can be used in converting water to gas

And carbon free. So no methane

Also thorium power is local

Build a Thorium plant anywhere
Moon or mars