GRA
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Re: Hydrogen and FCEVs discussion thread

Tue Mar 19, 2019 4:04 pm

RegGuheert wrote:
GRA wrote:I expect it will be at least five and maybe ten years before one or the other tech reaches the stage of virtually universal choice which fossil fueled MHE have held for the past century.
Do you have any evidence that Plug Power Fuel Cells are not powered by fossil fuels? My friend told me the hydrogen he provided for that purpose was steam reformed from natural gas.

Of course some of the energy for electric forklifts comes from fossil fuels, as well.

How the H2 is made is up to the supplier, and will of course be driven by price (and regulation). As I've said before, unless we move towards 100% sustainably-produced H2, it makes no sense to use FCEVs.
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WetEV
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Re: Hydrogen and FCEVs discussion thread

Tue Mar 19, 2019 5:38 pm

SageBrush wrote:
WetEV wrote:
SageBrush wrote:In its own way, H2 is no less idiotic than nuclear, and it tends to be hawked politically by the same fools.

I'd be interested in your solution to the last 10% problem.

Ask me when we are at 80%


Sounds like maybe you should think about hydrogen as season shifting storage.
And/or think about nuclear.

Maybe there is an answer. Maybe we will burn all the fossil fuels available, then crash back to the stone age. If we survive that long.

Oh, but you can't. That would make you "idiotic" and one of "the same fools."
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cwerdna
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 12:47 am

I recently heard an NPR story on FCEVs in Japan via their app.

I found it via https://www.npr.org/2019/03/18/70087718 ... rogen-cars but the text there doesn't match up completely w/what's in the under 4 minute audio clip (e.g. example is a mention of an H2 station that says they get a max of 15 customers a day).
Only about 11,000 fuel cell vehicles are on the road worldwide. Nearly half of them are in California, which has stringent vehicle emission regulations and tax credits that incentivize electric and fuel cell vehicles.

But in countries like Japan, where much of the population lives in dense urban areas, many people live in apartment buildings without a place to easily charge a car. It's here where companies like Toyota are banking on the convenience of the hydrogen fuel cell.

"There's just no behavior change as long as you have [hydrogen] infrastructure in place," says Matthew Klippenstein, co-author of the online publication Fuel Cell Industry Review. "We go to the same gas station and fuel up in the same few minutes and just keep on tootling on."

This might explain why RonDawg and I in late 2015 saw very few EVs (and Leafs) on the road in Japan.

I was there again in late 2017 (for a much shorter length of time) and also hardly saw any EVs on the road.

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RegGuheert
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 2:40 am

SageBrush wrote:It is said by optimists that electrolysis efficiency will reach 80%, and fuel cells will reach 70% efficiency in the future.
With a theoretical efficiency of about 83%, I'll guess that the 70% number is about right. Water electrolysis could top out at or above 100% given that the theoretical efficiency is around 120%.
SageBrush wrote:I'll wager good money that cell batteries will drop to $50 a kWh for the manufacturer, energy density will double, and charging speeds average over 200 kW long before the hoped for H2 improvements.
I think you are correct on all counts. But here is the rub: Many of the near-term improvements in batteries will be achieved by moving to a solid electrolyte. That change will increase energy density and safety and reduce cost. Unfortunately, it will also reduce the efficiency.

Instead of the 98+% round-trip energy efficiency which is achieved in the battery in your Tesla Model 3, battery efficiency could drop to somewhere between 60% and 90%.

So we will get back to the thesis that GRA has always held: People will choose convenience over efficiency any day. If we lower the round-trip energy efficiency of batteries to 80% and increase the round-trip energy efficiency of hydrogen to 60% or 70%, what will people choose for their vehicles?

I suspect there will be different preferences for different people:
- For someone like me who produces electricity on my roof and can charge at home, I will continue to prefer a battery-electric vehicle since the fuel is pre-paid and charging at home is more convenient than stopping for fuel. I will also prefer a Li-ion battery over a solid-state battery given the higher efficiency since that means I get more "miles per panel" from the investment on my roof.
- For others living in single-family homes, I suspect they will also prefer BEVs over H2 FCVs based on the convenience factor.
- For people like GRA who rent, I suspect the convenience of H2 FCVs *may* win out.

But even if the efficiency numbers do end up that close, then cost will end up being the deciding factor. Since I don't see the fuel or vehicle cost of H2 FCVs ever getting close to that of BEVs (again, there is NO crossover point), I suspect that even many without their own homes will choose BEVs, pushing for better charging infrastructure to make that option viable.

As always, time will tell.
RegGuheert
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Titanium48
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 9:29 am

RegGuheert wrote:
SageBrush wrote:It is said by optimists that electrolysis efficiency will reach 80%, and fuel cells will reach 70% efficiency in the future.
With a theoretical efficiency of about 83%, I'll guess that the 70% number is about right. Water electrolysis could top out at or above 100% given that the theoretical efficiency is around 120%.

Is somebody randomly switching numbers for liquid water and water vapor? Shouldn't both theoretical efficiencies be 100%?


RegGuheert wrote:
SageBrush wrote:I'll wager good money that cell batteries will drop to $50 a kWh for the manufacturer, energy density will double, and charging speeds average over 200 kW long before the hoped for H2 improvements.
I think you are correct on all counts. But here is the rub: Many of the near-term improvements in batteries will be achieved by moving to a solid electrolyte. That change will increase energy density and safety and reduce cost. Unfortunately, it will also reduce the efficiency.

Instead of the 98+% round-trip energy efficiency which is achieved in the battery in your Tesla Model 3, battery efficiency could drop to somewhere between 60% and 90%.

200 kW charging and 60% round trip efficiency don't work together. Assuming equal losses on charge and discharge, you would be putting 40 kW (20% of 200 kW) into heating the battery. That would require an ICE-scale cooling system to keep the battery pack from melting, in addition to the reduction in range for the same nominal battery size and 50+% increase in energy cost. Definitely not worth saving a few thousand on battery cost.

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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 12:59 pm

Titanium48 wrote: Shouldn't both theoretical efficiencies be 100%?

No. 100% in the fuel cell case would break the second law of thermodynamics. Look up the carnot engine for the paradigm.
As for electrolysis, Reg's post implies (but I have not checked) that the Gibbs free energy of two O-H bonds is higher than H-H
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Titanium48
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 2:36 pm

A fuel cell is not a heat engine and should not be subject to Carnot efficiency limits. The thermodynamic limit is that the round trip from water to hydrogen + oxygen and back to water cannot be over 100%. Saying the theoretical efficiency of a fuel cell is 83% while electrolysis is 120% is consistent with that, but it suggests some odd accounting somewhere. A theoretically perfect fuel cell should be able to capture all of the 237.1 kJ of free energy change per mole of liquid water formed as electrical energy. A perfect electrolyser would require exactly 237.1 kJ of electrical energy per mole of water reacting.

Looking at it further, I think I may have figured out the odd accounting. Enthalpy of formation for liquid water is 285.8 kJ/mol, 120% of the Gibbs energy of 237.1 kJ/mol. Using that value calculates 20% more energy than is actually available from the fuel cell, and 20% more energy than is actually required for electrolysis.

WetEV
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 4:49 pm

RegGuheert wrote:But here is the rub: Many of the near-term improvements in batteries will be achieved by moving to a solid electrolyte. That change will increase energy density and safety and reduce cost. Unfortunately, it will also reduce the efficiency.

Instead of the 98+% round-trip energy efficiency which is achieved in the battery in your Tesla Model 3, battery efficiency could drop to somewhere between 60% and 90%.


I don't think so. Example of solid state batteries with low losses:

https://www.nature.com/articles/nenergy201630

Source for your assertion?
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GRA
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 5:38 pm

RegGuheert wrote:So we will get back to the thesis that GRA has always held: People will choose convenience over efficiency any day. If we lower the round-trip energy efficiency of batteries to 80% and increase the round-trip energy efficiency of hydrogen to 60% or 70%, what will people choose for their vehicles?

I suspect there will be different preferences for different people:
- For someone like me who produces electricity on my roof and can charge at home, I will continue to prefer a battery-electric vehicle since the fuel is pre-paid and charging at home is more convenient than stopping for fuel. I will also prefer a Li-ion battery over a solid-state battery given the higher efficiency since that means I get more "miles per panel" from the investment on my roof.
- For others living in single-family homes, I suspect they will also prefer BEVs over H2 FCVs based on the convenience factor.
- For people like GRA who rent, I suspect the convenience of H2 FCVs *may* win out.

But even if the efficiency numbers do end up that close, then cost will end up being the deciding factor. Since I don't see the fuel or vehicle cost of H2 FCVs ever getting close to that of BEVs (again, there is NO crossover point), I suspect that even many without their own homes will choose BEVs, pushing for better charging infrastructure to make that option viable.

As always, time will tell.

I had to look at this twice to make sure I didn't write it (I have, or words to the same effect, said the same things many times in the past). It seems that Reg and I are in near 100% agreement. I write this while lying on the floor, where I have fallen after being hit by a feather (but I can get up)! :lol: The major question to me aside from H2 cost, which I've always said is likely to remain higher than electricity for BEVs even if photo- or thermo-chemical production of H2 drops the price considerably (but I've also always said that H2 doesn't have to be AS cheap as electricity, only cheap enough, like gas), is the rate at which central fueling versus home (esp. MUD) charging infrastructure can be built.

Rework to install charging at millions of individual existing locations takes a lot more time than building central fueling facilities, and (at least in the U.S.) you also have to cater for on-street parking. Around the corner from me is a short residential block with a mass of detached single-family homes (and one small apartment building with off-street parking), but every night, despite the profusion of garages the street is lined with parked cars. While I figure a lot of those garages are being used to store people's stuff instead of their cars, that does show the relative value they place on each, as well as the convenience/time savings of not having to open/close garage doors and drive in/out. Only if we can radically reduce the total number of cars (through AV car-sharing/MaaS) can we avoid the expensive and time-consuming need to provide charging in both off-street lots AND curbside.
Last edited by GRA on Thu Mar 21, 2019 4:13 pm, edited 1 time in total.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

SageBrush
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Re: Hydrogen and FCEVs discussion thread

Wed Mar 20, 2019 7:45 pm

Titanium48 wrote:A fuel cell is not a heat engine and should not be subject to Carnot efficiency limits. The thermodynamic limit is that the round trip from water to hydrogen + oxygen and back to water cannot be over 100%.

https://journals.sagepub.com/doi/abs/10 ... lCode=piac

I didn't read the article and I doubt I would understand it anyway.
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

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