Featured Review of hydrogen

source please

 

On a page with a few hundred members there are 40 threads about freeze, frozen or freezing pump handles




in any event I thought the physical properties like the temperature inflection point of a gas like hydrogen was common knowledge?

Freeze of Nozzle, Receptacle During Hydrogen Fueling | Hydrogen Tools

 

No. Curtailment of renewables just directly increases the cost - 2.5x curtailment = 2.5x higher cost of energy. This is not the case with our current high-curtailment grid because curtailment saves fuel.

Why would you want to pay 2.5x more for your energy because you're throwing away so much energy?

To keep renewables cost-effective, we need to keep curtailment to a minimum. This is done by having an alternative place to put the energy rather than throwing it away. Sadly, batteries are way too small for this on a seasonal scale. So, a good place to put it is into vehicle fuel - way better than throwing it away.

 

Why do people feed grains to livestock and eat meat instead of eating the grains directly? 80 to 90% of the energy is lost in the process. They do it because they think the benefits outweigh the increase in cost. But I don't think there is any grain-producing society on Earth where meats account for a larger share of people's calories than grains. The cheaper option always wins, but it does not have to be the only option.

If hydrogen costs can be brought down to perhaps $5/kg, there will be a significant minority of people who will prioritize the quick fill-up time over the increased cost. There is also significant room for fuel cell stack costs to drop further.

 

But energy isn't the same - people won't pay 2.5x more for the same thing, they'll pay 2.5x more if it's worth more. Shutting down your renewables production doesn't add value at all, it just adds cost.

As I keep saying, they should be PHEVs with the fuel cell as a range extender (i.e. 15kW instead of 150kW). That will reduce cell stack cost by a factor of 10 right of the bat. Further, H2 can be used in other vehicles, such as off-highway trucking, shipping and aircraft, where batteries are just a non-starter (getting there for short-haul aircraft but nowhere near for long-haul).

 

I would think that for some people, the increase in cost to fill hydrogen compared to charging the car would be negligible compared to the time savings.

I agree that fuel cell PHEVs make a lot of sense. I think Mercedes is the only company even considering this atm.

 

Above -80C, hydrogen gas heats up as it expands through a nozzle. The freezing seen here is because the gas was at -40 in the dispenser tank. It needs to be that cold for repeated quick fills. Higher temperatures mean more of the fills are at longer times, and will be short fills. No chilling, and temperatures can reach the point of damaging the car's tank if the system doesn't stop at a partial fill.

A small heating element that turns on at the end if frozen should solve the issue. Until then, I'd tell hydrogen car owners to carry a bottle of rubbing alcohol for de-icing.

Only a third of the hydrogen in California is renewable. The rest is cheap steam reformed natural gas for $2 to $3 a kg. Assuming the renewable is $10/kg, which is a high estimate, the hydrogen for cars is around $5/kg. A bit of that $16/kg price balance is profit, but the large majority of it is for transportation and the energy to get it into the car. I don't think California is taxing it yet.

Projections for getting green hydrogen down around the price of fossil hydrogen involve large central plants. Without a break through in hydrogen storage, you will still be tacking on $10/kg to get it into a car.

Mercedes did, but Diamler gave up on hydrogen cars. They are only doing commercial trucks now.

 

yes - but any time you have two sources for propulsion, you increase the vehicle's cost - & it's likely that's why no manufacturer (other than MB - who gave up on it) is willing to produce it.

Whether or not that is true is best determined by users of the product. How many more electric vehicles are there compared to hydrogen? therin lies the answer.
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No.

Having two sources of *energy*, each 1/10th as big as having only one or the other, and one source of propulsion (electric motor), decreases the cost.

 

and yet hundreds of Engineers that actually get paid for those decisions differ.

 

I may not have my facts straight, but aren't most (or all) of the FC vehicles hybrid in some form or another? Doesn't the FC charge a battery that is used to provide peak power needs? I understand that this allows you to reduce the size of the FC significantly. Unlike an ICE, doubling the output of FC is not as cheap as adding a supercharger and increasing the displacement. It requires doubling the expensive parts of the FC.

 

Barely.

This is tens of seconds worth of storage, not tens of minutes like I recommend - with all power coming from the battery. Ultimately, the fuel cell has to provide of the peak power for the car beyond a few seconds - something fuel cells are lousy at doing.

But they are still huge - at least ten times as big as necessary. And they aren't plug-ins.

Right - which is why making it smaller is so beneficial.

The battery in a Mirai is less than 1/7th the size of the battery in the Prius Prime (1.24kWh vs 8.8kWh, gross). It should be twice the size of the battery in the Prime (for ~50 miles of plug-in range), and be plug-in chargeable. Then you only use H2 when out of town instead of all the time. And the fuel cell should be something like 10kW instead of 128kW (https://www.toyota.com/mirai/features/mileage_estimates/3002/3003).

 

Toyota basically said making a plug in FCEV would result in lower demand for hydrogen, and that would delay growth of the infrastructure. It would also mean a change from the design they, and most others, have been pursuing, big fuel cell:small battery. Nissan is taking a different approach, small fuel cell:big battery. In fact, one of their test mules was their BEV mini work van with the fuel cell installed to charge the battery. they took the charger out, but that can be added back.

Toyota tried getting them called hybrids for marketing, but they aren't in technical terms. A hybrid has two different sources of motive force. Usually they both help move the car, but don't have to in the case of series hybrids. FCEVs only have the one; electric. They also aren't a bi/dual-fuel car like a PHEV, because the user only adds one energy source/fuel to it.

Fuel cells have a slow ramp time when changing output. The battery is a buffer between driver demand and the fuel cells slow response. make the battery bigger, and the fuel cell can be smaller. Then you can even add a charger. The issue for a personal car is in finding space for the big battery and bulky hydrogen tanks. Nissan's solved this by using ethanol for the fuel instead of hydrogen., though in the case of their Brazil tests, the van also needed to carry water as it actually runs on 55% ethanol, and pumps only had E100.

 

Yes! And that's a good thing! Infrastructure is expensive. The idea is to put in infrastructure like Supercharger stations, just using much smaller electrical feeds (and probably only one "wand") and make and store hydrogen on-site. Store a few days worth and you can meet the peaks of demand. You also have lower electricity costs because the demand charge is way lower. Yes, it's way less efficient, but only for the 25% or so of the miles not driven on the plug-in battery, and the car is way lighter than a BEV because the fuel cell system is closer to 1000Wh/kg than it is to 250Wh/kg.

 

OK Trollbait has it...I knew I never had this "cooling" problem in my whole career handling H2.
Some of the new auto H2 dispensers are (complex new technology) cooling off the Hydrogen to -40C because H2 actually heats up a little. And I guess the "Green H2" from electrolysis of water is a little wet with moisture. They need to knock this water out, which is easy.

Look I handled H2 my whole career. There is no big show stopper about H2 within the field of chem engr. I mean we might ban it in America because it is politically incorrect here, but the rest of the world can use it.

 

No. Curtailment of renewables decreases cost. Overbuilding renewables and curtailing surplus electricity generated has no fuel cost and is more economic than alternatives. There is a role for energy storage, but it is much smaller than you suggest.

 

The battery in the Mirai is approximately the same size as the one in my gen1 Prius. That battery was enough to overcome the weaknesses of the Atkinson cycle ICE. It appears to be providing the same role in the Mirai.

In addition, Trollbait said:

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It's a serial hybrid, plain and simple. The FC creates electricity that powers an electric motor. When the FC output is insufficient the battery contributes energy to drive the motor. That's pretty much the definition of a serial hybrid.

Dan

 

Yes - and that role, like in your Prius, doesn't allow the fuel cell (engine in your Prius) to be down-sized from peak power (for hill climbing, etc.) to average power (for charge sustaining). It also doesn't allow you to do most or all of your in-town driving on grid electricity.

Those two elements are key. The lack of them are why vehicles like the Mirai are both dumb and failing.

 

The hydrogen needs some moisture for the fuel cell, but it doesn't matter. The freezing is on the outside from ambient humidity. The orifice is tiny, any interior freezing would probably be easy to break.

It's not because a fuel cell produces energy, not force. In a series hybrid, an engine makes torque to spin a generator to make electricity for a motor. A battery is totally optional to the design.

A fuel cell is like a battery in which the reactants and products aren't contained in the cell, and creates electricity directly. An EV with two battery types, or battery plus capacitor, isn't a hybrid, and a FCEV isn't for the same reason. A hybrid has an engine and some kind of motor.

 

You need compelling fuel car, and access to to a charging network first. I think Toyota has a compelling HFV now. Charging network obviously needs more work.