The Toyota Mirai (FCV) Thread

I need to get wealthier friends. The Lincolns my family only had comfy bench seats.

I believe is the definition USBSeawolf is referencing: A hybrid is defined by SAE [4] as: “A vehicle with two or more energy storage systems both of which must provide propulsion power – either together or independently."
http://www.media.gm.com/content/dam/Media/microsites/product/volt/docs/paper.pdf

So bi-fuel can be a hybrid by that.

Fuel cells are batteries, but different. They have an anode, cathode, and electrolyte. The reactants are just supplied from outside instead off all being contained within itself like a battery. The FCV drive train is all electric. Yes, the voltages and amps coming from the battery and fuel cell differ, but so would the electric from a Li-ion and NiMH pack. The chances of BEV having the two aren't likely, but a super capacitor or Al-air battery in conjunction with a main battery isn't that far off. Should we call such BEV's hybrids?

Toyota has had great success with Prius and their hybrids. They hope by calling their fuel cell system HSD that the success can transfer. No issue with that. The issue is that every one else is calling them EV's. If we want any of these options to succeed and make a difference, the best way to do so is by not confusing the general public.

 

The DoE, Argonne national Labs, and nearly all the other car manufacturers call them electrical vehicles. I didn't until at first until USB convinced me the fuel cell was a different type of battery a few years ago. We call the hydrogen a fuel simply because it is easier than saying or typing out energy carrier. It and atmospheric oxygen are reacting in a fuel cell to produce electricity. Like the chemical reaction going on within a battery. Unlike burning a fuel to create heat in an engine to to convert it to motive source, which then is used to make electricity through electromagnetic fields.

Phinergy has a concept EV with the regular, rechargible battery and an Al-air for a range extender. Like a fuel cell, a metal-air battery doesn't carry all its reactants onboard; it uses atmospheric oxygen and water. Since Phinergy has a partnership Alcoa, and is in talks with Renault/Nissan, we might see a production BEV with an Al-air range extender in few years. Should we call it a hybrid?

The public sees a hybrid as a car with an electric motor and a normal engine, and there is still confusion. I think we agree calling a bi-fuel car a hybrid is silly, and would just lead to confusion. They just have one ICE drive train with two different fuels. A FCV has just an electric drive train; there is no other type of propulsion. To the end user is even just taking one fuel. A BEV w/ Al-air would need to fed grid charge and distilled water. Calling cars a hybrid based on the energy source alone is just going to add to the public's confusion and delay adoption.

PS: The GM paper that I quoted the SAE definition from was from 2008. The latest document of HEV and EV terminology is from October 2014, J1715: Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) Terminology - SAE International. There is also one for fuel cell vehicles, J2574: Fuel Cell Vehicle Terminology - SAE International.

 

toyotajpchannel

 

What about brakes? Coolant system?

 

Those are in section 9 of the manual. There might be a separate book for actual intervals.

 

This review states 4.3kg for the 650km range.
Google Translate

 

The tank weight was listed along with the other specs at 87.5kg. The 5.7% Toyota listed is the hydrogen amount from an empty tank; 4.9875 kg capacity. With the DoE and others, the percent hydrogen amount they use is based off the weight of a filled tank; in which case the Mirai tanks are 5.39%.

A gas vessel with a small opening can never by completely emptied of a gas without the use of a pump. Once a vented tank hits ambient pressure, the remaining contents get trapped. A FCV's tank with 'empty' before that time because a minimum tank pressure is required to over come the regulators, tubing, and too feed the fuel cell at a minimum rate and pressure.

The tanks likely hold nearly 5kg total, but the 4.6kg is probably the point at which the tank pressure can no longer feed the fuel cell.

 

Which was just the conditions, along with temperature, in affect at the time the tank was filled for the run that the range was calculated. The SAE standard for filling a light FCV tank are protocols to prevent the pressure and temperature of the hydrogen in the tank don't get too high at a fast as rate as possible. The amount of hydrogen in the tank at the beginning of the fill has a bearing on that.

In short, the car wasn't run 'dry' for the range test, and still had about a 1kg of hydrogen in the tank when it pulled up to the pump.

 

Toyota ran the car under JC08 conditions. It sounds like they just recorded the miles traveled and divide by the amount of fuel used to fill the tank afterward. I'm guessing measuring the water produced by the fuel fell for fuel consumption likely isn't as accurate as measuring carbon in regards to ICEs, since ambient humidity needs to be accounted for.

The ambient temperature and tank pressure listed in the footnote is just the conditions at the time of that fill up. SAE J2601 uses a look up table of varying ambient temperature and car tank pressures. This tells the pump computer the target pressure to pump fuel for to reach full 90% to 98% SOC without too much temperature build up within the tank. There also ones that give the fill time. Page 15 of this presentation has the table for fill time with type B pump, https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/webinarslides_h2_refueling_protocols_022213.pdf. Page 21 has one with the target pressure. 90% SOC is the target for non-communicating cars, and 98% for communicating ones. The tables allow tank pressure to exceed the tank rating; which I take is to allow for the hydrogen cooling after being dispensed. For the communicating ones, the tables are used as a guide line to compare the data coming from the car too.

The tables have a tank pressure low of 2MPa. Which is also the 'empty' pressure of tanks in a paper I once linked too.(don't remember which thread it was in) The typical 3 minute refuel time is only possible with type A pumps with -40C pre-cooling. The typical time with a type B(-20C pre-cooling) is 15 minutes.

 

Using kilograms is more apporpriate since hydrogen will eventually be sold by the kilogram, and 1kg of hydrogen is roughly equal to 1 gallon of gasoline; amking comparisons simpler. Talking kilograms is also easier in that the pressure and temperature doesn't need to always be stated. A kilogram of hydrogen compressed in a tank or in a weather balloon is always a kilogram.

There is a volume based measurement that is part of the energy density targets. It is kg hydrogen / system volume. Page 6 here, http://ceramics.org/wp-content/uploads/2012/02/mcare12-hydrogen-fuel-cell-tech1.pdf, has the table with the most up to date targets.

The newer Japanese refueling stations can fill tanks to 82MPa(about 11.9k psi). The longer range is du to more hydrogen getting stuffed in.

This is one of the reasons for the anti-FCV commercialization sides. The industry hasn't settled upon a fuel storage standard yet. California is building for 70MPa. If 82MPa becomes the standard here, as in Japan, the cost of upgrading the stations vs. building for 82MPa to start will be a loss. Then there are other hydrogen storage options under development, along with different fuels.

 

Some interesting technically detailed H2 and fuel cell information in a new ongoing series of blog posts from someone with an anti-FCV bent:

Why fuel cell cars don't work - part 1 - mux' blog - Tweakblogs - Tweakers

One of the issues these blog posts reminded me about was hydrogen leakage from the pressurized tanks. Has anyone seen specific details on the leakage rate from the Mirai's tanks or recent Toyota prototype tanks?