New Airstream self powered trailer

[sherminator]

BEVs are where the action is. The company I work for started doing some small projects for Tesla a few years ago, and we worked up to building large sections of their battery assembly lines. We now have orders from 4 different BEV battery suppliers (or direct consumers) for equipment for automated battery assembly lines. The line I'm working on is for an electric bus manufacturer, who has been building electric buses for several years now. Their business is heading up at a pretty steep curve.

[Brian B-P]

Originally Posted by Centex

I have to think that the vast majority of RV tow-vehicles have substantial towing power capability that's utilized for only a small fraction of that vehicle's total miles. There's bound to be an efficiency penalty in that when that power is not utilized.

With an engine, certainly, but an electric motor can be substantially over-sized with little loss of efficiency. The sizing problem is the battery - carrying around far more battery than required is a real weight penalty.

[John in Santa Cruz]

Originally Posted by JeffreyG

Conceptually, all hydrogen vehicle concepts for GHG reduction anticipate that the hydrogen will have to be manufactured with electrolysis, and the power will have to be solar / wind.
....

electrolysis produces equal amounts of oxygen and keeping the two seperate is very much a non-trivial process. The H2 and O2 gases bubble up around the + and - electrodes with no pressure to speak of. Those electrodes have to be in the same container of water so the current can pass between them, any any pressure differential will push the water back and forth. isolating the electrodes in tall columns means less ions transfer through the electrolyte (water).

the other 1000 lb gorilla in the room is storage. Hydrogen is very difficult to store, it embrittles metals, as a compressed gas it has ridiculously LOW energy density, even as liquid H2 under extreme pressure, it still has low energy density. The energy equivalent of one gallon of gas or diesel or LNG or LPG takes something like 16 times the volume in cyrogenic liquid H2, and far more in compressed H2.

[JeffreyG]

Originally Posted by John in Santa Cruz

electrolysis produces equal amounts of oxygen and keeping the two seperate is very much a non-trivial process.

Industrial processes for electrolysis of H2 are well understood. The only real barrier is cost.

the other 1000 lb gorilla in the room is storage. Hydrogen is very difficult to store, it embrittles metals, as a compressed gas it has ridiculously LOW energy density, even as liquid H2 under extreme pressure, it still has low energy density. The energy equivalent of one gallon of gas or diesel or LNG or LPG takes something like 16 times the volume in cyrogenic liquid H2, and far more in compressed H2.

If H2 is to be the energy storage media of choice (as opposed to batteries, for instance) then it will be in liquid form.


Liquid H2 is bulky relative to diesel or gasoline, but not prohibitively so. It's less bulky / massive than batteries, for example. We can see a path to fitting adequate range in H2 onto long haul trucks, for example.


Gazing at my crystal ball, I think personal vehicles, urban buses, school buses, and most trucks will all just become BEV. I don't see a universal hydrogen system.



But that doesn't mean we won't have hydrogen fueled trucks in some remote applications, plus airliners.

[John in Santa Cruz]

Hydrogen only remains liquid under very high pressure AND extremely low temperatures, like below -240C, even at extremely high pressures. It freezes at -260C. Liquid H2 has a density of only 70g per liter, ot 14 liters/kg.

these are laws of physics, no magic technology will let us bypass them.

[JeffreyG]

Originally Posted by John in Santa Cruz

Hydrogen only remains liquid under very high pressure AND extremely low temperatures, like below -240C, even at extremely high pressures. It freezes at -260C. Liquid H2 has a density of only 70g per liter, ot 14 liters/kg.

these are laws of physics, no magic technology will let us bypass them.

Well, yeah. Cryogenic fuel is implied in the term 'liquid hydrogen'. It's not a liquid at STP.

[Centex]

Originally Posted by Brian B-P

With an engine, certainly, but an electric motor can be substantially over-sized with little loss of efficiency. The sizing problem is the battery - carrying around far more battery than required is a real weight penalty.

Yes of course, the battery is the pertinent point with a BEV.

[Sean Murry]

I know didley about Hydrogen other than it burns. I do recall reading somewhere that BMW was looking at hydrogen fuel cell vehicles and were going to store the hydrogen in a hydride form. Supposedly eliminating the explosive factor if involved in an accident.

Does anyone know anything about this? Plus and minus of such technology?

[Keith3]

A lot of diy rv owners are pushing towards da all electric rvs. This seems like a natural extension of that trend. Count me as interested.

[Brian B-P]

Originally Posted by John in Santa Cruz

Hydrogen only remains liquid under very high pressure AND extremely low temperatures, like below -240C, even at extremely high pressures. It freezes at -260C. Liquid H2 has a density of only 70g per liter, ot 14 liters/kg.

these are laws of physics, no magic technology will let us bypass them.

Hydrogen has a critical point of 33 K (-240 C) and 1298 kPa (about 13 times atmospheric pressure); it stays liquid at that point and I don't know if that's what was meant by "very high pressure". At even lower temperatures less pressure is required to keep it liquid; at -253 C (20 K) only atmospheric pressure is needed.


In practical terms it is never solid (frozen).

Practical storage as a compressed gas does require very high pressure: typically as much as 70 MPa (10,000 PSI)... but fortunately at room temperature.

Density is a very real problem. Even though the energy content per unit of mass is high, the density is so low that storage is bulky, either as a gas or as a liquid. Construction of the storage vessels is also a problem (in cost and weight), whether due to the need for insulation of cryogenic liquid or due to the need to contain the high pressure of compressed gas.

The problems don't mean that it can't be done - hydrogen has been stored for decades and thousands of ordinary consumers are driving cars with compressed hydrogen fuel tanks now - but it's expensive. To me, the larger problems are producing hydrogen and the inefficiency of the whole production and distribution system.

[Brian B-P]

Originally Posted by JeffreyG

Cryogenic fuel is implied in the term 'liquid hydrogen'. It's not a liquid at STP.

And it's not a liquid at standard temperature, regardless of pressure.

[Brian B-P]

Originally Posted by Centex

Yes of course, the battery is the pertinent point with a BEV.

Not really "of course". It is not uncommon for people to suggest that large electric motors have a significant efficiency penalty, extrapolating incorrectly from their understanding of internal combustion engines.

Batteries actually work the opposite way: higher battery capacity means lower discharge rate relative to capacity, which improves battery efficiency... the problems are the increased mass, volume, and cost, rather than efficiency.

[Brian B-P]

Originally Posted by Sean Murry

I know didley about Hydrogen other than it burns. I do recall reading somewhere that BMW was looking at hydrogen fuel cell vehicles and were going to store the hydrogen in a hydride form. Supposedly eliminating the explosive factor if involved in an accident.

Does anyone know anything about this? Plus and minus of such technology?

Hydrogen can be stored on or in various materials, including hydrides, but it means carrying a lot of material compared to the amount of hydrogen. This was a popular idea for a while, but practical hydrogen-fueled road vehicles have all gone with compressed hydrogen gas and massive storage (including rocket fuel tanks) are typically liquid.

U.S. Energy.gov: Hydrogen Storage - Basics

Burning hydrogen in a combustion engine was an easy thing for automotive companies to try, but it doesn't make much sense to me when hydrogen is the perfect fuel for a fuel cell that produces electricity for the electric motor powertrains that are now readily available.

[JeffreyG]

Originally Posted by Brian B-P

Burning hydrogen in a combustion engine was an easy thing for automotive companies to try, but it doesn't make much sense to me when hydrogen is the perfect fuel for a fuel cell that produces electricity for the electric motor powertrains that are now readily available.

Well, it turns out that that isn't so simple either.

Fuel cells cannot be used as a prime mover. They have very terrible transient response, so FC cars are really almost BEVs with a FC range extender (I mean, they are not as power does flow from from FC to motors, but they sure do need a big power battery to smooth out the load and handle regenerative braking).

Also, fuel cells are a real PITA to cool. They are something like 50 - 60% BTE, which sound great until you realize that something like 90% of the waste heat is rejected to coolant (not exhaust) and the waste heat is coming at 40-60C instead of the typical 90-110C of an engine. That waste heat requires a large heat exchanger to dump.

So ultimately FC vehicles become package / weight challenges. FC, cooling system, bulky fuel storage, power battery, power distrubution unit, inverter, and eMotor. It's not simple.

[Brian B-P]

Originally Posted by JeffreyG

Well, it turns out that that isn't so simple either.

Fuel cells cannot be used as a prime mover. They have very terrible transient response, so FC cars are really almost BEVs with a FC range extender (I mean, they are not as power does flow from from FC to motors, but they sure do need a big power battery to smooth out the load and handle regenerative braking).

Yes, a fuel cell is normally used in a series hybrid configuration for that reason (as well as to enable regenerative braking and - if desired - a plug-in hybrid mode), but everything past the fuel cell (battery, controller, motors, supporting systems for battery management, etc) is the same as it is in other series hybrids or battery-electric vehicles.

Originally Posted by JeffreyG

Also, fuel cells are a real PITA to cool. They are something like 50 - 60% BTE, which sound great until you realize that something like 90% of the waste heat is rejected to coolant (not exhaust) and the waste heat is coming at 40-60C instead of the typical 90-110C of an engine. That waste heat requires a large heat exchanger to dump.

So ultimately FC vehicles become package / weight challenges. FC, cooling system, bulky fuel storage, power battery, power distrubution unit, inverter, and eMotor. It's not simple.

It's neither simple nor cheap, but it works better than an engine burning hydrogen, driving a mechanical transmission. The waste heat exchanger ("radiator") of current fuel cell cars such as the Toyota Mirai apparently isn't large enough to be a problem.

[JeffreyG]

Originally Posted by Brian B-P

It's neither simple nor cheap, but it works better than an engine burning hydrogen, driving a mechanical transmission. The waste heat exchanger ("radiator") of current fuel cell cars such as the Toyota Mirai apparently isn't large enough to be a problem.

Probably easier in a passenger car as the loads are very low and the speed is always high. I'm often looking with the perspective of trucks where the load factor is much higher and speeds on grades can be low for extended duration. Cooling is already a challenge for diesel engines in such an application, and fuel cells are worse despite having higher BTE.

A pickup towing an RV is sort of between the two. As John suggested earlier in the thread, space is at a premium in a hydrogen vehicle because the fuel is very bulky. Fuel cells are certainly plausible, but have their own challenges.

Hydrogen ICE isn't automatically a bad alternative. Much cheaper for one thing, because we replace the eMotors, HV power net, invertor, and power battery with a simpler transmission and axle. The engine is cheaper than a fuel cell. But the H2 ICE is not zero emissions. Assuming we run a lean burn SI combustion approach, the engine will make something like 1/10 to 1/6 the amount of NOx that a diesel would make. Given an SCR system we can get the NOx down to very low amounts, but not zero. It's an option once the real challenge of no H2 infrastructure existing is solved.

[marsman]

This topic is near and dear to my heart. I do believe that there are some inherent design malfunctions with the current BEVs being designed. As stated by several others already, it just does not make sense to haul around a battery with 400 miles of range to commute 99% of the time with round trips below 100 miles, or, for many, much less than that!!

This problem is hugely compounded in a tow vehicle or even working pickup truck which is relegated to a daily average of <100 miles and carries an 800 mile battery around - TALK ABOUT A HUGE WASTE OF ENERGY! all that weight being lugged around.

One solution I'm surprised no company has considered yet is to design a car, or better yet a pickup truck with a 200 mile battery with a slot(s) to slide in a much larger battery (ies) which could be rented for long trips. Can you imagine having a truck that could carry a 1000 pound battery when required but then would give you an extra 1000 pounds of payload when you weren't carting around the LONG RANGE BATTERY!!!!.
Look at the Korean company Gogoro and their business model. Or better yet check out the new bus engineered by the German company ElectricBrand called the XBus (link below) where the batteries are modular and you simply install however many you require.

https://electricbrands.de/en/myxbus/

In terms of hydrogen fuel; as others have commented it's efficiency, although improving is still not great compared to BEVs. That said, when it comes to commercial long haul vehicles like airplanes, ships, long-haul transports etc this is probably the most viable technology.

We certainly live in incredible times! I'm 63 years old and witnessed the entire computer/internet revolution. Now we're at the start of the "Energy" revolution where we're going to see a complete restructuring of the energy infrastructure; it's gonna be a great show WOW

[Sean Murry]

Not sure if car battery technology has the same limitations as lithium RV batteries, but for RV batteries you are not supposed to mix and match brands of batteries or different ages of the same brand of battery.

[Vermilye]

Originally Posted by marsman

This topic is near and dear to my heart. I do believe that there are some inherent design malfunctions with the current BEVs being designed. As stated by several others already, it just does not make sense to haul around a battery with 400 miles of range to commute 99% of the time with round trips below 100 miles, or, for many, much less than that!!

This problem is hugely compounded in a tow vehicle or even working pickup truck which is relegated to a daily average of <100 miles and carries an 800 mile battery around - TALK ABOUT A HUGE WASTE OF ENERGY! all that weight being lugged around.

One solution I'm surprised no company has considered yet is to design a car, or better yet a pickup truck with a 200 mile battery with a slot(s) to slide in a much larger battery (ies) which could be rented for long trips. Can you imagine having a truck that could carry a 1000 pound battery when required but then would give you an extra 1000 pounds of payload when you weren't carting around the LONG RANGE BATTERY!!!!.
Look at the Korean company Gogoro and their business model. Or better yet check out the new bus engineered by the German company ElectricBrand called the XBus (link below) where the batteries are modular and you simply install however many you require.

https://electricbrands.de/en/myxbus/

In terms of hydrogen fuel; as others have commented it's efficiency, although improving is still not great compared to BEVs. That said, when it comes to commercial long haul vehicles like airplanes, ships, long-haul transports etc this is probably the most viable technology.

We certainly live in incredible times! I'm 63 years old and witnessed the entire computer/internet revolution. Now we're at the start of the "Energy" revolution where we're going to see a complete restructuring of the energy infrastructure; it's gonna be a great show WOW

With the idea of added battery capacity for long trips in mind, a trailer with a huge battery makes some kind of sense. Most trucks have a far greater towing capacity than payload. Put the weight of the travel batteries in the trailer, beef up the chassis and tires, etc of the trailer to deal with the extra weight, and run power from the trailer batteries to the truck for traveling. It still doesn't solve the problem of recharging the batteries - there is no way you are going to put enough solar on a small (or even large) trailer to replenish what it takes to haul the truck & trailer 200 - 300 miles.

[Brian B-P]

Originally Posted by marsman

I do believe that there are some inherent design malfunctions with the current BEVs being designed. As stated by several others already, it just does not make sense to haul around a battery with 400 miles of range to commute 99% of the time with round trips below 100 miles, or, for many, much less than that!!

That's mostly a marketing issue, not a design issue. Since customers will not objectively assess their needs, they will buy capabilities that they do not need; everyone commuting to work solo in a large all-wheel-drive station wagon or pickup truck illustrates this issue.

Originally Posted by marsman

One solution I'm surprised no company has considered yet is to design a car, or better yet a pickup truck with a 200 mile battery with a slot(s) to slide in a much larger battery (ies) which could be rented for long trips. Can you imagine having a truck that could carry a 1000 pound battery when required but then would give you an extra 1000 pounds of payload when you weren't carting around the LONG RANGE BATTERY!!!!.

Not only has this been considered - for decades - it has even been tried in limited production. Everyone gives up on the idea of battery-swapping when they realize the many practical problems. A dedicated extended-range battery like this is more functional than swapping all of the battery (as is usually proposed), but managing dissimilar parallel batteries isn't ideal and half a ton of battery would not be an easy thing to handle or a trivial thing to secure. Regardless of the size, a functional modern battery requires a massive electrical power connection, low voltage and network communication connections, and fluid connections for thermal management (heating and cooling).

The "Gear Tunnel" of the Rivian R1T would be ideal for this type of battery pack, and if I recall correctly this was discussed years ago, but it is not offered - apparently it didn't work out to be viable. Rivian did file a patent for an add-on battery in the truck bed (not the Gear Tunnel), but they don't actually offer that, either. It's interesting what they say about it:

The patent describes the installation method as either via forklift or being lowered in from above via winch and cables. Then it is bolted into place along the sides of the bed.

If the only time the extra battery capacity is needed is while towing, then permanently installing that battery in the trailer is easier. Of course the in-truck scheme is more flexible.