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David Freeman
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I really hope this allows them to use more exotic sealing and lubricant solutions, reducing or removing the need to burn oil.
As usual, there is the concern about unsprung weight. I wonder if something like this would work better for urban buses, where the ratio of unsprung weight is minimal compared to the body weight.
Low Temperature PEM is a dead end technology. They've been at this for decades and nothing to show for it.
I doubt it's all that efficient, since the temperature differential is pretty low. CO2 is probably similar to ORC, so expect ~10-12% efficiency. The value is not the generation of electricity with the CO2 turbine, but the production of heat/cooling for industrial/building purposes. The temperatures are not low enough for the CO2 to actually condense - this isn't a Rankine cycle with phase change. Rather, the cooled CO2 is easier to compress.
@HarveyD - the article mentions that charging is slower, so the battery chemistry seems to be the limiting factor, not available charge current. Thus, a 1MWh battery pack would take 90 minutes to charge, even with infinite power.
Not sure PHEVLER makes much sense, unless you have a _really_ compact generator. EREV seems to hit the sweet spot covering most average daily usage. With PHEVLER you get the double-whammy of ICE generator and (mostly) unused battery weight.
The only way FCEV's can compete in the light vehicle sector is by dropping hydrogen as a fuel and using existing liquid fuels.
@Myself I should clarify what I mean by 'slow'. It takes several minutes for HT_PEM FC's to warm-up, so without a large battery, you can't just get in the car and go.
@Roger Pham Syn-fuels are definitely an option, though I think the most efficient processes won't have an intermediate H stage. I don't think there's a real reason to convert syn-fuels into hydrogen before fueling a vehicle. Use advanced reactors/processors at the point of use. Ammonia isn't that much more toxic than gasoline and is widely used on farms in the mid-West. I agree that it's unlikely to achieve retail acceptance as-is, but there are ammonia compounds that could be used. Ammonia dissociates relatively quickly in the environment. Hydrogen volumetric density is incredibly low. Liquified hydrogen is 70kg/m^3, compared to LNG at 660kg/m^3. It's annoying to handle and store, requires heavy high-pressure or cryogenic tanks. Alternative storage remains fairly low density. HT-PEM FC's are _slow_. Development of the FC was supposed to replace the ICE, not simply act as a range extender for an electric vehicle. This led to huge amounts of resources dumped into things like making FC's extremely responsive. The first available membranes were low-temperature only. That attitude seems to have been ingrained in FC development - the FC cabal at GM was against the Volt, for example (probably because it reduces engine use by 80%, making the choice of generator almost irrelevant). Now with the sunk costs in LT-PEM, who wants to repeat that work with HT-PEM's? I think the other piece of it is that hydrogen is, after all, the most 'green' fuel out there (disregarding well-to-wheels efficiency). Who wants to use yucky gasoline with their super-green-and-clean fuel cell? I think what will happen in the end is that most cars will be BEV or EREV with very limited FC penetration (if any). SOFC fuel cells will be used for long-range heavy travel, reforming liquid fuels internally (LNG/CNG, synfuels, biodiesel). Fuel cells are 5 years too late. By the time the first reasonable FC car is introduced (ignoring fueling concerns), everyone will know what a Tesla is. The idea of plugging in your car like a phone won't sound quite so crazy, and you'll already have Level 2 charging stations popping up everywhere like mushrooms. With the minimum cost of a hydrogen fueling station at $2 million and $20,000 for a Level 2 charging stations, there's no competition. This isn't about capacity, but about _visibility_.
Both eci and HarveyD are (generally) wrong when it comes to long-distance heavy transport. Batteries just don't have the energy density for long-distance travel, and the fast-charging infrastructure would be immense. The only real gamechanger would be aluminum-air (either recyclable or rechargeable) batteries. While there's a better chance of hydrogen PEM fuel cells becoming an option (there's plenty of room for those tanks) the hassle of hydrogen just doesn't seem worth it. Why not just use existing fuels with next-generation SOFC, later migrating to bio- and syn-fuels? Even if warmup takes 'forever', you can easily carry a battery pack capable of powering the truck for the first bit of a long-distance journey. Basically the architecture would look like an EREV diesel-electric locomotive (with batteries). If you really want to go hydrogen, why not just burn it in an ICE? There's no need for a fuel cell, and you could even move to an optimized engine like Mazda's hydrogen Wankel. In a serial hybrid mode there's no need for the massive torque of a diesel engine. Heck, you could probably even justify using a 'light-weight' fuel-efficient engine with traditional fuels in a serial hybrid mode - forget fuel cells, hydrogen, or massive battery packs...
In my opinion, low temperature hydrogen PEM fuel cells are not the right approach. They are easily poisoned by CO and sulfur, and unable to process any fuels other than pure dry hydrogen. High temperature PEM fuel cells do not require platinum catalysts or humidification, vastly simplifying system design. Temperatures are 150-250 C, so metals are required in construction rather than plastics, but within bounds for all common automotive materials (aluminum and steel). Even better, they are resistant to CO poisoning. This really opens up the opportunity to avoid hydrogen altogether and use liquid fuels (LNG, petrol, diesel, ammonia) instead of hydrogen. What's the downside? You need a drivetrain architecture more like the Volt than the Prius, since you need margin for warming up the fuel cells. This does, however, significantly reduce the complexity of system design since the fuel cell itself just has to provide average power to the vehicle (e.g., 55kW peak instead of 150kW). In cold-weather situations, running the fuel cell at 'idle' could provide cabin heating for a Volt-architecture vehicle. Personally, I think the fascination with hydrogen is really holding up fuel cell progress in general. The ability to use liquid fuels would at least drive acceptance of fuel cells in general. I think it would basically kill a hydrogen future in favor of bio- and syn-fuels, though. I guess you could always sell hydrogen as 'improving performance', though well-to-wheels efficiency would continue to be horrific.
Full doors are available. I would expect them to be installed by default in CAN since you don't have the same weight restrictions that Europe has.
As GM found out with e-Assist, trying to improve performance by moving to a mid-level performance platform (e.g., 120V) doesn't provide enough performance or efficiency boost to attract consumers. Using a low-cost 48V platform could drive the low end of the market, enabling start/stop and some torque assist. Much like e-assist, I doubt that such a small system would actually be able to move the car without the engine running (except for very slow speeds).
@DaveD, I disagree. The 4MJ flywheel is running at 36,000rpm, and 60,000rpm should be achievable. That would allow them to more than double the energy available in the flywheel to >8MJ. I wonder why they haven't done so yet? They may be limited by the armoring necessary to keep the driver safe if the flywheel disintegrates.
I'm surprised to see the HSS still so expensive. I think CARB is really skewing the market with their HFC credits. Replace the expensive HSS with a regular fuel tank and an on-board multi-fuel reformer. No problems with finding a fuel station. The use of standard, low-temperature FC's, does, of course, require dry clean hydrogen, whereas reformed fuels may introduce contaminants (sulfur, CO, H2O) that poison the FC. GM should instead transition to a high-temperature (150-250C) FC design that would greatly simplify the FC BOP. For example, CO poisoning won't be a problem, and simple fuels (methane, ammonia) can be reformed directly in the cell. No more complex liquid cooling, since everything can be air-cooled. Higher temperatures increase catalysis activity, reducing (or removing) the need for platinum.
@CheeseEater88 FC lifetime is rated similar to that of a BEV, that is, end-of-life is at ~70-80% of rated power. Efficiency may also decrease, but it's generally the power loss that defines the lifespan. Used automotive FC's would be perfect for low-power whole-house generators running off of reformed natural gas.
E-P, you're looking at the wrong market. Energy storage systems are not competing with energy _production_ (e.g., nuclear), but rather with peaking simple cycle gas turbines. In a 'srong' RE solution, the biggest bump in unmet demand comes in the four hours after peak. That's realistically achievable with batteries. Maintaining base load for the entire night is a wholly different matter, and I don't really see how that can be achieved with battery energy storage systems. Bringing us back to nuclear... Which, of course, raises the question - why not just over-build the reactors and throttle as necessary to meet demand? The marginal costs should be minimal once you start building the power plant.
@D - most likely their estimates of EPA range. Look at Volt today and adjust accordingly, since it is likely that GM will use a similar packaging strategy to avoid the battery issues of the Leaf. So probably figure ~120m in the winter with the heater going in comfort mode. If you're traveling more than that in the winter, I'm sure it will have quick-charging (since the Spark did). If that still doesn't work for you, get a Volt.
@mahonj - crumple space is not necessarily composed outside of the wheels. Most likely, since it is pure BEV, the entire front end is one large crumple zone (like the Model S frunk). Also, this is apparently using a skateboard chassis, which would include crumple zones underneath the passenger compartment.
@EP - That kind of use (quickly) shortens the life of a Lead-Acid battery. They're probably not concerned so much about regen charging as it is about life. The same reason Toyota uses only 50-60% capacity for Prius NiMH batteries.
@DaveD - I couldn't tell either :-) but I hope it's for batteries. Even A123 batteries (with high power ratings) have trouble in cold weather. If this approach lets batteries approach super-capacitor power rating, than we can use smaller batteries for hybrids, create a wider range of performance cars off of a single battery pack and even push LiIon batteries down into regular cars as the starter battery.
@Nick - this is perfect for long-haul applications. As long as the AVERAGE power consumption <65kW, the turbine will charge the batteries for acceleration and mountain-climbing. Capstone can use either diesel or NG, so it's just a matter of changing the fuel system. What you need to compare is the capital cost of the turbine+batteries plus lifetime fuel costs to the capital cost of a diesel/NG engine plus lifetime fuel costs. @HarveyD - Capstone turbines are rated for 45000 hours life. Assuming no idling (battery is used for that) and average speed of 60m/h, expected lifetime is 2.7 million miles. Granted, that's 45000 hours in CHP applications (stable, environmentally isolated environment), so that could come down a bit. Still, I'd say it's likely they'll reach a million miles lifetime.
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Oct 19, 2011