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Calliban

Member

From: Northern England, UK

Registered: 2019-08-18

Posts: 3,722

Re: Why the Green Energy Transition Won’t Happen

Very simplistically, maybe something like this:

Or maybe this for the vac tank, using concrete with a clay and rubble filling.

Or maybe the tank can sit within a weather proof enclosure, like a shed.  This ensures that the clay providing the compressive strength is kept dry.  You may notice that I am trying to use as little concrete as possible, as the tank needs to be cheap.

Pumping water instead of air allows greater energy efficiency overall, because water is an incompressible medium.  Pumping water therefore minimises heat generation.  But it is also presents a problem as concrete and cob, rammed earth and adobe, all lose a great deal of compressive strength when wet.  So a good waterproof lining is important.

Last edited by Calliban (2024-09-05 08:39:26)

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"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

kbd512

Administrator

Registered: 2015-01-02

Posts: 7,776

Re: Why the Green Energy Transition Won’t Happen

Calliban,

We've seen steel compressed gas cylinders used for welding fail during highway crashes.  They don't blow entire vehicles hundreds of feet into the air.  They can't generate enough force to do that.  Heck, even fuel-air explosions with gasoline and natural gas don't do that.  Lithium-ion battery explosions don't do that, either.  10 feet, sure.  50 feet, maybe.  Some of the most powerful high explosive detonations can toss a vehicle or heavy chunk of metal like the engine block that far, but they tend to rip the vehicle apart, which is worse in some ways.  Let's not wildly over-exaggerate any particular danger.  A Lithium-ion battery fire is not going to burn a hole through the center of the Earth (China Syndrome), nor will a nuclear reactor meltdown ever do any such thing.  The cap or valve on a compressed gas cylinder might get blown that far from the vehicle, but the entire vehicle is not going to be launched into the air, Hollywood style, unless it's done with high explosives.  Granted, the energy release from any of these energy stores is fairly spectacular, but it's also a relatively rare event (ignoring severe quality control issues with Chinese products), and we are in fact running H2 powered vehicles on American highways which are laden with highly combustible Hydrogen gas pressurized to 700bar.

On the issue of "range anxiety", I think the "real anxiety" revolves around the myriad of other related issues with Lithium-ion batteries, such as waiting 1 to 2 hours for the battery to recharge on a "fast charger", the fact that the vehicle cannot be left unattended during that process, and all the other supposed benefits which turned out to be pure marketing drivel not tethered to the practical operation of an EV as most people use them.  No significant planning process is required to use a vehicle that can be refueled in a matter of minutes.

Vehicles made from the 1970s backwards frequently had a range of 200 miles if they had large displacement V8 engines or poorly tuned carburetors and ignition systems.  Some burned so much fuel that you could literally see the fuel gauge needle rolling back while the engine was running.  Assuming "range anxiety" wasn't a serious issue back then, it was because there was a gas station every 50 feet and you could refuel your car in about 5 minutes for a reasonable price.  You can still do that with compressed air.  You get your 200 miles and then you can fill the tank up again in less than 10 minutes.

For the EVs, if you recharge at night from the convenience of your own home, then you're not drawing power from renewable energy in most cases.  Unfortunately, this is when it's most convenient to recharge the car, because grid demand and prices are low and you're not using the car.  You cannot put your car in your garage, plug it in, and then go to sleep while your car recharges.  If anything goes wrong, your house might burn down if you're not present to unplug the vehicle.  EVs typically quit functioning entirely if it has an internal electrical short somewhere that the computer detects, which causes it to turn off the car, so then the vehicle cannot be moved to a safer spot where a vehicle fire might be inconvenient but not life-threatening.  Worse still, serious failures during operation frequently leave you trapped in a car that might go up in flames, due to "electronic everything", which includes the stupid door handles.  Someone needs to accept that not everything can or even should be electronic.  Door handles are one example of a device that should remain mechanical forever.

If you routinely fast charge the car, doing so rapidly degrades the battery capacity, decreasing its useful service life and increasing the risk of a thermal runaway that destroys or seriously damages the entire car.  If some cell or electronic component within the battery pack fails, you have to replace the entire battery pack.  If minor damage occurs during an accident, then the insurance company typically totals the vehicle.  An accurate mechanism to evaluate true vs superficial or repairable damage doesn't seem to exist.

If a pressure regulator valve fails in a compressed air car, you don't have to replace the air tank, which is the most expensive part of the propulsion system, nor all the other valves and connected components in the car, in most cases.  No power electronics are required to operate the propulsion system.  The electronics in a modern car, especially an EV, represent 50% of the cost of the car.  If anything but the air tank fails, all the rest of the components can be repaired or replaced in isolation from the air tank, at nominal cost.  A pressure regulator valve is a rather cheap and simple part to replace using hand tools.  No special skills are required, beyond knowing how to use a torque wrench and how to check for leaks.  Special test equipment is not required to "know" that the valve repair was successful.  If it was not, then you can both see (using soapy water) and hear the air escaping, as well as monitor the pressure inside the main tank.

As a mechanic, you don't have to worry about being instantly electrocuted by a battery subsystem capable of delivering hundreds of kilowatts to about a megawatt of power.  Due to its complexity and materials costs, a very large battery pack is never going to be "cheap" in the sense of it being something you stock on the shelf as a spare part.  It's so large and heavy that it's literally integrated into the frame of the vehicle to save weight.  Thus, removal is never going to be fast and easy, in the same way the removing an engine is not fast or easy.  On top of that, a variety of highly specialized and very expensive electronics diagnostics tools are required to test the entire battery pack and evaluate serviceability.  A diagnostics check can be run very quickly in most cases, but that's the extent of how user-friendly maintenance and repair will ever be.  It's certainly still doable, but never fast / cheap / easy.

If I roll into a compressed air car repair shop and tell the mechanic I hear a hissing sound from this spot near the tank, he's going to be able to rapidly figure out what's leaking, how badly using a pressure gauge, and how much time and materials it will cost to fix it.  There could be other problems discovered after the initial repair, but all the parts except the tank, engine, and atmospheric heat exchange radiator are low-cost bits of mass manufactured metal that you can hold in your hand and replace with your hands using hand tools.