Upon rereading, I see that I was mistaken in how I corrected your statement. Your bolded statement above is, strictly speaking, correct, but does not apply to this situation.
The reason is that you can’t simply multiply by 1 hour. Any time unit you incorporate has to come from somewhere. The 600 cars/hr is a rate, and would be true if we were talking 1000 hours or 0.001 hours. You can’t simply pick “1 hour” out of the blue just because that happens to be the denominator of the chosen rate.
The actual time unit is 0.01 hours. That comes from our estimated speed of 100 km/hr and that we’re talking about a 1 km stretch. There is no way around this. Since the piezo road works by deformation from the weight of the vehicle, the amount of energy captured is independent of the speed. What the speed tells us is how many cars are on the road at any given time.
Above, you’re effectively declaring that the cars are traveling at 1 km/hr. That would mean there are 600 cars on the road (which is ridiculous since there’s not even enough physical space for them). This would indeed make the power numbers work out a little better, but is obvious nonsense for physical reasons.
The rolling resistance of a tire on pavement or concrete is due almost entirely to the deformation of the tire, and negligibly due to the deformation of the pavement. If we’re not going to make the car burn any extra fuel (by making the pavement deform much more than is typical), then the only energy that’s available for harvest is that which is currently dissipated in the pavement.
And that ain’t much.
At highway speed, a car uses anywhere from 10-30 kW to maintain its speed (the exact figure depending on speed and aerodynamics), with rolling resistance eating up maybe 10% of that, so 1-3 kW.
As mentioned, most of that energy is currently dissipated in the tire. I’ll be verygenerous and assume that 10% of it is dissipated in the roadway, so 0.1-0.3 kW is available to the PE system for harvest. If you have six vehicles per kilometer of road, then each kilometer of road can produce, at absolute most, 0.6-1.8 kW of power, assuming *all/I] of the deformation of the pavement goes into compressing the PE generating units (the actual amount of power that would be sent to the grid by the PE units is certainly much less).
That strikes me as a pretty weak return on investment, unless PE pavement is extraordinarily cheap and durable.
Thanks for stating it like this, because I’d been scratching my head over why I’ve been calculating a value so much lower than I expected. But now I see a fundamental error here in the way I was applying the coefficient for rolling resistance.
First, we have to remember that it’s incorrect to refer to rolling resistance as a percentage of power. Instead, it’s that percentage of force required to overcome friction and deformation in the contacting surfaces (tires and road, pistons, bearings, etc.) and power conversion factors (since we’re rotating the wheels through a transmission instead of pushing on the vehicle with an “outside” force).
So, while the power required to maintain a certain speed is much less than the power required to accelerate to that speed, the combined forces required to move the vehicle are still equal to the normal force. Applied force goes down (resulting in reduced power requirement from the motor) because it’s combined with inertial force.
So looking at rolling resistance as a portion of the power applied by a car motor at highway speeds gives an erroneous estimation of the power required to overcome rolling resistance. I’d say that, at running speed, the 10-30 kW you’re estimating would be exclusively the power required to overcome aerodynamic resistance plus rolling resistance. Of the two I’d think rolling resistance would be the smaller load for most cars on the road, and probably even smaller proportionally for most tractor-trailer combos.
TLDR, it’s probably a closer back of the envelope calculation to consider at least 25% of engine power at speed as “the power required to overcome rolling resistance” rather than multiplying that power by a coefficient. (Or, you could apply the coefficient to the calculated normal force to come up with F[sub]r[/sub] and then take a percentage of that rolling resistance force as ‘road deformation force’ and then do your power calculations. Which is a long way to go for a casual estimate.)
Having said this, we’re still left with a pretty small generation of power from the pz roadsurface, even assuming maximum efficiency of the system. It’s probably a much more feasible line of inquiry for EV manufacturers looking to reclaim some energy from tire deformation. Possibly some traffic control systems could be fully powered by a road system, but as most of us have noted, the return on investment is probably not sufficiently rapid at this point.
Renewable means it can be renewed. A field of grain is, in theory, renewable: Harvest a crop, plant a crop, and you’ll continue to have crops. The resource gets renewed through the normal process of having and maintaining a farm.
The sun cannot be renewed. There’s nothing humans can do which will renew the sun. The fact that isn’t our fault doesn’t magically make the sun renewable.
If you want to say “Carbon-neutral”, say it. If you want to say “Non-polluting”, say it. If you want to say “All-natural”, say it. Nobody’s stopping you.
Just don’t get all shocked and amazed when someone reads a word as meaning what it appears to mean.
Are you aware that not considering solar as renewable energy is not how everyone else defines it? Heck, even the United States Department of Energy lists solar energy among renewable sources.
I think we’re dealing with a words-only-have-the-one-meaning-I-think-they-should-have obtuseness one often observes in the mildly autistic, like my cousin who exhibits this trait. Never mind that language doesn’t work that way. Never mind that solar flux is replenished at the rate is used. And never mind the generally accepted dictionary meanings of the word, which are consistent with this use.
If crops are to be considered renewable, then surely the energy source that facilitates their growth must also be considered renewable.
If the sun is to be considered non-renewable, then surely the same must be said for anything that depends on the energy emanating from it - to include crops.
Pick one or the other. Can’t decide? I’ll give you a hint: anyone working in the field of renewable energy considers the sun to be a renewable energy source, along with all of the things that are driven by the sun (wind, rain waves) and several things that aren’t (tides, geothermal). Do you hold them all to be irredeemable morons, or do you think just maybe they might know something about the field in which they labor?
The crop only grows because of the energy provided by the sun, which you say is non-renewable. You can only grow crops as long as the sun has hydrogen to fuse. Therefore, crops can’t be renewable either.
If you seriously argue that solar energy isn’t renewable, because the sun will eventually expire, you have to also concede that no energy can ever be renewable because of the eventual heat death of the universe.
Or you can just accept that everyone else says that solar energy is “renewable” because it will outlast humanity as we know it.
As trolls go, he’s rather long in the tooth, having been a member since Y2K.
Some kinda sleeper troll maybe? Acts smart, blends in, earns everyone’s trust - and then at the right moment, he changes tack and just starts saying stupid shit, catching everyone totally off-guard and sowing chaos?
I haven’t been following this argument much, but I popped in to see how it was progressing, and I couldn’t let this stand.
No, both of your presentations are wrong. The correct way to write this is “kW/km-veh-hr” - I have no idea how that affects your argument, but I’ll pop in again some time and see how it went.
"I said “both of your presentations are wrong.” In other words: cite for “per vehicle per hour” meaning “per (vehicle per hour)” and not the far more rational “per vehicle, per hour”?
There are other units to use as a model. Acceleration is expressed in “meters per second per second,” and that doesn’t mean meters per (second per second); impulse is measured in “meters per second per second per second,” and that doesn’t mean “(m/s)/(s/s)” - it means “m/s-s-s” as God and Newton intended.
I didn’t come up with the unit; that’s from the paper. Table 16 has 3 numbers, “power per km”, “vehicles per hour”, and “kW per km per vehicle per hour”. They do not add extra parenthesis, but the first number is just the second times the third, as you would expect from unit analysis if the interpretation is (kW/km)/(veh/h). The unit analysis fails with your interpretation.
With a little additional analysis, the unit becomes 3600 N/veh. This has its own obvious physical interpretation–the road is applying a force to the car, just as wind resistance and tire deformation does. But Genziko claims they can extract 22 times this, or 79200 N/veh. This is a huge number! It means a 1600 kg car would decelerate at 5 gees on this road surface. The Innowatttech numbers of 0.16-0.3 correspond to 576-1080 N/veh, which a normal car would be able to sustain in a low gear, but it’s still way above the normal drag value.
