EUC efficiency vs. electric cars vs. IC cars

[travsformation]

So, I was watching the video below, and reading the comments, and it got me thinking about how much more efficient EUCs (and PEVs in general) are, compared to electric cars and internal combustion cars.

First, there's are the usual and obvious suspects: the overall efficiency in obtaining and transporting the energy powering the vehicle, the efficiency of the vehicle's engine (how much of that power is converted into kinetic energy), the engine's overall efficiency (MPG equivalent/how much energy it takes to move the vehicle x distance), AND more importantly, and not mentioned in the video, how much energy it takes to move a kg/lb of human being. And this latter variable is where I think a point really needs to be driven home about PEVs.

Comparing a Tesla to an internal combustion car is one thing. For the IC, there's the fuel extraction, refinement, transportation, etc., and then on the car's side, the engine efficiency (40-50% max., in the best of cases?), emissions, etc. An electric car is more efficient and sustainable overall, despite poor percentile of renewable energy powering it, BUT, how much of the useful energy actually goes to moving the person, and how much of it is used to move around a couple of tons of metal?

That's my issue with electric cars. It's the business-as-usual model. I think it's great that people are switching to electric cars instead of using IC ones (they're the lesser of two evils), but we're stuck in the same old transportation paradigm...no collective/public transportation, the use of 1500kg+ cars as personal (IC) vehicles (known, hereinafter, as PICVs ), etc.

Compare an electric car to a PEV, on the other hand...

A Tesla Model 3 SR+ (RWD, standard range) weights 1,600 kg (3,500 lb); I weight 70 kg (154 lb). So:

• The car weights nearly 2300% my body weight
• Little over 4% of the energy is used to move ME, while the other 96% goes to moving the car.

My 18XL, for instance, weights 25 kg. So:

• The wheel weighs roughly 36% of my body weight.
• 26% of the energy is used to move the wheel, while the other 74% is used to move ME.

And that is a little piece of info I don't see anyone rambling about on Youtube, which merits a hell of a lot more attention than it gets.

It would be interesting to calculate the overall efficiency of an EUC vs. a Tesla vs. a IC car... (if anyone is bored...)

 

BTW, if you decide to watch the video, here's some forenotice before your blood starts boiling: Yes, it's ridiculous how he takes fossil fuel industry efficiency figures at face value (81.7 %? ), without taking into account the electricity used to extract the fuel & refine it, the fuel used to transport it (and corresponding additional emissions), while he does break down every possible loss in efficiency in the production and transmission of electric energy. No mention of the efficiency % of IC engines either (losses in the form of thermal energy, etc.). Anyone care to challenge his figures?

 

 

P.S. Considered putting this in off-topic, but figured it's relevant enough for it to be in general discussion

Edited November 5, 2019 by travsformation

[meepmeepmayer]

4 hours ago, travsformation said:

P.S. Considered putting this in off-topic, but figured it's relevant enough for it to be in general discussion

I appreciate your thoughtfullness considering where to post this, as evidenced by you posting it in the forum rules section But you want it in General Discussion so I moved it there

[meepmeepmayer]

On topic, yes I hate it when people discuss "electric vehicles", I get excited, and then it just ends up being electric cars. They have all the problems of cars, minus the combustion-related ones (well, depending where the electricity comes from). An electric SUV is still a f****ing SUV.

Maybe electric vehicles need a Wh/km (kJ/km, Wh/mile, whatever) rating for typical use. Then electric cars don't look so good, I bet. Your idea of how much % is used for the rider as opposed to the vehicle itself is also a great way to quantize it, and one that is simple, easy, and can hardly be cheated

Edited November 5, 2019 by meepmeepmayer

[travsformation]

2 minutes ago, meepmeepmayer said:

I appreciate your thoughtfullness considering where to post this, as evidenced by you posting it in the forum rules section

Seriously?

Wow, that's bad, even for me...   

4 minutes ago, meepmeepmayer said:

But you want it in General Discussion so I moved it there

Thanks  

 

[mike_bike_kite]

• The car weights nearly 2300% my body weight
• Little over 4% of the energy is used to move ME, while the other 96% goes to moving the car.

I doubt if that's strictly true. Once the weight is moving then you only use power to overcome rolling resistance and air friction (guessing here). A person standing on an EUC creates a lot more air resistance than the car (apparently 4 times more). The air resistance goes up by the square of the speed (I think), so the faster you go, the more important this becomes. Rolling resistance would certainly be more on the car, there's 4 tyres for a start, plus they have larger contact patches. I'm going to guess 4 times larger than on an EUC which would mean the rolling resistance is x16 worse for the car. Luckily the resistance doesn't change with speed unless it's just the tyres heating up and becoming stickier. Then there's also the energy used in keeping the person upright on an EUC - I'm sure this can be minimised by good riding.

It should be easy to see how much energy is used to move someone 10 miles by just monitoring the plug output when recharging the EUC. That should give you a cost per mile. Then do something similar with the Tesla. It would be very interesting to include electric bicycles and something like a one-wheel. Not sure how you'd compare to an IC car or even to walking (calories burned?).

 

[meepmeepmayer]

5 minutes ago, mike_bike_kite said:

I doubt if that's strictly true. Once the weight is moving then you only use power to overcome rolling resistance and air friction (guessing here). A person standing on an EUC creates a lot more air resistance than the car (apparently 4 times more).

The drag coefficient is per profile area. You don't have more drag that a car, especially the suburban tanks sold nowadays.

You're right that energy per distance is a measure that should be looked at then.

[mike_bike_kite]

9 minutes ago, meepmeepmayer said:

The drag coefficient is per profile area. You don't have more drag that a car, especially the suburban tanks sold nowadays.

The Tesla model 3 has a drag coefficient of 0.23Cd. A person standing has a drag coefficient of between 1Cd and 1.3Cd (a few sites state 0.6Cd but then perhaps this is for slim Asians rather than ample Americans). In short the Tesla does have a better drag coefficient than a person.

Edited November 5, 2019 by mike_bike_kite

[PLEASE_DELETE]

Deleted.

 

Edited March 18 by PLEASE_DELETE

[meepmeepmayer]

4 minutes ago, mike_bike_kite said:

The Tesla model 3 has a drag coefficient of 0.23Cd. A person standing has a drag coefficient of between 1Cd and 1.3Cd (a few sites state 0.6Cd but then perhaps this is for slim Asians rather than ample Americans). In short the Tesla does have a better drag coefficient than a person.

I think this is just language confusion. By drag I ultimately mean the power usage due to air resistance, which is proportional to drag coefficient times profile area. And a car has a much higher profile area in direction of travel than a person.

[mike_bike_kite]

The profile area is included in the formula for drag coefficient. If you stuck a Tesla 3 in a wind tunnel and a person in a wind tunnel then it should take more effort to keep the person stationary than the car for the same wind speed. People just aren't built for speed. Even a range rover has half the drag coefficient of a person.

I did try to read up on all this before posting but I won't be upset if someone proves me wrong

Edited November 5, 2019 by mike_bike_kite

[meepmeepmayer]

That's what I originally meant to say

A model car and a real car have the same drag coefficient (C_d), but not the same profile area (A). That's why they don't have the same drag/wind resistance/power usage at a certain speed. Same for a person who has a smaller surface area than a car, so (I say) despite a higher drag coefficient he has less "wind resistance" than a car.

[mike_bike_kite]

I think you're right and what I was saying might actually be wrong. I have been trying to get a definitive answer on the web but can't seem to find one that I can understand. You'd think if they quote drag coefficients for different cars then these should be comparable ie the actual size of the car would already be incorporated into that number so you could see which vehicle slips through the air better. I'll carry on reading ...

[meepmeepmayer]

If drag coefficients were size-dependent, they would make little sense because everything would have it's own drag coefficient. E.g. every person has their own coefficient, depending on how tall they are. Coefficients would be useless then because they would not allow you to predict anything and you'd have to measure everything on its own. As you can see from the table, it doesn't list "small bird, slightly bigger but still small bird, little bigger bird, ..." but just "bird" for the shape of a bird, independent of size.

Drag coefficients encode the shape (and surface material friction and what else counts for air resistance) of what you're looking at, exactly because this is (as found by experiment, this can't be guessed) a fixed constant. The formula you linked to is essentially the definition of a drag coefficient: leaving all that varies and cannot be expected to give the same result for wind resistance (such as speed and specific surface area), we find something that is constant and therefore allows predictions.

So a drag coefficient tells you how "efficient" a certain shape is (super aerodynamic vs. like a parachute), but does not tell you how efficient a certain thing in that shape is, because that also depends on the size of the thing. Size is given by the surface area perpendicular to the movement direction. Bigger = more absolute air resistance (and therefore power usage etc.).

-

Side note: Since the formula only gives the drag force, but power is force times speed, the wind resistance power usage grows cubically with speed! Crazy! I didn't know that. Double the speed for 8 times loss due to wind resistance

That shows why wind resistance is the main power draw for EUCs. A good argument for seated riding.

-

More on topic, I'm surprised that a car gets so close to a EUC if you put more persons in it. But I guess that is only air resistance. Accelerating and decelerating that huge mass will have to cost something, too.

Edited November 5, 2019 by meepmeepmayer

[Mono]

On 11/5/2019 at 7:47 PM, mike_bike_kite said:

The profile area is included in the formula for drag coefficient.

It's not, the name coefficient gives a hint. c_d is proportional to the force and inverse proportional to the area. To compute the force you have to multiply the coefficient by the area.

On 11/5/2019 at 9:25 PM, meepmeepmayer said:

Side note: Since the formula only gives the drag force, but power is force times speed, the wind resistance power usage grows cubically with speed! Crazy! I didn't know that. Double the speed for 8 times loss due to wind resistance

Sounds logical, but I don't think so  The complication is that c_d depends on the Reynolds number and the latter is also proportional to speed. For low Reynolds numbers, which is the regime for air flow, c_d is inverse proportional to the Reynolds number, hence canceling the cubic depency of power on speed to quadratic:

Quote

Since the power needed to overcome the drag force is the product of the force times speed, the power needed to overcome drag will vary as the square of the speed at low Reynolds numbers and as the cube of the speed at high numbers.

On 11/5/2019 at 9:25 PM, meepmeepmayer said:

That shows why wind resistance is the main power draw for EUCs. A good argument for seated riding.

That really depends on the speed though. For small values, linear and quadratic terms dominate cubic terms. IIRC, drag starts to dominate between 15 and 20km/h.

Edited November 6, 2019 by Mono

[Aneta]

To achieve laminar flow around our bodies, we'd have to move not any faster than a snail (1mm/s?). For all practical purposes, the airflow around our bodies is always turbulent and drag is calculated by this formula:

D = (1/2)*C_d*ro*S*V^2

where C_d is dimensionless coefficient of drag, ro is density of air (1.25kg/m^3 at sea level and temperature 15C), S is cross-sectional area, V is airspeed. (e.g. when riding directly into the wind, it's the sum of rider's speed and wind speed)

Edited November 5, 2019 by Aneta

[Mono]

2 hours ago, /Dev/Null said:

Can it do 5 people at that same efficiency ? then you are at 35wh/km/person -- very similar to a 50km/h EUC, no?

Sounds about ballpark right, the number of people in a Tesla do not really change its consumption a lot.

[Aneta]

I think it's possible to achieve the same efficiency with Tesla car as with a 64-times lighter EUC. Here, it's probably less than 5 kilos of "metal" per person:

[LanghamP]

Why do people drive hugely inefficient vehicles when they have better options? Because the cost of driving is invisible and transferred.

The infrastructure to support the very heavy vehicles is ludicrously high, and it dwarfs car ownership costs.

If every homeowner and apartment dwellers had to maintain just the strip of street/road outside their domicile, how much would it cost? I estimated it being somewhere between 6,000 to 36,000 dollars per year per $100,000 of property value some time ago.

Here's what happens when the city bills the homeowners. Mind you, that's just for the cheap repairs, not the expensive initial build. That is, this article is the low-end cost of road "ownership"!

Lisa Sabin-Wilson said she and her husband would never have bought their home in 2016 had they known they would soon owe the city $42,000 for repairs to their street.

What's the carbon cost of building car oriented pathways?

The total CO2 emission from road, bridge and tunnel constructions was 5229 kg/m, 35,547 kg/m and 42,302 kg/m, respectively.

From both an emissions and financial viewpoint, car-oriented infrastructure is unaffordable, but consumers are shielded from the cost. In my opinion, this is the single biggest danger facing modern societies, and is the real reason your town is going bankrupt.

There's about seven parking spots for every car, and each parking spot costs about $3500 for the expected 20 year lifespan of parking lots. You could simply give $70,000 to each driver willing to give up his car, and you'd still come out ahead!!

I'd bet if you sent every person a $16,000 road tax bill every year, then you'd start to see people screaming for PEV and bike infrastructure. 

[LanghamP]

8 hours ago, meepmeepmayer said:

Side note: Since the formula only gives the drag force, but power is force times speed, the wind resistance power usage grows cubically with speed! Crazy! I didn't know that. Double the speed for 8 times loss due to wind resistance

Here's an algebra question I've not yet solved:

Given your fuel efficiency in a 10 gallon gas car is 400 miles at 55 mph, at 240 miles at 75 mph, and each fill up takes 20 minutes, then how fast should you drive on the highway?

[travsformation]

On 11/5/2019 at 7:12 PM, /Dev/Null said:

Can't you simply break this to wh/km ?

Good thinking!!! I can't believe I didn't think of it!

On 11/5/2019 at 7:12 PM, /Dev/Null said:

Example:  my inmotion V10 can take me ~ 40km on 650wh (if I ride at say 15km/h)

So it takes 650wh/40km=16.25wh/km to get myself somewhere.  On a worst case basis, maybe 30wh/km @ 50km/h

A tesla model3 has an 85kwh pack and can go ~ 480km (not exact...but ballpark?)

85000/480=177wh/km.

Can it do 5 people at that same efficiency ? then you are at 35wh/km/person -- very similar to a 50km/h EUC, no?

I have to admit,  given that the Tesla weighs about 80x what a 20kg EUC does, the fact that consumption is only 59x is actually pretty impressive. And with 5 people aboard, about the same Wh/person/km...Comes to show how wind resistance is a much greater consumption variable than weight (past a certain threshold and speed)...

But my point still stands in terms of the transportation paradigm: how many times do Teslas (or cars in general) actually seat 5 people in the real world? With 4 occupants, consumption goes up to 44 Wh/km/person; with three, to 59Wh/km/person and with two, 88Wh/km/person.

If you take a three-occupant scenario as an example (2 adults + 2 kids, round it up to 3 adults), the difference doesn't seem dramatic, but it's still 29Wh/person more for every km. Take a conservative 20 km commute (round trip), 48 working weeks/year (assuming 4 weeks paid vacation/year, and to give cars an advantage, zero driving while on vacation), and we have 20km/day * 5 days/week * 48 weeks * 29Wh/person more than on an EUC = 139 kWh more in a year. 

With electricity production emissions at 340g of CO₂ per kWh (EU, combined average), that's an additional 47 kg CO₂ per year, per car, compared to riding an EUC. 

There are approximately 263 million registered cars in the US alone. If every single one of them were electric (imagine that!), we'd still be talking about a difference of 12 million additional metric tons of CO₂/year (in the US alone). And that's assuming an implausibly optimistic 3 occupants/car and a 20 km commute. Switch to slightly more realistic figures (2 occupant/car, 40 km commute, round trip) and we have (40 km/day * 5 days/week * 48 weeks * 58,5 Wh/person more than on an EUC) an additional 561 kWh / 190 kg of CO2 per year when compared to the EUC used in the example (times 263 million cars = 50 million additional metric tons CO₂). 

These figures are, needless to say, highly inaccurate rough estimations (and sadly, unrealistically optimistic...), but when considering the differences being discussed (electrics cars vs. PEVs) on a larger scale, they really put the problem with our current transportation paradigm into perspective. Especially if one considers that this example is based on the beyond-unrealistic premise that every single gas-guzzling car in the US is magically replaced overnight by a Tesla...

Nor do they take into account the plausibility/implausibility of the increased electricity demand, the carbon footprint of producing said energy without a shift towards renewable energy sources (or at least, not back-tracking by increasing coal %...), nor the excellent points and hidden costs mentioned by @LanghamP, plus a million other variables involved.

Replacing IC-engine cars with electric cars just isn't the solution. The solution involves changing how we view transportation, how we choose to move around, and necessarily required a shift in how mobility is planned and designed on a local, state and national level: pro-PEV legislation and initiatives (incentives and tax breaks like with electric cars), proper PEV and bicycle infrastructure for urban and inter-city mobility, improved and non-polluting public transportation (more occupants/vehicle = less Wh/person/km) and efficient, affordable, electric high-speed rail links for longer-distance travel. 

But of course, all that's just wishful thinking... 

It's tempting to blame the issue on political short sightedness and plain old stupidity/inability to view past the current transportation paradigm (that's ruled over the past 60 years) and adapt to current times, but I'm afraid that as usual (at least from my point of view,), savage, deregulated, perpetual-growth-oriented, sociopathic-level capitalism (lobbying, special interests, revolving doors, corruption) and its firm grasp over politics/democracy is the main issue standing in the way of any kind of significant change...

As stated in the video below, "High-speed rail is an existential threat to oil, airline and road industries".

 

 

A similar conclusion, but with a more nuanced approach, is drawn in the video below (from CNBC) 

 

And here's some food for hope, to counter the pessimism (involved in realism...)

 

 

Edited November 7, 2019 by travsformation

[travsformation]

P.S. And while I'm derailing my own post, it might be worth mentioning that, regardless of the type of electric vehicle one drives---be it a Tesla or an EUC---, switching to a 100% certified renewable energy company or cooperative brings down emissions stemming from energy production* to ZERO...

 

* Not counting the environmental footprint of producing and installing the infrastructure (but that isn't factored into fossil fuel or combined energy production emissions either, so it's a fair comparison)

[Nic]

[meepmeepmayer]

2 hours ago, travsformation said:

given that the Tesla weighs about 800x what a 20kg EUC does

80x

11 hours ago, LanghamP said:

Here's an algebra question I've not yet solved:

Given your fuel efficiency in a 10 gallon gas car is 400 miles at 55 mph, at 240 miles at 75 mph, and each fill up takes 20 minutes, then how fast should you drive on the highway?

Hey I'm not doing your math homework

Given that the question is incomplete (how fast should you drive to do what?) and the numbers are... interesting (10 gallon car? 20 min to fill up?), I say stick to the speed limit for smooth traffic flow

[LanghamP]

2 hours ago, travsformation said:

tempting to blame the issue on political short sightedness and plain old stupidity/inability to view past the current transportation paradigm (that's ruled over the past 60 years) and adapt to current times, but I'm afraid that as usual (at least from my point of view,), savage, deregulated, perpetual-growth-oriented, sociopathic-level capitalism (lobbying, special interests, revolving doors, corruption) and its firm grasp over politics/democracy is the main issue standing in the way of any kind of significant change

Almost all drivers don't want to share the road, and barely tolerate each other. Just look up "road diet" on YouTube and see that the majority of comments play "bike bingo".

There's problems and there's predicaments. Some people will ludicrously claim that air pollution hasn't killed people when good science shows air pollution is the leading cause of death in Asia. IC engines, as you point out, could be replaced by renewable (or cleaner) electric engines. We know what happens should LA continue its course of unchecked road and car growth, because we can look at cities that have failed to regulate their emissions.

Automotive and industrial emissions fill the air with nitrogen, sulphur dioxides, and “black carbon,” the latter of which includes tiny particles that penetrate deep into the lungs. Over the past days, levels in Delhi have exceeded 10 times what the U.S. Environmental Protection Agency deems safe. (The idea that any level is “safe” is disputed, as even very low levels have been found to cause disease.) The effect is lethal, in India and beyond. Air pollution is the leading cause of premature death in parts of the world. It already accounts for more than a quarter of deaths from lung cancer and heart disease, according to the World Health Organization. A Lancet study found that particulate matter alone killed some 1.9 million people in Asia in 2015. In some parts of China, one in 20 deaths is due to bad air.

Yet convincing drivers to chill out is difficult.

1. They spend huge amounts of time in traffic.

2. They average 70 month car loans.

3. They see crashes every day. They know 36,000 people are killed by drivers.

4. They know about double that are killed by participate pollution drummed up by cars.

5. They can easily find out that their government spends huge amounts of money so people can drive.

Drivers, perhaps people, are bizarre. When confronted with facts they usually double down instead of changing their minds. I mean, something is expensive, it kills lots of people, it's not comfortable to do, and we can have alternatives, then you'd think we'd change.

Nope.

[LanghamP]

12 minutes ago, meepmeepmayer said:

I'm not doing your math homework

Given that the question is incomplete (how fast should you drive to do what?) and the numbers are... interesting (10 gallon car? 20 min to fill up?), I say stick to the speed limit for smooth traffic flow

Pretty please with ice cream on top?

It's a somewhat complex question that moves around depending on how it is phrased.

Suppose you want to travel 5,000 miles. Should you drive faster but then stop 40% more often, considering each fill up cost you 20 minutes to get off the freeway, find a gas station and fill your car? And if you spend $50 instead of $30 to go 400 miles, then isn't that an extra hour lost via working? That is, each fill up might cost you 140 minutes (20 minutes to fill up + 2 hours of work to fill that gas tank).