Tensions concerning charging stations.

I'm more interested in carbon footprint than in fuel cost. The hydroelectric plant that produces our power is less than a mile from us, and we also "sponsor" wind power elsewhere in the state to make up for it. So we use lots of "hydro" and as little gas as possible.

Those who think global warming means just "warming" have some studying to do.

 

You seem to be arguing against yourself. Using your logic there should even be more of a discrepancy between electric vs gas miles.


Sorry, MPGe is math, at least as far as energy is concerned.

There are capture and distribution costs of both types of energies. You think the gas gets into your tank without any energy expenditure to get it there?

 

Our 7.1kW PV system ( it will have fully amortized itself some where by the middle of next year ) on our roof takes very little expenditure to get it down to the car & the rest of the house. Too bad folks can't build gasoline refineries in their garages to make their own fuel. Best of all, PV doesn't sponsor al Qaeda flight school. On the other hand almost half of the country's electricity comes from coal. Have you ever seen pictures of hundreds of acre feet of coal ash sludge pouring down into a river? Yes every energy source has its downside. Pick your poison. And pick your price point.

 

I am fighting for using electricity, too. That's why it surprised me when you said that it takes just as much energy to use EV as it does HV on a PiP.

 

I did not understand hill's arguments as well. MPGe is not a fiction, it is a measure to compare between two different sources of energy the car can use.
If you achieve 160 MPGe in EV you are driving as efficient (energy wise) as a 160 MPG gasoline car that's all it's saying.

 

I do agree, however, with hill that price of gasoline in the US is a fiction.
I my country, with over 110% taxes on gas, it is at least treated as 'necessary devil' (so I hope).

 

Agreed.

A gallon of gasoline has about 114K BTUs. It isn't an absolute fixed amount. Winter blends have a bit less...about 112K BTUs. And when you add in ethanol you get about 3% less.

A Kilowatt-hour has about 3412 BTUs. The unit of MPGe just converts, mathematically, how far you go on a BTU of electricity to the number of equivalent gallons of gas for the same number of BTUs.

If you get about 50 mpg on gas, this means you consume about 114K/50 BTUs per mile...or 2280 BTU/mile (summer blend)...or 2220 BTU/mile (10% ethanol blend.)
In EV, if you are using about 200 watt-hours per mile (or 1/5 of a kwh) this means you are using about 3412/5 or 682 BTUs/mile. Feel free to add in a charging penalty and/or a trucking penalty for the gas...or any other penalty or values that you get.

The bottom line is, basically, that the vehicle consumes about 3x as much energy per mile traveled when using gas. So getting 150 MPGe in EV is about right. This has nothing to do with costs of gas or costs of electricity.

Mike

 

What about at 60 mph? In theory a PiP should get about 60 MPG or a hair higher. What about in EV? I wouldn't get anywhere near 180 MPGe. I'd be curious to see a graph on PiP economy at different speeds and different modes. My guess is something like 80 or 90 MPGe at 60 MPH in EV. (that's a total guess though)

 

The math is quite easy...(111,000 BTU per gallon) / (60 miles per gallon) = 1850 BTU per mile...as compared to whatever number you have for BTUs per mile in EV. If you are at 200 wh/mile that is still ~682 BTU / mile. Yes only 2.7 times better in this case.

There is no "fixed" amount of difference between HV and EV...it is just "about" 3 times. Obviously, if your EV miles are at night, with the seat heaters on it won't be quite as large a difference.

 

I'm obviously not as good at math as you are. But would it be fair to assume that if you can get 18 miles in EV at 30 mph that you can only get 6-8 at 60 mph? That would be somewhere around 65-85 MPGe in EV. That would only be about 1.3x better than HV. So you could say that the higher speed you go the closer in economy HV vs EV get.

 

No. But if you use 200 wh/m at 30 mph, it might be 250-300 at 60 mph. I'm sure there are some charts somewhere that show some measurements, I've seen them here, but I can't find them. But certainly it is not as drastic as you seem to think.

The number of watts being used goes up a lot for overcoming wind resistance. But the overhead watt-hours being used to power the computers in the car for example, go down (the watts stay the same, but the time is less because you are going faster)

Mike

 

Is this the right calculation to use?

horsepower = (MPH^3 X frontal area in square feet) / 150,000

If it is, then it takes MUCH more energy to go 60 mph than 30.

As far as power overhead, according to Torque the system only uses 1.5 amps while resting. That's a pretty small overhead, especially in comparison to energy used while driving.

 

First, 200Wh/mile is unrealistic for the average pip driver. That's 5 miles per kWh. Realistically it's about half of that, which significantly skews the similar range of the two energy fuels. The Leaf gets 2.9 miles/kWh.
Mark it doesn't matter if you calculate by BTU's or THERMs or kWh's. When pointing out that the Prius travels roughly the same distance on the ice verses electricity, remember the differences between both power sources' losses. Gasoline energy efficiency is only (roughly) 30% ... after friction from all the mechanical interaction that's roughly one-third left, to move the vehicle forward. On the other hand, battery electric motors are roughly 70% efficient (energy loss, battery weight, & AC/DC/AC conversion losses). So even if you start by presuming gasoline having roughly 30kWh's of energy per gallon (ignoring the lost 1/3 energy of getting gasoline into your tank) the Prius gets you down the road on only 20kWh's of equivalent electrical energy. The same 30kWh electric motor/BATTERY has a usable capacity of roughly 80% (not using the bottom or top end of capacity to extend battery life) ... which roughly leaves you with 24kWh's. Knock 30% off for electric motor/battery efficiency and you're left with roughly 17kWh's of energy to get you down the road. At 50mph & 2.5miles per kWh, a prius might travel about 43miles when a 17kWh battery is brand new. Knock off an additional 10% of range for capacity loss, once the pack has 50k +miles on it (capacity loss is non linear/bell curve - so lithium losses slow past that point ) which roughly leaves you with 38 plus miles to get you down the road. Those are the issues that MPG/e fail to factor in, and that's what bugs me. Being honest in this fashion leaves you with roughly 10% energy/fuel differences. That was my point. Yet people get all pissy when their free charging station goes away ... or god forbid the owner wants to recoup the expense of his investment by charging a buck or two per hour. Those are the numbers that make me shake my head

 

What a twisted calculation!
Per EPA Prius is:
Driving in EV 11 miles using 0.29 kWh/mile (including all losses) +0.01 gallon.
Driving HV at 50 MPG (after all losses).
So, in HV you invest 1 gallon of gasoline (33.7 kWh per EPA) and you get 50 miles out of it. 33.7/50=0.67 kWh/mile, how can you say it is "more or less" the same as 0.25-0.3 kWh/mile people are getting (from the wall) in EV mode?
MPGe is not a fiction.

 

...and that was not free either.

 

I get 4.2 (currently, in cold weather, with snow tires) to 4.5, according to the car's admittedly imperfect instrumentation. While 3.x isn't uncommon, you have to drive pretty hard - especially in mild weather - to get as low as 2.9 M/kwh.

 

Use paragraph's next time. Not reading through all that mess.

I did read the first part about a non-PiP driver thinking they know everything about the PiP, such as getting 2.5 miles per kWh. Um no, only the worst PiP driver in the middle of winter will get 7.5 miles of range out of their PiP. Most people can routinely beat double that during months that aren't winter. So please stop acting like you know everything about our car just because you have a few solar panels on your roof. Oy

 

Some pretty realistic numbers:
You go just 10 miles on a charge, and it takes 3 kwh to charge (measured from the wall...with 2.7 kwh actually going into the battery)...this gives you 270 watt-hours per mile as indicated in the EV ratio screen, while actually being about 300 wh/m. Or ~3.3 miles/kwh.

I'm pretty sure that range loss has nothing to do with it. What happens is that when you charge your battery it now consumes 10% less kwh and you get 10% fewer miles. The distance you go per kwh is still the same (assuming the rest of the car is still in the same working order, etc).

Mike

 

That's the physics way of computing it...but it is better to just measure the actual. The fact is that the best I've been able to do over several charges is about 175 wh/mile...going about 30-40 mph, with some starts, stops, coasting, etc. And when I've done 100% freeway in EV, 60 mph, etc. I get only 9-10 miles per charge. I've never had a charge of >3 kwh (ChargePoint, L2 only EV portion depleted). This has less than 300 wh/m written all over it (closer to 270 measured via EV ratio). And I should note that I usually only get 2.6 - 2.8 kwh per charge.

Mike

 

I got 8.0 miles this AM on a charge. EV range showed 12.4 leaving a heated garage. Outside temp was 44F. Speeds were generally 45MPH for the first 4.5 miles then 55 MPH for the next 2.0. Stopped to go shopping and returned the same way and ICE came on at exactly 8 miles from home. That 55 MPH section killed the EV.

Last month when temps were in the 60-70F range, I made the same trip completely in EV on several occasions.