The electricity from the ICE driven generator can actually power the traction motor directly, through the inverters, without being sent off to first charge the batteries. It is also possible for this electricity to simultaneously propel the vehicle and charge the batteries. The attached blurry screenshot, displays the narrow window in which Engine Drive Mode operates. It is my understanding, a single speed that will not engage below 45mph. The car is designed to operate as efficiently as possible. By default, much to the chagrin of some, it starts out in EV mode. Once the batteries are “depleted” it switches to HV mode where it chooses the most efficient means of propulsion. There’s been plenty of debate as to which mode is most efficient. I’ll leave it to the car to decide.
Yes, you are right, the car can run the generator and send the electric power directly to the EV traction motor, but it requires a few steps extra over direct mechanical drive. In that case you have losses in the motor turning the generator, AC to DC coming out of the generator, capacitor storage, DC to AC in the inverter, and the EV traction motor, to turn the same output gear the engine can drive directly. The paper linked below describes the design process for the original "Previous PHEV" noted in the Figure 7 you posted. In Figure 12 (attached) of the presentation below they note. "Engine Drive" has superior fuel economy compared with "Hybrid Drive" in red areas, and both driving modes have similar efficiency in blue areas. This diagram represents that the efficiency of "Engine Drive" is better than "Hybrid Drive" in the areas of cruise and slight acceleration. https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.evs24.org/wevajournal/php/download.php%3Ff%3Dvol2/WEVJ6-2-039.pdf&ved=2ahUKEwj0ybWQkefYAhVIjVQKHYeKD2MQFjACegQIDxAB&usg=AOvVaw1d6kzNGVrPfzTHdfr0-cFU
There are mechanical losses in Engine Drive Mode as well. The screenshot that I attached is from a document published on 4/13/18, that specifically discusses the development of the Clarity Powertrain. It may or may not be more relevant than the link you provided to a document published in November of 2013. The screenshot displays graphs for both the previous PHEV and the Clarity PHEV. EDM only engages above ~45mph and remains engaged in a very narrow window of operating conditions. I trust the Honda engineers that claim the car is more fuel efficient, in EDM, within that window. Outside of that window, EDM disengages because the engineers determined that it was no longer the most efficient mode given the current set of conditions. Personally, I don’t think the difference in efficiency between EDM and HV mode amounts to a hill of beans. I just let the car do it’s thing.
What Landshark said was: "All in all, I’d argue that the electric motor is more efficient than the ICE. It takes the same amount of energy to do the same job. There is just more energy in 7 gallons of gasoline than there is in a 17kWh battery." This is absolutely true - no way to spin it otherwise. Just a couple of observations.... I will just use the definition of "efficiency" as the conversion of available stored "potential" energy to usable vehicle motion "kinetic" energy. The electric traction motor wins hands down in ALL operating environments. The ICE is there to supplement the only current EV limitation, the small battery (gas tank). The ICE running, either as an HV (gear mode driving the tires in cruise) or HV Gen (free wheeling generator) will never convert watts to watts, nowhere close. However it is necessary, until we get batteries that can store 200kWh+ of energy easily and repetitively at a weight, and price, of similar equivalence to an ICE. Example ICE powered Toyota Camry, ~30 MPG average, 14.5 gallon tank = 435 mile max range, using 478kWh of energy... (yes, the conversion losses published around 60% of available fuel energy). Tesla is achieving a max published range of 370 miles on 100kWh of electric energy. Using this example, ICE Toyota = 1.10 kW per mile / BEV Tesla = .37 kW per mile.... which is more efficient.... We get only 40% of the fuel into the engine out as useful work, that is then lost further in both gen to traction motor conversions and further mechanical losses. The PHEV, in serial or parallel hybrid mode, has a higher total efficiency than a conventional vehicle. The conversion of "electricity" PER WATT, will always be higher for an electric motor (traction motor) than an internal combustion motor. Our ICE is almost 40% thermally efficient, and that is very cool - but that is within a very confined RPM/Torque range (it is an Atkinsons engine and would do very poorly direct drive even with "gears" as it is very low torque compared to conventional ICE's). LIB's have about a 99% charge efficiency (not charger efficiency, that is about 93% but still...) You put 100 watts into a battery it has stored 99 watts... Again, ICE's cannot and likely will never convert at this level. A gallon of gasoline has about 33kWh of energy in it - we get 40% or, likely, much less than that out if it in work. An electrical watt, is well - an electrical watt. If you put in 746 of them, and get 1 shaft brake horsepower at 1 RPM (or any RPM) of the motor it is 100% efficient. Most traction motors are approaching 95% efficiency with all above 90%! That is WAY better energy conversion than 40% of an ICE. @Landshark is very correct in his statement. I have attached an old study of this, things are even better now! The motors now being tested in electric aviation are approaching 97%+ efficiency, since cost is less of a concern on an airframe already costing millions of dollars before the motors are attached. Cheers, Cash
I think you cool, smart engineer types are simply misinterpreting what us uncool business-types mean when we say "efficiency" or even "energy efficiency." I have a feeling that many of us inherently include the cost of gas/electricity in our mental calculations of "efficiency" such that (even if we don't explicitly admit it), when we ask which mode is the "most efficient," we are asking which one will save the most money. That implies the answer depends on where you are and how much you pay for gas/electricity.
You've just described MPGe Clarity PHEV using gas to power the electric motors = 42 MPG Clarity PHEV using battery to power the electric motors = 110 MPGe (measured from the wall and includes charging losses) Tesla Model 3 SR+ = 133 MPGe
Good stuff. Two points to consider. 1) The Camry can likely achieve 400+ miles in various conditions, time and time again. The Tesla will likely never reach its claimed 370 miles. Not when it’s 30F outside, not going 75mph on the interstate. I’ve seen plenty of them drafting semi-trailers at 60mph in central CA. What a miserable way to travel. 2) It takes more than 1kW to get 1kW into the battery. ~60% of the electricity in the US is generated from fossil fuels, so we’re back to an energy source that is 30-40% efficient. Would you believe a pound of coal per kW? Transmission losses are estimated at ~7%. Then we have our chargers. The 7.5K diesel generator on my motorhome burns a gallon of fuel per hour at full load. That would, potentially, put 7 kWh’s in the Tesla battery giving it a range of ~19 miles. Or, I could put that gallon of diesel in my Jeep Grand Cherokee with a 3-liter EcoDiesel and get 28mpg at 80mph. I may have just convinced myself that the ICE is more efficient than the EV.
Well to wheels emissions on a Model 3 vs that 30 MPG Camry will vary between 10% (cleanest grid region) and 58% (dirtiest). This is derived from actual emissions data from every power plant with the most recent data available (2018). It is very likely better now. https://www.epa.gov/energy/emissions-generation-resource-integrated-database-egrid It also takes 6 kWh hours of electricity to refine 1 gallon of gas. Transmission losses (GGL) are <5% in the continental US (https://www.epa.gov/energy/emissions-generation-resource-integrated-database-egrid-questions-and-answers#egrid5a) And comparing charging a Tesla with a diesel generator to driving a Jeep? Seriously? How about comparing charging a Tesla with Solar vs drilling/pumping/transporting/refining/transporting/pumping/burning that diesel in your Jeep?
Well, we were talking about efficiency not emissions. It is comforting to know that the 6kWh’s of electricity required to refine a gallon of gas could be generated from a clean green grid.
I hereby submit that even Al Gore can’t find the carbon footprint of my Clarity driven 95% in EV and powered 100% (as is my house) of the 95% EV driving by this:
Since it seemed to apply here. The industry knows that the "human" factor is what hurts EV range (or can help it as some hypermilers here have proven). I fall on the "bad driver" side and only turn that little window with the car in the circle (green/blue) "drive nice now" when I want to stretch range to the max. While searching for an SAE course I ran across this article. The solution, not surprisingly, was to take the human driver out of the equation to get the greatest efficiency. I found this interesting as although I do not agree with several of the things that George Hotz (comma.ai) says about the industry. He did say that autonomous vehicles are a joke (paraphrased here). He said that we have Uber, it's called Uber, etc. If you want to get someplace and it take twice as long to get there then use an autonomous vehicle. Now, there are a lot of caveats to that statement but the article here is about driving efficiency versus "driving excitement" (I am guessing no Acura commercials are involved). We noted that in the case of the OP, the range reduction was likely due to increased speed due to "reduced" imposed regulatory control (no traffic forcing efficient behavior). https://www.sae.org/news/2018/11/av-programming-for-ev-range reference to statement above: https://www.theverge.com/2018/7/13/17561484/george-hotz-comma-ai-self-driving-car-scam-diy-kit (yes, I know this is not a scholarly forum, but hey - we got some armchair intellectuals here!) Cheers, Cash
One simple, cost effective method to increase EV range (efficiency) would be to install less powerful motors. Problem is, no one wants an EV that is slower than a Hindustan Ambassador.
