The “range–extended” EV (BEVx) considered

N952JL said:

DrInnovation said:

I see lots of people tossing out long trips as an issue, some dismissing it as infrequent. Individual's of course vary but long trips are a real issue for the average American.



What about the economics of an add on RE?
With a 25mpg ICE the 12 trips > 194 miles need about ~100 gallons of gas, which is < $400/year and it will be hard to justify an expensive range-extender. (Total long distance travel 7500 is about 300 gallons or < $1200 a year).
60% of families have second car, so the car is not and added cost, just gas. A rental ICE would obviously add more.
With respect to the total cost of covering one can argue if renting an ICE or a Range Extender makes more sense.
Renting a range extender might make sense if its efficient enough and the price < price of gas for the ICE. With a limited market for while that may be difficult to make cost effective.




If you are focused on minimizing cost this is totally moot as no new BEV or Range Extended EV (REEV) is the right choice. The right choice is used Prius or other high MPG car (because of the vehicle cost and rapid depreciation no new vehicle is a good financial investment), at least until used BEV or REEV are on the market and a decent price.

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I feel you have made some very good points. In the end, I do not want us to import any oil as that is a complete drain on our economy. I only have one small point. You made an assumption that all families have two cars so the only added expense is the expense of the gas necessary to run the car vs the range extender. That may not be true. I am looking forward to the time I only need one vehicle. Without a Range Extender or longer range BEVs I will be forced to buy a Prius or simular vehicle which is more than just the cost of gas.

My lease for the Leaf will be 39 months. I am hoping that within 39 months we have improvements that will allow me to keep using a BEV. Till then, I fall within the 12 per year longer 200+ round trip trips. But the leaf does meet my everyday needs.

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Actually, the 2-car case in general worse case as the cost of the ICE is already there. If you have to rent an ICE for trips, the cost equation tilts to the EREV even more. As you say you take average number of longer trips, if you only have 1 car, unless your daily commute is > 52miles you'll be more efficient with a Volt-like EREV, than a PiP, and either is better than BEV + average rental ICE for trips. If you can always rent a Prius (or some >40MPG ICE) for those longer trips, then you are doing better in total gas usage with your Leaf for everyday and high MPG rental.

Hopefully in 39months there will be a lot more choices on both the BEV and EREV side.

edatoakrun said:

DrInnovation said:

edatoakrun said:

I agree that it's not a bad hybrid, but the Volt's EV performance is just not comparable to any of the BEVs you mention, with about half the electric range, higher initial cost, worse energy efficiency, and almost certainly, far higher long term operating costs.

Why buy a car that operates so poorly, in the mode in which it is intended to be used the most?

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"DrInnovation"...As I posted earlier, the "average case" for long trips really does make a good case for a range-extended EV, for me its both financially and ecologically way better than a BEV + ICE...

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I thought, in my OP, I made a pretty good case for the same point?

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I guess I miss-read it. But either way, I was adding more detail with data on the longer-trips.

edatoakrun said:

But nothing you have said supports the case that the Volt is an effective means to meet these REEV objectives.

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Well its more effective than a Karma.. And they are the only commercially REEVs out there now.
Furthermore, I don't know if we'd even be seeing a Leaf or PiP, if there had not been a Volt. Companies have been doing concepts for years. It's not until someone stepped up to do production that other comaoies decided it was time to move beyond basic hybrids. The Volt may not be the best choice for you, but its enough for many and that drives competition and innovation.
Also as I said, the Mode-3 (parallel+serial hybrid) in the volt design is unique and the added 10-15% efficiencies help ameliorate some of the other issues.

edatoakrun said:

To restate my main points, IMO, the Volt's principle inadequacies are as a result of GM’s decision to use an existing ICEV traction engine, that is fundamentally unsuited for the role of an ICE generator, as an EV range extender, since:

It is far too large to be used efficiently for the task required.

It runs on an unstable and highly polluting fuel, gasoline.

Which also prevents (edit-replace prevents with reduces the practicality of) the hydrocarbon fuel from being used for the one purpose for which these fuels are ideally suited, to heat the passenger cabin (and battery pack, if so required) using a combustion heater.

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Agreed that there could be more efficient designs, but there are financial and timing constraints. I'd have preferred E100/E85 or disel (like the ford reflex concept they let die) or even CNG, but those might have added time/cost making just a concept. (Personally I really wish the E85, which is pretty much the same engine and can run at the volt's compression rations, was an option. I've have paid more than the cost of its parts). I'm really annoyed that they did not give us an "Eco mode", where the optimize ICE usage in CS mode for maximum efficiency. I've done trips using Mountain Mode games in the Volt to get 47mpg in the cold with mostly at 70+ highway speeds (and without hyper-mileing tricks). Its noisier but more efficient to run the ICE at high speeds and generate electricity, then shut it off. (I think we don't have ECO-mode for the same reasons we don't have Hold mode-- it violates some silly CARB/EPA guidelines).

edatoakrun said:

This results in the Volt’s inferior efficiency to other hybrids, when operating in ICEV mode, and also notably inferior in efficiency to any BEV, when operating in EV mode.

The only thing recommending the Volt, that I can see, is the fact that it currently is the only vehicle on the market that can operate in both modes.
[\quote]
And while inferior in either dimension, its overall efficiency, for the average household, is superior. Actually, the Volt is not the only one, Karma is an EREV as well.
iMev, Volt, Prius, each has their own Pareto-optimal position in the current market.

And of course the Volt has only won a dozen or so "major awards" (Green and regular), so its not really a good car. Its a Great car.

edatoakrun said:

When the PIP and other “small battery” plug-in hybrids are introduced, I think their superior hybrid performance will attract a lot of buyers.

And as I wrote in my OP, I hope that many manufactures will also soon introduce REEV designs, that have far superior efficiency and range, in BEV mode.

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I'm still hoping for a software update for the 2011 Volt to give it better efficiency (which I know it can achieve, albeit with a little more noise). Not really expecting it but maybe we'll be able to reverse engineer it. But for the 20 or so long-trips a year I take, I'm still doing over 40mpg, which is better than many hybrids on the market.

I agree the PiP will attract many, and for those with a small daily commute (or just random errands), it may well be the most efficient choice overall.

Progress, but still stuck on the idea that the "range extender" must be scaled to replace, rather than supplement, battery output.

You suppose Lotus could build a 400 CC version, weighing only about 40 pounds, and producing 8-12 kW?

...how would you design an engine for the express purpose of making electricity?

If you are Lotus Engineering, you keep it simple. Both the range extender’s intake and exhaust manifolds are integrated into the cylinder head, which reduces the number of parts. There is no variable valve timing, which adds weight, cost, and complexity. The generator housing is mounted directly to the block, which increases stiffness and reduces vibration. And the engine is optimized to run at low speeds, with a long, 95.5-mm stroke.

The 1.3-liter inline-three’s final output figures (they’ve varied slightly throughout its development) are 51 or 74 hp, the latter with the addition of a supercharger. Both power peaks occur at 3500 rpm. Peak torque is 79 or 111 lb-ft, both at 2500 rpm. The generator in Lotus’s example (automakers could alternatively use their own unit) puts out 35 kilowatts with the naturally aspirated engine and 50 kilowatts with the supercharged unit.

The numbers might not seem too impressive, but consider the size of the engine: just 20.1 inches long, 16.9 inches wide, and 24.0 inches tall with the generator attached. That’s about the size of two pieces of carry-on luggage, and it weighs between 112 and 128 pounds...

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http://blog.caranddriver.com/in-depth-with-lotus%E2%80%99s-electric-vehicle-range-extender/" onclick="window.open(this.href);return false;

Hello,
Part of the paradigm shift that must happen in the limited fossil fuel future is the need to live closer to where we work and grow food closer to where we live. The exact opposite has been the norm during the fossil fuel era. It will happen by necessity or design depending on how much time/money is spent now planning ahead (or not). That being said, everything now is interim planning. How can I limit my usage and keep my rural lifestyle?
Yeah, but the only job I could find is 150 miles away and I don't know how long it will last so why uproot my family?
I can't sell, I'm under water in my home and the only job that pays enough is 100 miles away.

All economic & logistical forces driving the paradigm shift in society. My situation dictates travel is a luxury not often undertaken. Because of that and a 10 mile commute, the Leaf is the perfect car for us. I live close in suburbia but also have a Gen 1 Prius for those occasional longer trips once or twice a year and I also have a full sized van I keep to pull the sailboat and a 66 Mustang I have owned since high school. There are days I feel like selling everything off because I'm tired and owning things means time/cost that I find more and more difficult to maintain. Slowly my "things" accumulated during the acquisition period of my life are becoming irrelevant. Too bad I didn't figure that out sooner or I would have more to retire on (& would have lost more of in 2008).

Everyone's situation depends on where they are in their life and how much the forces have shifted their lifestyle. No one vehicle can do it all. For you guys traveling 100 miles to work the flying car seemed a possibility in the 50s / 60s (commuting like Bob Cummings).


Has anyone considered the Bloom Box? 3 times more efficient than ICE or turbine. It's capable of producing 34 kWh from 1 gallon of gas.

DrInnovation said:

Actually, the 2-car case in general worse case as the cost of the ICE is already there. If you have to rent an ICE for trips, the cost equation tilts to the EREV even more.

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Have you run the numbers ? Let us see them.

Here are mine.

A. 2 Cars in the family. As you can see BEV+ICE is better than PHEV+ICE, even though BEV+PHEV is the best.



B. Single car family. BEV+ICE rental still better than PHEV.

bowthom said:

Has anyone considered the Bloom Box? 3 times more efficient than ICE or turbine. It's capable of producing 34 kWh from 1 gallon of gas.

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Do they make one small enough to go in the vehicle. The model I see is ten tons.
http://www.bloomenergy.com/products/data-sheet/

bowthom said:

...Has anyone considered the Bloom Box? 3 times more efficient than ICE or turbine. It's capable of producing 34 kWh from 1 gallon of gas.

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Not suitable for vehicles, and not fueled by gasoline, IMO.

I believe the best location for fuel cells will always be where their efficiency can be maximized by utilizing the "waste" heat.

Install your fuel cell at home, fueled by much cheaper and less polluting natural gas, use the electricity to charge your BEV batteries, and the "waste heat" to heat your home, or domestic water.

According to the U.S. Department of Energy, fuel cells are generally between 40–60% energy efficient.[35] This is higher than some other systems for energy generation. For example, the typical internal combustion engine of a car is about 25% energy efficient.[36] In combined heat and power (CHP) systems, the heat produced by the fuel cell is captured and put to use, increasing the efficiency of the system to up to 85–90%.[23]

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http://en.wikipedia.org/wiki/Fuel_cell#Theoretical_maximum_efficiency

evnow said:

DrInnovation said:

Actually, the 2-car case in general worse case as the cost of the ICE is already there. If you have to rent an ICE for trips, the cost equation tilts to the EREV even more.

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Have you run the numbers ? Let us see them.

Here are mine.

A. 2 Cars in the family. As you can see BEV+ICE is better than PHEV+ICE, even though BEV+PHEV is the best.

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I've posted my numbers before (http://www.mynissanleaf.com/viewtopic.php?f=10andt=6762&hilit=option&start=83_" onclick="window.open(this.href);return false; and
and discussed why yours are biased/wrong (http://www.mynissanleaf.com/viewtopic.php?f=10&t=6762&p=150146&hilit=option#p150146" onclick="window.open(this.href);return false)
as well as an analysis using national average data.(http://www.mynissanleaf.com/viewtopic.php?f=10&t=6847&p=152121&hilit=median#p152121" onclick="window.open(this.href);return false

Your long-distance travel is well below average so not it may not be surprising that your data works out better for the leaf. However, you also stacked the numbers in the analysis, and if you fix them, the PHEV40 is the winner.

As I had already posted in my comparison, we use the Volt (PHEV in your table) for the long trips, which would convert Option I to 439 miles, making it the lowest of any of the options with the CUV. With more miles in the long-trips the bigger the advantage for it). The 35mpg is being disingenuous as the ICE in the PHEV40 for >50miles means its being used for long trips. Thus the EPA highway 40MPG make more sense to use as its highway driving. The result is under 63 gallons for the long trips in the PHEV for an overall 429gallons in option 1. This is a saving of 45 gallons over the BEV + CUV. As I've said, small changes in assumptions and the answers can flip between BEV and EREV and PHEV and people should run their own numbers to reach a valid conclusion.
I recommended the calculator at squiddo (its not mine, and not cooked for a particular outcome). http://www.squidoo.com/a-free-calculator-for-economy-hybrid-and-electric-cars" onclick="window.open(this.href);return false;

evnow said:

B. Single car family. BEV+ICE rental still better than PHEV.

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This has some of same issues as above, the 40mile PHEV should have used 35mpg city, 40mpg HW so gas used is 14 (using 35 for short trips), 26.25, 20 and 63.75 for a total of 124 rather than 140, reducing the cost by $56/year to $4487/yr.

Your BEV+Rental ICE presumes the long trips are a single day. (Estimated using your stated 50 a day, which I also note is very low for rental price of a Prius, when I rented one last year it was $95/day + tax, and I've tried other times and the price was well over $100/day.)
You seem to have 6 days of rental over the 5 trips of 200s, and 7.76 days(?wierd?) of rental for the 550mile trips. The majority of my 200mile trips are to the airport and often means 2-3 days of waiting, and my 600+ are usually 5-6 days. Nevertheless, even if you just presume 2 days for 200mile trips and 3 for 550-mile trips, then the total for RentalICE increases by 612.5 bringing the yearly cost to $4662.50/yr (even at $50/day for a Prius). And this is with below the average number of long trips, and lots of 75mile but no 100mile trips. ( 75m is doable with a leaf on one charge. 100miles would be pushing it).

You are underestimating the costs of maintenance, which other sources put the leaf at $425/year. (I agree in years 8-15 it will be lower than a EREV, when the ICE miles start racking up, but in this time frame its nearly a wash, tire rotations and replacement dominate this number!)

Plugging in the corrected numbers the PHEV40 is cheaper with your mileage at $4487 compare to BEV+RentalICE at $4987.5, or a saving of just over $500 a year.

If you want to stick in my number uses 55days <10miles (or including parked), 235 days at 35miles, 28days at 50 miles, 20 days at 125miles, 12 days at 250 miles and 5 days at 600 miles. I've many >50m days but assuming only 40miles per charge, 35mpg on short ICE days and 40 on long trips. My expected fuel usage in the volt is 0, 0, 8, 63.3 and 75 gallons for 145 gallons overall. With a Leaf+rental I would need 20+24+20 days of rental, which would more than eat-up the saving of 28 gallons of fuel.

I will note that in my case, the total family cost could be cheaper as we've already paid for an ICE car, and the increased fuel costs are only 200 or so per annum. Even if we used a BEV + my wife's 28mpg outback) for the long trips, it would take an added 52 gallons of fuel over the Volt. (However, the BEV+ICE would also mean my wife could not take long trips when I'm on one, which currently happens 5-8 times a year -- She travels when I'm away on business.) As I said, a BEV + existing above-average ICE is the worst case of comparison for a EREV, as the ICE is paid-for and it takes a lot of miles for the fuel cost to make up the price difference.) Then again, I did not make the decision on finances alone. In fuel use/oil avoidance, the EREV is better for me, and for cost its comparable. I prefer the EREV technology and the flexibility it gives our family.


As I said, the numbers for this type of decision, here are very personal, and anyone considering this should be doing their own math on their data.

A couple questions:

For occasional longer trips, why wouldn't you just take the other car? If you don't have another car, rent one.

If you did have this turbine thing, would the exhaust point to the rear like the batmobile? Or to the side, so it can double as a track dryer?

All these solutions seem inferior to HSR autotrains, so you can go 250mph, arrive with your car fully charged, and relax during the trip not having to worry about falling asleep at the wheel... all with zero emissions.

http://ev.sae.org/article/10227" onclick="window.open(this.href);return false;



"The ICE is designed to have two main operating points: If the battery needs to be re-charged, the engine is run to deliver 15 kW (20 hp) at the crankshaft. If the battery charge is to remain high despite a fast cruising speed, the RE is taken to full load at 4000 rpm to deliver its nominal 30 kW.

“The prototype has confirmed these performance targets on the engine test bed,” Mahr told AEI. Specific consumption is said to be 250 g/kW·h at 4000 rpm (0.41 lb/hp·h) and 240 g/kW·h (0.30 lb/hp·h) at 2000 rpm.

Fully dressed, the engine/generator unit weighs 65 kg (143 lb), with a 2.15 kg/kW power-to-weight ratio. When a full 40-L (10.6-gal) fuel tank plus controller are added, the RE's total weight (as installed in a vehicle) is 130 kg (287 lb)."

bowthom said:

Has anyone considered the Bloom Box? 3 times more efficient than ICE or turbine. It's capable of producing 34 kWh from 1 gallon of gas.

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It's about 50% efficient at converting natural gas (or similar fuel) to electricity. A therm of gas would produce about 16-17 kWh in a Bloom Box.

Less efficient than your most efficient combined cycle gas turbines, but more efficient than the average fossil fuel burning plant.

A fuel cell would make a good range extender if they could make it small enough, especially in the cold where one might want to use the waste heat to warm the cabin.

Herm said:

http://ev.sae.org/article/10227

"The ICE is designed to have two main operating points: If the battery needs to be re-charged, the engine is run to deliver 15 kW (20 hp) at the crankshaft. If the battery charge is to remain high despite a fast cruising speed, the RE is taken to full load at 4000 rpm to deliver its nominal 30 kW.

“The prototype has confirmed these performance targets on the engine test bed,” Mahr told AEI. Specific consumption is said to be 250 g/kW·h at 4000 rpm (0.41 lb/hp·h) and 240 g/kW·h (0.30 lb/hp·h) at 2000 rpm.

Fully dressed, the engine/generator unit weighs 65 kg (143 lb), with a 2.15 kg/kW power-to-weight ratio. When a full 40-L (10.6-gal) fuel tank plus controller are added, the RE's total weight (as installed in a vehicle) is 130 kg (287 lb)."

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Interesting article, now if only it put things in useable terms. Lets see, the 250g of fuel is about .1gallons per kwh so if it is providing its nominal 30kW (which should be enough to support maybe 66 mph travel for an hour), that is 3gallons per hour or about 22mpg. If the nominal provides enough to maybe 100miles it would still only reach 33mpg. Did I miss something there, or is the Volt looking better and better?

Still this might make a rental unit, (if it were air-cooled), that could be rear-mounted maybe on a trailer-like hitch. The lower MPG might be acceptable if the cost to rent was reasonable (and if there was a way to integrate it into the Leaf Charging).

DrInnovation said:

Interesting article, now if only it put things in useable terms. Lets see, the 250g of fuel is about .1gallons per kwh so if it is providing its nominal 30kW (which should be enough to support maybe 66 mph travel for an hour), that is 3gallons per hour or about 22mpg. If the nominal provides enough to maybe 100miles it would still only reach 33mpg. Did I miss something there, or is the Volt looking better and better?

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Well... 30kw of power will give you 85mph in a Tesla Roadster (about the same in a Volt or Leaf), so that works out to about 28mpg.. at 15kw you get 60mph or about 46mpg at the improved efficiency.

If you are an efficient Leafer and get 6 miles per kwh then you get 69mpg, but you would have to run the genset intermittently (at the 2000 rpm setting) to charge the battery.

Not bad for a range extender that will be used occasionally... if a top speed of 85mph is acceptable.

Herm: I don't know where you got 30kw providing 85mph in a roadster, but its total power (kw-h) needs time as well.
(and did not follow the rest of your computation).

Was curious about this so I went looking for a better way to compute it. (Using mph and time seemed error prone).

The Mahle's more efficient 2000rpm mode uses 240g of gasoline to produce 1kw-h. A gallon of gas weights 6.073lb or 2754g, so that yields .0872 gallons per kw-h.
Looking at the EPA numbers, the Leaf uses 34kw-h for 100miles on its test cycles, or 2.94miles/kw-h
So it seems the Mahle generator would only yield 2.94/.0872 = 33mpg for a Leaf (using EPA estimated miles, ignoring the added weight of the RangeExtender and its fuel).

(Using ultra-efficient drivers is not really fair, I've done way better than EPA in Volt, but EPA keeps it apples to apples).

That seems like a good apples/oranges way to look at it, using the EPAs mpge.. I assume thats a city/hwy combined number. The Volt is rated at 37mpg combined so its in the ballpark.

I got the 85mph at 30kw number from the Tesla charts for the Roadster, they also apply pretty well to the Volt and perhaps not as well to the Leaf due to aerodynamics.. but probably not too far off at 60mph.

What power consumption do you get in your Leaf at a steady 60mph on the hwy?

take the heat the generator provides and combine it with the Leaf's climate control and i would take a 2nd look. (still wouldnt do it)

i agree that modifying any product has its benefits. this way of extending the range is simply not an option for me.

Herm and DrI,

Any way you calculate it, you come to the conclusion that an ICE generator is a grossly inefficient means to generate electricity, that will never significantly exceed conventional ICEV mileage.

That was the premise of my OP, that any well designed EREV will minimize ICE use, and maximize battery use, which will give something on the order of 100 mpg equivalent energy efficiency, from combined cycle natural gas electricity generation.

Big ICE + small available battery capacity = inefficiency (Volt).

Small ICE + large available battery capacity = efficiency (could nearly match a BEV, with the significant range advantages I pointed out in my OP).

Maybe we’ll see this on the road with the BMW BEV/EREV rollout.

Herm said:

That seems like a good apples/oranges way to look at it, using the EPAs mpge.. I assume thats a city/hwy combined number. The Volt is rated at 37mpg combined so its in the ballpark.

I got the 85mph at 30kw number from the Tesla charts for the Roadster, they also apply pretty well to the Volt and perhaps not as well to the Leaf due to aerodynamics.. but probably not too far off at 60mph.

What power consumption do you get in your Leaf at a steady 60mph on the hwy?

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Yes the 34kw-h/100m is the EPA combined.

I don't drive a Leaf, and I don't drive that slow on the HW.. (I'd be run over.. highway speeds here are 75mph until one gets into town and I'm routinely passed at 75 )

Herm said:

What power consumption do you get in your Leaf at a steady 60mph on the hwy?

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0.256 kWh per mile at 60mph on a flat road, 70F, no wind, etc.

So, I get 15.36 kW consumption rate at 60mph.

At 80mph, that's about 0.375 kWh per mile, or about 30 kW.

As we all should know by now, changing speeds has a HUGE effect on economy.

edatoakrun said:

Herm and DrI,

Any way you calculate it, you come to the conclusion that an ICE generator is a grossly inefficient means to generate electricity, that will never significantly exceed conventional ICEV mileage.

That was the premise of my OP, that any well designed EREV will minimize ICE use, and maximize battery use, which will give something on the order of 100 mpg equivalent energy efficiency, from combined cycle natural gas electricity generation.

Big ICE + small available battery capacity = inefficiency (Volt).

Small ICE + large available battery capacity = efficiency (could nearly match a BEV, with the significant range advantages I pointed out in my OP).

Maybe we’ll see this on the road with the BMW BEV/EREV rollout.

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Just curious what is the basis for you conjectures of 100mpg equivalent and your statement that small ICE + large Battery = efficient. The recent discussion/analysis of a small ICE (.9L 2 cylinder Mahle RE) show an expected lower MPG (using the manufactures ideal numbers) than the EPA of the Volt in CS mode.

Curious why you hold out hopes for the BMW.. the i3's range extender is officially a petrol engine ( and by current rumors based on a BMW motorcycle engine) and the i8 has a 1.5L engine (Volt is 1.4). The super-lightweight i3 could get a lot of MPG out of a small motorbike engine, but even on a BMW motorcycle, which is literally a ton lighter lighter, the best was 62MPG (on a F650GS I believe). I wish you were right, but wishing does not make it so.

Not sure how you define/measure "100mpg equivalent". If you mean EPA MPGe, I don't see that in the next decade for anything other than a BEV. Nothing using traditional fuel will get there, even if its to generate electricity. The best I'm aware of from fuel-cells (for which hydrogen is more efficient, albeit more complex to mange) is about 60MPGe. Mass will hurt so until energy density goes way up a long-range BEV may have a breaking 100.

If you mean actual gas usage over time, (ignoring charging energy), we are already there. Check out the stats at https://www.voltstats.net/" onclick="window.open(this.href);return false;
you'll see that over 1.2Millon miles, the 230 drivers there have a 118mpg.

You wishing there was a small highly efficient Range-Entender does not make one viable. Fuel Cells are the most efficient way to convert fuel into electricity but the reasonable cost ones are that efficient enough to get to your goals. Don't see more efficiency in their short-term development (more focused on reducing cost).

I would content that no RE that provides for pure serial PHEV operation will be as efficient as the Voltec design that provides for BEV when possible, serial EV when that is efficient and parallel+serial when that is more efficient. Yes they could do a more specialized engine and a Voltec with a larger battery would increase amount of battery we could use, but both add substantially to the cost which many already consider too high.


Can the Voltec do better. Yup (just with GM gave us that choice).
Check out this article
http://green.autoblog.com/2011/11/03/where-does-erev-technology-go-from-here/
quotes GM folks as saying

The range-extender engine? "When we modeled the Volt's engine, theoretically we could have gotten to high 40s or low 50s mpg in gasoline mode. But we would have had to run it continuously at 3500-3800 rpm and just switch it on and off, and the noise and pleasability wouldn't work. We had to drop it down, which got us to 37-38 mpg. But I think a lot of fuel economy still can be gained without major expenditures in tooling or engineering."

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I play some mountain-mode games in the Volt and get high 40's and the occasional 50mpg for HW travel (at 65-70mph).
Only a few other cars can do that, so I would not agree with your statement the volt is inefficient.