The Economist: Electric cars Difference Engine: Tailpipe truths

Just because the power generation source has no fuel cost does not mean that it magically makes sense to throw energy away. And as others have mentioned - the wind curtailment in the northwest is a local and temporary phenomenon. Enhancements to grid transmission will eliminate the issue and allow exports of excess wind/hydro power in the region during the spring time to areas which burn fossil fuels for electricity.

I don't see how getting hydrogen to the tank at 70% best efficiency and then burning it in an ICE at 20% efficiency can beat 60% CCGT power plants which can get 93% of that electricity to your wall and 90% of that electricity into the battery on an EV (50% total efficiency).

Oh, don't worry, we're not talking about replacing the entire fleet yet. Just a substantial portion of it. Gas/diesel burners will be the majority of the fleet for decades though I would like to see long-haul trucking move to CNG or maybe even CNG fuel cells with battery buffers.

We might see HFC vehicles for applications where energy density beats batteries. But by the time we see any sort of rollout of these vehicles we're going to have a million plug-ins on the road. Batteries will continue to improve at ~7% a year in energy density - by the time the manufacturers say they will have a mass production HFC vehicle out batteries will be significantly better, cheaper and DCQC infrastructure will have reached a point making 95% of trips possible with a 100 mi BEV.

I know that currently with my LEAF there have only been a couple times where I've needed more range in the last year - and most of those would have been solved with either 25% more battery capacity and/or a DC QC station and a 10 minute top-off. 2,000W of solar panels on my roof generate enough electricity to drive 10,000 miles a year in my EV. If I had to generate hydrogen it'd be half that far.

 

Sagebrush already brought up the question of just burning the NG, and I'll add that it is possible to make a fuel cell that runs on NG. A NG fuel cell may not be as efficient as a hydrogen one, but there is loss in converting it to hydrogen. Also, there is already an extensive pipe network to move it around. Hydrogen needs to be trucked, or produced on site.

Carbon fiber tanks are light when compared to steel. A steel tank for for those pressures would weigh 100 times the weight of the contained hydrogen. We have a high pressure hydraulic vessel at work that reach 100k psi. It's stainless, about a meter high and across, weighs a literal ton, and only holds 2 liters.

The numbers I posted earlier are with carbon fiber. It's the design goal the DOE had for 2005. Then the DOE was looking for contained hydrogen to be 4.5% to 5% of the weight of the combined tank and gas. The FCHV has a 6 to 7kg capacity, so its tanks weight around 120kg. The required thickness of the tank walls also makes them bulky for their volume. It's why Toyota needed 4 tanks. A single one probably would only fit the cargo area.

CNG faces the same tank weight and space issues if we want to store it at higher pressures. Fortunately, NG has a higher energy density than hydrogen. So 3500psi tanks work now to meet daily commuting needs in an ICE, and trucking doesn't have the space limits as personal vehicles. With the space of batteries and range extender, liquid fuels will still likely be best for plug-ins.

 

Burning NG in the ICE would probably 23% efficient (around gas non-hybrid tank-to-wheel). If it is NGHV, it'll be around 37% (around Prius efficiency).

If NG is reformed to H2, it is around 80% efficient (Steam Reforming). H2 tank-to-wheel is 59% efficient. The overall efficiency is 47%.

 

The graphic from Toyota you posted earlier has well-tank-wheel for a FCV at 40% currently. That is no where near enough of an improvement over our present $20k HVs to even consider; and remember that Toyota already has plans using direct injection to take ICE efficiency up to 45%.

My son was working in a DOE grant lab that was trying to improve the catalytic reformation of methanol to hydrogen. It is a tough nut to crack. The catalyst is poisoned quickly.

 

Correct. All that harnessed, paid for wind power should not be wasted. Plus being sustainable, domestic power, it has huge indirect costs savings in trade deficits, military spending, national security, climate change.

"Local" as in US West coast...that's a large area of huge population and massive energy use on a world scale.

"Temporary" as in ongoing battle with entrenched utilities for the last 20 years.

The wind power was just one example of where hydrogen could be generated in sustainable, non-import way and cover 14% of US gasoline use.

You might want to review the posted efficiency comparison done by Toyota which is somewhat opposite of yours. But even assuming your numbers, the problem is EV has hit a wall due to the range and refueling issues. Toyota who has skin in all the games so a neutral party to large degree recognizes it and that is why they are doing the H2 build up and build out.

On natural gas, certainly no reason to not do as Pickens recommends and look to run cars on it directly. Domestic fuel, home fueling even and lower green house gases. Problems there are that we still import 15% of our natural gas and that kind of massive increase in use would mean US imports would go back up to 30-40% range. The natural gas extraction methods are not really sustainable at current technology, costs in water and air pollution are just too high.

Use the natural gas to replace coal in the base load power plants. Use the solar, wind to generate the hydrogen when not contributing to base load (happens a lot due to nature of solar wind power availability). If 25% of cars are hydrogen powered via sustainable solar, wind generation, that's huge progress.

 

Those are all bogus numbers. The prius isn't 37% efficient, its engines peak efficiency is there. Its best to stick to mpge.

Prius is around 50 mpge, and a cng version would be close to the same, but slightly more expensive because of the tank. Maybe it will sell for $30K

That honda clarity is around 60 mpge, it only has 4 seats but hey, you need to put the tank somewhere. Pump it up to 10,000 psi and you might get interior volumes the same. It takes 80% of the energy of the natural gas to get 48mpge. It takes about 10% of that energy to get from 3600psi to 10000psi though so 44mpge. But wait there's more, honda will lose money on every one leasing them at $600/mo.

Now what if we say when this happens around 2016, toyota added a bigger battery to get maybe 20 miles aer at 95mpge. If that covered half its distance that prius phv cng would get (100/(50/95+50/50)) = 65 mpge. It still would likely cost less to produce than the clarity and could take renewable electricity much more efficiently. There you have the bogus numbers cng phev at 65 mpge versus 44 mpge for the fc vehicle. That is why that fuel cell vehicle is going to get batteries and a plug. I would be very surprised if in 2018 a fc vehicle had less than 10 miles electric range.

http://www.fueleconomy.gov/feg/fcv_sbs.shtml

What will these vehicles actually cost to make in 2015?
http://www.greencarreports.com/news...-car-for-2015-gets-a-whole-lot-more-expensive

 

40% from Toyota graph is well-tank-wheel. The 47% is NG-to-wheel without the well-to-NG.

I think 40% WTW for hydrogen is good considering Prius WTW at 31% and EV WTW at 33%.

I am excited about the next generation long stroke Atkinson cycle DI engine as well. Even with the 45% thermal efficiency, WTW would be 38%. Of course, the advantage of Prius would be lower purchase price and gas station availability.

The advantage of FCHV is that, it can be 100% domestic and the refueling speed and driving range are on par with gas, unlike EV with those limitations.

 

How are you determining that it is bogus? My calculation shows 37% is not a peak efficiency.

1 US gallon = 33.7 kWh

33.7kWh / 50 MPG = 674 Wh/mile

674 Wh/mile x 0.37 = 249 (usable) Wh/mile

Prius ICE has peak efficiency of 220 gram/kWh. This means it can generate 17.2 kWh of usable energy. At 249 Wh/mi, it should go 69 miles with a gallon of gas. Transaxle loss wouldn't take 19 miles out.

 

Tempting to think about it this way, but you do not know the drags on the car. Think of the Prius marathon where Wayne Gerdes managed 124 MPG. Your method leads to a silly number.

You are right though, a Prius' average thermo efficiency is often within 10% of peak for the spectrum of drivers. I personally shoot for 38% average.

 

Simple, your units don't work. I have no idea how many kwh/mi is 100% efficient. For me on a bicycle it sure takes a lot less than 0.1kwh/mi.

As you said if you built a prius cng it would be about as efficient as a prius gasoline. That would be 50 mpge. Now we can compare that to a 60 mpge vehicle like the clarity. But if we go from 3600 psi natural gas to 10000psi hydrogen it takes 80%x90% = 72% of a gge of hydrogen from 1 gge of cng. That means we must multiply getting 43.2 mpge from cng in that clarity. It is difficult to see how converting it in the fuel cell is more efficient. Hence there are bogus stats. I know you aren't responsable for them, but if you start with bad conversions you can't get to proper ones. Thus a clarity with 5000psi tanks would likely be 95% as efficient using steam reformation of the natural gas as a cng prius. If you make the tanks smaller by pumping the pressure up to 10,000 psi then efficiency drops further to 86%. That cng prius will cost more than a cng civic, but will cost much less than a fuel cell clarity. If you use real numbers that fuel cell vehicle will use more natural gas than an efficient cng hybrid. The most efficient way for both of them to use renewable electricity is to add bigger batteries and a plug.

You can only get to efficiency if you know how much power it takes to move. The bogus figures on the Toyota graph have assumptions like the ng must be burnt in a less efficient method. That fuel cell vehicles will be cheaper than phevs, that bevs must be much heavier, etc. I am unsure if a 120hp cng phev hylander would be more or less efficient than the fchv-adv, but I am sure that both would be so expensive and slow that they would not sell in high volumes.

 

Yea, 249 Wh/mile is under EPA cycle @ 50 MPG. I guess if you P&G and ICE running only 1/3 of the mile at low speed, you could get 124 MPG.

 

See my post #143. The main reason is the fact that combustion is very inefficient. It is better to reform NG @ 80% efficiency and then let the FC stack output it to the electric motor/wheel with 59% efficiency.

The way I see it, FCHV will have the best of both gas-electric HV and EV worlds. It'll have that quiet full electric drive, ability to generate fuel from any source (best to use domestic NG and avoid coal), plus the refueling speed and driving range is on par with gasoline. The best aspect of it is, FCHV is the most efficient (greenest) from well-to-wheel.

 

I'll try one more time. A 50% efficient engine can still get you 10 mpg, efficiency of a fuel chain does not mean efficiency of the vehicle. Let's use real vehicles on real tests to test the assumptions. Both the honda clarity fc and prius phv have gone through epa testing. The honda civic gx does have similar epa numbers and the gasoline civic, which means a cng conversion should net similar numbers in a prius phv.

prius phv epa combined cs = 50 mpg
clarity fc epa combined 60 mpg.

In your world view the clarity should be 47% efficient and the prius 37% efficient. That would leave us with (50*(47/37))= 64 mpg.

Now if we assume we can take natural gas from the wall and convert it to hydrogen at 80% efficiency we get the real world clarity

48 mpge (gge natural gas). One one gge equivalent of natural gas the fuel cell vehicle goes a shorter epa distance. Looking at your numbers its clear what the problem is, you are calculating numbers with no real meaning. Further if that hydrogen is pumped up to 5000 or 10000psi instead of 3600psi pumping takes more energy making it less efficient.

Now lets look at it with renewable electricity
Fuel Cell Vehicles

That prius phv is about 300 wh/mile 4 times more efficient.
You may say the real world more efficient fuel cell vehicle just has not been built yet, but remember phevs are getting better also. Your numbers just don't add up. FC vehicles are less efficient not more efficient than phevs especially when using renewable electricity. The problem with phevs is the price, but fuel cells cost a great deal more today. When people quote low prices, these assume technology breakthroughs and production of hudreds of thousands a year.

A phev actually has faster refueling speed if you are traveling distances. For the next 5 years you will need a hydrogen truck following you if you are going more than 500 miles. The only advantage a fchv is it can use renewable electricity instead of gasoline or cng or alcohol.

 

MPG(e) only looks at carTank-wheels; I agree with USB that is an inadequate POV.

Lets try and look at well-wheel pathway efficiencies:

Prius-NG (hypothetical)
well-tank -- uncertain
tank-wheel -- ~ 33% average
Total -- at best 33% average

Prius-FC
well-tank
NG reformation -- 80%
Pressurization -- uncertain
Delivery and tank losses -- uncertain
tank-wheel -- 50%
Total -- at best 48% average

Prius-EV (from NG)
well-tank
Powerplant 35-60% (US average about 40% I think)
Transmission 7%
tank-wheel -- 85%
Total -- 0.4*0.93*.85 = 31.6%

Please help fill in the blanks everybody. Btw, this discussion in my opinion is just academic. The costs and short lifetimes of fuel cells, infrastructure, reformation facilities etc are just nowhere near competitive.

 

I used the same fuel sources natural gas and electricity. The natural gas getting to the wall of the fill station is not going to take more energy whether it is converted to hydrogen or not. For 1gge of natural gas a prius phv cng would go 50 miles a fuel cell clarity 48. For 1gge of electricity that prius phv cng would go 95 miles a fuel cell clarity less than 30.

In 2015 that tesla S or X with 85kwh battery will have less of a fueling problem than a toyota fchv-adv, equinox fc, or honda clarity, go much further on renewable electricity, and cost tesla less to make.

Why does the phev get charged by the average grid, while the fc gets a brand new reformer. For much less money that phev or bev could fill with combined cycle or renewable (wind, solar). The assumptions are all wrong. The fuel cell vehicle efficiency is just made up. Certainly if you are using renewable electricity how can the theoretical fc be more efficient than a EV? Real wold again tesla roadster 119 mpge. Assume that is renewable, has to get converted to hydrogen then get run in a 60mpge vehicle, how can a fc be more than half as efficient even if you somehow sold the oxygen from electrolysis? Coal getting converted through steam reformation to hydrogen might make that fc more efficient than the tesla, but that requires building a lot of coal based hydrogen stations at a very high cost per station. fyi pressurization to 10,000 psi takes about 15% of the energy, but to cover the country likely many stations would need to liquify the hydrogen and truck it, as pipelines are difficult to build.

Counterpoint

 

+1 Exactly!

Why do FC proponents use the benefit of using pixie-dust for inputs while EVs don't?

 

Clarity FCX with 47% efficiency is sub-standard compared to Toyota FCHV-adv 59% efficiency. Both vehicles can get 60 miles to a kg of H2. The difference is that FCX is a car with SUV efficiency.

We'll have to see the official EPA figure of the production version of Toyota FCV-R. If it retains the same FCHV-adv efficiency, it should get 80 miles with a kg of H2. A Prius-NG would get around 50 MPGe.

 

You are right, if all the power plants are CCGT with 60% efficiency, and EV tank-to-wheel efficiency is 85%, the total WTW will be 51%. That will be ideal in term of WTW. In the realworld, the grid efficiency is about 39% (per Toyota).

However, EVs have the drawback of recharging speed, range, price, size and weight of the battery pack.

I agree with you that plugin gas-electric hybrids (properly sized battery) will be the best choice in near-term because they'll be the most affordable with existing electric infrastructure.

However, fuel cell vehicles are no where near as bad as the previous posts indicated. I am not pro-H2 or con-EV. I believe my posts are objectively neutral.

 

Honda claims the clarity has 60% efficiency on the LA4 cycle. Toyota wants to raise their demo to that level. The fchv is a test mule with very little power, so we can not guess what it would do on an EPA test, but certainly it is unlikely that will ever reach production. They claimed 68 mpge on a trip to san diago, but people have gotten huge numbers out of the prius phv also.

I would not hold my breath for that number. The only way a toyota fc gets 80 on a EPA test is if it adds more batteries and a plug. A guy hypermiling a volt got over 200 mpge, these claims should be kept in perspecive.

After looking at that graph full of misinformation, why would you take toyotas grid efficency. If we spend the same money as it takes to build these reformers and improve the grid, marginal efficiency does what? Instead the graph assumes huge investment for these cars, but no grid improvements. On most grids we are adding wind which makes evs charging at night how efficient compared to natural gas? How about compared to

Compared to FCells? How do EVs have a disadvantage in price and size? Tesla S, Tesla X, mitubishi imev, etc there are a lot of choices comparatively. For range we can go phev, which fc proponents want off the table. How fast does that fchv-adv go compared to a tesla roadster? A leaf is about the same speed as a clarity, but with more interior volume because it doesn't need the hydrogen tank just smaller batteries.

You seem to be repeating some FC misinformation, and you may just not understand. There may be a future for fuel cells as range extenders in phevs once the price of the fc stack comes down. But the advantages on those slides do not follow the real world. Build a cng hybrid truck, and use the gas it saves for phevs, and we have better solutions for the next 10 years. After that maybe the technology will improve. I like the tests with the fc plug in hybrid busses. These have centralized fueling, and small fuel cells can add charge to the batteries.

 

Why don't we use no-plug Prius to compare instead of the PHV (with external electricity to boost MPG)? FCHV-adv and Clarity FCX have no plug.

US Energy Information Administration said "About 2/3 of the energy used to generate, transmit, and distribute electricity is “lost†at power plants and in power lines." Toyota's 39% figure is generous for EVs. I happen to believe it is a worldwide figure as the rest of the world don't use as much coal (as U.S with decades old powerplants).

As the range increases, EVs have disadvantage in volume, weight and cost because battery pack scales in linear. The root issue is the energy density of the battery.

If you want to bring Gas-PHV to the table, we should compare it with FC-PHV. I happen to believe that FC-PHV is ideal but the price of FC has to come down first.