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Future Personal Mobility Visions, Part 3: The Vehicle Fleet

Schalk Cloete's picture
Research Scientist Independent

My work on the Energy Collective is focused on the great 21st century sustainability challenge: quadrupling the size of the global economy, while reducing CO2 emissions to zero. I seek to...

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  • Sep 28, 2016


  • The light-duty vehicle fleet of the future will likely be much more specialized than it is today.
  • Three important vehicle classes are discussed under the assumption that we adopt smarter mechanisms than the car for most city travel.
  • These include internal combustion engine powered highway vehicles, battery-powered delivery vehicles, and driverless taxis which may feature a range of drivetrains.  


The potentially game-changing trends of car-free lifestyles and autonomous driving covered in Parts 1 and 2 of this article will strongly impact the composition of the future vehicle fleet. Perhaps the biggest difference that may be expected is a much higher fraction of specialized vehicles – primarily long-distance highway vehicles, delivery vehicles and driverless taxis. Let’s discuss these in greater detail.

Specialized highway vehicles

Many cars on the road today are expected to do a great deal of multitasking between city and highway driving. This will become increasingly unnecessary as car-free and driverless technologies remove the need for a city car. Highway traffic will be less affected, however, and may even increase if autonomous driving makes long car trips much more comfortable.

It is therefore likely that a specialized new vehicle class emerges to cater to the consumer who meets all his/her city travel needs through telecommuting, SEVs, public transport (possibly driverless taxis) and delivery services, but still requires a car for longer-distance travelling. This vehicle class will cover by far the most miles of the three vehicle types discussed in this article and is therefore discussed first. For example, if city car travel demand halves and highway travel demand increases by 10%, highways will see more than double the miles of cities.

The future specialized highway vehicle will probably be quite similar to the specialized long-haul trucks of today, only for transporting small numbers of people and light baggage. It will be powered by a relatively small diesel engine tuned to operate most efficiently at typical highway speeds and have a high emphasis on aerodynamics, since these are the most critical components of efficiency in highway travel (below). Some electronic assistance to maximize the amount of time spent at peak engine efficiency is also likely.


There is no reason why future diesel engines cannot achieve 50% peak efficiency (the thermodynamic limit is around 65%). Toyota is already at 40% peak efficiency with their Prius gasoline engine and diesel engines can typically achieve about 20% greater efficiency due to higher achievable compression ratios. In comparison, peak efficiency in an electric car should be about 80% (product of ~95% efficiency for battery charging, discharging, motor controller, and the electric motor itself). In addition, a longer distance electric car will also be heavier due to the large battery pack, reducing its efficiency advantage.

In total, peak efficiency of future electric long-distance cars should therefore be about 50% greater than their diesel equivalents. Note that this is valid only for highway driving, possibly with some additional smoothing from autonomous technology. As an illustration, highway efficiency for regular cars is generally about 40% better than city efficiency, but 10% worse than city efficiency for electric cars. This is due to the high variable load efficiency and regenerative braking advantages of the electric motor. For perspective, the fairly realistic EPA cycles for city and highway driving are shown below:


To quantify this comparison, the graph below shows the equivalent electricity price that would result in identical fuel costs to diesel at various oil prices and electric motor efficiency advantages. It is clear that electric cars will only have a significant advantage under oil price spikes and may even be more expensive to fuel under normal oil prices ($30-60/barrel).


In addition, a diesel engine operated mostly under constant load can last for a very long time. For example, diesel generators typically run for about 25000 hours. At an average speed of 60 miles per hour, this equates to 1.5 million miles. A typical long-haul truck today can already reach a million miles before a major overhaul is needed. It is doubtful whether future battery packs will go a million miles while retaining sufficient range for long distance travel.

As a result, the diesel long-distance vehicle may be cheaper to fuel in addition to having lower up-front costs, a longer lifetime, no range anxiety issues and no need for a vast supercharger network. It will therefore be the rational choice for this vehicle class.

Ownership models will probably be split between private ownership for people who often drive long distances (or simply like to have a car tailored to their own tastes) and car rental services for people who occasionally need such a car. If the rental car can drive itself to the front door of the customer, it would certainly make the rental model a lot more attractive.

Delivery vehicles

As advanced telecommunications technology and SEVs increasingly remove the need for city driving, delivery services are likely to step up to completely remove the need for a city car. For example, people will do the weekly grocery shopping by a few clicks on their computers or taps on their smartphone as is already possible in some cities today. This is likely to be a major trend in coming years and many people want to try it (below).


Similarly, delivery services for other easily standardized items such as electronics and basic appliances will also become more practical and economic as economies of scale ramp up. Advances in virtual reality technology can even extend the doorstep delivery model to less standardized items like clothing and furniture. This trend will be greatly enhanced by increasing numbers of people working from home, enabling doorstep delivery services to operate efficiently through the whole day. This will make doorstep delivery not only much more convenient than driving into town, but also significantly cheaper.

The short-distance delivery vehicles used for such services will have to negotiate stop-start city traffic with heavy loads, implying large inertial losses if regenerative braking is not implemented. They will also need to come to a complete stop for several minutes at regular intervals to unload cargo. Using an internal combustion engine for this purpose will result in low efficiency and a short engine lifetime and the electric motor will therefore be preferred. Charging will also be convenient since it can be done during loading.

In addition, range requirements by most trips should not pose significant limitations. A certain percentage of these vehicles may be hybrids to cater for occasional longer trips, but battery electric drive is likely to dominate this segment.

Driverless taxis

Many people feel that driverless taxis will be the dominant component of the future transportation system. Yes, if the car-free technologies in Part 1 fail to live up to expectations and full autonomy is achieved, this may well be the case (in cities) even though there are real practical challenges that must be overcome. However, I think the large practical and economic benefits of telecommuting and SEVs combined with the attraction of low-traffic cities will prevail at the end (below). If full autonomy is achieved, my guess is that driverless taxis will consume 10-20% of light duty transportation energy – about the same as the short-distance delivery vehicles discussed above. The remainder of light duty transportation energy will be consumed by specialized highway vehicles (both privately owned and driverless rentals).

car-free Paris

Driverless taxis can still add substantial economic value though. It is not unrealistic to expect that driverless taxis will cut current taxi prices by about 75% – halving prices once by removing the need for a driver and another time by increasing the efficiency of operation. This would bring driverless taxi prices close to the level of private vehicle ownership costs today, greatly increasing demand from today’s levels.

The efficiency of future driverless taxi services will depend significantly on the sophistication of autonomous driving technology, particularly the coordination of the entire fleet to ensure smooth traffic flow. For example, it is theoretically possible that autonomous vehicles can greatly increase the traffic efficiency at intersections by closely coordinating the movements of different vehicles as explained in this post


Basically, all vehicles should move in batches through the city in a coordinated manner so that only non-interfering batches arrive at a given intersection at any given time. In this way, no vehicle will need to stop or even slow down when coming to an intersection. This seems quite simple for any individual intersection, but implementing this in a large city with lots of intersections, a large number of vehicles, and lots of other variables like pedestrians and bicycles is likely to be very challenging. Continuously optimizing such a system containing thousands of cars, each with a unique destination which is frequently updated as new customers are picked up, will be very difficult to achieve in practice, especially given that there will be zero margin for error (e.g. high-speed collisions at intersections). Hackers/viruses also pose a very real threat to such a centrally controlled vehicle fleet.

The success of implementing such smooth traffic flow is likely to strongly influence the type of vehicle preferred in the role of driverless taxis. If autonomous vehicles are only aware of their immediate surroundings and traffic flow is much like it is today, battery electric vehicles should be preferred. The stop-start driving conditions would be handled most efficiently by the electric motor and limit the distance per day for the average car to 200-300 miles – which should be economically feasible without having to recharge. This will allow driverless electric taxis to charge primarily overnight, capitalizing on off-peak rates and avoiding the need to construct lots of superchargers in town.

If traffic flow optimization is successfully implemented, however, the internal combustion engine will start to look quite attractive again. Cars with small gasoline engines (tuned for optimal efficiency and minimal emissions at city speeds) and low-cost mild hybridization will be highly efficient in such an environment. Cars will also easily do more than 400 miles per day, which may require uneconomically large battery packs in electric cars to avoid the need for rapid daytime charging.

Even in the most efficient case, however, I expect telecommuting, SEVs and efficient doorstep delivery services to remove the majority of city driving demand we are used to today.  In fact, as outlined in Part 2, I think it is likely that successful deployment of driverless taxis will further strengthen the case for carless value offerings, counter-intuitively reducing the total demand for driverless taxis.

Final word

The discussion in this article assumes a significant departure from the current car-based lifestyle, especially within cities. This movement will be driven by economics, practicality, environmental concerns and the steady spread of car-free city zones. However, large numbers of cars will still be required and autonomous driving can significantly increase their value to society.

In general, I expect these trends to favour the internal combustion engine over the battery-driven electric motor. Two big benefits of the electric motor; high efficiency in stop-go traffic and limited compromise between performance and efficiency, will no longer count for much. Traffic flow will be much smoother (driven by factors such as the migration of the car from the city to the highway, coordinated autonomous driving, and reduced traffic volumes) and performance will no longer be valued (fully autonomous driving will strive to minimize g-forces).

EV application map

Finally, we should also mention fuel cell vehicles. It is still too early to call whether costs can be reduced sufficiently to make this technology a real competitor, but there may be another problem. While the internal combustion engine and battery electric car are clearly at their best on long, smooth trips and short, stop-start tips respectively, the fuel cell does OK at both (illustrated nicely in the figure above). In that sense, it would have been great in today’s light-duty vehicle fleet of multitasking cars, but could be left out to dry in the future as the market becomes more specialized. Out of the three categories outlined above, fuel cells will probably do best as driverless taxis because these will do the most multitasking and it will be best to concentrate hydrogen infrastructure in large cities.

In summary, I see a healthy mix of vehicles with both the internal combustion engine and the battery-driven electric motor specializing in what it does best. Fuel cell and traffic flow optimization technologies are wildcards which could strongly impact the technology composition of driverless taxis in particular.

The key assumption in this analysis is the success of the car-free lifestyle where city mobility needs are met via telecommuting, SEVs, public transport (e.g. driverless taxis) and doorstep delivery services. We’ll have to wait and see, but in my opinion, this clearly emerges as the most attractive personal mobility future.

Original Post

Rick Engebretson's picture
Rick Engebretson on Sep 28, 2016

I agree with your projections for more reasons than you employ. Energy is one dimension, food and housing are other dimensions.

You are using the historic European model. A crowded urban area where people walk, surrounded by agricultural areas where people provide their needs. Many have now forgotten this model since WWII because food simply comes from the grocery store or maybe now e-delivery.

Farm immigrants to the US were confused by the 160 acre (1/4 square mile) homestead laws. Eventually they wanted a car to “go to town,” or see their neighbors, or have children in school. A car was as essential as a horse and wagon before. A lot of lonely farm families created a continental agricultural gold mine in 2 generations. However, the WWI song, “How you going to keep them down on the farm after they’ve seen Paris” is answered, “you aren’t.”

So you have your wonderful cities. But we in the country now have 4feet X 6feet TV screens to watch the best you have. And we are developing new farm technologies and lifestyles, and have homes costing 1/4 city housing costs. And people are moving back here as fast as they can. You are right, the small duty highway vehicle gets well over 30 miles per gallon of combined gasoline + biofuel blend.

Your analysis is excellent, of half the picture.

Schalk Cloete's picture
Schalk Cloete on Sep 29, 2016

Interesting perspective. I agree that there might be a shift away from crowded cities in the future, but I don’t know how large it will be. Telecommuting can enable people to add value from anywhere with an internet connection, but the wide range of physical stuff demanded by a modern consumer still requires relatively high population densities to be economically delivered.

I doubt that a very large portion of the population will move to the country and replace the supermarket with their own home-grown produce. However, smaller towns which are just large enough to economically deliver all the stuff of a modern lifestyle could be an interesting proposition for telecommuters wanting to escape the big city.

Nathan Wilson's picture
Nathan Wilson on Sep 30, 2016

Ammonia fuel (NH3) has great potential to replace diesel for long haul trucks, and maybe long range passenger cars. It burns much cleaner than diesel (potentially cleaner than any fuel, because ammonia is the secret ingredient for reducing NOx in some large engines), and can use the same high compression ratios that give diesel engines their high efficiency.

As we increase the amount of renewable electricity on the grid, there will be more and more time with near-zero electricity cost. Free electricity makes dispatchable fuel synthesis from electricity much more economical. The easiest fuels to make from electricity are H2, NH3, and CH4. Methane (CH4) of course emits CO2 when combusted, so might not be so appealing if CC&S is embraced.

Compared to hydrogen, ammonia is much easier to deliver by truck (triple the energy density of 5000 psi H2), so it works better for in-route refueling stations as pipelines are not needed.

The slide presentations from this year’s ammonia fuel conference are starting to get posted over at NH3 Fuel Association.

Engineer- Poet's picture
Engineer- Poet on Sep 30, 2016

As we increase the amount of renewable electricity on the grid, there will be more and more time with near-zero electricity cost.

Absolutely NOT.  Just because the value of the energy to the grid is zero or negative (because oversupply) does not mean the cost is free.  Someone still needs to build the generation and whatever it takes to put it on the broader grid.  If that’s subsidized, those subsidies are part of the cost.

Failure to consider subsidies as costs is part of what’s pushing us down the wrong road.  I am certain that the fossil-fuel interests behind it know this better than we do.

Helmut Frik's picture
Helmut Frik on Sep 30, 2016

Another possibility is simply overhead lines at the highway, a battery to fill gaps where overhead lines are to expensive and to get to and from the highway, and in special cases a generator placed with a fork lift on the back of the track if the target is more than 80-100km away from the highway (or 40-50km if there is no psiibility to charge. ) Efficiency is much higher than with ammonia, and it is in many cases more cost efficient than diesel.

Rick Engebretson's picture
Rick Engebretson on Sep 30, 2016

Thanks Schalk. We have record population, energy use, and atmospheric CO2. There is no way innovative agriculture can not be part of a meaningful adaptation.

While it has become clear to me that people don’t like to live like a peasant of yesteryear, they also don’t like the consequences of modern agriculture and energy production. Unless we leave the land of make believe, many people in cities will have neither food nor lights nor a way out.

As an alternative, exploiting new CO2 levels for food, fuel, and habitat is already in practice with good results to a small extent.

Nathan Wilson's picture
Nathan Wilson on Oct 1, 2016

Right, I should have said “near-zero electricity prices“, which results from over-supply. It is important to remember that dispatchable fuel synthesis requires very cheap electricity, but it does not prevent electricity prices from falling, so it does not change the fact that wind and solar will face continually degrading economics as the penetration approaches the capacity factor. Effectively in this scenario, electricity buyers would subsidize fuel synthesis.

Schalk Cloete's picture
Schalk Cloete on Oct 1, 2016

Yes, ammonia is an interesting alternative. It is apparently also usable in fuel cells (if these can become cheap enough). What is ammonia energy density (weight and volume based) compared to diesel? I guess it will still be substantially less practical to work with than liquid hydrocarbon fuels, but I fully agree that it will be much easier than hydrogen.

If the practicality advantage of liquid hydrocarbons over ammonia remains significant, hydrocarbon synfuels can also be a serious contender. The low-value wind/solar power you mention will also benefit this fuel class, and it will be further boosted by the low-cost availability of captured CO2.

Synfuel production involves a significant energy penalty, but if the value of the energy consumed is almost zero, this doesn’t matter. The more important factor is the low capital utilization rate, but this could become less of an issue as the time-value of money continues to fall.

Schalk Cloete's picture
Schalk Cloete on Oct 1, 2016

As I see it, dispatchable fuel synthesis will create more electricity demand during times of low electricity prices, thus moderating electricity price swings. This will increase the total value of existing wind/solar infrastructure by aligning demand better with supply, implying a net-benefit to consumers if the resulting synfuel is competitive with conventional fuels.

However, there will be a limit to the number of fuel synthesis plants that can be economically built. If too many are built, the electricity price will not reduce sufficiently during times of high wind/solar output for synfuel production to remain economically competitive, so there is a clear ceiling to this net consumer benefit.

Seen from a different angle, this technology could also allow greater buildouts of wind/solar as technology costs decline. As and example, it could conceivably change the Middle East from an oil exporter to a synfuel exporter if optimistic future utility scale solar PV cost projections are realized (<$500/kW fully installed).

It should be mentioned, however, that this will be practically easier with a nuclear power capacity which is higher than night-time demand. Dispatchable fuel synthesis can then work all through the night and more over weekends, economically utilizing excess nuclear power. Gen IV reactors with higher temperatures can also enable more economical fuel synthesis pathways than electrolysis. Let's see if Gen IV technology can make this happen.

Darius Bentvels's picture
Darius Bentvels on Oct 1, 2016

– wind & solar unsubsidized cost prices moving towards below 3cent/KWh on most places in the world; and
– nuclear costs rising (as plants have to become more safe) towards >15cent/KWh;

there is little chance that nuclear can compete. Neither with fuel synthesis nor at the whole sale market.

This position is supported by the fact that near all significant fuel synthesis activities occur now in Germany (some fundamental research in US). The country that is moving towards wind+solar share >50% and phases all nuclear out.

Darius Bentvels's picture
Darius Bentvels on Oct 1, 2016

Assuming that the production plant costs are zero*), how low should the electricity price (KWh) be in order to produce e.g. hydrogen for a price that can result in a car driving cheaper**) than similar car burning ‘normal’ fuel??
*) The plant costs are highly variable and will decrease strongly with mass production.
**) Let’s just look at the fuel costs only.
Otherwise the situation becomes too complicated to get a clear picture.
The higher costs of hydrogen cars will decrease. With mass production, those may even become cheaper than normal cars as the engine is much simpler.

Schalk Cloete's picture
Schalk Cloete on Oct 1, 2016

OK, let’s not start the nuclear vs. renewables cost argument here. This article is not the place.

The synfuel research can probably be explained by the fact that wind/solar start to generate excesses (negative prices) regularly already at about 10% penetration whereas this limit is upwards of 70% for nuclear.

Schalk Cloete's picture
Schalk Cloete on Oct 1, 2016

In the seeking consensus internalized cost articles, I generally included synfuel costs as a quantification of transport energy costs for electricity-generating technologies. You can see the cost as a function of electricity cost in the last graph of this article. As you can see fuel costs are about $1.5/gal if electricity is free. This cost would be competitive at today’s oil prices.

If oil goes back to $100/barrel, an average electricity price of $30/MWh is on the limit of competitiveness. A plant capacity factor of 50% is assumed, implying that electricity must be available at an average price of $30/MWh for 50% of the time.

These costs are for hydrocarbon synfuels. If we talk only about hydrogen, the cost reduces to $1.1/gal of equivalent synfuel if electricity is free because the Fischer-Tropsch step can be skipped. An electricity price of $15/MWh would be required for competitiveness at today’s oil prices and $40/MWh for oil at $100/barrel. Hydrogen cars will be more efficient than gasoline cars, but this advantage is negated by the costs associated by hydrogen distribution and storage.

Engineer- Poet's picture
Engineer- Poet on Oct 1, 2016

dispatchable fuel synthesis will create more electricity demand during times of low electricity prices, thus moderating electricity price swings. This will increase the total value of existing wind/solar infrastructure by aligning demand better with supply, implying a net-benefit to consumers if the resulting synfuel is competitive with conventional fuels.

The low capacity factor driven by the production characteristics of ruinables means that per-unit amortization and O&M will be relatively high.  That is going to set a relatively low ceiling on the electricity price which they can afford to pay:  they are reliant on the very price swings they are being pushed to moderate.

However, there will be a limit to the number of fuel synthesis plants that can be economically built.

Given the low capacity factor of wind and PV, I suspect that they are not going to be economic even if they get electricity for free.

Schalk Cloete's picture
Schalk Cloete on Oct 1, 2016

Sure, I thought I stated clearly above that there will be a ceiling to the benefit of increasing the value of wind/solar investments where synfuel plants are no longer economic.

About the low utilization rate, I mentioned in a different comment below that the time-value of money is an important factor here. Negative interest rates are now the norm in many countries and I see no reason for this trend to change. The lower the time-value of money, the less of a problem low utilization rates of synfuel plants presents.

Darius Bentvels's picture
Darius Bentvels on Oct 2, 2016

Thank you for those interesting numbers. They explain the interest of private investors in P2G(hydrogen) where the generated hydrogen is:

– injected in the natural gas gas grid in Germany, etc.
Up to 3% hydrogen seems to be none or little problem. So an huge expansion can be accommodated, taking the size of the gas consumption (nearly every building uses it for heating, etc) into account.

– to be used as car fuel. Specifically developments of unmanned sea-container sized plants that can be placed at car refuel stations. So no expensive hydrogen distribution needed.

Assuming that with mass production of those plants the costs come down greatly, an electricity price of ~€15/MWh may be low enough in order that hydrogen cars have cheaper fuel costs than ICE cars (taking all fuel taxes away for both)?

Of course the break even point towards hydrogen (for the fuel costs alone) is at a much higher electricity price when hydrogen isn’t taxed and petrol is taxed as usual in NW-Europe where often >60% of the price is tax. It may then be up to €40/MWh?

Injection in the gas grid implies that in the dark season gas plants can use the standard grid gas and still claim they run on renewable gas when they consume less than the injected renewable gas.
Storing the renewable gas and then use it, takes extra energy so that is worse for the climate.
So in the end it’s just a matter of accurate book keeping.

Nathan Wilson's picture
Nathan Wilson on Oct 4, 2016

Diesel has about the same energy density advantage over ammonia as ammonia has over hydrogen:

Diesel fuel (LHV, i.e. with warm exhaust) has 35.8 MJ/L; ammonia has about 11.2 MJ/L at room temp (i.e. as used for trucks). For jet aircraft or utility-scale storage, the ammonia would be chilled (rather than compressed), which boosts the density to 14.1 MJ/L (i.e. close to methanol at 15.9 MJ/L)

I think commercial trucks won’t mind the moderate density disadvantage of ammonia; they’ll use whatever is cheaper (after carbon tax). But H2 is so far beyond the pain threshold, it won’t reach critical mass to catch on. Studies have shown that Bas’ idea of H2 production at the retail outlet will be much more expensive than centralized production, transporting H2 by truck is impracticable, and using pipelines causes a chicken-and-egg problem. In contrast, ammonia can be delivered to the retail outlet via truck, so the barriers to startup are much lower than for H2.

Yes, hydrocarbon synfuel would be better for users, but capturing CO2 from fossil fuel fired power-plants to make fuel for vehicles is completely irrational. Better to use non-fossil energy for power plants and use the fossil fuel for transportation; so where will the CO2 come from? If you have it (e.g. from biomass), why not bury it, and pocket the carbon tax? If there’s no carbon tax, why bother with capture? (All of the reports I’ve seen say CO2 capture from steel and concrete will cost much more than at power plants.) That’s why I believe that German methane synthesis that Bas keeps praising is basically implausible.

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