The future of cars, a review of different drivetrain options

I was at a trade show for cars the other week and it struck me just how much vehicle fuel economy, within the EU at least, has improved over the last few years.

Figure 1 - There has been significant growth in sales of BEV’s (such as the Nissan Leaf) and hybrid cars [Credit: UPI, 2013]

Figure 1 – There has been significant growth in sales of BEV’s (such as the Nissan Leaf) and hybrid cars [Credit: UPI, 2013]

I recall it being suggested to me back around 2000 (by experts in automotive design) that getting to under 100 gCO2/km would be impossible for a “proper” car and 100 mpg was pushing things, even for a small car. However, these limits seem to have been surpassed and then some.

Just to give you a flavour of the field and what cars on sale are now capable of, I give a couple of examples below:

(note that all mpg and mpge figures are in UK (Imperial) gallons not US gallons unless stated, a conversion tool is available here)
 

· A Honda Civic (Diesel 1.6L, hot hatch sized car) boasting 78.5 mpg & 94 gCO2/km

· Toyota Yaris Hybrid  (first hot hatch sized hybrid car I’ve seen on sale), 81 mpg (hybrid mode, i.e. combined EV & ICE efficiency), 79 gCO2/km

· Volvo V40 (medium sized sedan) available with petrol 74.3 mpg (137 gCO2/km) or diesel 83.1 mpg ( 88 gCO2/km)

· The Volvo V60 diesel hybrid (executive estate), 155 mpge under electric power, couldn’t get a reliable figure for mpg under hybrid mode (they claim 49 gCO2/km), but a reviews here  and here put it at about 60 mpg.

· Nissan leaf, 169 mpge (although the EPA rates it at 116 mpgus or 140 mpgimp), officially zero gCO2/km (we’ll discuss that one a bit later!), range on full charge of its 24 kWh battery – 109 miles  (on a NEDC cycle).

· Peugeot Ion (effectively a Mitsubishi I-MiEV restyled for Europe), full EV, officially 155 mpge (claimed 200 mpge at the stand, if you drive it sensibly, which seems plausible, although I suspect the same applies to other EV’s, again more on that later), 100 mile range on full charge of its 16 kWh battery, again officially 0 gCO2/km.

· Renault Twizy, micro car EV, 62 miles on a 7 kWh charge (reasonably quick charge time! They topped up the battery by about 10% in the time it took me to drink a cup of tea…if that means anything!), mpge? This reviewer suggests around about 211 mpge.

· Hyundai ix35 Hydrogen Fuel cell Vehicle  (SUV). Claimed range of 300 miles on a full tank of hydrogen, 0.95 kg’s of H2 per 62 miles would imply a fuel economy of roughly 68 mpge (according to my back of the envelope calculation).

· Vauxhall Ampera (a plugin hybrid, effectively a restyled Chevy Volt for the European market), a somewhat dubious 234 mpge EV mode claimed (25-50 mile range) and 74 mpg   (hybrid mode according to the EPA) with a claimed 27 gCO2/km (again somewhat dubiously I’d argue, more on this later).

· And of course the latest version of the Toyota Prius plugin hybrid (medium sized sedan),112 mpge & 49 gCO2/km (but probably closer to 72 mpg & 89 gCO2/km on a more realistic drive cycle)

· While it wasn’t at this show, I thought I’d mention the VW Bluemotion Up! (small 3 door city car), 1.0L 3 cylinder engine, 63 mpg & 96 gCO2/km. Not hugely impressive compared to the above, but perhaps it serves as a bench mark for a small “conventional” petrol engined car.

So as the above examples show the previous long assumed limits to low carbon vehicle performance appear to have been exceeded. We can trace this down to four events.

Reasons for Change

Firstly, oil prices. In 2008 they hit an eye gouging $147 dollars a barrel. Previously the automotive companies had always accepted the mantra that peak oil was decades away. But this sudden spike in oil prices, coupled with the IEA suddenly changing its tune on peak oil, not to mention the apparent inability of the OPEC states to increase oil production, effectively served to scare a number of the auto manufacturers straight (as it were).

Of course the fact that many US owned car makers (notably GM and Hummer) who had prioritised SUV’s went bankrupt, while European and Japanese companies (who had prioritised fuel efficient vehicles) when from strength to strength (Toyota is now the largest car maker in the US) was a fact not lost on the industry. They learnt an important lesson, customers what good fuel economy and as the saying goes, the customer is always right.

Secondly, computers and the IT revolution. As I discussed in a previous post a modern car these days will have more electronics running it than the Apollo moon lander. One of the effects of this is to facilitate “engine downsizing” as a computer controlled engine will control fuel consumption and moderate power output much more efficiently. Where for example that Civic I mentioned would have previously needed a 2.0L engine, it now gets by with a 1.6 L engine. Also computers simulations have allowed lighter and more streamlined cars to be designed. Again, while the average European car back in the 60’s would have weighted over 2 tons, most are now around 1.4 tons or so in weight, closer to a ton for smaller cars (such as the the Up! mentioned earlier). Less weight, less fuel consumption!

Thirdly we have to credit the actions of governments, notably those in the EU and in Japan and their policies of aggressively cutting allowable vehicle emissions (both in terms of particulates, pollutants and carbon emissions). Legislation in several EU states directly links car tax to engine size and carbon emissions. This has more or less forced the industry to react and try to prioritise fuel economy and cut carbon emissions (hence why all the cars I saw had the carbon emissions and fuel economy displayed on the windscreen). Of course for certain car types (Sedan’s and Estate cars or larger) it became more or less impossible to meet the EU’s EURO 5 standard with a conventional powertrain, hence the sudden interest in hybrid versions of these vehicles.

Figure 2 - Falling vehicle emissions within the EU [Credit: SMMT.co.uk, 2012 http://www.smmt.co.uk/co2report/#new-car-co2-emissions ]

Figure 2 – Falling vehicle emissions within the EU [Source: SMMT.co.uk, 2012]

And this to me is an important point, the naysayers were wrong about low carbon vehicles. there is good reason to ignore the tea party types when they (for example) scare monger that more a renewable heavy grid will be bad for the economy (last time I checked Germany seems to be doing okay!) or that the lights will go out (indeed speaking of Germany, they’ve actually be increasingly exporting renewable electricity to neighbouring countries).

Finally, there was the Automotive X-Prize competition. Inspired by the Ansari X-Prize, this competition challenged researchers to produce cars as fuel efficient as possible.

Figure 3 - Automotive X-Prize entrant, Li-ion, 240 mpg+[credit Li-Ion, 2010]

Figure 3 – Automotive X-Prize entrant (and EV category winner), Li-ion’s Wave, 240 mpg+[Source: Li-Ion, 2010]

Of course there are “eco-marathon” vehicles with fuel economies of tens of thousands of mpge, but the automotive X-Prize focuses on “proper” cars, i.e. something that can carry 2-4 people in reasonable comfort and safety at a decent speed. The prize broke down into “alternative” categories with only 2 seats, often EV’s and Fuel Cell Vehicles with fuel economies of 200+ mpgus, that’s roughly 240 mpgimp (three good examples being the Aptera, Li-ion Wave (pictured) and the X-tracer), and “conventional” cars with a standard powertrain (i.e. a reciprocating engine up front, none of you’re fancy stuff!) where the winner was Edison2 with several competitors breaching the symbolic 100 mpgus (about 120 mpgimp).

The 1 litre cars

Now while one could question how relevant and practical some of these X-Prize cars would be (i.e. would anyone ever walk into a show room and try to buy one?) the point of the competition was not lost on the automotive manufacturers. The event served to show them what was achievable and that got people in the industry thinking. Hence several automotive companies, who had concepts for low carbon vehicles that they been quietly working on for some time suddenly gave these projects priority and began looking to move them into production.

Figure 4 - VW XLR 1.0L car [Credit: CNET.au, 2010]

Figure 4 – VW XLR 1.0L car [Source: CNET.au, 2010]

Indeed if the fuel economy for the X-Prize cars above (or the other vehicles I mentioned) sound impressive, VW have been working for some time on a 1L car  (a diesel electric hybrid, 0.8L, 3 cylinder engine, 98 mph top speed, pure EV range of 35 km’s). That is a car that consumes 1L per 100 km’s, roughly equivalent to 282 mpge (UK on an NEDC cycle). Indeed the 2011 version of the XLR 1 has actually achieved a fuel economy of 0.9L per 100 km’s  in tests (310 mpge!) or around 21 gCO2/km. A limited production run of the XLR 1 is being considered.

Meanwhile one of the X-Prize competitors, the Aptera 2 team, have previously claimed an even better level of fuel economy, with 300 mpgus (360 mpgimp) on a plugin hybrid powertrain. The Loremo AG concept car, which uses a combination of lightweight body components, low drag and a fuel efficient conventional 2 cylinder diesel engine to achieve 157 mpg with a 4 seat car.

A Sales boom

So essentially what we’re now seeing is the first couple of waves of these new more fuel efficient cats starting to hit the market. And all the indicators are that they are selling very well both in the US and in the UK. Again, the naysayers have been proved wrong about low carbon vehicles!

Figure 5 – Alternative vehicle sales are growing [Source: SMMT.co.uk, 2012 http://www.smmt.co.uk/co2report/#new-car-co2-emissions ]

Figure 5 – Alternative vehicle sales are growing [Source: SMMT.co.uk, 2012]

Powertrain options

Of course before going any further in this discussion it would be useful to consider the different power trains. I give a detailed breakdown of the different systems here.

But in summary, one of the key advantages of BEV’s – Battery Electric Vehicles is its much higher levels of energy efficiency. Typically an EV will achieve a system efficiency of 80% from battery to wheel (roughly 60% from grid to wheel), while with a conventional ICE it’s more like 15-25% efficiency.

Figure 6, EV powertrain layout [Source: Astroman.pl, 2009 http://www.astroman.com.pl/?mod=magazine&a=read&id=518 ]

Figure 6 – EV powertrain layout [Source: Astroman.pl, 2009]

Electric engines have a wider torque range than ICE’s (this is why conventional cars have a gearbox!) and can gain back energy from regenerative braking. Casing point I was test driving an EV a while back and every time I got to a hill I took off and the BMW behind would disappear into the distance! We are well past the milk float era!

One of the major disadvantages of an EV is that of the relative weight of batteries compared to an equivalent tank of fuel (about 40 times worse per kg!). Although this is compensated for somewhat by a greater power to weight ratio of an electric engine v’s an ICE.

Figure 7, Typical Vehicle Journey Ranges

Figure 7 – Typical Vehicle Journey Ranges [Source: J. Gartner EVblog, 2010 & Pike Research]

Also there’s the range issue. While the range of BEV’s has been steadily growing, Tesla claim ranges of up to 430 km’s for its latest Model X. However, while it takes just a few minutes to refuel a petrol powered car, an EV takes hours to recharge. This often leads to a phenomenon called “range anxiety”. Many conclude that even though +90% of their journey’s are within BEV range, as they can only afford one car, they need something that can also do the >10% of long range journey’s.

Perhaps the solution to the range problem could be hybrids, in particular “plugin hybrids”. Hybrid cars can be broken down into two general flavours, series and parallel. A series hybrid, is essentially a BEV, i.e. electric motors drawing current from a battery drives the wheels. The difference is that a series hybrid has an engine of some kind (diesel, Fuel Cell, two stroke petrol, etc.) which is connected to a generator rather than the wheels and keeps the battery topped up. Indeed we often refer to said engine as a “range extender”. Given that these typically operate at one set speed, and it gains all the benefits of an electric power train (regenerative braking, etc.) the result is a significant improvement on a conventional car.

Figure 8 - Series Hybrid layout [Source: Green transport blog, 2009 http://greentransportandenergy.blogspot.co.uk/2009_03_01_archive.html ]

Figure 8 – Series Hybrid layout [Source: Green transport blog, 2009]

A parallel hybrid involves the IC engine connected both to the wheels and to an electric motor. It gains from regenerative breaking and at low speeds the electric motor can drive the vehicle without the IC engine. Such a system tends to be much easier to implement, less costly and considerably less complicated to install than a series hybrid. The major disadvantage is that parallel hybrids generally don’t achieve the same levels of energy efficiency as the series hybrid.

Figure 9 - Parallel Hybrid [ http://forum.indogamers.com/showthread.php?t=309524&page=4 ]

Figure 9 – Parallel Hybrid

There is a common misconception that a hydrogen car has to run on a fuel cell, but there is no reason why a hydrogen car can’t operate using a conventional IC engine (or Stirling engine  or gas turbine engines for that matter), although these “Range Extenders” aren’t as energy efficient as a FC range extender.

As I’ve previously discussed the FCEV still has not yet reached commercial maturity, largely due to reliability issues, as well as the bulky nature of FC’s and they’re associated hardware (H2 tanks, controllers, etc.). This is why many of the FCEV’s currently on offer tend to be larger SUV or people carrier type vehicles (such as the Hyundai mentioned earlier or the GM FCEV below). Of course the cynic would query whether a nice small high efficiency diesel car (like that Civic or Up! mentioned earlier) would actually achieve higher fuel economy and lower carbon emissions than some big FC powered SUV.

Figure 4.2.7 - Fuel Cell vehicle from GM http://revocars.com/wp-content/uploads/2010/04/FuelCellEquinox.jpg

Figure 10 – Fuel Cell vehicle from GM [Source: Revocars]

Given these issues the jury is still out as to whether the hydrogen car of the future will be FC powered or just be a series hybrid with a hydrogen fuelled IC engine, or indeed whether it well ever become a reality!

Performance

Some worry about the performance of BEV’s or series powered vehicles. i.e. the petrol head top gear brigade types argue, that they cannot compete with an ICE car on a performance level. Again, my driving experience of such vehicles is that while they may have a point if you’re Mika Häkkinen, but so long as you’re not looking at winning the world rally championship (i.e. you want something that gets you A to B at a reasonable speed), a BEV or hybrid powertrain is more than adequate.

Figure 11 - Lotus Evora Hybrid supercar http://www.lotuscars.com/gb/engineering/evora-414e-hybrid

Figure 11 – Lotus Evora Hybrid supercar [Source: Lotus, 2013]

Indeed Tesla’s EV roadster has often been noted for its exceptional performance. As I mentioned I’ve never had any problem maintaining an EV at speed, even up to 80 mph (on a test track of course Mr Policeman ;0 ). Lotus, Nissan, Lexus and Jaguar are reportedly experimenting with series powertrains for their next generation of high performance cars. While achieving EURO 5 vehicle emissions standards is part of the reason (they face the stark choice of either making the cars more fuel efficient or stop selling cars in Europe!), but also it’s a matter of them recognizing the benefits of an BEV based system.

Battery maintenance

Traditionally one of the major stumbling blocks for a BEV or hybrid car has been the battery pack, as they tend to be expensive and have a fairly limited operating life. However the manufacturers claim to have greatly reduced these problems. Better battery management systems have eliminated the problem of battery “memory” problems (where if the battery is only partially discharged repeatedly it loses the extra unused capacity due to a lack of cycling of those cells), or other battery failure issues and the costs of production have fallen (by half in the last 3 years). Reliability has also improved (they used to be very sensitive to very rapid draw down on current) again largely due to better control technology.

Figure 4.2.2 - Battery technologies Compared [houseofbatteries.com http://www.houseofbatteries.com/custom-batteries-c-1-l-en.html ]

Figure 12 – Different Battery Technologies Compared

Toyota offers up to a ten year guarantee on a Prius battery and have even gone so far as to imply that they will replace the battery under warranty out to the ultimate life of the car. Now, that said, I’m skeptical that if I bought a clamped out old Prius in fifteen year’s time, with a couple of hundred thousand miles on the clock, that I could then drive into a Toyota garage and demand a brand new battery (probably worth more than the car is worth!) and Toyota would honour that?

But that said, cars these days are increasingly full of expensive gadgets and components. One of the perennial problems for a car is that as it ages it requires ever more expensive maintenance as bits and pieces of it hit their natural service life and need replacing. Eventually these costs can come to exceed the resale value of the car! So my way of looking at it is that the battery pack of future cars is really more of the same. People said the same things when they started to introduce catalytic converters and VCU’s within cars and now they’re standard components.

Sharing the road?

Also as I’ve discussed on another post, perhaps the problem isn’t the cars or vehicle technology but our car ownership habits. If you think about it, there is a certain insanity towards spending tens of thousands of pounds on a hunk of metal that spends 90% of its life slowly rusting parked up by the side of the road. Systems of collective shared ownership, such as car clubs, fleet vehicles or instant hire BEV’s schemes such as being trialled in Paris right now (like those Boris bikes in London) may all represent a better way of reconciling the higher service costs of cars of the future. Quite apart from the fact that such a system would mean ultimately less cars (thus less problems with congestion, greater public transport use easier to find parking, etc.).

Contrary to what the naysayers would have you believe there is more than adequate lithium in the world to support mass production of lithium-ion batteries for a couple of billion cars.

Safety?

As I discussed in a prior post, there is no reason to doubt the safety of BEV’s, hybrid cars of FCEV’s. The idea that a car is less safe because it’s small or safer by virtue of being big is not borne out by the laws of physics. Many of low carbon vehicles are merely evolutions of an existing chassis which have been crash tested and field proven already. Hyundai’s FC vehicle, the ix35 for example boasts a “top pick” safety rating from the US IIHS.

That said, some of those ultra-high low fuel consuming concept cars I mentioned probably wouldn’t perform that well in crash, as you would expect in any vehicle where fuel economy is prioritised over everything else. High performance sports cars don’t tend to perform brilliantly in crashes either (here’s a Lamborghini being crash tested, this is why it’s so expensive to get insurance with one!). I’ve seen supporters of a number of these vehicles try to claim that just because they are made of carbon fibre they are somehow safer. Unfortunately, car crash safety performance isn’t quite that straight forward (again as I discussed in a prior post its something of a “black art“). However, as far as “proper” cars subjected to the rigours standards and testing imposed by NCAP, NHTSA, IIHS (or similar bodies), I would not accept the idea that low carbon vehicles are in any way less safe than a conventional car.

There has been an issue related to Lithium-ion battery pack fires (often caused by issues  such as thermal runaway), both in cars as well as aircraft. I would counter by pointing out that anyone worrying about this seems to forget what happens when a petrol tank goes up nor that there is a statistic for vehicles (conventional ones that is) that just spontaneously combust, often due to a fuel leak or an electrical fault. So like I said, it’s a problem, but one that has to be put in the proper context.

Similarly much has been said about the perceived dangers of hydrogen tanks in future vehicles. However, again one has to remember that any such danger has to be balanced against the risks imposed in driving around in the self propelled petrol bomb’s currently in use. While vehicle hydrogen tanks are typically made of bullet proof Kevlar, petrol tanks are often made from mild steel (which do you think is more likely to fail?). People often forget that compressed natural gas vehicles have been in use for many decades and are very popular in some countries.

Figure 13 - Breach Test hydrogen tank compared to Petrol powered car [Source: Swain (2001) http://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/30535be.pdf ]

Figure 13 – Breach Test hydrogen tank (left) compared to petrol powered car (right), the H2 vehicle burns itself out after 1 & a half minutes, leaving only moderate damage to the rear of the car, the petrol power vehicle, burns & burns until the tire’s explode! [Source: Swain (2001)]

Furthermore breach tests of hydrogen tanks suggests that they are, at worse, no less safe than a petrol tank. Indeed given that as a gas hydrogen tends to burn upwards and produces very little heat or toxic gases nor is it as likely to explode as liquid fuel vapours, some would argue its actually safer.

But are the car companies cooking the books?

You will notice the wide variety in supposed performance from the cars I mentioned at the start with regard to mpg and carbon footprints. EPA say’s its mpg is X, the manufacturer say’s Y, autotrader says its Z…and you the car buyer say it’s something completely different! Indeed a number of motoring journalists (real ones that is, not the top gear types!) have lamented at this gap between actual driving performance and what it says on the label.

My response to this is that in fairness to the car companies, it is sort of like trying to ask how long is a piece of string. I’ve seen tests where we’ve taken BEV’s out, followed an identical route in the same car, in similar traffic conditions and ended up with radically different energy consumption levels. Different drivers over the same circuit can show up to a 25% or more variation in fuel consumption, due to differences in how they drive. Now factor in the effects of traffic, weather and other boundary conditions (e.g. is there only one person in the car or 5 people with lots of luggage) and you can see a significant variation in performance.

So yes, I suspect the car companies are often reporting their best possible results, and I would take what they say with a pinch of salt. But they should still be accurate within in a reasonable window of probability.

LCA – how much carbon do EV’s actually produce?

Holding that thought however, if there’s one thing that annoys me about BEV’s it is these claims that they produce zero carbon emissions. Similar claims are made for hydrogen vehicles and often the EV component of a plugin hybrid factors in a supposed zero carbon contribution. Of course such a view tends to forget that in many countries the bulk of electricity is still generated by fossil fuels.

Indeed both the DoE (summary of the 2011 GREET report findings here) and EU’s JRC (link to the 2007 report here) have conducted detailed Well to Wheel studies both on an energy efficiency basis and a carbon footprint basis. These reveal that the carbon footprint of EV’s is certainly not zero, but it is also certainly an improvement on conventional vehicles.

Figure 14 – Well to Wheels ratio’s[Source EUCAR, 2007]

Figure 14 – Well to Wheels ratio’s [Source: EUCAR, 2007]

For example, In the UK about 80% of electricity still comes from fossil fuels yielding an average UK grid carbon footprint of about 448 gCO2/kWh. Recalculating to account for this with an BEV (say a Nissan Leaf) yields a carbon footprint of 65-102 gCO2/km (depending on exactly who you believe as far as the Leaf’s fuel economy & range). This is around about the same ball park as a small diesel car. So the environmental benefits of a BEV aren’t quite as clear cut as it is often implied.

Figure 15 – WTW (well to wheel) GHG emissions for various vehicle powertrains and pathways [Credit: GREET, 2011]

Figure 15 – WTW (well to wheel) GHG emissions for various vehicle powertrains and pathways [Source: GREET, 2011]

That said, one of the advantages of a BEV is reduced air pollution, as all we’re transferring those emissions to a powerplant not having them pouring out into people’s lungs on a city street. It’s not just the carbon dioxide cars generate that’s the problem. The primary motivation in China behind BEV’s is the vast problem they’re having with air pollution. It is also far easier to implement carbon capture and storage at a power station that on a car. Consequently I would argue that those critics (such as Bjorg Lomborg) are missing the point when the use this line of reasoning to criticise electric cars.

Also perhaps what this little back of an envelope calculation yields is the dangers of failing to decarbonise the electricity grid. Many countries have a much less carbon intensive grid than the UK. Norway and Iceland are more or less carbon neutral (nearly all of both nations electricity comes from renewables). As I discussed before Portugal is averaging around about 70% renewables from its grid. Repeating the same calculation for the Norwegian grid (using data from the IPCC for Norwegian grid carbon intensity) and even accounting for the carbon footprint of its many dams, yields 1.26 – 2.7 gCO2/km….my suspicion is that this is not accurate….as in this scenario I expect the driver probably produces more CO2 than the car!

Figure 16 – Carbon intensity of hydrogen production, wind v’s natural gas [Credit: NREL]

Figure 16 – Carbon intensity of hydrogen production, wind v’s natural gas [Credit: NREL]

Similarly, hydrogen cars do have a carbon footprint. Currently the bulk of hydrogen production is via steam reforming of natural gas or as a by-product of petroleum manufacture. According to the NREL hydrogen produced in this way has a carbon footprint of 11,888g CO2/kg of H2. However, if the hydrogen is manufactured by wind power the NREL also reports a carbon footprint of just 970g CO2/kg of H2  (i.e. 1/12th that of the natural gas route!).

The exact powertrain choices we make with a hydrogen car also has a major bearing, how it is stored in the car (liquefied hydrogen v’s compressed), whether the hydrogen is made on demand at the filling station (which cuts down on leaks) or making it in bulk and trucking it in, do we use a series hybrid, FCEV or conventional engine. I came across a good paper on the implications of the various energy pathways, by Campanari etal (2009) for those with access to sciencedirect.

Figure 17 – Comparison of overall WTW ratio’s for different vehicle types and energy pathways (GHG emissions) [Credit: EUCAR, 2007 http://ies.jrc.ec.europa.eu/uploads/media/WTW_Report_010307.pdf]

Figure 17 – Comparison of overall WTW ratio’s for different vehicle types and energy pathways (GHG emissions) [Source: EUCAR, 2007]

While in the best case scenario for hydrogen, i.e. all the most energy efficiency carbon neutral options are taken you can end up with a reasonably efficient well to wheel performance with low carbon emissions (as shown in figures 15 & 17). However if you make all the wrong choices (e.g. liquid hydrogen, ICE (listed as a “PISI” Port Injection Spark Ignition in Figure 17) in a conventional drive train, large car, etc.) you can end up with a carbon footprint and energy performance much worse than any existing car, as a number of examples in figure 17 reveal.

So again, to me this emphasizes the need to make the correct choices when it comes to sourcing our future energy resources. It also highlights why I think some sort of carbon tax is essential. This would effectively sort out the environmental men from the boys and clearly insure the correct low carbon choices are implemented.

The cars of the future

My prediction is that if present trends continue, cars will get ever more fuel efficient and many of the powertrain options I’ve discussed will become the norm (indeed you’d could argue that’s already the case and I should have written this article a few years ago!). Indeed there are a number of other proposals for changes to vehicle powertrain’s that I’ve not covered here which may ultimately be proven viable in the future.

Cars will get smaller and they will probably be less of them on the roads, simply because with rising oil prices and rising vehicle costs (car prices have been going up for quite sometime and that has nothing to do with low carbon vehicles) I suspect people will simply trade downwards or give up car ownership altogether (either going car free or joining a car club).

I suspect there is no one size fits all solution to oil. We’ll probably be looking at a future where transport is met by a mix of BEV’s (better suited to fixed routes and limited ranges), parallel hybrids for longer range heavy vehicles (buses, long distance trucks) and series hybrids for long range cars. Both of the hybrid options being powered by a mix of hydrogen, biofuels and our dwindling reserves of dead dinosaur oil. Not to mention just walking and cycling more!

Indeed as I’ve discussed before there is an outside chance (if Google has its way) that we will be permanently relegated to the passenger seat, with the self-driving car.

Implications

The assumption among environmentalists has long been that getting any sort of meaningful reductions in carbon emissions would be impossible so long as we live on a world with a billion self-moving climate change machines running around. Of course the peak oil pessimists have also long argued that maintaining even a fraction of the present world vehicle fleet with dwindling oil supplies would simply be impossible. Thus sooner or later the assumption was that both of these two problems would essentially cancel each other out!

However, the dramatic increases in fuel economy achieved over the last few years represents something of a game changer. The amount of oil we need to sustain the global car fleet is now falling. And the reduced carbon foot print of vehicles, while it does not eliminate the problem (as I’ve highlighted even in the best of circumstances, they still contribute to climate change, dramatic cuts in this area are still needed, even if all cars became BEV’s). But it does make dealing with vehicle related emissions less urgent a task than it otherwise would be.

This allows more time for longer term planning and options such as the hydrogen car (and all the support infra-structure required) more realistic and plausible than previously thought.

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About daryan12

Engineer, expertise: Energy, Sustainablity, Computer Aided Engineering, Renewables technology
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16 Responses to The future of cars, a review of different drivetrain options

  1. neilrieck says:

    It is nice to see reductions in mass since this is directly proportional to energy (via Ek = 1/2 mv^2) and fuel. Do you know why some countries employ “Units of fuel per fixed distance” while others use “Units of distance per fixed fuel unit”?

    • daryan12 says:

      As with all energy stat’s the fuel economy of cars is a bit ad-hoc. I mean even though in Ireland we now sell petrol in litres and all the road signs are in km’s mention L/ 100 km’s to people and they’ll look at you cross-eyed, while give them the stats in mpg they’ll understand straight away as they can benchmark that against other cars.

      Personally I like this Wh/km figure as its quite easy to record energy output (via electricity or the calorific value in fuel) in Wh’s and distances are easily measured with a sat-nav in km’s.

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