Not too long ago the car makers where competing with each other on performance—mainly measured by horsepower and acceleration. Fuel economy did not have high attention in the benchmarks for premium cars. This has changed recently and fuel economy is suddenly a major trait that every OEM has on its list.
This trend was not only driven by environmental regulations of various governments but the fuel price itself. Also consumer behaviors have changed a lot and our society is undergoing a paradigm change with regards to our transportation concepts and mobility behavior.
These days more and more new car customers are looking at the datasheets and specifications for fuel consumption and emissions. The prestige and image of many cars are now largely driven by its benchmark fuel efficiency and emission values rather the pure horsepower backed driving performance and acceleration. So this changing consumer behavior and the strong government involvement via rules, regulations and incentives for environmentally friendly cars leads the automotive market towards a new generation of cars to satisfy this trend of “green transportation”. And that’s the main reason why hybrid-electric Vehicles (HEVs) are showing up in every fleet and product line of the major car manufacturers.
What we often forget, especially here in the U.S., is that fuel efficiency and low emissions are not only achieved via revolutionary game-changing technologies like the emission-free electric powertrain of a hybrid vehicle. Looking at the fuel efficiency of currently available or shortly announced HEVs, you would be surprised that this fuel efficiency can be pretty closely matched by a modern diesel engine using state-of-the-art direct fuel injection systems and an electronically controlled and well optimized motor control unit. The big difference comes with the price "bump up" for the technology that the buyer pays.
A diesel engine typically adds only moderat cost compared to a comparable gasoline engine (in the range of approximately $1-2,000). The price adder of HEVs vs their traditional standard combustion engine version is normally at least 2-3 times as high. The reason for this is that hybrid-electric vehicles need to incorporate a complete electric powertrain plus all the energy management and storage systems, a high voltage battery, and plenty of electric systems like inverter, converter, and charger applications into the vehicle architecture.
Therefore the additional electronic content in a HEV is much higher than the little electronics in the motor control unit plus some diagnostic and monitoring sensors which are needed to build a very efficient direct fuel injection system for a modern diesel aggregate in a much more cost effective way.
Checking the numbers
Let’s look at the table below, which shows the average highway fuel consumption in miles/gallon of HEVs vs diesel. There is not much difference between similar sized and powered diesel and HEV cars. The emission values of those cars are also in a comparable range. Only the pure city consumption of the HEVs seems to be superior since the HEV-engine typically shuts down (so called start-stop mode) every time the car is stopped in a traffic jam or at red lights. But adding relatively low cost start-stop functionality to a regular diesel engine (so called micro-hybrid) would push the diesel city mileage likely into the same range as the one advertised for gasoline-HEVs.
Looking at these numbers the diesel solutions could offer quite some threat to the penetration of HEVs. In countries in Europe where diesel is a well established engine type and the consumer acceptance is at least as high for gasoline powered aggregates we see already a very strong market penetration of diesel while HEVs seem to sell much harder compared to U.S. or Japan, for example.
To a certain extent the figures mentioned in the article make sense. IC engines rely on an optimum RPM for efficiency which is not exaclty the start-stop city traffic's cup of tea. So choosing a prime mover for those sections of driving is defntly going to make sense and micro-hybrid indeed serves the purpose at those points.
but to downplay the HEVs by pointing to microhybrids is a negative route to take. hybrids are a precursor to the EVs, a stop-gap arrangement till battery chemistry is gud enough and we have the infrastructure on the freeways to support it. As a general rule the rational mind shud favor the direction we are on, instead out pointing out things like 'they have the same mileage on a highway' .. hope we all realize hydrocarbon prices will only go up and electricity price can only come down, so no matter how strong the statistical figures at this point, they will always fails in favor of the EVs at some point of time.
Price depends mainly on taxes (in EU). Moreover, there could be a refining capability limitation: the ratio of diesel/gasoline production is heavily dependent on refinery technology and oil quality, can't be changed so easily.
Nice article Henning. The only downside of Diesel here in the UK is that it is more expensive than petrol (gasoline). Do not know why since it's cheaper than petrol elsewhere in Europe (to my knowledge).
I don't understand why everyone thinks that diesel is so clean. Go look at the data. EPA certification data is here:
If that URL gets filtered you can get there from epa dot gov, then search for "Annual Certification Test Results Data"
Not all models are in there. For example I don't see the Prius or the TDI. But I do see a hybrid Lexus and Diesel Audi Q7, which should be pretty comparable. Here are some numbers:
CO: Audi .3 Lexus .2
NMOG: Audi .023 Lexus .006
NOX: Audi .045 Lexus 0
FYI A suburban comes in at:
The numbers are in grams/mile, measured following one of several driving test procedures.
So we see that for NMOG and NOX, the important compounds, we see that an anemic luxury diesel that barely seats 5 is comparable to a luxury full size SUV that seats 8 in comfort and can tow a boat or travel trailer to boot.
This is a dramatic improvement from the past. If you were to look at data from early 2000s you'd find diesels at least an order of magnitude worse then gas. But diesels aren't the "new hybrid", they're not even the "new gas".
I spent some time between Texas and Colorado, and I noticed very few "corvette" or stuff with high torque around. Some were stopped by Police or stuck at 55mph speed limit...
What I did notice is the high number of pick-up that were running empty. Here you need big engines to carry stuff, but most of the time people use the pick up as a standard car and that creates the false illusion that a "chevy" may be a cheap alternative. Seen form outside, the impression is that in States beople simply tend to buy "big". Coming to horsepower, you will be amzed to see a "Corvette" outperformed by a Porche or Ferrari and discover 30% less gasoline consumption on the latters. TESLA is an US company making business in electrical sport cars. That is amazing as horsepower and drive torque, even better than a Ferrari. Just, try to plan a trip longer than 300mls with it...
In France and Italy, most of people I know drive Diesel, even turbo-diesel sport cars of 150 HP or more, in spite of higher taxes on the fuel. I tend to say that, dropping motorcycles and a handful of Porsche or Ferrari the penetration diesel is much around 80%. Also, 100 of european trucks are diesel. Diesel has the reputation to be much more reliable than gasoline. For example Mercedes-Benz Diesel are well sold after 250k Kilm (150k Miles) since the buyerknow they can easily go up to 450-500k before starting worry.
I recently had the opportunity to drive the new Volvo S70 (Diesel), not in such benchmark, that actually did implement the start-stop functionality. I had the amazed surprise to run more than 1,000Km (630mls) without stopping for re-fuel, in urban and extra-urban cycle on smooth and very silent cruise speed of 140 km/h (87mph). The tank was 75 liters (20 US gallons).
Autonomy is a weak point for HEV: on long trip, if you cannot recharge, than you are using conventional fuel AND bringing the additional weight of your empty batteries. Diesel stations are already everywhere, electrical network must be created and, more, a standard way to replenish your battery in sort term is yet to be available.
For HEV, I confirm that they need much more electronics, but the demand is now growing and already the related prices are moving down pretty fast.
Commenters & author, I am an engineer, and I am going to learn a lot at the EVS25 conference in Shenzhen, China, where the state of the art of hybrids, EVs and anything around it is displayed from the perspective of the far east situation. Visiting similar conferences in the EU I find a discrepancy between political fanfare that is broadcasted in the media, and the engineering, technical, physical, sociological, and financial reality presented on the conferences. Three major misconceptions about electric traction seem to live in the media (1) massive use of overnight charging is cheap and under the consumer's control (2) affordable accumulators are ready for the job (3) the battery and electric motor metal supply line of such vehicles is sufficiently large and is affordable. It is amazing how far we are from this state of affairs. The required performance and cost levels, as well as the 10s of thousands of tons of high-tech metals and chemicals, are factors if not an order of magnitude away from what the media proclaim. Welcome to the real world. So lets observe on the conference in November how human inventiveness copes with this. Regards Henk Mol
Join our online Radio Show on Friday 11th July starting at 2:00pm Eastern, when EETimes editor of all things fun and interesting, Max Maxfield, and embedded systems expert, Jack Ganssle, will debate as to just what is, and is not, and embedded system.