Posted on December 01, 2014 by Roger Pressman
With the introduction of the new hydrogen-powered Toyota Mirai (the name means "future" in Japanese), there has been a lot of media hype about vehicles that use hydrogen fuel cells as their power source. Toyota, Honda and a number of other automobile companies have announced plans to build cars based on fuel cell technology.
Fundamentally, a hydrogen fuel cell produces electricity via an electro-chemical reaction that drives an electric motor that creates the motive force for a car. The technology requires high-pressure storage of liquid hydrogen, a fuel cell to convert the H2 to electrons, a control system to deliver the resultant electricity to an electric motor and/or battery that in turn drives the wheels of the vehicle. It’s a workable, if somewhat complex system that produces zero emissions and water as a by-product.
In the media, there are three major claims that are being made about cars powered by hydrogen: (1) that H2 is a 21st century energy source and will ultimately become the preferred power source for automobiles; (2) that hydrogen-powered fuel cells represent a significant improvement in environmentally safe automotive fuel, and (3) that cars like the Toyota Mirai represent a major threat to battery electric vehicles (BEVs) like the Tesla Model S.
Are any or all of these claims true? We thought we’d take a look.
After going through the popular literature and government/academic reports, we decided that the best way to present the array of information collected was with an infographic, “Tesla Model S vs. Toyota Mirai: A Technology/Vehicle Comparison,” that examines four broad categories of concern:
-- underlying technology that powers the vehicle
-- the two vehicles themselves
-- technology required for refueling the vehicle, and
-- environmental impact
Check out the infographic below, to view it in larger format, click here.
To summarize our findings:
Technology. EV technology has been around for 100 years. It represents a remarkably simple method for automotive power that is constrained solely by the capacity of the vehicle’s batteries. Fuel cells are evolving rapidly and provide more energy capacity than modern Li-Ion batteries, but they require liquid hydrogen to be stored on board the vehicle in pressurized tanks. The Tesla Model S has an energy capacity of either 60 kWh or 85 kWh while the Toyota Mirai produces 114 kWh. The overall energy efficiency (from an environmental viewpoint) of BEVs is dependent on the efficiency of the electric grid from which a BEV obtains its diet of electrons. The efficiency of hydrogen-powered cars is impacted by the process that extracts hydrogen from other sources and the method by which hydrogen is transported to a refueling station.
The winner: It’s close, but the simplicity of the BEV system gives the underlying technology of the Model S a slight edge.
The Vehicles. Both the Tesla Model S and the Toyota Mirai are expensive, but that’s the price of new technology. The Model S is a premium, high performance automobile in every sense of the word. It is a visually beautiful car that conjures images of a Aston Martin or Jaguar and has been lauded as one of the best sedans in the world. It has won praise from virtually every automotive media source, and is one of the safest, roomiest cars on the planet. The Toyota Mirai has an eccentric look that gives it a boxy Prius-like feel. It appears to provide good, basic transportation, but it is not for those who want a bit more than good, basic transportation. Finally, the Tesla Model S is here today. By 2017, there will be about 160,000 Model S vehicles on the road. Toyota projects that only 3,000 Mirais will be in the field by the same date.
The winner: No contest! The Model S is far superior to the Mirai in virtually every respect except for range.
Fueling the Vehicle. In our view, one of the major benefits of BEVs is that you refuel them at home, overnight, while you’re sleeping, so that your Model S is “full” every morning. Unless you travel long distances on a regular basis, you will rarely need a Tesla Supercharger or any other refueling source away from home. That’s huge, and often get’s lost in the discussion of “range anxiety” that always seems to invade the thinking of those who don’t own a Model S. Although fuel cells are sexy, it seems odd to us that Toyota has returned to a 20th century fueling station paradigm. In essence, there is little difference between refueling a Mirai and refueling a Camry. Sure, the fuel is different, but you have to hunt for a specific refueling station as your Mirai slowly depletes its hydrogen. No charging at home—ever.
The winner: No contest! Refueling your vehicle at home is a convenience that represents 21st century thinking. Model S provides that convenience. Mirai does not.
Environmental Impact. Both the Model S and the Mirai are environmentally impressive. Both have zero emissions and relatively low “well-to-wheel” inefficiencies. In our view, the beauty of a BEV is that it becomes increasingly friendly to the environment as our electric grid infrastructure improves. There is no need to separately transport fuel to a refueling station (a requirement for a hydrogen fuel cell vehicle) eliminating both the cost and the environmental impact of secondary fuel transport.
The winner: It’s a toss up. Both cars are environmentally friendly and both will improve as the grid becomes cleaner and as hydrogen extraction processes become more efficient and cost effective.
As a young engineering student I was taught that when you consider alternative systems that both achieve the same result, always choose the less complex approach. That’s common sense, but it appears that when faced with the same choice, Toyota chose the more complex option. Possibly, their engineers or marketing people were driven by concern about range, but that’s simply not as big an issue as they think it is. BEVs represent simplicity, and in an increasingly complex world, that’s something that many consumers like.
Is the Mirai (or another similar H2 vehicle) a “Tesla Killer”? Not a chance!