Thursday, November 20, 2014

Hydrogen Powered Cars

This post is about the Toyota Mirai, a hydrogen powered car that is now entering production.

First, let us state that yes, we should all support technological innovation. And yes, when a new technology is introduced into the market, significant improvements tend to be made in a relatively short time.

However, after saying the above, let us make some pertinent questions.

One important sale point for a hydrogen car is that it produces no emissions (the car itself during operation), but since free hydrogen is not available on Earth, it first has to be produced. Thus, we come to the first question.

1. How is hydrogen currently produced? 
     Currently most hydrogen is produced from natural gas at an efficiency of ~80%*. Off the bat, this
     means two things: a) 20% of natural gas' energy is lost in the conversion and b) significant
     amounts of CO2 are produced during the conversion itself. Thus, these emissions need to be
     considered part of the system emissions of the hydrogen car.

2. What is the efficiency of the fuel cell (the device with which the Mirai converts the hydrogen 
     into useful electricity)?
     Without cogeneration, the efficiency of a fuel cell is in the range of 40 to 60%.**
     As a reference, rechargeable batteries have efficiencies above 90%. Consequently, just combining
     the production of hydrogen with electricity generation in the fuel cell, the combined efficiency
     drops to ~50%.

Thus it could be stated that the Mirai is competing with EVs (electric vehicles) on the one hand and with NGV (natural gas vehicles) on the other.

Today, the EV is clearly more efficient and lower cost than the Mirai. In other words, the EV would produce less emissions in most scenarios.

The NGV is much less expensive (and less efficient) than the Mirai. However, it remains to be seen if the considerably higher cost justifies moving to a Mirai rather than just buying a conventional electric vehicle.

Conclussion: Innovation should be supported but the hard questions need to be made.
Feel free to add to the conversation at Twitter: @luisbaram




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