Hydrogen Powered Vehicles

Automobiles, trucks, airplanes, and even rockets can be hydrogen fueled.

Hydrogen Powered Cars and Trucks

Ford Motor Company recently introduced the P2000, a new car with a hydrogen internal combustion engine (ICE) that "could help bridge the gap between gasoline vehicles and the fuel cell vehicles of the future." [1] The engine is not much different from an ordinary gasoline engine. The use of hydrogen greatly reduces emissions although nitrous oxides are still a problem. Engine efficiency about equals a diesel, about 35%. The hydrogen is stored in a tank that is rated at 240 atmospheres (240 bars). The range is only 62 miles. Ford does not give the price of the P2000, but it should be inexpensive given that all of the components are rather ordinary.

hydrogen carHonda has introduced the FCX, a car utilizing a fuel cell instead of an ICE. [3] This gives an overall efficiency of 45%. A fuel cell turns hydrogen into electricity which drives the wheels through electric motors. The hydrogen is stored in carbon fiber tanks at 333 bars. This gives the FCX a range of 150 miles. The fuel cells provide only the average power. Super capacitors provide extra power during acceleration and hill climbing. The tanks, the fuel cell, the super capacitors, etc. take up 4 times more space compared to a conventional design. There is not much room left for passengers and cargo. The FCX costs 3 million dollars, but Honda leases them for $500 per month to the state of California.

The engineers at Honda have also provided a solar powered hydrogen source. On sunny days in California it produces 16 liters per day. The tanks of the FCX holds 156 liters. The solar powered hydrogen source can move one FCX 16 miles each day.

Modern18 wheel semi-trucks are a formidable piece of engineering. The durable diesel engines can develop 500 horsepower continuously, and they achieve 35% efficiency. They can haul 80,000 pound loads at high speeds over mountains. Carbon fiber and aluminum are used to reduce weight. Designing a hydrogen powered replacement would be a very difficult project. Trucks need a lot of power all the time while cars need a lot of power only during short bursts of acceleration. Most of the time, cars need only a low power engine. The Honda FCX exploits that fact.

The diesel engine could be replaced by a hydrogen internal combustion engine. At 35% efficiency, there would no gain in fuel economy. The Bossel and Eliasson (B&E) section of this website discusses the problem of hydrogen storage in detail.

A fuel cell capable of developing the equivalent 500 horsepower of electrical power would cost millions of dollars. Improving overall efficiency from 35% to 45% hardly seems worth it.

Hydrogen Powered Airplanes

This is an artist's rendering of a hydrogen powered version of the A310 Airbus. It is also called the "Cryoplane" because of the very visible cryogenic hydrogen tank located above the passengers. Cryogenic hydrogen is the only possibility for aircraft as high pressure tanks would be too heavy. The physical properties of liquid hydrogen determine the appearance of the Cryoplane. Liquid hydrogen occupies 4.2 times the volume of jet fuel for the same energy which means that the tanks have to be huge. Jet fuel weighs 2.9 times more than liquid hydrogen for the same energy. The reduced weight partly compensates for the increased aerodynamic drag of the tanks. The Cryoplane would have less range and speed than the A310 Airbus. Whatever energy source is used, 30% will be lost in hydrogen liquefaction.

Boeing has also studied the feasibility of a hydrogen powered passenger plane. [4] The Boeing study explorers different tank configurations. They also mention the engineering challenge of designing a vacuum insulated tank of the required size and lightness.

Hydrogen Powered Rockets

The second stage of the Saturn 5 rocket that took 3 men to the moon used liquid hydrogen. A vehicle that can go directly to orbit has always been the dream of space travel. The X-33, now canceled, was designed to do that. Liquid hydrogen is the only fuel light enough and energetic enough to do the job. The X-33 had liquid hydrogen tanks with very little insulation resulting in rapid hydrogen loss. This is only a small problem because the tanks can be topped off just before launch. Travel time from earth to orbit is only a few minutes and so high hydrogen losses are tolerable.

[1] A Magazine article about the Ford P2000 may be viewed here.

[3] http://www.canadiandriver.com/articles/rr/03fcx.htm Canadian Driver reviews the Honda hydrogen powered car.

[4] http://www.pnl.gov/energy/hydrogen/presentations/daggett.pdf A feasibility study by Boeing. Includes the design of airports and schemes for generating and distributing hydrogen. A large 1.5 MB PDF file. Unfortunately, this URL disappeared.