Facts faulty on hydrogen car story

As a geophysicist and resident of Moorpark, I read your July 27 article on hydrogen-fueled cars with an informed interest. Unfortunately, you appear to have made a common error among nonscientists regarding this subject.

You began your article with the following statement: "The answer to our fuel problem is all around us: hydrogen, contained in the water that covers more than 70 percent of the earth's surface." However, that seems to reveal a fundamental misunderstanding of physics.

In order to extract hydrogen from water- and the catalysts you mention later will not change this fact of nature- you must break apart the H2O molecules into their constituent elements, hydrogen and oxygen. This requires energy, and the classical way of doing this, known as electrolysis, is to pass a current through the water.

The energy that you put into this process is always going to be greater than or equal to the amount that you get out when you "burn" hydrogen and oxygen in a fuel cell to remake water. The energy recovered will actually always be less because of fundamental thermodynamic limits to efficiency.

The energy you need to break water up into hydrogen and oxygen must come from somewhere. Of course, these days that would most likely be from fossil fuels, so that solves none of our energy problems. The only way we can avoid fossil fuel consumption for this process is to use another source of energy, such as solar power, wind power and nuclear fission.

The main point about hydrogen that the public misunderstands is that it might be an effective way to store energy, much like a battery, but it is emphatically not a source of energy itself since hydrogen, uncombined with another element, rarely exists in large quantities on or in the Earth. Brian Schlottmann Moorpark