I C engines

In a movie entitled The American President, the President's environmental adviser made the statement, "A car with an internal combustion engine is soon to be considered a collectors item." To that I say not so fast. IC engines may continue to be the norm.

What are the deficiencies of the current gasoline or diesel fueled IC engines? Mainly that they are polluting; exhausting both nitrogen oxide (NO_x) and carbon dioxide (CO₂). An over riding advantage of IC engines is they are 100 time less expensive than fuel cells. Some say that the fuel cell engines will be competitive by the year 2020 in terms of capital cost. Another concern about fuel cells is reliability. Fuel cell stacks can become fouled if the air and hydrogen intake gases are not very pure.

The thermal efficiency of I C engines is a function of their compression ratio. Modern engines are designed to have a compression ratio of 9 to 1. That is the gas-air mixture is compressed to nine times greater than when it enters cylinders when the piston is at the bottom of its stroke. Although higher compression ratios say 12 to 1 are more efficient engines, but as the compression ratio goes up the cylinders maximum temperatures are higher and produce greater amounts of NOx. This is an air polluting undesirable gas.

Diesel engines are designed with compression ratios around 16 to 1 and are thus more efficient than gasoline engines. But they are more polluting. In California a three piston Diesel engine is more efficient then the current hybrid engines, but Diesel auto cars are not allowed to be sold in that state. This is a big mistakes in my opinion.

Hydrogen Fueled IC Engines

It is possible to fuel IC engines with hydrogen and alleviate many of the problems cited for the fossil fueled engines. Let's assume that the supply problem of fossil fuels goes away when hydrogen is supplied by nuclear power systems. Now the pollution problem also is largely mitigated, and we gain an alternate fuel supply. Of course, there are delivery problems with hydrogen such as transporting it and the need for high pressure refueling stations. Hydrogen is liquid at about 27 kelvin (410 F below zero), so there is a loss of energy in condensing the hydrogen if it is to be stored as a liquid, as BMW does in their demonstration vehicle. The other prototype hydrogen vehicles (engines and fuel cells) store the hydrogen at a high pressure (3,600 to 5,000 psi, with plans to consider 10,000 psi in the future).

A hydrogen fueled IC engine produces an exhaust stream consisting of only water vapor, nitrogen, and controllable amounts of NOx. There are only trace amounts of unburned hydrocarbons or CO₂ in the exhaust, which comes from oil slipping by the piston rings. Since hydrogen promotes stable combustion at learner combustion ratios than other fuels, the IC engine can operate at temperatures below where thermal-NOx formation occurs, thereby providing inherently low NOx emissions, even before post-combustion cleanup.

Examples of hydrogen fueled I C engines

BMW, Ford, Mazda have all demonstrated hydrogen fueled I C engine autos. For example, on September 28, 2003, Ford issued the following press release.

Ford prepares fleet of hydrogen cars

Read in part:

SONMA, CALIFORNIA: Ford Motor CO is preparing a fleet of ordinary vehicles powered by pure hydrogen gas instead of liquid gasoline. They will be sold to government agencies for on road testing beginning in 2005.

At the Challenge Bibendum , an exposition of developing power trains, Ford showed two Focus automobiles modified to burn hydrogen. The early test cars confirm fuel use of about the equivalent of 40-45 miles per gallon.

Comparison of fuel efficiencies of Fuel Cell and I C Engines both using Hydrogen.

Many articles written by various authors assume that fuel cell engines get twice the amount of work out of using hydrogen as the fuel. For example Matthew Wald of the New York Times in an article termed "Promising method to produce hydrogen," stated that fuel cells, which work without burning get twice as much work out of each unit of fuel.

This is not true. A paper written by two scientists at Sandia National Laboratory showed the efficiencies of two hybrid engine systems, one using fuel cells and the other using an I C engine. The efficiency of the hybrid auto fuel cell engine was 48%, and the I C engine 38%. In other words the I C engine efficiency is within 80% of the fuel cell system.

To me this means that the efficiency advantage of fuel cell engines, currently being 100 time more expensive than I C engines, probably will never over come their cost disadvantage

Epilogue

The I C hydrogen fueled Ford autos are now being tested as of this writing and they appear to functioning quite well. This work of the automakers in demonstrating hydrogen fueled vehicles with I C engines is very significant. It shows that even if fuel cells remain too expensive, the IC engine can be produced at a reasonable cost as experienced in present day vehicles.

We really need to get on with hydrogen supplied by nuclear power plants. In the mean time we will have to resort to the current practice of reforming our diminishing natural gas supply to get pure hydrogen.

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