A team of MIT scientists has completed a study of using methanol as a gasoline substitute, and they’ve concluded that “methanol is a viable transportation fuel.”
Leslie Bromberg and Daniel R. Cohn of the MIT Energy Initiative spent more than a year exploring the advantages and disadvantages of using methanol in gasoline engines. They concluded that methanol offers both high flame speed and high octane when compared to gasoline. “These properties can increase the efficiency by 20-30% relative to standard port fuel injected gasoline engine by optimized use of existing engine components.” The research was sponsored by the Fuel Freedom Foundation.
The team did extensive testing with a four-cylinder engine completely powered by pure methanol – M100. They found methanol’s advantage to be associated with three of its properties:
- Lower combustion temperatures, which result in decreased heat transfer between the charge in the cylinder and the cylinder wall. This reflected a decreased temperature of combustion, the increased heat capacity of methanol and the increased heat of vaporization of methanol.
- Faster flame speeds, allowing more constant-volume (isochrhoric) combustion.
- Higher octane, which increases suppression of knock and thus enables improved performance and elimination of spark retard.
The conclusion: “Higher engine performance (mostly described as efficiency) can be achieved by intrinsic properties of the fuels with no changes to the operation of the vehicle.”
The team used Brake Mean Equivalent Pressure (BMEP) as a measure of torque produced by the engine. They found that even with no spark retard, methanol performed about 10 percent higher than gasoline, with or without the spark retard. “The improvement in efficiency in this case is both by the improved volumetric efficiency, as well as the elimination of the spark retard,” the report stated. “With no spark retard, the BMEP of the methanol powered engine is substantially improved over the gasoline engine.
The improvement in BMEP in the case of methanol is due to the cooler temperature, enabling slightly increased torques. In the case of higher rpm, the increase is substantial, about 10%. … The increased BMEP results in about 10% increase in both torque and power, at higher engine speeds.
Another factor adding to methanol’s improved performance is the higher compression ratio. “Higher compression ratios are possible with methanol, but not with gasoline (unless with very aggressive spark retard, thereby reducing efficiency.) Thus, increasing the compression ratio in a dedicated fuel vehicle will only operate at substantially reduced performance on gasoline.”
One more area in which methanol outperforms gasoline is in the release of particulate matter.
Methanol has distinct advantages when compared with heavier molecules such as gasoline and diesel that can readily form solid matter (particulate matter) as well as soluble organic fractions (SOF). Both the solid particular matter (in the form of soot) and the SOF formation process is facilitated by the heavy molecules and the aromatics in the fuel, and PAHs (polyromantic hydrocarbons) are created readily by some of the complex molecules in the hydrocarbon fuels under the combustion conditions. The PM emissions are substantial in the case of direct injection (both diesel and gasoline), with a much smaller PM generations in the case of port-fuel injected gasoline and natural gas.
Particulate matter, of course, has been found to be extremely toxic to health and to the environment. In particular, the smaller the particulate, the more likely it is to enter the lungs. Because methanol is such a relatively small molecule, it does not form the residual carbon compounds that have been implicated in air pollution.
In the case of methanol, with a simple molecule, formation of soot and SOF requires higher temperature and richer conditions. Both models and experiments using methanol and methanol blends have shown substantial reduction in particulate matter.
What is the problem with methanol, then? The main roadblock is that the Environmental Protection Agency has not approved its use in gasoline engines, even though it would substitute easily into our current infrastructure. This seems to be a holdover from the Depression Era, when methanol was feared as the deadly “wood alcohol.” It is dangerous when ingested, but no more dangerous than gasoline. In fact, small amounts of methanol are used to “denature” ethyl alcohol (corn alcohol) so people will not drink it.
Beyond that, methanol seems like an easy and economical substitute for foreign oil in our automobiles. As the authors conclude: “Methanol and ethanol could provide a near term, economically attractive alternative to oil-derived gasoline for light vehicles in the US. These alcohol fuels can be produced from shale gas on energy-based cost that is competitive with oil-derived gasoline. They can also be produced from various biomass feedstocks and waste.” In fact, the team is working with Research Triangle Institute of North Carolina and Columbia University to build a demonstration plant that can process 300,000 cubic feet of natural gas that can produce 1,500 gallons of methanol per day.
Methanol has been implemented in both China and the United States. It was used during a trial period in California in the 1980s and ’90s, successfully powering 15,000 cars. But as the MIT paper notes, that came during a time of “rapidly falling petroleum prices, which eliminates the economic incentive.” Also, methanol never had a strong advocacy, as ethanol has. “Methanol was then displaced by ethanol as oxygenate of choice in gasoline blends,” the study notes. “Nevertheless, these programs have demonstrated that methanol is a viable transportation fuel.”
At long last, the methanol revolution may be on the way.