The Sum of the Parts

One of the best indicators of the increased emphasis on new energy technology is how difficult it has become to monitor even a fraction of what's going on. This article from MIT's Technology Review is a perfect example. It came out in April, but it's taken me this long to get to it and consider its implications. The innovation in question is a novel auto engine design that boasts hybrid-like efficiency by capitalizing on ethanol's combustion properties, to allow greatly increased engine pressures with gasoline. This is really clever, and it could have sweeping consequences, if it worked out.

Compare gasoline and diesel engines. Although diesel fuel actually has a slightly higher energy content than gasoline, the bigger reason diesel cars go farther on a gallon is that their engines operate at pressures that would have a gasoline engine tearing itself apart from pre-detonation (a.k.a "knocking.") That extra pressure translates into higher thermal efficiency. The MIT engine apparently delivers the best of both worlds: diesel-like efficiency from cleaner gasoline fuel. The trick is injecting separately stored ethanol into the engine cylinders at key times, allowing much higher compression ratios from turbocharging, and smaller cylinders--and thus smaller, lighter and thriftier engines for the same output.

The author considers this system's requirement for delivering and storing ethanol separately as a big hurdle to overcome, and it could be, but part of that problem has already been solved. One of the biggest issues refiners have with adding ethanol to gasoline is that it forces them to ship sub-par gasoline through the long-distance pipelines, and then blend in the ethanol at distribution terminals close to the final point of sale. That's because ethanol creates serious problems in petroleum product pipelines, including corrosion and product contamination. This is the main reason most refiners opted for MTBE when they could, because it had none of these drawbacks. Instead, ethanol is shipped via rail and road, meeting up with gasoline only at the terminal.

So by the time MTBE phaseout is complete, most gas stations will have neat ethanol as close as the distribution terminal that supplies their gasoline and diesel. They'd still need to add an extra tank and pump--and protect it all from water contamination, but this is no different than the problems faced by dealers wishing to sell E85. Refiners, meanwhile, would save by eliminating the RBOB, as the pre-ethanol gasoline blend is called. That would relieve some of the inventory congestion that has contributed to higher prices and sporadic product outages.

What I find so appealing about this notion is that we're already blending ethanol into gasoline in large volumes, for environmental and political reasons. But if we can maximize the benefit from each component by separating them, this could simplify distribution and go a long way toward offsetting the high costs and meager energy benefits of our current grain-based fuel ethanol program. This idea will have to compete with many others, before it can reach the market, but it has a kind of engineering elegance you don't see every day.