There’s Nothing Micro about Microturbines

The real trouble with microturbines is the nomenclature. Yes, there are other troubles to be sure. However, nobody out there seems to know their micro from their macro, and it has caused a lot of confusion. Its almost as bad as naming a 3.5-inch X 1.6-inch MP3 player the Nano.

The first few hits I get by typing “microturbine” into Google are Capstone, Ingersoll-Rand, and Elliott. The distributed energy and back-up power industries recognize the companies I’ve listed as microturbine manufacturers, but to a purist, there is not a single microturbine maker in the lot. Certainly these companies make small, terrestrial gas turbines, offspring of aerospace power plants. However, aside from being small in size and power output compared to conventional jet engines, there is nothing micro about them. Following the metric prefix index, perhaps we would all be less confused by the moniker deci-turbines to denote the characteristic turbine dimensions of roughly 10 centimeters to 1 meter.

Another micro prefix offender is the research team led by Professor Allen Epstein at MIT, working on tiny silicon-based gas turbines. This work, called the MIT Microengine Project, was recently featured in a Mechanical Engineering Magazine article, “The Little Engine”. These tiny energy generators are slated to compete against battery technology for portable electronics and personal power applications. While these gas turbines are certainly much smaller than their aero-derivative terrestrial cousins, they still aren’t microturbines. Perhaps the term milli-turbine would be preferable, given the rotor diameter of roughly five millimeters.

In my opinion, true microturbines would be power-generating systems that employ gas turbine principles at micrometer length scales. I know of no practical system that meets this requirement. On the contrary, just about every gas turbine out there smaller than a refrigerator that isn’t pushing around an airplane seems to be called a microturbine… No, I stand corrected; apparently micro turbines propel planes, too. Advanced Micro Turbines (AMT) makes small engines that drive RC aircraft, and (as you might have guessed by now) AMT calls their products “microtuburines”!