It's no wonder inventors are racing to develop the best type of engine to power tomorrow's fleet of hybrids as automakers rush to get enviro-friendly cars on the road and consumers are tempted by a new $7,500 tax incentive being offered for buying one. But it's not only new inventions that are vying for a piece of the action: Microsoft co-founder Bill Gates, former Microsoft chief technology officer Nathan Myhrvold, and other entrepreneurs are attempting to put a new face on technology that's been kicking around for more than a century—an electromagnetic engine that turns mechanical into electrical energy.

The U.S. Patent and Trademark Office last week published a patent application describing an internal combustion engine that "converts mechanical energy of a piston to and from electrical energy during each piston cycle" submitted in October 2007 by Searette LLC, part of Intellectual Ventures, a Bellevue, Wash., company launched in 2000 to buy and license patents. Gates, who was still Microsoft's chief software architect at the time the patent was filed, is listed as one of 10 inventors on the application.

The patent app outlines several different options for configuring such an electromagnetic engine. Among them: using internal combustion of some sort of fuel (which the patent application refers to as a "reactant") to move a piston equipped with a magnet to generate electric current, or using electrical current (supplied by a battery or some other power source) to move the magnet (as well as the piston), or both. As Fast Company puts it, this is possibly a blueprint for a "hybrid engine without the need for two discrete drivetrains, as with today's hybrids."

Critics say Searate's proposed electromagnetic combustion engine is nothing new. The patent describes a conventional internal combustion engine with coils wrapped around the cylinder liners and a magnet on the bottom of the piston to react with this coil and move the piston during the engine's other three strokes (intake, compression, and exhaust), so that the engine doesn't lose too much energy while it's powering the car's drivetrain, says inventor Michael Walden, who in the 1970s designed, built, and demonstrated the first fully self-powered aircraft to use an electrokinetic, silent-field propulsion system. (The propulsion system works "like one of those room air ionizers—but a lot stronger," he adds.)

It's "not an efficient way they are talking about," he says. "How much energy are they going to use pushing that magnet through the coil?"

An engine built according to the configuration described in the patent application might require more gas to function (a definite no-no these days) than a normal combustion engine or it might include an external power source that adds more weight to vehicle, Walden says. He also notes that the patent application doesn't state how the engine would keep the relatively fragile magnetic materials cool or intact during the piston movement.

The invention of a type of electromagnetic piston engine that's far afield from the information technology that helped Gates and his colleagues make their name (not to mention their fortune) lends some ammunition to charges that Intellectual Ventures is little more than a "patent troll." A patent troll is a company that makes money by licensing the patents it buys (rather than offering its own products and service) and by suing those who infringe upon its patents. Indeed, the company (which is only nine years old) claims to own more than 20,000 patents.

"The situation with Intellectual Ventures is that nobody's quite sure what they're up to," says Ron Laurie, managing director of Inflexion Point Strategy, LLC, a Palo Alto, Calif. firm specializing in advising companies during mergers and acquisitions.

But Laurie points out that Intellectual Ventures has yet to file a lawsuit to protect any of its patents and that the company's founders have a strong track record of inventing important technologies.* "Within Intellectual Ventures there are actual research and development groups," he says, adding that to be a true patent troll, a company has to be a "non-practicing entity" (NPE). Laurie adds, "They're clearly more than an NPE."

Image of Bill Gates courtesy of Jose Gnudista, via Wikimedia Commons

*Correction (4/16/09): This blog originally stated that Bill Gates invented Windows. Rather, he was instrumental in bringing Windows to market.