Porsche has already built three plug-in hybrids, but the German carmaker hasn't yet shown much enthusiasm for pure electric cars.

Various rumors of different all-electric Porsche models have been shot down by executives in public comments.

Yet this may turn out to be a case of Porsche protesting too much.

RELATED: New, Smaller Porsche Four-Door Sedan To Be Electric Only: Rumor

A series of patent applications filed by Porsche in the U.S., Germany, and China include designs for both battery-electric and hydrogen fuel-cell powertrains.

These powertrains are intended for the sports-car maker's upcoming mid-size luxury sedan, according to Autocar.

Nicknamed the "Pajun"--short for "Panamera Junior"--the new sedan is expected to go on sale in 2017 or 2018.

2015 Porsche Panamera

2015 Porsche Panamera

It will be close in size to the BMW 5 Series, the report says, making the electric version a natural rival for the Tesla Model S.

While the basic platform would be shared with gasoline and diesel versions of the Pajun, the patent applications show that it would be extensively modified to accommodate battery or fuel-cell powertrains.

In the battery-electric version, the battery pack will be mounted underneath the floor--helping to provide extra structural rigidity.

ALSO SEE: Audi, BMW, Mercedes, Porsche Electric Cars To Target Tesla Model S (Plug-In Hybrids Too) (Dec 2014)

Both versions will use rear-mounted electric motors--one for each wheel--attached so that they help stiffen the back end of the chassis as well.

The fuel-cell version will feature a stack mounted under the "hood" at the front of the car, according to the documents.

With its high-end product line and emphasis on performance, Porsche seems particularly well suited among the luxury establishment to take on Tesla with an all-electric model.

2015 Porsche Panamera

2015 Porsche Panamera

This isn't the first time an all-electric version of the Pajun has been discussed.

Autocar reported on that model back in December, but Porsche development boss Wolfgang Hatz flatly denied its existence in a subsequent interview.

There have also been separate rumors of a small four-door all-electric model to be called the 717.

MORE: Why Nothing Competes With Tesla Today, Plug-In Hybrids Included

Also not confirmed by Porsche, that model would reportedly be electric only, and could feature sportier, coupe-like styling.

In a presentation two months ago, Volkswagen Group technical chief Ulrich Hackenberg provided what many have taken to be a hint at Porsche's green-car plans.

A chart showing future battery-electric and fuel-cell models for each VW Group brand included one of each for Porsche.

None of this confirms that Porsche will build battery or fuel-cell cars, but the patent applications appear to take the two cars out of the realm of rumor--and at least into design.

Stay tuned.


Follow GreenCarReports on Facebook, Twitter, and Google+.