Polestar will take over part of Saab’s former car plant in Sweden to extend its R&D operations in Europe. The EV maker will conduct powertrain development for the Polestar 5, a Tesla Model S rival, and the Polestar 6 roadster at a 15,000-square-meter building in Trollhattan, Automotive News Europe sister publication Automobilwoche reported. Polestar will also test powertrains, electric motors and batteries for the upcoming models at the new R&D center. Polestar will rent the building from the city of Trollhattan, Automobilwoche said. The site was previously used for powertrain development by Saab and then by National Electric Vehicle Sweden…