Various embodiments of the present invention are directed toward a linear generator, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a reaction section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the reaction section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the reaction section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.