A fluid-driven electricity generator includes a stator assembly and a rotor assembly. The stator assembly includes a stator core that includes a plurality of stator windings and one or more stator turbines connected to the stator core. The one or more stator turbines are configured to rotate in a first direction. The rotor assembly includes a plurality of permanent magnets that are substantially surrounded by the stator core. The rotor assembly also includes one or more rotor turbines connected to the plurality of permanent magnets. The one or more rotor turbines are configured to rotate in a second direction that is opposite the first direction.