Abstract: An energy extraction system located at an off-index run location of a fluid circulation system for harvesting energy in a moving fluid in a conduit, the energy extraction system that includes at least one turbine assembly that includes a housing and a plurality of discs to harvest kinetic energy from the moving fluid, an inlet that receives and directs the moving fluid from the fluid conduit into the turbine housing to drive the plurality of discs and an outlet that returns the moving fluid from the turbine housing to the fluid conduit. The plurality of discs may include an outlet aperture that maximizes a length of a spiral path of contact between the moving fluid and a disc.