NOVELTY - The power generating device comprises a first fluid reservoir containing a first fluid, a second fluid reservoir containing a second fluid, forward osmosis cells, and porous media. The second fluid has a higher concentration (4 M) of solute than the first fluid. The forward osmosis cell comprises a semi-permeable membrane. The semi-permeable membrane divides the cell into a first compartment and a second compartment. The first and second compartments are present in fluid communication with the first and second fluid reservoirs respectively.    USE - The power generating device is useful in a water desalination device (claimed), as portable power sources for electronic devices, home electrical appliance and lighting, and for a supplementary power plant to supply additional power that complements a main power plant such as a hydropower plant and a nuclear plant.    ADVANTAGE - The power generating device is economical and easy to maintain, and exhibits higher power output and excellent performance.    DETAILED DESCRIPTION - The power generating device comprises a first fluid reservoir containing a first fluid, a second fluid reservoir containing a second fluid, forward osmosis cells, and porous media. The second fluid has a higher concentration (4 M) of solute than the first fluid. The forward osmosis cell comprises a semi-permeable membrane. The semi-permeable membrane divides the cell into a first compartment and a second compartment. The first and second compartments are present in fluid communication with the first and second fluid reservoirs respectively. The porous media is arranged between the first fluid reservoir and the first compartment, is present in fluid communication with the first fluid reservoir and the first compartment and in fluid communication with the second fluid reservoir and the second compartment, and comprise a dielectric material that is glass. A mean diameter of pores in the porous medium is 10 nm to 10 mu m. The pores form micro-channels. A length of the microchannels is 1 mm to 5 cm. The semi-permeable membrane is a hollow fiber membrane and a spiral bound membrane. The forward osmosis cells are connected in parallel to generate a higher water flow rate. The porous media is arranged between the fluid reservoir and the forward osmosis cell in parallel to generate a higher current flow and in series to generate a higher potential across the porous media. INDEPENDENT CLAIMS are included for:    (1) a water desalination device;    (2) a method of generating power by forward osmosis; and    (3) a method of water desalination.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a self-sustainable electro-kinetic power generation unit.