A micro-algae growing method employs a greenhouse having a transparent, double-pane roof structure and containing an open-top receptacle for a bed of aqueous micro-algae medium, which roof structure and receptacle are substantially coextensive and rectangular. A series of remotely controllable nozzles, capable of producing thin, sheet-like discharges, withdraw the aqueous liquid medium from subsurface regions along the length of the bed and discharge it into the overlying space, thus optimally exposing the medium to solar radiation passing through the roof structure and thereby promoting micro-algae growth. Ambient air, heated during passage through channels in the transparent roof structure, is used in a second greenhouse for lofting small droplets that comprise sprays of the concentrated micro-algae medium received from the first greenhouse, thus promoting evaporation of free water and cooperating in harvesting of micro-algae product.
