Abstract: There is described a battery separator comprising: a porous membrane (preferably of a cellulose film) having a mean thickness less than about 25 microns (preferably 15 microns) and optionally with one or more of the following properties: a) a tensile strength when dry (measured in the transverse direction of the membrane web) of greater than about 120 Nmm−2; b) a wet ionic resistance of less than about 20 m&OHgr;.cm2; c) a membrane degree of polymerisation (D.P.) of greater than 350 chain units after being immersed for four hours in a bath of sodium hydroxide and hydrogen peroxide; and/or a) a tensile strength when dry (measured in the machine direction of the membrane web) of greater than about 200 Nmm−2. Preferred membranes comprise biopolymeric films, such as films derived from cellulose and/or polylactic acid, more preferably a regenerated cellulosic film made using NMMO as regeneration liquid.

Abstract: In a vertical axis wind generator incorporating a circular turbine supported by an uppermost part of an upstanding support, a stator surrounding and coaxial with the turbine comprises an upper annular body positioned adjacent and or above the upper end of the turbine and having an uppermost surface which over at least a part of its radial width is inclined downwardly towards the vertical axis, a lower annular body positioned adjacent and/or below the lower end of the turbine and, extending lengthwise between the annular bodies, a plurality of circumferentially spaced blades define the venturi. Preferably, the undersurface of the lower annular body over at least a part of its radial width is inclined upwardly towards the vertical axis. The wind energy convertor will convert into mechanical energy the energy of a wind blowing in any direction and is capable of self-starting, irrespective of the direction of the wind.