The Dimplex DXRCF 5" desk fan offers the ultimate in portability.  Thanks to its built in lithium ion battery you can move it from desk to sideboard or room to room without any constraint.  It has 4 fan speed settings and will run for up to 15 hours (on lowest speed setting) on a single charge.  To re-charge, you simply just plug the cable (supplied) into a USB charging port.  Thanks to its DC motor it is powerful acheiving a maximum air flow of up to 4.2m/s, whilst giving the ability to 'dial' the speed of the fan down for super quiet operation. The direction of airflow can be directed vertically thanks to a 90 degree manually adjustable tilting head. The DXRCF comes with a 3 year guarantee when regsitered online.