NOVELTY - The process comprises a fiber bundle (29) placed inside the casing of an electrochemical cell module (28) with a mandrel (25) extending through the casing. A tube sheet (26) is sealed by 'O' rings (27) with positive (31) and negative (32) electrodes connected to plates (33,34) to form positive and negative terminals. The casing has inlet (36) and outlet (37) to the lumen side of the cells and inlet (25) and outlet (39) to the shell side of the cells.    USE - For the construction of electrochemical cells such as batteries (rechargeable and non-rechargeable) fuel cells and other electrochemical reaction cells.    ADVANTAGE - The fibrous geometry of the cells provides an extremely high surface area to volume ratio when multitude of small fibers are packed into a given volume. Since the fibrous electrode is composed of one or more fibers having an outer diameter from about 10 mum to 10 mm, the surface area is very high. The high surface area available to electrodes translates into a higher number of active sites participating in the electrochemical reaction, hence giving rise to higher energy density batteries. A small amount of the electrocatalyst can be impregnated, coated or extruded on a fibrous substrate to form an electrode. This may be done for e.g. by plasma deposition of one or few atomic layer of the electrocatalyst on the fibrous electrode, resulting in lower material weight and cost.    DETAILED DESCRIPTION - The electrodes are formed from electrically conductive fibers in contact or coated with an electrocatalyst. The membrane separator has a bore side, the shell side and the lumen. The electrodes form the positive electrode and the negative electrodes. There is a feed inlet and a feed outlet at the electrodes for passing a gaseous or liquid feed. The feed is passed from the shell side or through the lumen of the bore side of the membrane separator. The fibrous electrochemical cells are placed in a casing and the shell or bore side of the electrochemical fibers are sealed and isolated. The electrodes are connected to plates to form the positive and negative terminals and the feed components are reacted on the electrodes to generate electrical energy.    DESCRIPTION OF DRAWING(S) - The figure shows the side view of the electrochemical cell module.    Mandrel (25)    Tube sheet (26)    'O' rings (27)    Electrochemical cell module (28)    Fiber bundle (29)    Positive electrode (31)    Negative electrode (32)    Plates (33,34)    Casing inlets (25,36)    Casing outlets (37,39)