Page - 135 - in Clean Water Using Solar and Wind - Outside the Power Grid

Handling variable production 135 electrolysers function in slightly different ways, mainly due to the different type of electrolyte material involved. Hydrogen Oxygen Cathode Anode Power supply - + H+H+ Figure 10.3 Principal electrolysis of water. Modified from Larminie and Dicks (2003). When an electric current is passing through the water, electrons from the electric current cause an oxidation-reduction reaction. The electrons flow through an external circuit and the hydrogen ions selectively move across the membrane to the cathode. At one electrode, the cathode, electrons pass into the solution and cause a reduction. At the other electrode, the anode, electrons leave the solution completing the circuit, and cause an oxidation. To carry out electrolysis the solution must conduct electric current. Pure water is a very poor conductor, so an electrolyte is added to enhance the water’s conductivity. In most places, however, there are enough minerals in the water that the ionic strength or conductivity of the water is great enough for electrolysis. One problem with adding electrolytes is that they can electrolyse more easily than water. At the cathode (the negative electrode), water dissociates into H+ ions and OH− ions. The H+ ions are attracted to the cathode and are converted (reduced) to a hydrogen atom: H+ + e− → H Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user