More recently Marlec has diversified into water current turbines -- another renewable energy technology which has great potential in rural Africa and South America, especially along the tributaries and upper reaches of the Nile and Amazon rivers. The operating principles of water current turbines are very similar to those of wind turbines, but they can operate at much lower stream velocities, as the density of water is roughly 800 times the density of air -- and power is proportional to density. Water turbines, therefore, have cut-in water speeds around 0.4 m/s, and they furl at around 1.5 m/s -- about half the cut-in speed of a typical wind turbine.
A novel application for small battery-charging wind turbines in Mauritania, west Africa, is reported by British manufacturer Marlec Engineering Company of Corby in Northamptonshire. The facility uses two 0.9 metre diameter rotors which power a central battery charging facility. Villagers can take their batteries to the charging station for "refuelling" for a small fee and then retrieve them for use for their domestic appliances. Other uses for the small rotors range from powering navigation beacons and small boats to providing emergency relief power for Antarctic expeditions.