Making small high-penetration renewable energy systems work — Scottish Island experience

The power systems on the Scottish islands of Eigg and Foula are presented. These systems were designed by Senergy Econnect Ltd and Wind and Sun Ltd, and make use of SMA´s Sunny Island battery inverter to generate a three-phase reference power supply. The renewable generation is sited at various locations around the network, and includes synchronous hydro generation, asynchronous hydro generation, inverter-connected wind turbines, and inverter connected PV arrays. Diesel generators are controlled automatically by the Sunny Island inverters to meet demand when renewable output is insufficient. Autonomous load control equipment allows surplus renewable power to be diverted to heating loads when it is available. The paper identifies the technologies which have made these systems achievable, outlines some issues associated with implementing such systems and highlights lessons learned.