Currently different technologies are studied to harvest energy from marine currents. As one of those, the Kobold turbine, a vertical axis marine current turbine, has been tested in the Strait of Messina, Italy since year 2001. Based on the positive results achieved by the working prototype, further plans were made aiming at applying the technology in developing countries. In a first actual application, a system for electrification of a remote village in Lombok, Indonesia, is planned to be installed.
For this application an electrical system was developed allowing for off-grid operation of the turbine and stable power supply to the consumers. The system comprises the generator-frequency converter system on the turbine and an onshore power station with grid-forming bi-directional battery inverters and battery banks for energy storage. An adapted turbine control scheme was evolved, reducing the turbine output power in case of coincidence of high tidal currents, high battery state of charge and low power consumption to prevent the system from overloading. The system was successfully tested in laboratory. Installation of the turbine in Indonesia is planned for the end of this year.
