Indonesia has abundant of renewable sources of energy, among others: geothermal, solar, water, wind and marine therefore the promotion of the utilization of the renewable and sustainable energy is urgent. Since 2006 Indonesian Hydrodynamic Laboratory (IHL) BPPT has conducted research and developed a technology converts the ocean energy resources into electricity, the kinetic energy of marine current and the potential energy of wave. The prototype of marine current turbine, 2 kW and 10 kW respectively, had been installed in Larantuka Strait in 2010 and 2011 (http://www.youtube.com/user/erw4ndi). Since mostly the maximum speed of the marine current of many straits in Indonesia are in order 1.0 - 2.0 m/s, we developed the turbine prototype that can convert not only the kinetic energy of marine current but also the potential energy of the wave, called as wave-current rotor turbine, in 2013. The current usually mixes with wave height with order 0.4 - 0.8 m. A 2 kW prototype was installed under Suramadu (Surabaya - Madura) Bridge close to pier no. 56. The prototype showed a good performance especially in converting the kinetic energy of marine current. The research was continued in 2014-2016 under Ministry of Research and Technology (INSINAS RISTEK) budget scheme. Some innovations have been done to improve the performance of turbines.

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This paper is the second report that describes the capability of projected light distribution method to measure the diffraction waves generated by a ship operating in regular incident waves. In this method the waves are projected onto a screen as light distribution images and the images are recorded using a CCD Camera. In order to obtain diffraction waves, experiments were divided into two steps. Firstly, incident waves were measured. Secondly, the combination between incident waves with diffraction waves around a ship model was measured. The diffraction waves can then be obtained by subtracting incident wave images from combined one. The Kochin function was obtained using the same method as explained in the previous paper6). The results are evaluated by making some transverse cuts on the image data in the y-direction (transverse cut). The obtained Kochin functions are compared with the longitudinal cut results based on Ohkusu method, and also with theoretical results based on slender body theory. Using the results of Kochin Function, the wave pattern are recalculated and they are compared with the results of measurement using super sonic wave height meters.