GEM, The Ocean’s Kite, has been patented and the concept consists of a submerged floating body linked to the seabed by means of a tether. The main hull houses electrical equipment and auxiliary systems. Two turbines are installed outside the floating body and are exposed to the external currents.
Due to a relatively safe and easy self-orienting behaviour, GEM, The Ocean’s Kite, is a good candidate to solve some problems involved with oscillating and reversing streams, typical of tidal current. An additional advantage of its configuration is related to the possibility of avoiding the use of expensive submarine foundations on the seabed, because these are replaced with a flexible cable connected to a single mooring point. Releasing the anchorage cable allows the system to pop-up for easy maintenance. A special diffuser (shroud) has been designed to double the output power keeping the blade length small.
After several numerical investigations, a series of experimental tests on two different scaled models has been carried out in the towing tank of the Department of Industrial Engineering – Naval Division at the University of Naples. The models tested were completely instrumented so that a dynamic behaviour and the off-nominal working conditions were investigated.
The real scale prototype system of 100 kW, with 5 knots of water current speed, has been built and has been deployed nearby Venice in a very slow speed current of about 3 knots downscaling the power to 20 kW. This prototype has been built by a consortium of Venetian companies thanks also to a financial contribution of Veneto Regional Authority.
The real field tests have demonstrated the fully correspondence of the system behaviour with respect to what had already been measured on the 1:5 model during the test campaign in the naval towing tank. A full scale prototype of 200 kW at 2.5 m/s water current speed is being designed and will be deployed in the Strait of Messina to definitively assess all the performances of the system.
The Kobold Turbine
The “Kobold Turbine” has been developed since 1998 by ADAG Group of the Department of Industrial Engineering, University of Naples “Federico II”, in collaboration with “Ponte di Archimede international Spa”, a company that works in the field of research and development into alternative and renewable energy sources, specialising in the environmental aspects of this work.
The Kobold consists of a submerged vertical-axis turbine for exploitation of marine currents installed in the Strait of Messina, 150 metres off the coast of Ganzirri since 2002. The realization of the Enermar prototype has been financed by Ponte di Archimede Company, together with a 50% fund paid by the Sicilian Region Administration (Regione Siciliana), in the framework of European Union Structural Funds. This project has been disseminated among the developing countries in which the United Nations Industrial Development Organization (UNIDO) operates and the first three countries that expressed interest were the People's Republic of China, the Philippines, and Indonesia.
A joint-venture was created, under the auspices of UNIDO, between “Ponte di Archimede” and the Indonesian Walinusa Energy Corporation. A prototype is being built and will be placed on the Lomboc Island (the island immediately at east of Bali), where it could feed energy to a small village. The Indonesian plant will have blades length 7 m, (chord 0,4 m) and diameter 5 m (intercepted area 35 m2). The power could be about 120-150 kW. The Ponte di Archimede company has now transferred its assets to the Horcynus Orca Foundation with the aim to leverage on the experiences gained with Kobold and the local workforce in the area to create a centre of excellence in the marine energy space.
Sea waves are one of the most interesting and well distributed renewable energy sources in the world. At the current state of the art, all the existing sea wave energy conversion systems are designed to operate offshore, mainly in the oceans where the waves height is definitely high. In the Mediterranean Sea, waves are generally low, except under particular meteorological conditions. Thus, it is necessary to develop devices that can exploit other properties of the waves instead of their height, like wave slopes. The mechanical conversion system, called ISWEC, that will be used for the development of the project has been analysed by Politecnico di Torino and results show that the system possesses good potential for energy conversion.
ISWEC device is composed mainly of a floating body with a slack mooring to the seabed. The waves tilt the buoy with a rocking motion that is transmitted to the gyroscopic system inside the buoy.
Full scale ISWEC drawing (CAD) with two gyros
The conversion device to be built will have the following features:
Trials at various levels have been carried out: in the first phase, a set of "dry tests" has been done on a controlled position mobile platform; in the second phase, a series of tests have been performed in the INSEAN wave tank, with suitably generated and controlled waves.
Finally the system has been placed and tested on Pantelleria Island for the real sea tests. Further tests will be carried out in order to develop and tune optimized control algorithms. Currently the real scale prototype is under development and it is going to be launched.
Last june, Enel Green Power, a world leader in renewable energy generation, and 40South Energy, a group of highly innovative companies operating in the field of marine energy at the international level, began the installation and commissioning of a first R115 generator, with a nominal capacity of 150 kW and installed capacity of about 100 kW, generating electricity from the energy produced by the waves of the sea around Tuscany. The 40South Energy wave energy converters comprise one fully submerged section – called Lower Member – and energy interceptors – called Upper Members – at different depths. The relative motion of the Lower and Upper members is converted directly into electricity on the machine. The depth of the machines is controlled automatically to respond dynamically to changing sea conditions. This ability to vary depth dynamically and automatically in response to any changes in the state of the sea also guarantees that the same machines can operate across the globe. Whether the installation is in Orkney, Tuscany, or Oregon, the machine will work within the same operational limits.
The new generator ensures full integration into the marine environment and ease of maintenance, and according to initial estimates will enable the generation of about 220 MWh per year, enough to meet the needs of over 80 households.
40South Energy has handled the installation and commissioning of the machine, which began to produce the first electricity. Partners will continue assessing the performance of the system in the marine environment during 2015 in light of installing the machine and connecting to the network on the Elba Island during second half of the year. 40South Energy, in its continuous efforts to strive for utilizing the marine energy resources, is also developing a 50 kW solution to install near shore and depth of 8 m within 200 m from the costal line.