Comparative analysis of winch-based wave energy converters

Sammanfattning: Renewable energy sources are probably the future of the mankind. The main points advocating wave energy in particular include its huge potential, low environmental impact and availability around the globe. In order to harvest that energy, however, engineers have to overcome, among others, the corrosive sea environment and the unpredictable storms as well as secure funding for research and development. A lot of effort has been put into building and testing WECs after the oil crisis in the 1970s and is now being used as a starting point to create the modern alternatives to fossil fuels. The purpose of this thesis is to analyze the available winch-based wave energy converters (WECs) in comparison with other devices of similar scale, such as linear and hydraulic point absorber WECs. First, an introduction to the physics and geography of waves is presented, covering wave formation and particle motion. Then a number of designs, their working principles and history are described – oscillating water columns, floating or bottom-fixed devices using translational or rotational motion. Environmental and economic effects in the long term have to be taken into account. Narrowing down to point absorbers, different power take-off systems are available – linear, hydraulic or winch-based, each of them with specific advantages and disadvantages. Focusing on winch-based systems, three different concepts are described – the counter weight, the counter buoy and the Lifesaver devices. A set of comparison criteria, covering technical, economic and environmental aspects of the device performance, is prepared. Using this set, the three concepts are compared and results are analyzed.