a b s t r a c tIn this paper, technical and economical studies conducted on the SEAREV Wave Energy Converter (WEC) are presented. This technology was first proposed in 2002 with the aim of addressing critical challenges in wave energy conversion. It consists of a closed floating hull in which a heavy pendulum oscillates. The controlled relative motion of the pendulum is used to produce electricity.The SEAREV WEC was developed over twelve years. Through the development process, three main generations of the technology were defined and studied in detail. They are presented in the paper, showing how each new generation brought significant improvements over the previous generation with respect to production and costs.In 2013, an economical model for wave energy farms was developed to assess the viability and competitiveness of the SEAREV technology. Although results show that the SEAREV technology is a sound technical solution, the cost of energy projection is still too high to allow direct access to mass electricity market in European countries in the short term.Finally, in light of the lessons learned from the SEAREV WEC development, the need for innovative technologies with higher technology performance level (TPL) or alternative markets is discussed in the context of wave energy.

Abstract. This paper deals with a new concept for the conversion of far-offshore wind energy into sustainable fuel. It relies on autonomous sailing energy ships and manned support tankers. Energy ships are wind-propelled ships that generate electricity using water turbines attached underneath their hull. Since energy ships are not grid-connected, they include onboard power-to-X plants for storage of the produced energy. In the present work, the energy vector X is methanol. In the first part of this study (Babarit et al., 2020), an energy ship design has been proposed and its energy performance has been assessed. In this second part, the aim is to estimate the energy and economic performance of such system. In collaboration with ocean engineering, marine renewable energy and wind-assisted propulsion’s experts, the energy ship design of the first part has been revised and updated. Based on this new design, a complete FARWIND energy system is proposed, and its costs (CAPEX and OPEX) are estimated. Results of the models show (i) that this FARWIND system could produce approximately 70,000 tonnes of methanol per annum (approximately 400 GWh per annum of chemical energy) at a cost in the range 1.2 to 3.6 €/kg, (ii) that this cost may be comparable to that of methanol produced by offshore wind farms in the long term, and (iii) that FARWIND-produced methanol (and offshore wind farms-produced methanol) could compete with gasoline on the EU transportation fuel market in the long term.

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Abstract. This paper deals with a new concept for the conversion of far-offshore wind energy into sustainable fuel. It relies on autonomous sailing energy ships and manned support tankers. Energy ships are wind-propelled ships that generate electricity using water turbines attached underneath their hull. Since energy ships are not grid-connected, they include onboard power-to-X plants for storage of the produced energy. In the present work, the energy vector X is methanol. In the first part of this study, an energy ship design was proposed, and its energy performance was assessed. In this second part, the aim is to update the energy and economic performance of such a system based on design progression. In collaboration with ocean engineering, marine renewable energy and wind-assisted propulsion experts, the energy ship design of the first part has been revised. Based on this new design, a complete FARWIND energy system is proposed, and its costs (CAPEX and OPEX) are estimated. Results of the models show (i) that this FARWIND system could produce approximately 70 000 t of methanol per annum (approximately 400 GWh per annum of chemical energy) at a cost in the range EUR 1.2 to 3.6/kg, (ii) that this cost may be comparable to that of methanol produced by offshore wind farms in the long term and (iii) that FARWIND-produced methanol (and methanol produced by offshore wind farms) could compete with gasoline on the EU transportation fuel market in the long term.

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