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.

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.