Dimensioning the equipment of a wave farm: Energy storage and cables

Still largely untapped, wave energy may represent an important share in the energy mix of many countries in the future. However, the power fluctuations generated by most wave energy devices with little to no storage means, or without suitable control strategies, may cause power quality issues that must be solved before large wave energy farms are allowed to connect to a network. For instance, large power fluctuations may induce an excessive level of flicker in the distribution networks to which they are currently envisaged to be connected. Although storage appears to be a technically feasible solution, the minimum amount of storage required for a wave farm to become grid compliant with respect to typical flicker requirements is still unknown and is therefore investigated. This study constitutes the first part of this paper. Another issue, on which the second part of this paper focuses, concerns the optimal dimensioning of wave farm electrical components, which is traditionally performed assuming steady-state conditions (i.e., a constant current level), and is thus irrelevant in the case of wave farms outputting power fluctuations of significant amplitude. Hence, a second study, the results of which are presented in this paper, focuses on the minimum current rating for which a submarine cable may be safely operated without thermal overloading. Addressing both these issues is essential to the economic viability of a wave farm as the cost of both storage means and electrical components is highly dependent on their rating and may represent a significant percentage of the capital expenditure.