Standard log-capture differentials as performance metrics for deepwater wave power generation

Abstract

As a support to performance assessment of deepwater wave energy converters, this work quantifies susceptibility of output power to short duration variations, independent of source wave statistics. Introduced as ς-metrics, the quantified measures may be a basis for technology comparisons, with possible convergence to a choice for implementation. The metrics further allow comparison between different versions of a specific converter technology, thereby helping in design revision and refinement.With power conversion represented in terms of a technology specific capture width function, the log-capture differential is defined relative to a hypothetical benchmark characterised by negligible power variability. Root-mean-square aggregation of the differential further leads to standard log-capture differentials as site independent ς-metrics for a capture-and-conversion mechanism.Study results are included in three phases. First, three established wave energy conversion technologies are analysed at respective power maximums, so as to illustrate applicability of log-capture differential and ς-metrics. Next, the metrics are analysed at fractional output power to realise converter performance at reduced variability. Finally for a given marine environment, ς-metrics are shown to be useful in projection of output power variability across technologies, together with the mean output power as fraction of rated maximum.