Marine testing of a small-scale prototype of the FLASC offshore energy storage system

Abstract

With increasing implementation of offshore wind, power the need for offshore-based energy storage technologies is also expected to grow. This is particularly relevant for floating wind, which will tend to be a late-comer to the grid, and face more significant integration challenges. The present work focusses on such an offshore-tailored solution, relying on a hydro-pneumatic liquid piston concept. A small-scale experimental set-up was installed at a sheltered location in the central Mediterranean island of Malta. The system operated for over a year, undergoing hundreds of charging-discharging cycles. Results from this experimental campaign show that the cycle performance is favorable, with a consistently high thermal efficiency (> 93%) across the year. A numerical tool developed to predict the performance of the proposed storage system is validated against this experimental data. A sensitivity analysis of the heat transfer coefficients, which are particularly difficult to accurately predict numerically, indicates that variations of up to ± 50% in these coefficients translate into very minimal changes in the predicted cycle performance. Overall, the numerical tool was shown to be in good agreement with the experimental data, and is generally more conservative when it comes to predicting the efficiency.