Power variability of tidal-stream energy and implications for electricity supply

Research output: Contribution to journalArticle

  • External authors:
  • Matt Lewis
  • James McNaughton
  • Concha Márquez-Dominguez
  • Grazia Todeschini
  • Michael Togneri
  • Ian Masters
  • Matthew Allmark
  • Simon Neill
  • Alice Goward-Brown
  • Peter Robins


Temporal variability in renewable energy presents a major challenge for electrical grid systems. Tides are considered predictable due to their regular periodicity; however, the persistence and quality of tidal-stream generated electricity is unknown. This paper is the first study that attempts to address this knowledge gap through direct measurements of rotor-shaft power and shore-side voltage from a 1 MW, rated at grid-connection, tidal turbine (Orkney Islands, UK). Tidal asymmetry in turbulence parameters, flow speed and power variability were observed. Variability in the power at 0.5 Hz, associated with the 10-min running mean, was low (standard deviation 10–12% of rated power), with lower variability associated with higher flow speed and reduced turbulence intensity. Variability of shore-side measured voltage was well within acceptable levels (∼0.3% at 0.5 Hz). Variability in turbine power had <1% difference in energy yield calculation, even with a skewed power variability distribution. Finally, using a “t-location” distribution of observed fine-scale power variability, in combination with an idealised power curve, a synthetic power variability model reliably downscaled 30 min tidal velocity simulations to power at 0.5 Hz (R2 = 85% and ∼14% error). Therefore, the predictability and quality of tidal-stream energy was high and may be undervalued in a future, high-penetration renewable energy, electricity grid.

Bibliographical metadata

Original languageEnglish
Pages (from-to)1061-1074
Number of pages14
Early online date1 Jul 2019
Publication statusPublished - 15 Sep 2019