TY - JOUR

T1 - Power variability of tidal-stream energy and implications for electricity supply

AU - Lewis, Matt

AU - McNaughton, James

AU - Márquez-Dominguez, Concha

AU - Todeschini, Grazia

AU - Togneri, Michael

AU - Masters, Ian

AU - Allmark, Matthew

AU - Stallard, Tim

AU - Neill, Simon

AU - Goward Brown, Alice

AU - Robins, Peter

PY - 2019/9/15

Y1 - 2019/9/15

N2 - 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 may be undervalued in a future, high-penetration renewable energy, electricity grid.

AB - 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 may be undervalued in a future, high-penetration renewable energy, electricity grid.

UR - https://ars.els-cdn.com/content/image/1-s2.0-S0360544219313192-mmc1.xml

U2 - 10.1016/j.energy.2019.06.181

DO - 10.1016/j.energy.2019.06.181

M3 - Article

VL - 183

SP - 1061

EP - 1074

JO - Energy

JF - Energy

SN - 0360-5442

ER -