ORKNEY'S ENERGY FUTURE
TIDAL ENERGY
ELECTRICITY FROM TIDAL ENERGY
EMEC’s grid connected tidal test site is at the Fall of Warness, southwest of the island of Eday. The site was chosen for its high velocity marine currents which reach almost 4 m/s at spring tides [1]. Devices have successfully generated electricity to the National Grid at the site, however none have been deployed at scale thus far. The Pentland Firth, between northern Scotland and Orkney is also an area that experiences high velocity currents (Figure 1; [2]).
Despite tides being predictable and therefore having the potential to provide firm power, in contrast to wind and solar power which are unpredictable, tidal power faces significant challenges to its large-scale deployment. These include capital cost and competing against more advanced technologies such as solar and wind, the corrosion and abrasion that devices are subject to when deployed in rough seas, maintenance in difficult sea states and access to power transmission.
Figure 1: Peak current speed of mean spring tide [2].
ORKNEY TIDAL ENERGY GENERATION
It is possible that tidal devices may be deployed in future, therefore a calculation has been carried out to quantify the power and energy that could be generated by one device operating at the EMEC tidal test site location. Current speeds from 1 January to 19 March 2017 were provided by EMEC (proprietary data) and the energy generated over this time frame was scaled up to calculate the power generated in one year. The ‘SeaGen-S 2MW’ device was used as the basis for the calculation; an earlier generation of the device with 1.2 MW has been successfully operational in Strangford Lough [3]. The power output was calculated using Equation 1:
where Cp is the capacity factor, ρ is the water density (kg/m ), A is the rotor swept area (m²) and v is the stream velocity (m/s).
The calculation shows that one SeaGen-S 2MW device could generate 6.65 GWh of electricity in one year (Figure 3).
(1)
3
Figure 2: Power generated by SeaGen-S 2MW tidal device in one lunar cycle.
Figure 3. Parameters used to calculate energy generated by one SeaGen-S 2MW device in one year and its power curve.
REFERENCES
[1] EMEC, "Grid-connected tidal test site," 2021. [Online]. Available: http://www.emec.org.uk/facilities/tidal-test-site/. [Accessed 15 February 2021].
[2] ABPmer, "Atlas of UK Marine Renewable Energy Resources," 2008. [Online]. Available: http://www.renewables-atlas.info/. [Accessed 15 February 2021].
[3] Atlantis Resources Ltd, "SeaGen-S 2MW," 2016. [Online]. Available: https://atlantisresourcesltd.com/wp/wp-content/uploads/2016/08/SeaGen-Brochure.pdf. [Accessed 7 March 2021].