Variability and phasing of tidal current energy around the United Kingdom

Abstract

Tidal energy has the potential to play a key role in meeting renewable energy targets set out by the United Kingdom (UK) government and devolved administrations. Attention has been drawn to this resource as a number of locations with high tidal current velocity have recently been leased by the Crown Estate for commercial development. Although tides are periodic and predictable, there are times when the current velocity is too low for any power generation. However, it has been proposed that a portfolio of diverse sites located around the UK will deliver a firm aggregate output due to the relative phasing of the tidal signal around the coast. This paper analyses whether firm tidal power is feasible with 'first generation' tidal current generators suitable for relatively shallow water, high velocity sites. This is achieved through development of realistic scenarios of tidal current energy industry development. These scenarios incorporate constraints relating to assessment of the economically harvestable resource, tidal technology potential and the practical limits to energy extraction dictated by environmental response and spatial availability of resource. The final scenario is capable of generating 17 TWh/year with an effective installed capacity of 7.8 GW, at an average capacity factor of 29.9% from 7 major locations. However, it is concluded that there is insufficient diversity between sites suitable for first generation tidal current energy schemes for a portfolio approach to deliver firm power generation.

Optimal phasing of the European tidal stream resource using the greedy algorithm with penalty function

“…In agreement with Iyer et al [7], and extending the analysis to the entire NW European shelf seas, there is minimal phase diversity across the high energy European tidal stream sites to deliver firm power generation. This is primarily because the resource is concentrated at a relatively low number of sites, e.g.…”

“…Iyer et al [7] demonstrated through an examination of the Atlas of UK Marine Renewable Energy Resources that there is insufficient diversity between UK tidal stream sites to deliver firm power generation. However, the conclusions of this study were based on a limited number of sites, since first generation tidal stream technology was assumed, which requires mean spring peak current speeds of 2.5 m/s, and water depths in the range 25e50 m. Further, the Atlas of UK Marine Renewable Energy Resources does not span international boundaries, and so the results are UK-centric.…”

Assessment of the Malaysian tidal stream energy resource using an upper bound approach

“…It may even be possible to exploit the phase differences between sites to compensate, to a certain extent, for temporal variations and thereby produce a more regular power supply (e.g. Hardisty 2008;Iyer et al 2013;Neill et al 2016). …”

Tidal Turbines’ Layout in a Stream with Asymmetry and Misalignment

“…In these latter regions, the water depths are not sufficient to set up tidal turbines. However, potential sites with larger surfaces are identified by applying the criteria adopted by Iyer et al [44], retaining spring peak flows in excess of 2.5 m s −1 and water depths between 25 and 50 m. These areas correspond to two latitudinal branches extending from the southern extent of the strait till the islet of Tévennec (Figure 4). The potential sea space for extracting tidal kinetic energy covers almost all the strait from its southern to northern extents if second-generation technologies, designed to efficiently harvest lower currents with a mean spring peak over 2.0 m s −1 , were considered [7,22].…”

“…Instead, high energy sites suitable for first-and second-generation technologies are selected following Iyer et al [44] and Lewis et al [7] by retaining locations with a minimum mean spring peak current speed over 2.5 m s −1 or 2.0 m s −1 and water depths in the range of 25-50 m (criteria Ca1 and Cb1, Table 1). As exhibited in Section 3.2, the application of these criteria highlights the interest in the "Raz de Sein" for the exploitation of tidal stream power (Figure 11a,d).…”