Abstract
Costs of tidal stream energy generation are anticipated to fall considerably with array expansion and time. This is due to both economies of volume, where arrays comprising of large numbers of turbines can split fixed costs over a greater number of devices, and learning rates, where the industry matures and so arrays of the same size become cheaper due to lessons learned from previous installations. This paper investigates how tidal energy arrays can be designed to minimize the levelized cost of energy (LCOE), by optimizing not only the location but also the number of devices, to find a suitable balance between decreased costs due to economies of volume and diminishing returns due to global blockage effects. It focuses on the Alderney Race as a case study site due to the high velocities found there, making it a highly suitable site for large-scale arrays. It is demonstrated that between 1 and 2 GW could be feasibly extracted as costs in the tidal industry fall, with the LCOE depending greatly on the assumed costs. A Monte-Carlo analysis is undertaken to account for variability in capital and operational cost data used as inputs to the array optimization. Once optimized, the estimated P50 LCOE of an 80 MW array is £110/MWh. This estimate aligns closely with the level of subsidy considered for tidal stream projects in the Alderney Race in the past. This article is part of the theme issue 'New insights on tidal dynamics and tidal energy harvesting in the Alderney Race'.
Highlights
The Alderney Race contains a significant tidal energy resource, with a maximum average power potential of 5.1 GW and large regions of the Race exhibiting velocities of up to 5 m s−1 [1]
This paper investigates how tidal energy arrays can be designed to minimize the levelized cost of energy (LCOE), by optimizing the location and the number of devices, to find a suitable balance between decreased costs due to economies of volume and diminishing returns due to global blockage effects
A new, validated Thetis model set-up for the English Channel with non-uniform mesh resolution has been used to minimize the LCOE of tidal stream turbine arrays in the Alderney Race
Summary
The Alderney Race contains a significant tidal energy resource, with a maximum average power potential of 5.1 GW and large regions of the Race exhibiting velocities of up to 5 m s−1 [1]. Developed methods for optimizing the placement of tidal stream turbines within arrays have demonstrated the potential to increase array efficiency (energy yield per turbine) by up to 100% in some cases, thereby providing an avenue for further cost of energy reduction [2] This gradient-based optimization approach is implemented within a full hydrodynamics solver in order to link the changes to the hydrodynamics caused by the iterative movement of turbines within the optimization to the resulting power of the array. The viscosity is increased to a value of 1000 m2 s−1, over a region extending 50km from the open boundaries This acts as a further stabilization mechanism for any spurious flow behaviour that can be generated through minor inconsistencies (e.g. due to different resolution and bathymetry data employed) between our model and set-up, and the configuration used to generate the tidal harmonic forcing data. The Coriolis forcing, f u⊥, is represented by the beta-plane approximation, due to the size of the domain, such that;
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