Marine renewable energy, including tidal renewable energy, is one of the less exploited sources of energy that could contribute to energy demand, while reducing greenhouse gas emissions. Amongst several proposals to build tidal range structure (TRS), a tidal lagoon has been proposed for construction in Swansea Bay, in the South West of the UK, but this scheme was recently rejected by the UK government due to the high electricity costs. This decision makes the optimisation of such schemes more important for the future. This study proposes various novel approaches by breaking the operation into small components to optimise the operation of TRS using a widely used 0-D modelling methodology. The approach results in a minimum 10% increase in energy output, without the inclusion of pumping, in comparison to the maximum energy output using a similar operation for all tides. This increase in energy will be approximately 25% more when pumping is included. The optimised operation schemes are used to simulate the lagoon operation using a 2-D model and the differences between the results are highlighted.
Tidal energy has a significant advantage over many other forms of renewable energy because of the predictability of tides. Tidal Range Structures (TRSs) are one of the main forms of tidal renewable energy. Designing the operation of TRSs is one of the challenging aspects in early stages due to the large variety of scenarios. Traditionally this has been done using a grid search. However, grid search can be very elaborate and time consuming during the design of TRSs. This paper proposes a novel and more efficient method to optimise the design of the operation of TRSs by maximising their electricity generation using a Genetic Algorithm. This GA model is coupled with a 0-D model which breaks the tides into small units and considers flexible operation. This approach delivered more than a 10% increase in electricity generation when compared to non-flexible operation, i.e. using fixed heads for all tides, just by optimising the operation. The GA model was able to achieve the same amount of electricity compared to the best grid search method with flexible operation more efficiently, i.e. with about a 50% reduction in simulation time. The feasibility of the elite operational scheme is validated through a developed 2-D model.
Firstly, a new reconstruction strategy is proposed to improve the accuracy of the fifth-order Weighted Essentially Non-Oscillatory (WENO) scheme. It has been noted that conventional WENO schemes still suffer from excessive numerical dissipation near critical regions. One of the reasons is that they tend to under-use all adjacent smooth sub-stencils thus fail to realize optimal interpolation. Hence in this work, a modified WENO (MWENO) strategy is designed to restore the highest possible order interpolation when three target sub-stencils or two target adjacent sub-stencils are smooth.Since the new detector is formulated under the original smoothness indicators, no obvious complexity and cost are added to the simulation. This idea has been successfully implemented into two classical fifth-order WENO schemes, which improve the accuracy near the critical region but without destroying essentially non-oscillatory properties. Secondly, the Tangent of Hyperbola for INterface Capturing (THINC) scheme is introduced as another reconstruction candidate to better represent the discontinuity. Finally, the MWENO and THINC schemes are implemented with the Boundary Variation Diminishing (BVD) algorithm to further minimize the numerical dissipation across discontinuities. Numerical verifications show that the proposed scheme accurately capture both smooth and discontinuous flow structures simultaneously with high-resolution quality. Meanwhile, the presented scheme effectively reduce numerical dissipation error and suppress spurious numerical oscillation in the presence of strong shock or discontinuity for compressible flows and compressible two-phase flows.
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