Tidal energy converters have the potential to become significant contributors in the generation of low carbon energy. Operational cost, driven mostly by planned and unplanned maintenance, is one of the most significant barrier limiting their widespread adoption. Accurate numerical models can be used to predict structural loads and help improve their reliability, and thus reduced maintenance costs. Blade element momentum theory is a common numerical model that is used for design and performance evaluation of tidal energy converters. It offers acceptable accuracy for evaluation of turbine design iterations with significant computational saving. This paper will investigate the prediction improvements possible by allowing non-uniform blade properties in a previously uniform model. The capability of assigning unique lift and drag characteristics to each element based on its geometry and Reynolds number will be implemented, resulting in improved blade geometry modelling in the numerical model, and thus the turbine performance predictions. Three turbine rotor blades are analysed: Magallanes ATIR, Sabella D12, and IFREMER-LOMC. Results from the improved numerical model are compared to laboratory data to quantify any improvements in its predictions. Prediction of optimum turbine performance from the numerical model has improved by an average of 8.1%, to an accuracy of 94.4%, which will directly enhance the design and evaluation of tidal energy converters.