Abstract
Representing the velocity at a tidal energy extraction site in a standardized manner is essential for the development of the tidal energy sector. The International Electrotechnical Commission (IEC) have issued a technical specification to determine the mean representative current velocity (MRV) relative to a tidal energy converter (TEC). This method determines the MRV using an acoustic Doppler profiler (ADP). This is used to evaluate the power performance of a TEC and so can have a significant influence on the power performance uncertainties, due to the cubed relationship of the MRV and power. This paper investigates these uncertainties in the MRV by considering four sources of uncertainty in the ADP. These are turbulence intensity, tilt, Doppler noise and beam misalignment of an ADP. A synthetically generated dataset is used to define current velocity and profile using the characteristics of currents and ADP. The generated synthetic dataset is processed to calculate the MRV based on the standard IEC method. An alternative method to calculate the MRV, called the temporal-spatial method (TSM), is proposed and the two methodologies are used to assess the error of the MRV. A sensitivity analysis shows that the errors of the MRV based on the standard IEC method are always higher than the TSM. The biases in the MRV based on the different combinations of the uncertainty are investigated and it is found that the bias for the MRVs based on the TSM method is generally less than that of the IEC method.
Highlights
The International Electrotechnical Commission (IEC) has published a technical specification IEC/Technical Specification (TS) 62600-200 [1] as a guideline to assess the power performance of tidal current energy converters, which provides guidelines to determine the mean representative current velocity (MRV) at a particular location
The Results section focuses on investigating the error in the MRV due to the four uncertainty factors, which have been identified as major factors that may contribute to the uncertainty of the MRV
It can be seen that the MRV based on the temporal-spatial method (TSM) is always closer to the true value of the MRV than the values of the IEC standard method
Summary
The IEC has published a technical specification IEC/TS 62600-200 [1] as a guideline to assess the power performance of tidal current energy converters, which provides guidelines to determine the mean representative current velocity (MRV) at a particular location. A better understanding and characterization of the uncertainties of tidal currents is essential due to the need to obtain reliable estimates of the annual energy production (AEP), which depends on the power curve during site investigations and economic projections. It is important to know the level of uncertainty and identify methods to reduce it to facilitate potential investors to predict reliable energy estimates [3]. This will lead to improvements in the accurate financial modelling of wave and tidal energy projects and provide an increased level of confidence for commercial lenders and investors
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