Work Package 5
Applicability and Extension of IEC Technical Specifications using Open Sea Data
Objective: Accelerate the establishment of standards for the wave energy sector.
The lack of established standards introduces uncertainties at every level of the value chain of the wave energy sector, e.g. on the specifications necessary for operation at acceptable level of risk within specified conditions, or on the ways to measure and report power production and quality. This results in technological and business uncertainty which strongly impacts cost of capital and reduces the range of investment opportunities. A normative process for wave energy is ongoing with the International Electrotechnical Commission Technical Committee 114 and first editions of sector-specific Technical Specifications (IEC/TS) have recently been approved. To become established practices and standards, the IEC/TS need documented real-case application to open-sea deployment and operation.
This Work Package will provide the first documented application of the ongoing normative process for the wave energy sector, the International Electrotechnical Commission (IEC) Technical Specifications (TS) for marine energy, reduce the uncertainties in their application and provide recommendations to the relevant technical committee of the IEC (TC114) that will accelerate the establishment of standards based on these technical specifications. Specifically, the following IEC TS will be assessed:
- 62600-10 Assessment of Mooring system for Marine Energy Converters
- 62600-30 Electrical power quality requirements for wave, tidal and other water current energy converters.
- 62600-100 Electricity producing wave energy converters – Power performance assessment
- 62600-101 Wave energy resource assessment and characterization.
- 62600-102 Wave energy converter power performance assessment at a second location using measured assessment data
The WP is approached in two stages; firstly the IEC TS are investigated as they are in their current publication state. Secondly, the application of the TS are evaluated and investigated in further detail in areas such as the effect of the measurement resolution on power performance scatter, and grid compliance, so that these results can provide recommendations and enhancements to the IEC TS.
For these purposes, this Work Package will:
- Provide the first documented real-case application of existing IEC Technical Specifications.
- Evaluation of uncertainty in power performance, power quality, yield and their reporting.
- Extend the data sets using validated at-sea measurements to create full normalised power performance and power quality profiles, and predict the performance at other sites, scales and moorings.
Task to be performed
Methodologies to Conform to IEC Specifications
This task will examine the IEC Technical Specifications relating to (1) Power performance (2) Power Quality, and (3) Wave Resource Characterisation. These TS will be applied to the technology and data collection methods at bimep. This will ensure that WP3 and WP4 will collect the data needed to apply the IEC requirements from the outset. This task will also provide relevant measurement data requirements and recommendations on the open sea database framework and data collection strategy for WP1.
Documented real-case application of IEC Specifications
- “IEC/TS 62600-100 – Power Performance Assessment” The systematic methodology, outlined in IEC 62600-100, and detailed in practical terms in OPERA will be followed to measure the WEC power output in a range of sea states and identify the difficulties that may arise in developing a WEC power matrix using this methodology. Following this step, recommendations for refining the IEC TS will be proposed, particularly in the areas of uncertainty in power performance parameters due to the varying standard deviation values of different data sources, and dealing with missing or spurious measurements. The impact of the moorings on the power performance will also be investigated. The Power Performance IEC TS maintenance group is already examining ways in which the current publication may be improved. One such modification is to improve the accuracy by moving the dimensionality of the power matrix from the traditional 2D to 3D. The effectiveness of this will be investigated using at-sea data, and the results disseminated to the IEC maintenance group.
- “IEC/TS 62600-30 – Power Quality” This work will apply the IEC 62600-30 Technical Specification to assess the power quality of the deployed WEC. The following power quality phenomenon of the WEC will be assessed; Voltage fluctuations, Flicker, Harmonics, Inter-harmonics, Active Power, and Reactive Power at the Mutriku plant. Measurements will be analysed beyond the resource characteristics specified in the TS to ensure that power quality parameters are still within allowable limits. In Mutriku, the TS will be applied to both a single turbine and the plant as a whole, obtaining valuable conclusions about how aggregation of multiple turbines affects the power quality.
- “IEC/TS 62600-10 – Mooring standards” The outcomes of this WP are twofold; firstly, improvements in evaluating power performance, power quality, and yield prediction reduces the costly business risk due to uncertainty in evaluating these parameters. This is essential to the marine industry to increase investors’ confidence and trust regarding investments in marine energy. Secondly, a critical part of the transition phase from Technical Specification to Standard, is real-world trialling and validation of the TS to further the ongoing maintenance and development. In this regard, this work package will fulfil an important role from the perspective of the IEC and the marine industry, while providing technology validation for the device developer.
Wave-by-wave assessment of power production to reduce uncertainty in IEC/TS 62600-100
In this task, wave-by-wave power assessment at bimep will be used to produce a finer temporal resolution scatter plot to identify sources of scatter in the performance data in the hourly or 3-hourly time series. Such data complies with IEC Specifications, but is expected to have high standard deviation leading to high uncertainty in prediction of power output. Analysis of this scatter will be carried out to identify and reducing sources of uncertainty in WEC power performance assessment and prediction. The power performance will be examined for both individual waves, and response to wave groups, with emphasis on predicting the growth of resonant modes during a series of large waves, and subsequent decay time.
Improvement of yield prediction modelling at multiple sites, and scales
The power performance analysis work will be extended to determine Mean Annual Energy Production (MAEP) prediction using the model and wave climate scatter diagram at bimep. The same methodology will also be applied to obtain the energy yield at other test locations based on IEC TS 62600-102, and assessing and examining the issues of the wave spectrum shape and wave conditions on the energy yield. Detailed assessment of the energy yields will also be determined using wave-by-wave assessment. Predicting power performance with a scaled prototype will also be investigated to examine the issues involved in scaling power performance, and detailing problems and solutions that developers face when testing at sea with scaled prototypes. The outputs from this task will feed into WP7 to inform LCOE modelling.
Extending dataset beyond sea-trails data
As per the IEC Specification, if it can be shown that the WEC power quality phenomenon are assessed and this model is validated, then simulated models may be used to assess the power quality for other operating conditions, such as varying control algorithms, resource conditions, grid strengths, and control using a dry-lab to create a wider profile for the WEC. This task also includes “Low Voltage Ride Through” verification. Once the open-sea models have been validated, the emulation of grid faults will be carried out. This is an issue in the wind industry where there is no standard approach in emulating faults of grid connected generators. A fault emulation system will be developed and connected to the dry laboratory test rig to investigate the electrical and mechanical performance of the system. In addition, this task will observe the thermal, mechanical stresses and vibrations experienced during the fault. This work will feed into the work package on power conversion chain reliability, examining the reliability of the power chain conversion components (WP3). The dry lab will also be used to extrapolate the data produced in the previous task (power performance assessment at other test location), in order to create a fuller, more useful profile. This work will assist in defining recommendations that are more generic.
Wave and wind reanalysis data for bimep site characterization. TRL+ National research project (RTC-2015-3836-3) funded by Ministry of Economy and Competitiveness. (MINECO). Secretariat of state for research, development and innovation. National Programme for Research Aimed at the Challenges of Society. IHCantabria (2016).
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 654.444