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RC PLUS

In progress

Development of a marine data toolkit for resource characterization and energy cost reduction

Coordinateurs du projet

Context

The technical and financial engineering of MRE projects relies at various stages on the availability of reliable and proven environmental data upstream, compared to in situ measurement methods. In addition, the processing of this data using documented methods and proven tools intended for technology developers provides a guarantee of quality upstream of any technology-specific calculation loops.

This RC-PLus project is backed by the European OceanERA-Net ResourceCode project, which won the 2018 call for proposals and started in 2019. ResourceCode brings together a unique consortium of specialists in hydrodynamics, environmental modeling, and data processing (Ifremer, University College Dublin, University of Edinburgh, INNOSEA, OceanDataLab), associated with European test sites (SEM-REV, EMEC, SmartBay) that also collect field data and host developers at sea.

This project therefore represents an excellent opportunity to work together on the analysis and processing chain for data from measurement and replay databases, specifically designed to meet the description requirements associated with MRE. While these databases have in the past been generated and exploited in isolation, one of the benefits of this project will be to create a unified database and common analysis tools, in order to provide a better description and improve standardization for the industry.

Scientific breakthroughs and innovation

This project aims to build on the work carried out to compile and analyze the HOMERE database, which is a benchmark in terms of high-resolution replay databases, but covers only a small portion of European waters centered on the French Atlantic coast. To date, HOMERE has provided:

  1. High-precision, high-resolution replay data, focused on sea states, with forcing from wind reanalyses and tidal effects taken into account, covering 23 years;
  2. A tool tailored to the needs of industry (>50% of requests for access to HOMERE come from industrial players in the MRE sector);
  3. Data that has led to upstream R&D work on resource aspects and environmental conditions.

The replay from RC-Plus and RESOURCECODE will provide an unprecedented extension of HOMERE, from southern Portugal to northern Scotland, and will enable the project to further expand the area covered. The databases of in-situ measurements made available by the partners will enrich the comparisons and validation of the models.

Beyond a simple database, access and use of which is quickly limited to expert users, ResourceCode and RC-Plus aim to enrich the interfaces so that pre-processing and initial qualification, visualization, and analysis tools can be easily implemented through a user-oriented access portal.

 

Expected technical and economic impact

  • Development of a database of sea state, wind, and current replay data covering the Atlantic coast from Portugal to Scotland over a period of more than twenty years.
  • Evaluation of the performance of this database compared to in situ measurements from European networks and the project’s three partner test sites (SEM-REV, EMEC, SmartBay).
  • Database performance superior or equal to HOMERE in terms of description accuracy.
  • Access to a tool for visualizing the data generated.
  • Access to tools for processing and analyzing meteorological and oceanographic data for use in the pre-design phase of MRE projects (visualization interface, statistical processing and analysis tools, etc.).
  • Implementation of an e-infrastructure for managing data from offshore test sites as part of GIS Theorem, the major national hydrodynamics research infrastructure bringing together the Ecole Centrale and Ifremer, and foreshadowing the European solution in Marinerg-I.
  • Contribution to the evolution of standards in an international committee (IEC, ITTC, etc.).

Results

ResourceCode database

The calculations for the ResourceCode replay database were performed by IFREMER and cover the years 1993 to 2020 with a temporal resolution of one hour. The database was generated using the WaveWatch III spectral model developed by the US National Oceanic and Atmospheric Administration (NOAA). For each hour of the period covered, 39 meteorological and oceanographic parameters and frequency spectra are available for 328,000 grid nodes stretching from southern Portugal to southwestern Norway via the Faroe Islands. Directional spectra are available for a subset of these nodes. The spectra have a frequency range from 0.0339Hz to 0.91526Hz, which is subdivided into 36 bands of non-uniform width, and the directional spectra are composed of 36 bands of 10° each. Wind forcing conditions are taken from the ERA5 database. Currents and tidal ranges are also taken into account by the model.

Database validation

The database was validated using satellite altimetry data and in situ buoy data. Satellite data provide broader spatial coverage than buoy data, but at the expense of temporal coverage. The satellite data were taken from the CCI Seat State V1 database, and the in situ buoy data were sourced through the various European partners of the OceanERA-Net ResourceCode project. Validation focused mainly on significant wave height, but spectral validation was also performed at points where in situ buoy data are available in spectral form, as illustrated in Figure 1.

Toolbox

The ResourceCode toolbox provides graphical access to the weather-ocean database via a web interface and also provides a set of statistical analysis tools for processing this data.

The web interface allows the main integral parameters (HS, TP, etc.) to be visualized in the form of time series and bivariate statistical distributions.

The dedicated post-processing tools for the database enable the following operations:

  • Data visualization.
  • Estimation of wave energy resources.
  • Analysis of extreme values.
  • Estimation of weather windows.
  • Estimation of energy yield for wave energy conversion systems.

All these tools can be downloaded as Python code that can be run locally. Some of these tools can also be run directly online from the web interface.

The two main contributions of the RC-plus project to the ResourceCode project are the spectral validation of the replay database using in situ buoy data and the tool for estimating the energy yield for wave energy conversion systems. The latter led to a more in-depth study of the different techniques traditionally used to estimate energy yields. More specifically, methods based on estimating wave resources using integral parameters were compared with a reference approach where the resource is described using spectra. The wave energy conversion system chosen for this case study is a pilot buoy with two bodies modeled numerically in the time domain. Preliminary results show that methods based on integral parameters tend to overestimate the energy produced by about 6% compared to the reference method for the site and year considered. This modest annual overestimation hides much larger overestimations (up to 70%) for certain sea states, as illustrated in Figure 2.