Previously, software allowing users to simulate WECs, from meshing through power absorption, has only been commercially available. However, now, in order to give wave energy researchers and students an easy-to-use, all-in-one WEC simulation tool, the software openWEC has been created.
openWEC is written in python, and uses the Qt design language for the GUI development. Both the source code and a compiled executable are available open-source via Github:
When executing the program, the user can choose between several WEC simulators:
- Wavestar Simulator
- Oyster Simulator
- Pelamis Simulator
- Custom Simulator
The first three options are simplified versions of actual wave energy converter prototypes. Here, the user has only limited control over the parameters. When a user wants to develop a completely new WEC device, the Custom Simulator should be selected.
After selecting a simulator, the user enters the main GUI. There are 4 tab windows, each with a different purpose (see Figure):
- Mesh tool: creation of the mesh. The device can be constructed by combining different basic shapes into a single WEC device
- Nemoh: frequency-domain modelling of the WEC. Here, the hydrodynamic parameters are calculated using the open-source BEM solver Nemoh.
- Simulation: time-domain modelling of the WEC in a specific sea state. Regular and irregular waves are possible. Two PTO strategie can be chosen: a linear damper or a coulomb damper. The position and velocity of the WEC are calculated, together with the absorbed power.
- Post-processing: a simple post-processor allowing the user to plot the frequency-domain and time-domain parameters.
The user has the ability to save all the selected parameters and reload them when the model needs to be rerun. The current version only allows for single body WECs, but multibody simulations will be supported in the future.
At EWTEC 2015, a great project wave presented: WEC3 (pronounced WEC cubed), which stands for Wave Energy Converter Code Comparison. From their EWTEC paper (which can be found here):
The objectives of WEC3 are to verify and validate numerical modelling tools that have been developed specifically to simulate wave energy conversion devices and to inform the upcoming IEA OES Annex VI Ocean Energy Modelling Verification and Validation project. WEC3 is divided into two phases. Phase 1 consists of a code-to-code verification and Phase II entails code-to-experiment validation.
The codes under consideration are:
Comparison of codes to one another and to experiments benefits the code developers, giving them confidence in their results (something which is very important in numerical modelling), and benefits the community as a whole, providing validated tools for WEC design.
Version 1.2 of WEC-Sim is now available on GitHub, and there are lots of great updates!
The NREL/SNL team is also implementing a multi-branch approach, allowing users to use the stable ‘master’ branch or the more advanced/under development ‘dev’ branch.
Updates in ‘master’
- Nonlinear Froude-Krylov hydrodynamics and hydrostatics
- State space radiation
- Wave directionality
- User-defined wave elevation time-series
- Imports non-dimensionalized BEMIO hydrodynamic data (instead of fully dimensional coefficients)
- ‘Variant Subsystems’ implemented to improve code stability (instead of if statements)
- Bug fixes
Updates in ‘dev’:
- Morison Elements
- Body2Body Interactions
WEC-Sim (Wave Energy Converter SIMulator) is an open source wave energy converter simulation tool being developed as a joint effort between the National Renewable Energy Laboratory (NREL) and Sandia National Laboratories (SNL) with funding from the U.S. Department of Energy’s Wind and Water Power Technologies Office. The code is developed in MATLAB/SIMULINK using the multi-body dynamics solver SimMechanics. WEC-Sim has the ability to model devices that are comprised of rigid bodies, power-take-off systems, and mooring systems. Simulations are performed in the time-domain by solving the governing WEC equations of motion in 6 degrees-of-freedom as described in the WEC-Sim Theory Manual.
The NREL/SNL team would like to receive feedback on how WEC-Sim can be improved in the future and to facilitate this process a questionnaire has been created. It is highly encouraged of all users to fill out the questionnaire as soon as possible. Thank you for your time and please direct any questions about the current release to Nathan Tom, Nathan.firstname.lastname@example.org.
The number of open-access journals and publications is growing rapidly. These publications can be viewed and assessed by a wider audience, allowing for a broader and more rapid spread of the research. Open-access publishing operates in the same manner as a traditional journal, except that the cost of publishing is covered by the author or a funding body. Once a publication is accepted, it becomes available for free online. A lot of offshore renewable energy research is undertaken by small companies with limited budgets, and just like in the case of open-source software, having free resources can have a huge impact.
But wait, there’s more!
Offshore renewable energy should be fun too! Researchers in Oregon, USA have developed a simple working model of a wave energy converter (a direct drive linear generator) that you can make at home with your kids! Actually, it looks like the kids can make it by themselves:
The device was designed as part of a teaching curriculum. For more, including paper instructions and how to make the project into a full-fledged science experiment, see the article by NNMREC: