IEC TS 62600-3
Marine energy – Wave, tidal and other water current converters – Part 3: Measurement of mechanical loads
|Publication Date:||1 May 2020|
|ICS Code (Hydraulic energy engineering):||27.140|
This part of IEC 62600 describes the measurement of mechanical loads on hydrodynamic marine energy converters such as wave, tidal and other water current converters (including river current converters) for the purpose of load simulation model validation and certification. This document contains the requirements and recommendations for the measurement of mechanical loads for such activities as site selection, measurand selection, data acquisition, calibration, data verification, measurement load cases, capture matrix, post-processing, uncertainty determination and reporting.
Informative annexes are also provided to improve understanding of testing methods. The methods described in this document can also be used for mechanical loads measurements for other purposes such as obtaining a measured statistical representation of loads, direct measurements of the design loads, safety and function testing, or measurement of subsystem or component structural loads.
Through a technology qualification process, the test requirements can be adapted to the specific marine energy converter.
This document also defines the requirements for full-scale structural testing of subsystems or parts with a special focus on full-scale structural testing of marine energy converter rotor blades and for the interpretation and evaluation of achieved test results. This document focuses on aspects of testing related to an evaluation of the structural integrity of the blade. The purpose of the tests is to confirm to an acceptable level of probability that the whole installed production of a blade type fulfils the design assumptions.
Subdivision of marine energy converter types
There is a wide variety of marine energy converter types, especially concerning wave energy converters (WECs). For tidal energy converters and other current energy converters (CECs) the working principle of a turbine comprising blades connected to a rotor shaft, is common, whether seabed mounted or mounted to floating structures. However, there are also other types of tidal energy converters under development without blades connected to a rotor shaft and there are wave energy converters under development with blades connected to a rotor shaft. This document aims to cover all types of hydrodynamic marine energy converters, being wave energy converters (WECs) and current energy converters (CECs). Therefore, this document provides requirements and recommendations for all wave energy converters and current energy converters. For wave energy converters and current energy converters with blades connected to a rotor shaft, the requirements are specified in more detail, since in this case there is more knowledge about the technical components of the device.
For all wave and current energy converters a subdivision can be made between seabed (or shore) mounted devices (see Figure 1) and floating devices (see Figure 2). The seabed can also be a riverbed and the shore can also be a pier, a bridge girder, a canal lock gate or another artificial construction. The seabed (or shore) mounted devices generally consist of the following subsystems:
• prime mover;
• power take-off (PTO);
• foundation and/or substructure.
There can be marine energy converter types that do not fit in this characterization like the magneto hydrodynamic device (MHD), where the seawater itself is the prime mover. For such a device the scheme can be reduced to only "foundation and/or substructure", "power take-off" and "control". At the oscillating water column device (OWC), air is used to transfer power from the moving seawater to the turbine. Here the air turbine is the prime mover.
Figure 2 gives a scheme for floating marine energy converter working principles. The floating marine energy converters generally consist of the following subsystems:
• prime mover;
• power take-off (PTO);
• floating device;
• mooring system.
Other configurations of the subsystems in these figures are also possible. For example, for wave energy converters the power take-off and prime mover can be inside the floating device. Also, a marine energy converter can be composed from more than one subsystem of any kind. The subsystems can also be connected in series, such as alternating series of prime movers and power take-offs, or in parallel. The floating device can also be moored above the seabed but below the free surface.
Special requirements are provided for marine energy converters with one or more blades connected at a single end to a rotor shaft. The rotor forms the prime mover of the marine energy converter. The rotor can rotate with respect to a substructure. The power take-off connects the rotor to the substructure and houses an energy conversion from mechanical power to electrical power or some other form of transportable power such as hydraulic power. This is also called the drive train. The power take-off can be housed in a nacelle. The substructure connects the power take-off to the foundation fixed to the seabed or shore (see Figure 3). A control subsystem can be applied to control critical functions like rotor speed, rotor torque and rotor braking.
There are also optional mechanical components in a control subsystem for example:
• mechanism to allow yawing of the rotor towards the direction of the current (e.g. for the ebb and flood current direction);
• mechanism to allow pitching of the rotor blades for example to optimise power production, to shed loads or to adjust to the direction of the current.
The rotor and power take-off can also be supported by a floating device which is connected to the seabed (or shore) by a mooring system (see Figure 4).