Managing Risk in the Wave and Tidal Energy Industry
include the design load cases, appropriate safety factors, design conditions and specified tests to be carried out for the system to be certified, as well as providing a robust and consistent methodology for description of performance.
The traditional certification process therefore starts at the design stage with design assessment and approval. There then follows verification of procured items, fabrication and assembly, testing, installation, commissioning and operation. For ‘series-built’ systems a ‘type approval’ process is normally followed, whereby a prototype is used as part of the testing so that the accuracy of assumptions used in the design can be assessed and any changes made before the commercial systems are produced. Type approval allows production of large numbers of the same system with the same design to be covered under one certification. In the case of marine energy systems, this implies that a further stage of certification is required, where specific requirements for a site are included. This is known as project certification in the marine energy industry, and allows the specific energy converters – as opposed to the common designs – to be certified.
The diagram in Figure 2 shows the certification process for wave and tidal energy converters. The part of the process in the lower rectangle corresponds to a ‘traditional’ certification process for mature technologies and systems, starting at the design assessment with the standards and success criteria already defined. The process shown here is similar to that used for certification in the wind energy industry, with prototype certification, type certification and project certification.
For wave and tidal energy converters, there are no specific standards in place that define the assessment criteria, and that cover all the relevant failure modes. Due to the diversity in designs of wave and tidal energy converters, it is not possible – or desirable – at present to implement a prescriptive standard. The problem is solved in this certification process by the addition at the initial stage of the project of a systematic and traceable process, where the success criteria are defined, novel aspects and failure modes are identified, and the risk in the system is assessed considering all of this. This part of the process is the part in the upper rectangle in the schematic in Figure 2.
The process used to deal with the novel aspects of the technology is further broken down in the schematic in Figure 3, again in the upper rectangle. This is equivalent to defining a standard specific to the device, against which certification will be performed. The first step is to define the targets for the device in terms of loading, design life, reliability targets, operating environment and power outputs. This forms the certification basis.
The next step is to break down the technology into subsystems and components, and to make an assessment of the novel aspects of the system. This is accomplished using the matrix in Table 1.
The technology status corresponds to the amount of history the technology (i.e. the subsystem or the component) has in operation, while the application area relates to the intended operating environment, loading, accessibility for maintenance, etc. By using the matrix in Figure 3 to combine the score for technology status and
MODERN ENERGY REVIEW – VOLUME 3 ISSUE 1
Table 1 : Classification of Novel Technology Technology status
12 3
Application area 1. Known 2. New
Proven Limited field history New or unproven 1 2
2 3
3 4
application area, a technology class (between 1 and 4) can be identified. The technology classes are defined as follows.
1. No new technical uncertainties. 2. New technical uncertainties. 3. New technical challenges. 4. Demanding new technical challenges.
Increasing levels of technology class (i.e. novelty) are addressed in increasing levels of detail at the failure mode identification and risk ranking stage. This ranges from use of existing codes and standards for systems with technology class 1, to full investigation of failure modes for individual components at technology class 4. The principle is that all failure modes should be identified and dealt with either through standards or by identification of failure modes due to the novel aspects of the technology.
Following the risk ranking, a list of actions can be generated to reduce any unacceptable risks to a tolerable level, based on the level of tolerance defined in the risk matrix (see Figure 1). These actions are to be performed in the subsequent stages of the certification process along with normal processes associated with certification/approval of known technology.
By basing the requirements for extra actions in addition to standards on the risk matrix, the level of risk tolerated in the design can be clearly presented to all stakeholders involved with the technology. In the absence of a standard covering all aspects of the technology, this provides a demonstration that risks are being managed to a consistent level across the system.
Conclusion
Although risk management is a daily activity, in its formal aspect it is not necessarily widely used in a sector where prescriptive standards exist. However, there is no alternative when dealing with new technologies. The risk management leads to solutions that are balanced and adjusted to specific needs spanning from safety to reputation and operation.
Although one could define a unique measure to define success in the marine sector (such as profit) the range of risk elements involved in achieving this is large and complex, with the different elements interacting. The only way to produce a sound solution in an effective way is to adopt an integrated approach provided by risk management. Risk-based certification and enterprise risk management are available now for the marine renewable sector, and are based on processes used in diverse industries from subsea technology to food and beverage. The success of these techniques at dealing with risks induced by novel technology make them ideally suited to demonstration of risk management in the wave and tidal energy sector, which is a fundamental key to the success of the industry. n
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