Wave Energy -STATE OF THE ART, ASSESSMENT AND MITIGATION OF NON-TECHNOLOGICAL BARRIERS

STATE OF THE ART, ASSESSMENT AND MITIGATION OF NON-TECHNOLOGICAL BARRIERS

4.1. State of the art

Ocean Energy, and in particular wave energy, extraction has captured the interest and imagination of inventors and engineers in the same way early flight and cotton manufacturing did in the last century. Perhaps, now that it is a media discussed topic connected to climate change and security of supply issues, even more so.

Unfortunately, but not unexpectedly, most of the schemes and designs will not advance beyond the drawing board and concept validation phase. Impartial, balanced and equitable due diligence to evaluate the potential of such devices is important, even essential, if the limited commercial resources available to wave energy convertor (WEC) development are to be used efficiently. To advance, the wave energy industry will require focused effort and support for the current vanguard SME’s who have proven they have machines that possess a chance of success and continued operation in the harsh environment these units must reside in.

Over recent years there have been several European and national reviews of the range of wave energy (and tidal energy) devices being investigated at any particular point in time. Reference to them shows how the interest changes from one period to another, despite the belief in each unit at the time. Unlike the wind industry, which quite quickly converged on one model of air turbine, the horizontal axis type, there is no single unit, or even generic type, of WEC that is proving more successful than another. This statement, however, requires clarification, since it depends on how the machines are classified. Most rely on the physics of two inertial masses reacting against each other in such a way that power can be generated between the opposing forces. It is actually only the size, shape, colour and components that differ. This is even the case if one of the inertial masses is fixed, usually to the seabed.

The power take-off utilising the imbalance between the masses is a variable but to date only six options exist:

• Air turbines (Figure 1.1)

• Close circuit oil hydraulics (Figure 1.2)

• Direct (linear generator) drive (Figure 1.3)

• Low head water turbine (Figure 1.4)

• Water Pump (Figure 1.5)

• Open circuit water hydraulics (e.g. Hose Pump) (Figure 1.6)

There is a higher potential for variation in the mooring arrangement and it is possible that non-conventional type anchorage systems will suit some, or all, of the prototype devices. It is also probable that different configurations will match individual buoyant wave energy devices.

This report will therefore not attempt to classify the different devices described in the Appendices but rather regard then all as similar units capable of wave energy conversion. In addition, since the document is charged with describing the current state of the art with regard to wave energy extraction it will not be simply a list of ephemeral devices currently being proposed and investigated at various stages of their development. Rather, a set of criteria was agreed by which a device would qualify for inclusion in the review.

The rationale placed on the study was to identify units with a real potential for preproduction activity in the near future. After informed discussion between the Waveplam partners the two primary requirements for qualifications to the first group were:

• The device had to have achieved sea trials, at least at a large scale (circa λ > 1:4)

• The company must have followed and exhibited evidence of a structured development programme prior to sea deployment.

Depending on the stage of development, a follow up group are also reported based on adherence to the second specification. As can be seen from the information sheets in the Appendix some flexibility was necessary for almost all devices and the caveat relaxed. It is expected that this document will be updated over the duration of the Waveplam project but the same qualifying criteria will still be applied.

The first condition was easy to observe and verify. For the second the soon to be introduced International Energy Agency ~ Ocean Energy Systems (IEA-OES) Development & Evaluation Protocol was employed.

The purpose of this review is to provide technical information that should assist policy makers, investors, project developers and other interested stakeholders to make informed decisions regarding the scheduling of wave power into future energy plans and portfolios. Many estimates have already been declared in a variety of prediction documents but they are usually based on energy market forces rather than technology readiness assessment (TRA) of the devices.

It is widely accepted that wave power has the potential to become a significant contributor to the world’s (clean) energy supply needs, as shown by the differing forecasts listed in Table 1. However, it is also the case that in the 1980s WE was expected to be commercial within 5-7 years. This same lead time was further endorsed in 2000 when a new generation of devices were under development. These ambitious time frames have lead to the contradictory perceptions that either the industry is more advanced than it actually is, or it is not really progressing. The true situation is somewhere in-between, so the following device based report should enable more appropriate introduction dates to be specified. Once established it ought to be only the time targets, not the power targets, that may be difficult to achieve.

It is further hoped that the TRA approach will assist in focusing future product funding programmes since the correct support mechanisms are essential if even modified delivery dates are to be met. The device development recommended requirements are summarised in Table 4.1. The actual details of current and required future fiscal policies to stimulate and accelerate project progress are covered in separate Waveplam studies. Here only the on-going principal European and national research projects are described.

To help achieve the objectives, particularly funding packages, a structured device development programme is proposed and this is used as the foundation for setting the machine evolution status. The technical information is presented in the Appendix as developer based specification sheets. This approach will enable the information to be easily updated and expanded as required.

The technology development times being experienced by a selection of leading companies are summarised in Figure 1. The graph illustrates the different approaches that can be followed and the consequences of certain decisions. It will be seen from the device tables that there are a large and varied number of machines undergoing testing. To-date no one type of technology

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