WAVE ENERGY
Wave power technologies have been around for nearly thirty years. Setbacks and a general lack of confidence have contributed to slow progress towards proven devices that would have a good probability of becoming commercial sources of electrical power. For example in the UK, arguably one of the world’s best locations for establishing wave power, owing to the strength of the resource, no Government funding was available to support R&D for the ten years from 1989 until 1999.
What has made the difference over the last three years since the WEC Survey of Energy Resources in 1998?
This commentary first sets out some of the milestones around the world that have made a contribution: including the issue of climate change and its impact on the thinking of governments and the major multinational energy companies.
The matters of wave resource and updates in technology for wave energy conversion are briefly touched upon. The Country Notes following this commentary give a flavour of worldwide activities in more detail.
Following this, the need for diversification of the offshore hydrocarbons industry is discussed and also the synergies between that industry and the emerging offshore marine renewable energy industry, of which wave power is an important part.
The way forward is outlined in general terms (applicable worldwide) and includes a generic "roadmap" of future R&D requirements for wave energy conversion technologies. Finally the commercial position for electricity from wave is reviewed in the light of recent investment forecasts and the expected unit costs of the leading-edge technologies.
Milestones for Wave Power
There have been several influential events in the last three years:
Kyoto Treaty 1997 - has provided the driver for various governments to set targets for increased proportions of renewable energy over the first decade of the new millennium. Major concerns remain that China, the FSU and India are not showing significant commitment to implementing such targets, and more fundamentally, over the announcement in March 2001 that the USA did not intend to implement the terms at all;
UK Review of Renewables 1999 - as part of this, wave power RD&D funding was re-introduced for the UK. Some influence for this came from a report from the Marine Foresight Panel Task Force entitled "Energies from the Sea – Towards 2020" (Ref. 1);
Increased focus on Climate Change issues over the period - has become heightened as a growing consensus in the scientific community, owing to real evidence of the climate-altering effects of greenhouse gas emissions. The phenomenon at the Poles of increased numbers of icebergs and larger ice floes breaking away has been a graphic illustration. More recently, reports of an inland Arctic sea area where ice measurements historically showed a thickness of around three metres, have brought matters into the news and focused public attention. The degree of flooding experienced in East Africa, Bangladesh, India and in parts of Europe as well as mudslides in Ecuador has created awareness that there is more to this climatic instability than just scientific speculation;
The large increase in the price of oil in 2000 from the very low levels of 1998 - has caused re-evaluation of economic thresholds of conventional energy projects and improved the attractiveness of emerging renewable technologies, including wave energy conversion, when measured against fossil fuel energy sources. Greater effort to maintain the oil price is now being made within the OPEC group of countries. This has meant that existing wave energy technologies are in the present economic regime competitive in, for example, isolated communities currently served by diesel-driven generators.
Figure 15.1: Global Distribution of Deep Water Wave Power Resources
Wave Resource
Despite the climate change phenomena, the world resource for wave remains very much as set out by Dr Tom Thorpe of ETSU (author of the 1998 Wave Energy Commentary) (Ref. 2) The highest energy waves are concentrated off the western coasts in the 40o–60o latitude range north and south. The power in the wave fronts varies in these areas between 30 and 70 kW/m with peaks to 100kW/m in the Atlantic SW of Ireland, the Southern Ocean and off Cape Horn. The capability to supply electricity from this resource is such that, if harnessed appropriately, 10% of the current level of world supply could be provided. Work is still needed to determine how much more may be captured by other products (such as pumped water for desalination or electrolysis), once the storage technology for hydrogen is suitably developed.
Technology Update
Once again, the technologies outlined in 1998 based on Oscillating or Assisted Water Columns (OWC), buoys and pontoons (the Hosepump), flaps and tapered channels (the Pendulor and TAPCHAN) still exist or continue to be developed.
In the recent period, the following new developments have been noted:
The pelamis (named after a sea-snake), under development by Ocean Power Delivery Ltd in Scotland, is a series of cylindrical segments connected by hinged joints. As waves run down the length of the device and actuate the joints, hydraulic cylinders incorporated in the joints pump oil to drive a hydraulic motor via an energy-smoothing system. Electricity generated in each joint is transmitted to shore by a common sub-sea cable. The slack-moored device will be around 130m long and 3.5m in diameter. The pelamis is intended for general deployment offshore and is designed to use technology already available in the offshore industry. The full-scale version has a continuously rated power output of 0.75MW. Currently a one-seventh-scale prototype is being prepared for deployment in 2001.
Figure 15.3: The Pelamis Wave Energy Converter (Ocean Power Delivery Ltd.)
Figure 15.4: Pelamis – prototype (Ocean Power Delivery Ltd.)
Energetech of Australia has developed a two-way turbine that is claimed to be significantly more efficient than the Wells turbine. This will be utilised in an OWC device that employs a parabolic funnel to focus the wavefronts into the shoreline device for greater power capture;
Denmark has two recent devices with some innovative elements:
The Waveplane - is a wedge-shaped structure which channels incoming waves into a spiral trough, this produces a vortex to drive a turbine. A one-fifth-scale model has been on test off Jutland since mid-1999;
The Wave Dragon - is a floating tapchan but using a pair of curved reflectors (of a patented design) to gather waves to overtop a ramped trough where water is released though a low-head turbine. A one-fiftieth-scale model has been tested and a quarter-scale prototype is being designed for deployment in a fjord. The full-size device (estimated to have a generation peak of 4 MW) is large, with a "span" across the reflector arms of 227m;
In the USA, a company called Ocean Power Technologies (OPT) based in New Jersey is utilising a sheet of piezo-electric polymer material which, when deflected mechanically, produces electricity directly.
The technology scene for wave power is becoming more vibrant as various techniques and devices continue to be developed. It is evident that the range of types of device is far from exhausted, thus providing encouragement for the future.
Synergies with the Offshore Industry
A key fact that emerged from the UK DTI’s Marine Foresight Panel Task Force on Energies from the Sea, was the need to transfer technology and knowhow from the existing offshore industry to the new marine renewable energy industry. It is also becoming clear to many companies in the offshore oil & gas industry that their future lies in a capability to diversify their skills and services into future renewable energy sources. This coincidence of needs is becoming a key driver to the development of marine renewables.
The offshore industry is highly skilled in working in construction operations and maintenance in the unforgiving marine environment and has, over the past 25 years, been able to develop equipment with levels of survivability and reliability that the wave energy community cannot yet aspire to. The offshore industry has lost a large part of its manufacturing and fabrication market in NW Europe and is seeking ways to replace the jobs whilst retaining the knowledge and skills of the workforce. Marine renewable energy is an excellent way to begin this process. In the UK in early 2001, a conference and exhibition was held which, for the first time, focused on the opportunities that exist for companies to diversify towards marine renewable energy. The event was attended by more than two hundred people and has set the scene for follow-up activities.
The offshore industry has been involved in several initiatives targeted at cost reduction; this experience will benefit wave energy system economics as developers seek to drive down costs – a key challenge for the next 3 to 4 years. Technology transfer of this type will be vital to wave power developments throughout the world.
R&D – The Way Forward
One effective way of planning future R&D needs is by use of the Roadmap – a diagram with a timeline, showing the main R&D targets and the associated events and activities, set against the timeline as a high-level plan. It displays the generic issues that must be addressed if wave power is to become commercially realisable in the next few years.
Figure 15.5: Roadmap of R&D targets and associated events and activities
At a more detailed level below this generic indication, there are a large number of topics to be tackled; a few of them are given here for illustrative purposes:
moorings – long-term fatigue of lines and connections;
standard couplings for quick-release and re-attachment of moorings and cables;
standard flexible electrical connectors;
reduced-cost production of cables, construction and laying offshore;
modelling of arrays of multiple wave energy devices;
real-time wave behaviour forecasting;
environmentally acceptable fluids for hydraulic systems;
direct-drive power generators;
power-smoothing systems;
electrical power storage techniques and devices.
Benefits would undoubtedly be gained from greater international collaboration on as many as possible of the pre-competitive aspects of R&D. At present, the EU funding opportunities provide a major incentive to encourage collaboration, but there is room for other mechanisms to bring the international wave community closer together and avoid duplication and waste.
The Road to Commercial Wave Power
Estimates of the forecast cost per unit of electricity for various wave devices were made by Thorpe (Ref. 2) in 1998. They show offshore and nearshore devices producing power in the 5-7 pence/kWh range (based on 8% discount rate). The trends shown in the same report show a halving in the predicted cost over a period of six or seven years. This is borne out by the experience of onshore wind energy costs, which have been seen to fall by a factor of five over 12 to 15 years. Based on these results, it is reasonable to expect that wave energy unit costs can be made to fall to the 2-3 pence/kWh range within 3 to 5 years.
The success or otherwise of meeting this trend will depend on several factors including:
the ability of developers, manufacturers and installers to engineer-out cost from devices, especially as greater numbers are manufactured and deployed in arrays;
the commitment of governments and local authorities to streamline planning and regulatory processes;
the development of suitable approaches to grid connection, both for smaller "embedded" supplies and major power sources. This requires governments, electricity distributors and the financial community to collaborate in new ways;
the flow of innovation from R&D on more cost-effective materials, design and construction methods;
mechanisms being made available (under national electricity regulation regimes) to support specific emerging technologies with access to long-term contracts and/or to include wave power in capital grant mechanisms while the technologies mature;
the ability of the wave power industry to show good practice in standardised independent testing and performance assessment methods from an early stage;
the willingness of the financial community to recognise the key role of renewable energy technologies (including wave energy conversion) as a significant future proportion of the energy balance and to seek positively to invest into it.
Having focused on the need for many external agencies to find ways of tackling these challenges, it is incumbent upon the wave power device developers and the companies who will manufacture them and provide support services, to start to collaborate now. There is always more to be gained from collaboration than is ever lost by the "poaching" of ideas between collaborators. The way forward to commercial wave energy installations on a major scale will be highly sensitive to a proper degree of collaborative working. If it can be achieved, some very exciting things will be reported upon in the next WEC Survey of Energy Resources.
John W. Griffiths
JWG Consulting Ltd,
United Kingdom
www.worldenergy.org
