Talking wave & wind

31 January 2008

The recent Tidal Energy Summit in London drew delegates interested in a range of wave and tidal energy information from technology to project finance

With the upsurge in activities in the wave and tidal energy sector as renewables come increasingly into favour, not least because of higher oil and gas prices as well as extra revenue potential from Kyoto Protocol-derived carbon (CDM) credits, those involved in research and development are enjoying greater opportunities. There is a confluence of near-ready technologies with more conducive regulatory environments and increased availability of investment funds and debt finance.

One result of the rising activity levels is increased discussion and information sharing, such as at the recent two-day Tidal Energy Summit in London. Another is IWP&DC’s increased coverage of the diverse work, news and milestones in this growing subsector of hydropower, such as in this regular ‘Wave & Tidal’ feature section and the many articles over the following pages.

At the London conference, delegates heard from speakers on themes of strategy, finance, research, site development, regulations, licensing, operations and maintenance, international projects, prototypes, scaling up and also novel ideas, such as a proposal for an iconic tidal-powered ‘Moon Clock’ to be built for the 2012 London Olympics. Panel debates on technical and finance challenges were also key aspects of the event. While not based on the panel debates, those two themes are reflected in a report spotlighting the technical development of the Kobold marine turbine and also a banker’s review of the financial challenges facing the sector.

Kobold marine turbine

A presentation was made on the latest progress with the Kobold marine turbine, which energy company Ponte di Archimede International has been developing in Rome in co-operation with the Insean navy ship model testing facility. A prototype has also been in the field off the coast of Italy for almost seven years and three are planned for Asia this year.

The Kobold concept is one of a vertical axis turbine with free oscillating blades, which Ponte di Archimede patented 10 years ago. The architecture of the turbine was inspired by the Voith-Schneider marine propellers. Delegates were told that the main characteristics of the Kobold devices are:

• The direction of rotation being independent of current direction.

• Its high starting torque, and therefore it is self-starting.

• The flexibility of layout, from floating to base-mounted arrangements.

• High efficiency.

• Reliability, sturdiness and simplicity.

• The blades are self-adjusting.

• There are no moving mechanisms.

Eight years ago, Ponte di Archimede began a new phase of research and development with tow tank and wind tunnel tests at the University of Naples ‘Frederico II’ facilities. The laboratory tests were complemented by computer modelling by Insean, which created computational fluid dynamic (CFD) models that helped in validation of experimental results.

The aims of the scale model experiments were to:

• Establish both qualitative and quantitative observations of the turbine working conditions to further enhance understanding of the hydrodynamic and mechanical behaviour.

• Establish data sets for comparison with full scale tests and also the outputs from numerical modelling.

• Collect data to help optimise the blade configurations (either with three or four blades) as well as the best angle oscillation range and optimal advance coefficient.

A 1:5 scale model of the Kobold turbine without a floating buoy was built for the experimental phase. The diameter of the turbine was 120cm, and the blade span and chord were 100cm and 8cm, respectively. Measured data included rotational speed, delivered torque and power.

The experimental results confirmed “excellent” starting torques and, therefore, the self-starting capability of the turbine concept, delegates were told. While blade oscillation was confined in a sector between two angles, it was noted that dynamic stall of blades was observed. In terms of the number of blades, the tests showed a slight improvement when passing from three to four blades with respect to the change in the wake interference. For either number of blades, however, it was separately noted that there was “significant” improvement by adopting free-oscillation blocks at 0° and +10° compared with -10° and +10°.

In terms of output, the maximum delivered mechanical power was obtained for a 1.0-1.5 advance coefficient. From the ‘Angle-v-Torque’ chart, the peaks in torque were found at angles of approximately 15° and 60°. In the tested flow velocities of 0.6m/s, 0.8m/s and 1m/s, the torque at those peak points were approximately an average of 6Nm, 13Nm and 20Nm, respectively.

Ongoing research is looking at the characterisation of the unsteady flow features affecting turbine performance, establishing efficient tools to allow parametric analyses, and both turbine optimisation and site customisation. Specifically, studies will employ boundary element methodology for unsteady inviscid flows and also look at:

• Unsteady trailing wake alignment technique.

• Wake-to-blade interaction modelling.

• Viscous and dynamic stall effects.

In 2001, a full scale prototype of the Kobold turbine was launched 150m offshore in the Strait of Messina in an area where water depths are 18m-35m, and the average speed of the tidal current is 1.5m/s-2.0m/s though it can peak at more than 3m/s. The device was subsequently, in 2005, connected to the national transmission grid. The Enermar pilot plant was financed by Ponte di Archimede, the Sicilian Government and the EU.

The rotor diameter of the three-blade prototype turbine was 6m, the blade height 5m and chord length 0.4m. The blades were manufactured in carbon fibre and epoxy resin, have a closed-cell foam inner structure, and three internal stainless steel bars down the length at 50cm spacing. The blades are connected to the rotor arms with rubber blocks and counter weights.

The associated floating platform, below which the turbine was suspended, was 10m in diameter, 2.5m deep and displaced 35 tonnes. The platform was moored using four 35 tonnes concrete blocks. On the site, with the turbine revolutions at 18rpm and the average flow rate of 2m/s, the power produced was 25kW-30kW. The design power of the prototype is 80kW. The global net efficiency (including both electric and mechanical losses) was estimated at about 25%. The rotating turbine also develops a thrust in the direction of the current, and in standard working conditions the force is approximately 10 tonnes.

Experiences from the field since ongoing operations began, assisted by funding from the UN Industrial Development Organization (UNIDO), have identified problems to be:

• The blade-arm connection – the weakest part was found to be the rubber blocks, which are used to set the blade oscillation angle. Diver intervention was needed to remove fishing lines and nets.

• The thrust bearing – the original thrust bearing was made of Ertalon, which is used for propeller bearings, but gave problems of water absorption and radial stress weakness.

• Galvanic currents – the presence of carbon can generate strong galvanic currents in the steel structure elements and requires effective corrosion protection.

• Biofouling – diver intervention was periodically needed to clean the blades and arms of biological materials.

Next steps for the testing and development includes deployment this year of three further prototypes – in China (Zhoushan Archipelago), Indonesia and the Philippines. UNIDO wants the technology to help provide renewable energy for remote islands in south east Asia.

In hearing of UNIDO picking up on prospective technology and providing financial support, delegates also had the opportunity to gain a wider insight into funding for wave and tidal energy projects. One speaker, Stephen Jennings of Barclays, outlined where such financing fits within the industry specialisms within the bank.

He said that the sector has potential for funds of up to £100m (US$200M) for debt and mezzanine arrangements as well as direct loans from the bank, though this was at the lower end of its debt involvement in projects. A sister unit, Barclays Capital, for example provides bank syndication contributions that can be more than £150M (US$300M) in debt or bond issues to the utility and infrastructure sectors.

Much of the funding that Barclays has provided in renewables has gone to wind energy projects. In terms of wave and tidal, he noted that the UK, for example, had significant resources and the bank does not need convincing about the potential size of the sector, investment opportunities and the benefits of supply security and climate change mitigation. However, he added that the sector was still in relative infancy. As such, as research and development work continues, even with the deployment of prototypes and grid hook-ups, there is a significant financial challenge in the pre-commercial phase – in effect, a ‘funding gap’.

The problem, he said, comes as the market does not see sufficient short-term incentive to contribute investment at levels needed to accelerate the take up of technologies despite there being solid long-term prospects. Investors and financiers want to see more proof of technology, lower costs and, not insignificantly, considerable levels of operating experience. Relative to onshore wind power schemes, he said that wave and tidal projects are based on “emerging technologies”.

Gaining Interest and Confidence

Jennings added that as research and development continues through the pre-commercial phase, investors gain interest and confidence and take stakes which then dilute the holdings of the entrepreneurs. Towards the end of this stage there may even be possibilities for initial debt finance, he noted. However, due to perception of higher risk at this phase then rewards have to be commensurately greater than in the later, commercial phase. However, to get this far requires the funding gap to be bridged, and the likely sources of funds are governments, grants and revenue support.

What will help convince those with money, either in government or markets, to back technologies and projects to various degrees? He pointed to various factors, such as: relevant experience; a strong and stable management team; healthy balance sheets; permits and licences; risk management on construction, performance and reliability; whole life cycle costs; power sales agreements; insurance; legal, regulatory and political regimes; and, whether the technology will have sufficient market opportunities if it is not to be the dominant system.

Though not said at the event, the message is one that echoes that given to any entrepreneurial or private infrastructure proposal – and, in fact, was said a decade ago to delegates of a IWP&DC finance conference: there is no automatic right to money, no implicit merit seen in one sector versus another, within energy or renewables or indeed hydropower, that will make funds flow to a project. It’s business. Competition. Show them experience and justified good numbers or the financial markets will simply look elsewhere.

At the London event, Jennings said that it was not a question of whether wave and tidal energy projects would be financed, but when. In the meantime, he advocated building strong relationships to tell financiers of strategies made, support won and ventures being proposed for development.

For further information on the Tidal Energy Summit, contact Louise Gray, Tidal Today, on +44-207-375-7159 or email: [email protected] The multimdeia conference pack is available on CD at a £100 discount to IWP&DC readers to give an offer price of £150 + VAT.

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