Author: Mark Healy, research engineer - marine renewable energy, National Ocean Test Facility, Beaufort Research
Marine renewable energy – i.e. wave, tidal and offshore-wind – has long been a tantalising prospect for engineers, energy planners and entrepreneurs. As a new source of abundant, clean, renewable energy for the world, it has few parallels and is an immense resource.
This is particularly so for Ireland, one of the most energetic locations in the world in terms of our wave and offshore-wind climates. These are huge natural resources for the country, which could be harnessed for national energy use or for export to power-hungry neighbouring countries.
So, where are all the wave-energy devices, tidal turbines and deep offshore-wind turbines? Whilst there has been some successful commercial technology development to date, most notably in the tidal field by Irish-based DCNS company OpenHydro – one of the leading tidal energy players in the world – the general marine renewable energy sector still remains largely under-developed and pre-commercial.
The engineering challenge of developing cost effective, energy-harnessing technology in the marine environment has proved immense, with many technologies and companies not succeeding, despite countless millions having been spent.
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NEED FOR RIGOROUS R&D
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Irish engineers make use of MARINET to test abroad: IFREMER Hexwind Test[/caption]
The crux of the challenge lies in developing technologies which produce cost-competitive energy. Numerous technologies have been shown to be successful from a technical point of view, but their cost-of-energy is far from competitive. In order to achieve this, technologies need to be developed with cost-of-energy being the main consideration at every iteration of the research and development (R&D) process.
This process is well defined in the marine renewable energy industry, which uses a five-stage structured development plan as the main development and assessment method for technologies developed in the US and Europe. This is mapped to the familiar concept of technology readiness/performance levels, which indicates how far along a technology is to commercialisation.
The challenge lies in technology developers and investors having the patience and wisdom to follow such a plan, rather than – as so often happens – being tempted to skip steps and stages in their eagerness to get a technology into the ocean. These technologies require research and testing to be undertaken at a series of progressive scales at specialised facilities along the path to commercialisation – from small models and laboratory tests through to prototype scales and open sea tests.
A full suite of wave tanks and test facilities already exist throughout Europe and it is up to developers to make full use of these facilities and their associated expertise.
ACCESS TO TEST FACILITIES
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MARINET network (click to enlarge)[/caption]
In order to encourage this, a European initiative being led by Beaufort Research at University College Cork is opening up free use of Europe's leading test facilities for marine renewable-energy R&D. This is open to anyone based in the European Community – from start-ups, entrepreneurs and research groups through to well-established companies.
The main condition is that the facility to be accessed must be located outside the state where the applicant is based. Majority-funded by the EC, the €11 million MARINET (Marine Renewable Infrastructure Network) initiative offers facilities for periods of free-of-charge access in order to test devices at any scale in areas such as wave energy, tidal energy, offshore-wind energy and environmental data, or to conduct tests in cross-cutting areas such as power take-off systems, grid integration, materials or moorings.
In total, over 700 weeks of access is available to an estimated 300 projects and 800 external users, with five calls for access applications over the four-year initiative, which started in 2011. Some 45 different facilities are available from 29 institutions spread across 11 European Union countries.
The range of scales and size of facilities required for complete offshore renewable energy research is very wide and cannot be provided by one country alone. By co-ordinating the unique capabilities and services in various countries, MARINET provides this breadth of capability and essentially provides a one-stop-shop for marine renewable energy research and testing.
Co-ordination avoids future duplication of these capital-intensive research infrastructures, maximises their use and streamlines the testing process. MARINET also brings together a network of personnel in the marine renewable energy sector with expertise at all scales of marine technology research and development.
The EC funding seeks to remove financial barriers for companies and research groups who may not qualify for national grant aid for tests taking place outside their home state.
GROWING NETWORK
Originating as a European initiative in 2011, the initial network of 29 partners is spread across 11 EU countries and one FP7 (Seventh EU Framework Programme) partner-country, Brazil. Worldwide interest in the network has since grown significantly and many other research infrastructures internationally are keen to apply to become associate partners in the network. National Cheng Kung University, a Taiwanese university with significant testing infrastructures, became the first associate partner to join the network in November 2012.
Beaufort Research at UCC (formerly the Hydraulics and Maritime Research Centre) formed the MARINET initiative and manages the €11 million, four-year programme. Beaufort Research hosts one of the world’s largest complement of marine renewable energy engineers and researchers, having been involved in marine renewable energy R&D for over 35 years.
It is home to Ireland’s National Ocean Test Facility (NOTF) and two of the NOTF infrastructures are available through MARINET – the Ocean Wave Basin and the Rotating Electrical Test Rig. The other Irish partner in MARINET is the Sustainable Energy Authority of Ireland, which operates Ireland’s quarter-scale ocean energy test site at Galway Bay and the full-scale ocean energy test site at Belmullet.
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Ocean Wave Basin[/caption]
The Beaufort Research Ocean Wave Basin is a basin that is 25m long, 18m wide and 1m deep. It can generate waves in order to test the performance of wave-energy concepts. The wave-generation system incorporates 40 flap-type wedge shaped aluminium paddles attached to the 18m side of the tank. Each of these paddles has a hinge depth of 0.75m and is fitted with an active absorption system.
Each paddle can move independently, with the result that the wave generating system is capable of directional irregular seas up to a significant wave height of 0.18m and period of 2.5s. Active absorption is incorporated into the paddle system; this uses a feedback signal to adjust paddle motion. Monochromatic, panchromatic and recorded time series waves can be applied to the device undergoing testing. This allows for the fundamental characteristics of the device to be obtained as well as modelling the device in real sea conditions.
Such testing can determine hydrodynamic performance in a range of conditions, power take-off performance, site-specific wave generation, naval architecture set-up in terms of motion setup, weight distribution, balance and stability, sea-keeping, mooring set-up, validation of pre-completed numerical models, limited survival (based on scale) and power map production.
- Rotating Electrical Test Rig
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Rotating Electrical Test Rig[/caption]
An important stage in the scaled approach to the development and testing of marine energy converters is laboratory scale testing of power take-off equipment, control and grid integration. This requires test and control equipment operating at power levels corresponding to scales around 1:3-1:4 in order to match with typical scales for initial power take-off testing at sea.
Beaufort Research offers a suitably scaled rotational test-rig for generator type selection, control strategy design and optimisation and power quality analysis. The flexible design of the test rig facilitates islanded, direct- and indirect-connection to the grid of many different types of generator (Permanent Magnet SG, Wound Rotor IG, Squirrel Cage IG). For far lower costs than at-sea testing, results from the test rig can inform device developer’s decision-making before, during and after expensive at-sea trials.
For further details on MARINET and to apply to access a test facility free of charge, please see www.fp7-marinet.eu. Information on UCC Beaufort Research, part of the Irish Maritime and Energy Resource Cluster (IMERC), can be found at www.ucc.ie/beaufort.
Mark Healy is a research engineer - marine renewable energy at the National Ocean Test Facility, Beaufort Research, University College Cork