Rubber 'snake' could help wave power get a bite of the energy market
A project led by University of Southampton researchers is developing a device consisting of a giant rubber tube which may hold the key to producing affordable electricity from the energy in sea waves.
Invented in the UK, the 'Anaconda' is a totally innovative wave energy concept. Its ultra-simple design means it would be cheap to manufacture and maintain, enabling it to produce clean electricity at lower cost than other types of wave energy converter. Cost has been a key barrier to deployment of such converters to date.
Named after the snake of the same name because of its long thin shape, the Anaconda is closed at both ends and filled completely with water. It is designed to be anchored just below the sea's surface, with one end facing the oncoming waves.
A wave hitting the end squeezes it and causes a 'bulge wave'* to form inside the tube. As the bulge wave runs through the tube, the initial sea wave that caused it runs along the outside of the tube at the same speed, squeezing the tube more and more and causing the bulge wave to get bigger and bigger. The bulge wave then turns a turbine fitted at the far end of the device and the power produced is fed to shore via a cable.
Because it is made of rubber, the Anaconda is much lighter than other wave energy devices (which are primarily made of metal) and dispenses with the need for hydraulic rams, hinges and articulated joints. This reduces capital and maintenance costs and scope for breakdowns.
The Anaconda is, however, still at an early stage of development. The concept has only been proven at very small laboratory-scale, so important questions about its potential performance still need to be answered. Funded by the Engineering and Physical Sciences Research Council (EPSRC), and in collaboration with the Anaconda's inventors and with its developer (Checkmate SeaEnergy), engineers at the University of Southampton are now embarking on a programme of larger-scale laboratory experiments and novel mathematical studies designed to do just that.
Using tubes with diameters of 0.25 and 0.5 metres, the experiments will assess the Anaconda's behaviour in regular, irregular and extreme waves. Parameters measured will include internal pressures, changes in tube shape and the forces that mooring cables would be subjected to. As well as providing insights into the device's hydrodynamic behaviour, the data will form the basis of a mathematical model that can estimate exactly how much power a full-scale Anaconda would produce.
When built, each full-scale Anaconda device would be 200 metres long and 7 metres in diameter, and deployed in water depths of between 40 and 100 metres. Initial assessments indicate that the Anaconda would be rated at a power output of 1MW (roughly the electricity consumption of 2000 houses) and might be able to generate power at a cost of 6p per kWh or less. Although around twice as much as the cost of electricity generated from traditional coal-fired power stations, this compares very favourably with generation costs for other leading wave energy concepts.
"The Anaconda could make a valuable contribution to environmental protection by encouraging the use of wave power," says Professor John Chaplin, of the Universit7y of Southampton's School of Civil Engineering and the Environment, who is leading the EPSRC-funded project. "A one-third scale model of the Anaconda could be built next year for sea testing and we could see the first full-size device deployed off the UK coast in around five years' time."
Notes for editors
Three images are available from Communications on request.
An animated movie of the Anaconda is also available at: http://www.checkmateuk.com/seaenergy/links.html
The two-year project 'The Hydrodynamics of a Distensible Wave Energy Converter' is receiving EPSRC funding of just over £430,000.
*A bulge wave is a wave of pressure produced when a fluid oscillates forwards and backwards inside a tube.
The Anaconda was invented by Francis Farley (an experimental physicist) and Rod Rainey (of Atkins Oil and Gas). Their website on the Anaconda is at www.bulgewave.com. Manufacturing rights for the Anaconda now belong to Checkmate SeaEnergy, part of the Checkmate Group (www.checkmateuk.com). There may be advantages in making part of the tube inelastic, but this is still under assessment.
The Anaconda is named after the enormous South American snake that hunts for its prey in water. It is the largest snake that spends a high proportion of its time in water environments.
The Anaconda is one of the new concepts identified by the Carbon Trust's Marine Energy Accelerator initiative as having potential to deliver breakthrough reductions in the cost of energy. See http://www.carbontrust.co.uk/News/presscentre/2007/250907_MarineAccelerator.htm
Wave-generated electricity is carbon-free and so can help the fight against global warming. Together with tidal energy, it is estimated that wave power could supply up to 20 per cent of the UK's current electricity demand. For an estimate of wave energy's future contribution to UK power supplies, see
http://www.ukrenewables.com/newsletter/Jan07/wave_tidal.htm
The mathematical studies undertaken by the EPSRC-funded project are novel because the Anaconda's response to pressures induced by surface waves is much more complex than that of a ship or an offshore structure. It has many more degrees of freedom, and motions of each kind (vertical and horizontal bending, bulging, stretching, ovalling, twisting) all interact because of the compliant nature of the rubber.
Hydrodynamics is part of fluid dynamics, which is the study of fluids in motion.
The University of Southampton is one of the UK's top 10 research universities, offering first-rate opportunities and facilities for study and research across a wide range of subjects in health, humanities, science and engineering.
The University, which has over 22,000 students, 5000 staff, and an annual turnover in the region of £325 million, is one of the country's top institutions for engineering, computer science and medicine, and home to a range of world-leading research centres. These include the National Oceanography Centre, Southampton, the Institute of Sound and Vibration Research, the Optoelectronics Research Centre, the Centre for the Developmental Origins of Health and Disease, and the Mountbatten Centre for International Studies.
The Engineering and Physical Sciences Research Council (EPSRC) is the UK's main agency for funding research in engineering and the physical sciences. The EPSRC invests around £800 million a year in research and postgraduate training, to help the nation handle the next generation of technological change. The areas covered range from information technology to structural engineering, and mathematics to materials science. This research forms the basis for future economic development in the UK and improvements for everyone's health, lifestyle and culture. EPSRC also actively promotes public awareness of science and engineering. EPSRC works alongside other Research Councils with responsibility for other areas of research. The Research Councils work collectively on issues of common concern via Research Councils UK. Website address for more information on EPSRC: www.epsrc.ac.uk/
For more information:
Sue Wilson, Communications, University of Southampton,
Tel. 023 80595457, email: sjew@soton.ac.uk
Professor John Chaplin, School of Civil Engineering and the Environment, University of Southampton,
Tel: 023 8059 2843, email: J.R.Chaplin@soton.ac.uk
Professor Grant Hearn, School of Engineering Sciences, University of Southampton,
Tel: 023 8059 3769, email: G.E.Hearn@soton.ac.uk