Preparing the World’s largest wave energy power plant
By Mike Hanlon
April 25, 2006
April 26, 2006 Wave Dragon is an offshore wave energy converter of the overtopping type. In 2003 Wave Dragon was the first wave energy developer to connect a prototype device to the public grid. Operating automatically this device has been online in the U.K. for 15,600 hours. Now, in a Joint Venture with UK renewable energy project developer, KP Renewables, Wave Dragon is to construct and deploy the world’s largest wave energy converter off the Pembrokeshire Coast in Wales, UK. After the initial test period, the test unit will joint 10 new units as a 77 MW power plant around 10 miles south west of initial site.
The first stage of the project will deploy a 7 MW Wave Dragon demonstration unit to be located five miles from Milford Haven and tested for three to five years. The plant consists of two wave reflectors focusing the incoming waves towards a ramp, a reservoir for collecting the overtopping water and a number of hydro turbines for converting the pressure head into power.
Wave Dragon is by far the largest wave energy converter available today. Each unit will have a rated power of 4-10 MW or more depending on how energetic the wave climate is at the deployment site. The utilization of the over-topping principle as opposed to power absorption via moving bodies means that the efficiency grows with the size of the converter. Only practical matters, such as for construction, set limits for the size of this wave energy converter.
Prior to going offshore a comprehensive test program has been carried out in wave tanks in Denmark and Ireland. Further on real sea testing has been going on for more than 3 years with a grid connected prototype of the Wave Dragon in a Danish fjord (a scale 1:4.5 of a North Sea production plant).
The demonstrator device will be located five miles from the South West Wales coast, off St Ann’s Head, north and west of Milford Haven.
Wave Dragon is a large floating barge structure. The main structural parts will be constructed in reinforced concrete with additional structural steel elements. The total design weight of the Welsh demonstrator device is 33,000 tonnes. The geometrical layout of the device will be identical with the tested prototype.
On the device are mounted 16-20 low-head hydro turbines to drain the reservoir, each with a 440kW PM generator. Additional electrical systems, step-up transformers and service systems are placed in closed compartments.
The 7MWe Welsh Demonstrator device will initially be deployed in a wave climate much lower that its rated power and size justifies. This will enable a thorough testing programme. The demonstrator project is linked to a further development of a total 77 MW wave energy farm in the Irish Sea following the successful demonstrator testing. As significant cost saving exists when a series of reinforced concrete structures and hundreds of turbines are to be constructed it has been possible to put together a fully commercial project. The overall total project investment for this 77 MW project is approximately £1,740 per installed kW.
An estimate of the total wave energy resource that is available to be utilised in a short term perspective varies depending on how far offshore it will be technical feasible to deploy devices. As a conservative example the International Energy Agency (IEA) and the World Energy Council (WEC) has estimated the potential world-wide wave energy contribution to the production of electricity could be between 10 and 50% of the world’s annual electricity demand of 15,000 TWh.
A recent study by the Department of Trade and Industry (DTI) and The Carbon Trust in UK (Renewables Innovation Review, 2004) states that 200,000 MW installed wave and tidal energy power by 2050 which with a load factor of 0.35 would result in annual power production of 600 TWh (4% of the electricity demand in the world). Independent of the different estimates the potential for a pollution free energy generation is enormous and the development of a completely new industry is underway. The development can be compared with what has happened in the last 25 years within the wind turbine industry.
The planning process for new technologies like wave energy takes time, so the company already has several projects in the pipeline. The first to follow the Welsh demonstration project will take place in Portugal where a company TECDRAGON Lda has been formed with the purpose of establishing 50 MW by 2009-2010.