Dublin, Ireland [RenewableEnergyWorld.com] It’s been a long, challenging endeavor, but there are signs that the economic ecosystem built up around wave and tidal power generation is at long last gathering enough momentum to make the jump from R&D-driven to full-fledged commercial industry.
Scotland, with its long stretches of west-facing coastlines, North Atlantic latitude and longstanding tradition of maritime engineering and commerce, is now at the leading edge of change when it comes to fostering development of marine renewables.
Wavegen’s Limpet 500 system has been pumping electricity from the western Scottish Isle of Islay shoreline since 2000 while the company and project developer npower renewables have continued to move forward with plans to develop the Siadar Wave Energy Project, potentially the first under the Scottish government’s Marine Supply Obligation program.
Marine Current Turbines is getting ready to flip the switch and fully commission a grid-connected 1.2-megawatt (MW) Seagen tidal turbine-based system in Northern Ireland’s Strangford Narrow, while elsewhere in the EU, project developers and the marine renewables community await the much-anticipated commissioning of Pelamis’s novel, serpent-like wave power system off the northern Portuguese coast.
Time, Tides & Waves
Long stretches of western coastline open to energy-laden North Atlantic waves and tides make Scotland a prime candidate for developing wave and tidal power generation systems and a vibrant, long-lasting marine renewables industry. Capital-intensive and dependent on building large-scale wave and tidal power systems that can connect to the grid, progress has been slow and difficult in coming, however.
It’s been estimated that marine renewable power systems built along Scotland’s west coast and outer islands can produce more than 20 gigawatts (GW) and as much as 80 terawatt-hours of electrical power per year, equivalent to one-fifth of UK consumption. The islands of Orkney and Shetland, and the west coast areas of Galloway, Kintyre, Pentland Firth and West Scotland were identified as particularly promising sites in a recent study undertaken by the Energy Systems Research Unit at Glasgow’s University of Strathclyde.
Former UK Dept. of Trade & Industry energy minister Brian Wilson in 2003 stated, “Wave and tidal power have huge potential to supply a significant proportion of the country’s future energy needs. Britain is already a world-leader in this technology. However, it is essential that we move from the research and development phase, which has been going on for many years, into commercial application.”
Five years on and the situation remains pretty much the same today, though Scotland’s government is credited with fashioning one of, if not the most, supportive environments for developing marine renewables.
While installed renewable power capacity increased 12% (from 2,357.16 to 2,629.43 MW) in Scotland in 2007, wave and tidal power accounted for less than 1 percent of that increase (a mere 0.5 MW) of the total. Hydro and wind dwarf all other forms of installed renewable power sources, which also include biomass to electricity and biomass heat, according to statistics compiled by industry trade body Scottish Renewables.
Marine renewables haven’t stood out amidst a rapidly expanding universe of renewable power alternatives when it comes to competing for private sector and limited government funding and support. Looking at private sector cash flow powerhouses, oil and gas industry giants have been investing in biofuels and wind power, while multinational giants like GE, which dominates the market for turbines and industrial equipment, have likewise directed the vast bulk of their investments into wind power.
The list of wave and tidal power technology developers that have been able to build, test and demonstrate the viability of system designs rated at 1 MW or more is hence a short one. As it happens, the UK is home to two with a third on the cusp of joining the list. Their success may give the fledgling marine renewables sector in Scotland, the UK and farther afield the push it needs to make the transition to mature commercial industry.
Producing electrical power since 2000 on the northwest Scottish Isle of Islay, Wavegen’s 500kW-rated Limpet (Land Installed Marine Powered Energy Transformer) system captures the power of incoming and receding tides and waves by compressing air and channeling it across turbine systems to generate electricity.
And Gathering Tide
In Northern Ireland’s Strangford Lough, the day is fast approaching when Marine Current Turbines and partners will turn on the power and attempt to fully commission Seagen, the world’s first megawatt-scale grid-connected tidal power system — for the second time.
The Seagen system is already connected to the grid connected and has been putting power into Northern Ireland’s grid, as well as that of its southern neighbor, the Republic of Ireland, thanks to new interconnections recently completed by the Irish republic’s grid operator, ESB (Electricity Services Board) and Northern Ireland Electricity. In addition to concluding a five-year extendible power purchase agreement, ESB owns a stake in the Strangford Lough project, as does EDF Energy and Guernsey Electricity, which is interested in bringing tidal and wave power to the UK’s Channel Islands.
Bristol, England-based Marine Current Technologies’ engineers and staff have been working diligently and as quickly as possible to repair damage done to one of the twin turbine systems’ rotors earlier this year. “It was a rather strange set of unanticipated events: three levels of defense all failed during the commissioning process, recounted technical director Peter Fraenkel.
New procedures have been introduced and the failsafe systems tested to ensure they are operating properly, Fraenkel continued, but nonetheless it has led Marine Current to test plans to fully commission the system using one turbine while it awaits delivery of a replacement rotor blade, a 12-week process.
Tidal Power in Northern Ireland
“Assuming that the analysis confirms that it will be okay, we look to run at full power on one rotor in one month, then on two rotors two to three months down the line…We’re just going through the process, doing a bit of very rigorous analysis to ensure we won’t damage the system by running it on one rotor.
“We’re being very cautious; it’s very important not to break anything else. The system’s rated power is based on 2.4 meters/second current or more, about 4.8 knots. We’re very confident it will perform as expected. Seaflow [Marine Current Turbines’ previous generator wave turbine] delivered almost exactly to our design specifications.”
Marine Current’s latest Seagen turbines operate at kinetic energy conversion efficiencies of 45-50%, “comparable to what you get with modern wind turbines,” and approaching the theoretical maximum of nearly 60%, Fraenkel explained. “The technology of choice is the pitch-controlled, variable speed axial flow rotor…You get diminishing returns — it costs more and more to squeeze a bit more energy out of it.
One of the advantages of the company’s patent designed rotors is the ability to “pitch them through 180 degrees. That means they can work efficiently with the current working in either direction, something that wind turbines are unable to do,” Fraenkel elaborated.
And off the Welsh Coast
Marine Current Technologies is also moving ahead with plans to use its latest SeaGen tidal turbine system in an npower renewables-led project off the coast of Anglesey in northern Wales. The showcase tidal array scheme is being designed to generate 10.5 MW of clean, renewable power drawn entirely from the strong tidal currents 25-meters deep in an area of open sea called the Skerries.
npower and Marine Current Turbines are moving the project forward through a jointly held development company, SeaGen Wales. Commissioning may come as early as 2011 or 2012 subject to successful planning consent and financing, according to the project partners.
“There is significant scope at the site for future expansion to a much larger scale of generation, up to around 120 MW. The consenting project, including EIA (environmental impact assessment) and initial studies commenced in the spring/summer of 2008, and a planning application is expected to be submitted in early-mid 2009. If consented, the scheme could be commissioned by late 2011-early 2012,” explained npower spokesperson Alda Forbes.
Wave power: from coastal to offshore
Elsewhere in Scotland, Inverness-based Wavegen, part of Voith Siemens Hydro Power Generation division, is taking the benefits of its near-shore experience and applying it offshore at Siadar Bay on the Outer Hebrides’ Isle of Lewis, where its oscillating water column technology will be the centerpiece of an active breakwater power system that includes a 4-MW wave power generating plant. Forty Wavegen 100-kW turbines are to be used in the Siadar Wave Energy Project, which will be located about 350 meters offshore in water depths of around 7 meters.
Project developer npower renewables in April submitted a planning document that’s slated for discussion at the local Western Isles Council, after which it will be taken up by the Scottish government, explained Wavegen CEO Matthew Seed.
Scottish energy minister Jim Mather has promised that the government will require no more than nine months to review such projects, “so we’re hopeful that this will be the case here,” he commented.
The partners’ Siadar wave energy plan is currently under consideration, with a decision expected in Q1 2009, commented npower’s Forbes. “If granted the relevant consents, the scheme will begin a circa 18-month build program, and could be operational by 2011,” she said.
“The major challenge to the scheme at present is an economic one, with costs significantly increasing over the life of the design so far. Grid connection is also a challenge for the project, given that there is a queue for connecting to the grid which could take until 2013.”
Project Development Choke Points
While nearly all the technical problems related to building viable tidal and wave power facilities have been addressed, access to capital, as well as grid connectivity, have not. Capital expenditures typically make up more than 90 percent of a wave power systems’ development and production costs, writes Wavegen technical director Tom Heath in a 2007 paper, “Realities of Wave Technology.” Longer-term, he notes, the big question is ‘Can it be delivered at a cost the consumer is willing to pay?’
“This is in marked contrast to fossil fuel plants where the input fuel is a high proportion of cost. A successful wave energy device will therefore have a minimum capital expenditure and a maximum electrical output. This rather obvious fact creates a dilemma for the designer of a wave energy plant: striking the correct balance between surviving the worst sea or shore conditions and minimizing the capital investment and design required to do so,” Heath explains.
How to go about proving and building up tidal and wave energy systems and generation capacity-whether to go through a step-wise, multi-phase progression from test to large-scale systems, or to make the jump from small demonstration to commercial-sized in one fell swoop-is an ongoing debate within the marine renewables community. What role shoreline systems, such as Wavegen’s Limpet, can play in the development of the industry is also contested.
Wavegen sees definite benefits accruing in its approach of building shore-based wave power systems and then scaling them up and moving off-shore. “Siadar is taking it to the next step,” Seed elaborated.
“The fact that we have this plant at Islay that we can access every day means we can develop the technology and make modifications and service equipment very easily. It’s not like dealing with an offshore floating device. The other advantage is that since it’s a pneumatic device, we don’t have moving parts in the water.”
The company has focused on making its technology and equipment robust enough to operate in the harshest coastal and offshore marine conditions. “We’re now getting levels of equipment availability — nearly 90% — and have nearly eight years of grid-connected experience, so now we’re looking at Siadar and a project in Spain, at Mutriku between San Sebastian and Bilbao, built into an existing breakwater. The output is relatively small but so are the incremental costs, and it’s likely to be first grid-connected plant in Spain,” Seed said.