The National Renewable Energy Centre (Narec) has invested over £150 million from UK government, European Regional Development Funding and private sector sources over the last ten years in establishing world-leading open-access research and test facilities for the offshore renewable energy industry – wind, wave and tidal.
Although perhaps best known for its work with the wind industry, in particular wind turbine blade testing, Narec is developing its services for marine renewables and subsea sectors. On its port-side site in Northumberland, Narec operates a wave flume, dry/wet docks and a simulated seabed for equipment trials and design verification work.
The Department for Energy and Climate Change (DECC) granted funding of £10 million in July 2009 and £6.4 million was secured from ERDF for their Nautilus project – an onshore 3MW capacity tidal turbine drivetrain test facility.
In October 2012 Atlantis completed testing of its AR-1000 tidal turbine device in the new facility – the first drive train test undertaken at Narec – following a period of at-sea trialing at EMEC during 2011. Accelerated life tests, conducted from the relative sanctuary of the onshore test facility, simulate the forces on the device that it is likely to experience in the sea. Narec can compress many months of tidal exchanges down to a testing programme lasting a matter of days and this gives developers in the UK a real edge as the marine energy industry approaches commercialisation.
The AR1000 is, according to its developers, well placed to be one of the world’s first commercially-deployed open ocean turbines. The horizontal access turbine features a single rotor set with highly efficient fixed pitch blades. The turbine is rotated as required with each tidal exchange and fixed in place for the optimal heading for the next tide. Testing of the device at Narec focused on the powertrain and control systems.
Dave Rigg, senior project manager at Atlantis, explains that testing at Narec has added a great deal to the AR-1000 technology development process. “Our focus on the mechanical system verified manufacturing quality, powertrain alignment and the current balancing of the powertrain,” he says. “Furthermore, by turning the generator and generating megawatts we can verify that all the electrical systems are in good order and generating as expected.
“There are limitations to an onshore test system in that you cannot precisely replicate subsea conditions,” Rigg continues. “However, you can generate torque and speed curves that represent
your modeling of the environment and input those to the shaft – your control system should be able to respond accordingly in maintaining the required rpm and current output.”
Rigg explains that the testing process at Narec was highly cooperative as Atlantis engineers needed to work closely with staff at the test facility throughout the trialing period.
Mark Taylor, currently a project manager at Narec having moved through the ranks over the last six years from mechanical design engineer, is responsible for ensuring clients are able to get the most from their time at Narec. He worked closely with Atlantis to ensure the requirements of the AR-1000 device were met during the company’s time at the testing facility.
“Atlantis had a reasonably clear definition of what they needed to do,” says Taylor. “We were to look at mechanical engineering, electrical engineering and control systems. It was certainly a logistical challenge to move large pieces of kit around the site, especially considering that last year the facility was not yet complete.
“Atlantis arrived on site with their device in validation mode. They had already deployed in water [at EMEC in 2011] – the advantage of coming to Narec is that we offer a controlled environment allowing developers to drive turbines irrespective of what a tide might be doing.”
Working on Narec’s 3MW drivetrain facility, Atlantis wanted to validate certain aspects of the AR-1000’s mechanical efficiency and control systems operation. “We were satisfied with the device’s mechanical performance but we needed to optimise some of the parameters within the control system,” explains Dave Rigg. “A significant amount of work is required in tuning that dynamic system and bolstering the level of redundancy within the electrical system.”
Following further testing, the most likely commercial deployment opportunity for the AR-1000 is the MeyGen project in Pentland Firth – a 400MW tidal array project that is set to commence its first phase of installation in 2014. Atlantis is a key strategic partner and has made a conditional agreement to supply turbines to the project.
From Narec’s perspective the ambition is to continue to develop the testing provision for wave and tidal devices. One aspect of Narec’s longterm strategy in this area is to collate real tidal flow data to then input to the control system and drive the test rig accordingly.
“The feedback we have had from Atlantis is that they would very much like to engage with Narec again as a partner and they have a development underway that we are interested in getting involved in,” says Taylor. “Narec now has a number of different customers that we are engaging with – all are interested in testing in some similar fashion to Atlantis.”
The job for Atlantis is now to turn attention towards open ocean installation and operation. Having tested at EMEC before coming to Narec (a decision made due to facility availability), Atlantis already has valuable experience of working in the offshore environment.
“In conducting our offshore test programme we, almost inadvertently, became very experienced in offshore construction operations,” adds Dave Rigg. “Our methodology for putting the turbine in and taking it out improved enormously.
“The connectivity between the turbine and permanent subsea equipment has evolved significantly as well. Things need to be designed for reliability and robustness first and foremost,” Rigg concludes. “By taking that approach we can overcome some of the challenges that the offshore wind industry has had to battle with.”
Source: By Alistair Welch, ENERGY ENGINEERING