A shore thing

Interest in marine renewable technologies has never been so high. So why aren't more products making it to the marketplace? Kevin Cleminson explains how two key words - reliability and maintainability - are vital to success

Marine renewables is a sector that has traditionally shown a lot of promise, but which has simply not had the track record to prove itself.

However, times are changing, and a number of marine renewable projects are starting to gain momentum – both from a technological point of a view, and a commercial one. And with wave and tidal power projects having the potential for making a significant contribution to the UK’s future energy needs, is this the time for the sector to be taken more seriously?

Development in the marine renewable technologies field over recent years has certainly been brisk. But this alone is not enough to indicate the future direction of the sector.

For that, two factors hold the key – reliability and maintainability. Arguably these two factors alone help differentiate between a technology that succeeds and one that fails in a commercial environment. The marine renewable devices currently in development might be technologically advanced, but in order to be successfully deployed and useful over the longer term, such devices must meet critical levels of reliability and maintainability, or risk sinking the profit margins which ensure the device’s long-term survival.

Systems engineering consultancy, Frazer-Nash is pioneering work in this area and has been assessing these two crucial elements on one of the first wave energy machines to be used in a commercial energy farm.

Pelamis is the leading wave energy converter developed by the Edinburgh-based company Ocean Power Delivery (OPD), and is due to come into service off the coast of Portugal later this year. In addition, the device has in recent months started attracting interest in markets off our own shores.

The Pelamis converter concept is a unique one. As the tubular elements of the device pass over the surface of the waves, the flexing of the joints between them activate hydraulic rams and generate electricity – giving the system the moniker “the sea snake”. Several devices can also be linked together to form wave farms. As a result, a typical installation occupying a mere square kilometre of ocean could provide enough electricity for 20,000 homes.

Conventional on-site

maintenance strategies can be prohibitively expensive in the offshore environment (especially with the need to transport personnel and equipment to site), but the Pelamis system is robust and easy to repair when trouble strikes.

No onboard personnel, divers or remote operated vehicles are required for

connection/disconnection of the Pelamis machine – important not only from a cost perspective but also in terms of health and safety. This strategy maximises accessibility as only relatively short weather windows are required for retrieval operations, compared with maintenance on-site which can require much longer (and statistically less frequent) weather windows.

OPD’s strategy has been to carry out all maintenance activities for Pelamis off-site. The device features a quick-connect/disconnect mooring attachment system that enables the machine to be brought to a sheltered location such as a quayside for any major maintenance activities. OPD has spent the past eight years testing and refining the articulated Pelamis converter concept. But in order to ensure that the device is reliable and easily maintained going into the future – following its forthcoming deployment – a range of further independent tests were required.

Experts from Frazer-Nash were called in because of their experience and reputation in reliability engineering, especially in relation to the harsh marine environment.

The company conducted a detailed modelling analysis to understand just how sensitive the overall reliability of Pelamis was, and to assess the likelihood of components failing – something that could be significantly problematic while the device is in service out at sea.

Also, Frazer-Nash was able to predict the likelihood of individual component failure, highlighting those components that represented the highest risk, allowing OPD to prioritise elements of their maintenance strategy, and further refine it on an ongoing basis.

As a result of this work, OPD has been able to start re-evaluating their existing test data, and have also begun retesting key components – which in turn will enable the company to better forecast its in-service costs, and in the longer term minimise the costs of intervention when maintenance is needed.

In addition, the results of the reliability tests will help point the way to further design improvements on the Pelamis system – ensuring it stays at the forefront of this quickly developing sector.

The example of Frazer-Nash’s work on Pelamis demonstrates the supreme importance of reliability and maintainability to the marine renewables industry, and shows how taking these two issues seriously is helping to drive forward development in one of the most promising areas of marine renewable energy.

Yet several factors are holding the sector back – the most critical being that the marine renewables industry has still to attract and sustain the large-scale investment it needs if it is to develop into an accepted and viable green energy source.

Pelamis is one of the notable exceptions, to the point that the device will soon be going into commercial service. But the wider picture is that the marine renewables sector has historically been viewed as a high-risk one when it comes to securing investment, not least because of the natural challenges that the offshore environment itself presents. As a result, financiers have been reluctant to support a sector that has yet to prove itself in the marketplace.

Far beyond the ability of renewable devices to successfully generate electricity over a sustained period, investors need to be able to clearly identify the commercial viability of such technologies. And the simple fact is that without the assurance of a clear return on their investment, banks and other financial institutions are likely to continue to view the sector as high risk.

Once again, reliability and maintainability are crucial factors. Frazer-Nash has been providing independent technical support to the marine renewable sector for longer than any other engineering services supplier, with nearly all the devices being considered for deployment already subjected to the varying types of operational and engineering analysis the company specialises in.

But while the requirements and demands of investors might vary significantly from what the technology developers need, what they do share in common is the need for impartial information on reliability and maintainability when it comes to a fledgling industry such as this.

Ian Watson, who is leading Frazer-Nash’s services to banks in the renewable energy sector, said: “It is widely viewed that marine renewable technologies carry with them a significant amount of commercial risk, so banks need to be given the confidence to invest in them in the first place – and be able to set appropriate terms and repayment levels as a result.

“We have been providing due diligence services to the device developers for many years, and have an unparalleled expertise in the challenges of the marine renewable environment. It seemed like a logical progression to make this knowledge available to banks and other financial institutions, now that operational deployment in many cases is becoming more likely.”

The marine renewables sector is showing great promise, but taking the next step and developing technologies that are as reliable as possible, easily maintained and an attractive investment is an absolutely vital one.

Developers need the expertise to refine their technologies, and to iron out reliability and maintainability issues at the design stage. Investors meanwhile need to be given the tools that allow them to truly understand the individual potential of each piece of technology.

The next step might not be an easy one to make, and uncertainty may remain, but if we are to see the sector mature in the way we want and need it to, there is no other option.

Kevin Cleminson is chief engineer at Frazer-Nash. Visit www.fnc.co.uk

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