Q&A: Tide and trusted - wind and wave energy

Materials World magazine
7 May 2012

The answers are tangled in the wind and waves, but we haven’t teased them out yet. Neil Kermode, Managing Director of The European Marine Energy Centre (EMEC) in Orkney, UK, spoke to Eoin Redahan about advances in marine testing facilities and renewable technologies.

From your perspective, how much more streamlined have wave and tidal technologies become?

We’ve certainly seen some streamlining in how quickly devices can get into the water, and some marine operations have become quicker and more routine... In the tidal arena, the vast majority of machines seem to have settled on horizontal axis and generally three blade devices. There is definitely a centroid of type there. In wave, there isn’t the same consolidation of form, so only time will tell which direction that takes. I think people are [now] getting back results that are broadly in line with what they expect. There are significant and useful amounts of energy being delivered, but we’ve also got to recognise that these technologies are still very new and very early in their development paths.

Are new materials being used?

Materials suppliers are starting to pay attention to the market… There are people testing more elastic materials, so we are starting to attract the attention of companies with materials other than steel or concrete, but it is early days.

Is it difficult to test long-term performance?

Yes, and one of the things that has been built at the UK National Renewable Energy Centre (NAREC) is an on-shore drive train test rig that allows them to do accelerated testing. To a large extent, we are at the behest of the weather. If there is a calm period, there’s nothing we can do about it, so creating synthetic conditions has its uses. The combination of dry test rigs alongside EMEC’s scale and full-scale prototype testing in real sea conditions provides a great opportunity to accelerate the learning process.

How have the European Marine Energy Centre’s test facilities improved in recent years?

We have installed additional cables at our sites, and brought in shallow water berths at the wave energy test site that use pipelines rather than cables. We’ve also built nursery facilities, which are in more protected waters around Orkney to allow developers to test scale size machines and processes.

What have been the major advances in testing equipment been in recent years?

I would say they have principally been two-fold: NAREC’s dry drive train test facility, and some of the changes we’ve made to our cabling infrastructure. We have capped the ends of our cables in a way that allows us to test up to 11kV without having devices on the end of them. That means we can be absolutely sure that the testing infrastructure is in good order prior to someone plugging in several million pounds of equipment at sea.

What are the current shortcomings in tidal energy and wave energy?

We haven’t got far along the road yet to get a perspective on things we should be designing out or designing in. We’ve proved we can turn seawater into electricity, but what we haven’t yet been able to do is prove that machines continue to work as expected for a long period. But that will only come with experience or years on the clock.

What do you hope the new Offshore Renewable Energy Catapult Centre will achieve?

We’re delighted to see the Catapult is being set up and that it has remained focused on areas where the UK has a major strategic advantage, for example, offshore wind, wave and tide. We expect that the focus will initially be on the offshore wind side of things because, frankly, that’s where the biggest amount of energy exists for the UK and we are further along the development process. But wave and tidal will be close behind.

What have been the most exciting technological developments in the past two years?

We have shown that very large oil vessels can be operated with dynamic positioning systems that handle the tide and lower huge weights to the seabed in a very short period of time in hard conditions. We’ve had a ship sitting at sea with a robot drill sitting on the seabed for about a week. The drilling was done by Bauer (based in Bishops Stortford, UK). I think it was the biggest hole that has ever been drilled in the seabed in such tidal conditions. It was about 2.5 metres in diameter and 11 metres deep. The tide runs up to eight knots on this site, and half a billion tonnes of water goes through the site in an hour. It was powered hydraulically from a power pack on the vessel. There were no anchors. It was just holding itself against the tide, and it had hydraulic lines running down to the robot drill.

There are many different methods of generating energy from waves. Which of these is the most efficient?

At the moment I don’t think it’s possible to say, because it is not just a matter of efficiency, but also effectiveness at using resources…[You must take into account] what is going to be the most durable, because these devices are being deployed in harsh sea conditions...Part of the measurement of success is how long it generates for before it needs maintenance or replacing.

Why are tidal and wave energy quite far behind the offshore wind turbines in terms of energy efficiency?

Principally because we have a lot more experience in wind energy…Land-based machines have been scaled up, and some of them have been put out in the sea. So, companies started with a technique that had been proven on land and, then they put it in the sea. With wave and tidal energy there is no land equivalent, so you have to go in the water from day one.

Do you see marine renewable energy technologies playing a significant role in the coming years?

Yes, I do. I really am seeing good, solid political support at all levels. The Scottish Government is very determined to make it happen. The sooner we can get to do this stuff, the sooner the payback happens. I think the signs are very positive. Frankly, the Government can’t keep going with oil and gas. We need to power the UK for generations to come, and wave and tide are always going to be there.

Has anyone tried anything really audacious to exploit tides and wind in a single structure or is it just not viable?

Something always sticks in my mind from a conference I went to a few years ago. One of the delegates said that he was always taught in university never to put a prototype inside a prototype inside a prototype. Developers have got to get these devices going individually, and then work out how to continually push and exploit them.