The O2 Tidal Generator

Relatively few companies have demonstrated commercial viability in open sea tidal stream trials. In order to receive government support, companies must be producing electricity and supplying that to the grid. This stage of development is sometimes referred to as the valley of death. When a startup has begun operations, but not generated revenue. This is sort of where all the startups in the marine renewable space are. One of the pioneers in this space is Orbital. Their CEO Andrew Scott tells Chris Smith about the O2, a device currently generating electricity off the shores of Scotland...

Andrew - Our technology's a little bit different, very innovative. It doesn't look like a wind turbine, a miniature wind turbine bolted to the bottom to the sea bed. Some people kind of think it looks like a spacecraft or an aircraft. So it's got two big wings and a fuselage and actually the whole thing floats. And at the end of the wings, we've got our power trains. So there's two power trains, one at either end and it's anchored on site with a big set of moorings and the wings are hinged, so they can come up to the surface so we can get access to everything at low cost and then they can drop down to start generating power.

Chris - Now, when you say power trains by that you mena the turbines for want of a better phrase, that's going to extract the energy from the water flowing past your structure?

Andrew - Yeah. As one of your previous guests was saying it's a very similar technology to actually generate the power as wind turbines. Some people call them the cells or power trains, but it's really the rotors that take the kinetic energy and turn it into rotational energy. And then you couple that with a gearbox and a generator.

Chris - And how big is the whole thing?

Andrew - Yeah, that's the other thing that will probably surprise people is it kind of looks like a plane and it actually is about the size of a jumbo jet 747.

Chris - And how much juice comes down that cable?

Andrew - The turbine that we've built and launched last year, we call it the O2, it's the world's most powerful tidal turbine. And when flow speeds get up to 2.5 mps, it reaches rated capacity, which is two megawats per hour.

Chris - Would you then envisage a fleet of these that you would anchor in optimal locations, presumably so they don't all interfere with each other or bash into each other, but you would therefore be optimising the extraction of energy from where the tidal flow is fastest?

Andrew - Yeah, absolutely. In the same way that you get wind farms that are multiples of 1, 2, 3, 4 megawatt turbines we envisage that we would have multiple of these inner tidal stream sites that are all generating power onto a cable back to shore.

Chris - And I suppose one of the massive advantages of doing this is that because the tide comes in and out twice a day, you know, when, and so it makes the generation and therefore the provision of energy that you know, is gonna be there very predictable and therefore very reliable.

Andrew - Yeah. That's the beauty of tidal stream energy, you know exactly how much energy you're gonna produce and you know exactly when you're gonna produce it. And there's actually value in knowing when you're not gonna produce it as well. If you've got planned maintenance and things, you can schedule it for times when there's very little or no tide. So you can do work without really disrupting the overall performance or yield of the turbine.

Chris - One of our other guests was pointing out that, you know, it's a pretty harsh environment the marine environment. I suppose that by having something that is not stuck to the seabed, you can lift those wings up to get to the business end of the operation quite simply, you've actually made it much easier to maintain. And therefore you presumably have saved quite a bit of money?

Andrew - Yeah, absolutely. There's kind of a golden rule or a rule of thumb in the offshore environment. A job that will cost You maybe a pound offshore will cost you 10 pounds offshore at the surface, but it'll probably cost you a thousand pounds at the bottom of the sea bed. So, being able to get access to equipment quickly and cheaply on the surface is absolutely key.

Chris - When is this gonna be realised? So it is actually beyond the prototype generating little bits of power stage?

Andrew - Well, O2 two is generating power right now into the UK grid. So, we built it and launched it last year from Dundee. The aspirations are, and we're planning on building more of these in the coming years to start creating these arrays, both in Scotland and around the UK.

Chris - For comparison then Andrew. So if I build a big wind turbine megawatt for megawatt, what's it cost to have the same generating capacity with one of your devices?

Andrew - The average cost for a megawatt offshore is probably today around about 3 to 3.5 million pounds per megawatt. And for us, we built the last turbine at just a little bit over 5 million pounds of megawatt.

Chris - So you're not far off what we're already achieving with wind?

Andrew - No, not very far at all. Now the overall cost of energy is a function of a lot of other things. Obviously your resource is free, but how you generator performs, you know, one of your previous guests was talking about improving the performance of rotors and all these sorts of things. So these are things that wind have benefited from for the last 20, 30 years. And indeed they've benefited from a volume of scale, economies of scale. So those are all things that have allowed their overall cost of energy to come down a lot and certainly landing where we are from a manufacturing cost where we are, we think is, you know, really exciting.

Chris - Have you now got an order book then to do this, not just for the UK, but internationally, or is this still very much at the stage of hand to mouth? It's making some electricity, you're proving the point, but you're still waiting for those calls to come in?

Andrew - Well, we do have commercial projects here in the UK and we anticipate this summer, we should get clearance from government support hopefully to move forward with them. And indeed, actually we've got another turbine to build and put up in Orkney and combine with an electrolyser and battery storage as well. So yeah, we're moving forward, with some exciting commercial projects here in the UK and we're seeing definitely an up turn of interest from regions around the world that have got tidal stream energy that are very interested in what we're doing.