Martin Murphy with the DeltaStream

Talking tides: Martin Murphy of Tidal Energy

Managing director of Tidal Energy and incoming president of IMarEST Martin Murphy discusses the role tidal stream renewable electricity could play in Britain’s energy mix.

Martin Murphy is a busy man. The managing director of Tidal Energy is telling me about how his six-year development project to produce a prototype tidal stream renewable electricity generating system is reaching its critical implementation phase. He is also the incoming president of the Institute of Marine Engineering, Science and Technology. Completely at home in a career full of challenges, as we sit in the boardroom of his Cardiff offices he tells me he’s also a man with salt water in his veins. “There’s been a strong marine current running through my life,” says the 57-year-old Briton with a twinkle in his eye that suggests it’s not the first time he’s made that pun. Murphy’s father and grandfather were mariners, and he followed in their footsteps by joining the Royal Navy on coming down from university, spending 12 years as an engineering officer at sea.

He later jumped ship and served his time in corporate industry, working first with Alstom for a dozen years, followed by L3 Communications, a US company with interests in the UK, which specialises in defence and homeland security.

He joined Tidal Energy - a marine energy technology company - exactly six years ago. Since then he has “been charged with the construction, operation and future wellbeing of the company as we build our prototype tidal stream generating device: a new concept in renewable energy in the marine energy space.”

Creating energy

Murphy routinely describes the prototype Tidal Energy is developing as ‘the device’. It’s an underwater horizontal-axis turbine designed to sit on the seabed on a triangular frame, which will generate electricity by means of the turbine rotating under the influence of tidal flow. “It responds to the kinetic energy of waters that are moving as a consequence of the tidal phenomena related to the gravitational effects of the moon, earth and sun.”

Murphy says that this is a different concept from that of tidal lagoons, which capture water behind a barrage, releasing it through gates or sluices to create turbine generated electricity after the tide falls. “The lagoon concept is responsive to the potential energy caused by the rise and fall of tides. But what we are doing here is responding to tidal flow.”

The ideal geophysical situation for Murphy’s device is a site where tidal flow is fast, typically around headlands or through narrow channels where currents “are accelerated by and around those geographic features. Around the coastline of the UK there are a number of specific sites that are very well suited to this type of technology, where companies like ours can examine and investigate the prospect of putting these turbines on the seabed to see if they can generate power.”

Tidal Energy has selected for its trials Ramsey Sound off the coast of Pembrokeshire in south-west Wales. The first criterion for site selection is speed of flow. “This is because power generated by turbines is directly related to the cube of the velocity of the water. If the water is flowing at 2 knots it will generate a certain amount of power, depending on the diameter of the turbine. If that speed increases by factor of two, then the output power increases by a factor of eight. Obviously, the greatest power is going to be achieved from high-velocity sites. What this means is that we are typically looking for a site that has a flow in the region of 4-5 knots in a spring tide flow condition.”

Further considerations include depth, together with suitable seabed geology. “Once we’ve got those parameters established, we can look at how the associated infrastructure is situated in relation to that. We need to ask if there is good access to the National Grid. Is there the distribution network in place for us to actually pump the power in? Are there good port and support facilities nearby for operation and maintenance reasons? These secondary issues become important once you’ve understood that there is a practical solution for putting the turbine in place, and how to make it happen as a holistic power generation station.”

Finally, there are environmental concerns associated with putting heavy machinery on the seabed. “What is the effect on sea mammals, birds, and the benthic community on the seabed?” he asks. “All these things have to be put into the pot to establish whether that site is a reasonable prospect for the delivery of power.”

Blue sea - red tape

Before anyone can start putting a heavy plant at the bottom of the ocean there are a number of administrative hurdles to take into account. And these are every bit as important as the engineering and geophysical challenges associated with the project.

“There are three things you need to do,” says Murphy. “First, we need to secure a lease on the seabed.” The seabed around the coastline of the UK is owned by the Crown Estate, which meant that Murphy needed to apply to them to install the device. “Second, if we have to put any infrastructure ashore then we need to get planning permission for that. Third, and this is one that really involves a lot of effort, is securing an operating licence for once the device is actually installed on the seabed. There are regulatory authorities charged with the protection of the environment around our coastline. There is legislation in place on a national scale and at European Union level to ensure that companies like ours don’t just start generating power without taking these considerations into account.”

Murphy goes on to explain the effect of this planning and that the environmental impact assessment has to be scoped out at a very early stage. “Then we do the actual environmental impact assessment itself by gathering together a database of information. Then we apply for a licence. From doing the scoping work to arriving at the point where we were awarded consents and granted a licence took about three years of work for our particular site.”

None of which is cheap. By Murphy’s own admission Tidal Energy is a small to medium enterprise (SME) and so to achieve its aims it needs financial backing. For the most part this comes from ECO2, a renewable energy project development company, which shares a building with Tidal Energy. “ECO2 is our principal shareholder and it has supported us with funds to actually build the device and secure the associated paperwork. Obviously, what they ultimately want is to obtain a return on that investment.”

Beyond the business space, Murphy says there is considerable governmental interest in investigating the development of marine renewable energy as part of the overall national power mix. As a result, there is a developing groundswell of interest in this form of energy, bolstered by the assumption that as a small island nation with nearly 8000 miles of coast, we are rich in untapped marine energy resources. “With tidal flow renewable energy there is the opportunity to take advantage of that,” says Murphy. “And so you can see why at this stage governments are providing support. In our case, through the Welsh government, we have secured a grant from a European Regional Development fund to help us in support of this technology.”

Where are we now?

Over the past six years Tidal Energy has completed the fundamental design work, manufactured the seabed power-generating machinery and obtained installation and operational paperwork. This means that the device is now ready to be put into Ramsey Sound. “We’ve done pre-works on site and the infrastructure is installed. The subsea cable, which will carry the power from the device offshore to our onshore substation compound where we are connecting to the distribution network, is now in place. And where we are today is literally waiting for the right weather and tide windows to coincide, so that we may install the device at Ramsey Sound.” At the time of writing this is the status of the project, although according to Murphy “this could change at any moment.”

As tempting as it may be to say that this will be the moment when the job is done, it is in fact the moment when the real work starts. “As soon as we get the device in the water and it’s connected, we will have to test all the operating systems and then we will be generating electricity.” This is where Murphy takes a pause to reflect on what the two main purposes of the device really are. “First, we’re doing it to prove that it actually works and to validate all our design calculations. The second element is to explore the environmental impact question, because this is a crucial part in the development of the industry. We need to know that turbines like this in the underwater environment do not have an adverse impact.”

Feeding into the mix

Murphy is nothing if not passionate about renewable energy. He thinks that there is a real opportunity at Ramsey Sound: “We have the resource. It’s now a question of whether we can technically exploit it. The challenges in the marine environment are significant: the undersea marine environment, with its fast flowing tides, is probably the most hostile environment apart from space. But we can draw on the experience that has been gained in the oil and gas industry in terms of operating complex technical machinery underwater.”

Further to this, Murphy believes that the renewable portfolio is playing - and has to play - an important role “in our overall energy requirement.” He doesn’t claim for a minute that the future of energy lies only in the renewable sphere, “but it does have a role to play, from security of supply to an involvement in our decarbonisation associated with climate change. I believe that renewable energy is here and that it is here to stay, and that the marine sector can be a part of that.”

He goes on to say that one of the main criticisms of renewable energy is the issue of intermittency. With wind energy there is always the doubt as to what will happen to the supply if the wind stops blowing; with solar PV there is a similar (though lesser) concern for when the sun does not shine; but with marine the key strength is, as he says, “it is entirely predictable. It’s not constant, but it is predictable. If we can develop a role for marine tidal stream energy within the overall power generation portfolio in the UK - and estimates are placing its eventual contribution at somewhere between five and 10 per cent - then we are producing baseline energy, because we know when we can have it.”

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