Many people wonder ‘what is the story of wave energy, why is it not in use, is there not a massive resource sitting off our Atlantic coast in particular’? This includes those who work on the basis that if man has been able to go to space since 1969, why can’t we harness a resource that sits on our coasts’, to engineers who say, ‘it can’t be that difficult, can it’? Well, it can!
For a start, how are waves formed, how do they move, how do they carry energy? I believe there has been a large gap between hydrodynamicists who know how waves function but not how to make them work, and engineers who might make them work but often do not understand them enough to do so. This is –maybe more so was – a 'technical gap' and requires more than a few lines to explain. In simple terms, the water from the South Atlantic stays there.
Circular motion
Starting out, ripples on the water are pushed forward by eg the prevailing SW wind and form a circular motion. This momentum is passed on and grows as the wind blows, the longer the horizontal distance (called ‘fetch’ by mariners) the more crests build and the more vigorous this circular or orbital motion, which is at its strongest near the surface and falls off with depth. Somewhat like a car rear-ending a traffic jam, the car at front is shot forward, except with waves this effect is continuous and growing.
Fig 1: Use of 'TRL' s is risk-related, denotes project status and is vital to wave energy projects. Developed by NASA, this ‘metric’ is widely used in R&D: developers and investors can relate to it. From TRL7 on, applications would be expected to be under test at sea with partners.
The second gap, in my view, is an 'industry gap' – this is the lack of comprehension of the marine sector and its development that is common to most landlubbers.
We are not alive to the cost difference multiple of work performed at sea versus that on land. We are not aware that for many days each year the sea is too inhospitable and dangerous for work to be done, so that special-purpose equipment may sit waiting, clocking up costs of literally millions per day, that a sudden storm may undo weeks of uncompleted work within hours. And many other factors. Most of the ‘actors’ in the wave energy race had little or no real experience of the sea (inshore yachting does not qualify).
RISK is part of this – consideration of the hugee and sometimes freak conditions at sea frightens off developers and investors alike. The necessarily long development time to commerciality, likewise, is negative.
There remain the normal questions applying to all business ventures, relating to customer acceptance, costs, margins. And, oh yes – the state, as state inaction, delays, uncertainty, when all other barriers are overcome, can sink a venture. Finally, history, several overhyped and underprepared renewable energy developments in the marine sector have understandably scared off investors.
So why did I, we, get involved? To what extent has it been a success or a failure? Where is wave energy now – read on, this being the first of two articles; for the answer, you must await a follow-up article.
Background
Realisation of the significant wave energy potential off the Irish Atlantic coast began in about the year 2000. By 2005, the government, alongside the European Union, initiated the first steps of a development programme aimed at harnessing this resource. There was a great deal of enthusiasm surrounding this promising asset, leading to the launch of various ventures in the sector.
By 2008, during the peak of the Celtic Tiger era, many engineers saw this as a unique opportunity. Among them were the founders of JOSPA – Joss Fitzsimons and this author (Patrick Duffy) – giving the company its utilitarian name.
The Celtic Tiger's economic boom fuelled interest in exploring wave energy, and the government actively encouraged new ideas and ventures in this emerging sector. Wave energy was seen as a potential game changer, attracting about 20 different groups, including JOSPA, to pursue this new opportunity: we had worked together previously with success.
The 'Irish Tube Compressor' (ITC)
Fig 2: The ITC attains 1-2 bar without, 2-4 bar with, airlift pump.
The first Jospa idea was to use waves to push alternate slugs of air and water forward in a tube, accumulate in a receiver and discharge both elements through dedicated turbines with attached generators (Fig 2).
The build-up of head is accompanied by the compression of the air, resulting in a back-spill of water and a gradual increase of pressure along the tube. What you capture is wave momentum, not its speed. To gain the benefits of the speed, termed ‘celerity in this instance, it is essential to add a powerful feed.
Power is proportional to the square of speed, so water at celerity has at least 49 times – say 50 times the power potential of the water entering the simple tube. Hence our addition of a Chuter, designed and improved to make the water attain celerity. This was vitally important to Jospa; in filing patents, it transpired there were three prior patent applications on the concept (one of them a ‘lost’ Soviet one), but they had missed it that a powerful feed is needed.
Optimum tube dia. approached 2m and its length should be upwards of 300m. To the ITC we added an airlift pump to almost double pressure, and a tube designed to limit energy loss (see Fig 3) as without our patented reinforcing it would tend to be rigid.
Fig 3: Tube with longitudinal reinforcement to avoid distortion.
Extruding the tube (ideally approaching 2m dia. and at least 300-400m long) and feeding in its various reinforcements did not represent much technical challenge but presented a financing leap, so we produced and demonstrated a Chuter + Vortex Turbine (Fig 5) at this point to express visually the way we were extracting power (which would always make far more impression on interested parties than graphs and tables of data).
The diversionary time and cost were minimal as we made up the turbine with simple household items, a large plastic bowl being the main one. This worked very well and made an excellent impression.
Fig 5: Chuter on LHS, Vortex Turbine with draft tube. The Vortex bowl smoothed flow, and with added field current regulation of the generator would enable a reasonably steady output, particularly when the spacing of several devices in an array would be added. The bowl also stabilises the turbine, and its length will avoid reverse flow risk.
We placed coloured plastic floats in the Vortex stream and their vigorous turbine flow was impressive, showing the efficacy of the Chuter.
Concentration on the Chuter: Improvements/attachments to increase its contribution
Fig 6: LHS Tank tests of identical tubes one fitted with aerofoils to demonstrate 'ACF'. RHS Final Chuter in tank fitted with eccentrically mounted buoyancy bottle as a ‘buoyant fulcrum.
At this stage one might ask 'why did you keep trying different technologies, why not perfect one' – the answer is that we not trying new technologies, but were improving the technology, at this time by close attention to Chuter design and adding special attachments to improve its performance.
It was not that we had four different WECs, as the Chuter was one of them and fundamental to the other two – ie, central to the ITCI on its own as the Chuter/and at the core of the Vortex turbine – so being part of all three its optimisation was vital. The Chuter already had basic Overtopping action, with Channelling in addition:
First, we attached out-of-balance buoyancy bottles/cylinders to each side. Oncoming waves made them flip dramatically, increasing the amplitude of water thrown forward. We termed this ‘the Buoyant Fulcrum’.
The second effort merits a lot of attention as it pointed a way to the future we could not then anticipate. We called it 'the ACF', use of specially positioned rigid fins, and we put the idea through two series of tank tests – first for proof of concept, then for power measurements – before adding them to the Chuter. The results were so good that the Irish authority on wave energy and its performance, UCC’s what is now LIR Centre, said, and with their permission we quote: “Wave energy devices can typically take 10-20% of available energy from the sea (but using ACF):
- "Where that’s 10%, it could increase it to 34%.
- "It's 20%, it could increase it to 44% (as measured at 6-9s periods).”
These fins deliver amplitude (heave of the Chuter) and bandwidth (response to a wider range of wave periods) improvement, while the ‘circular’ diagram of wave motion, Fig 7, is essential to understand how they function.
Fig 7: Particle motion of wave energy.
At the top of the wave the water particles move in nearly circular orbits, whose diameter decreases rapidly with depth. These orbits are propagated onward by the next particles, the wave moving at ‘celerity’ with the upper water particles moving in the same direction as the wave albeit more slowly. (That is why the Chuter also has its ‘top-cutting’ shape to cut the energetic tops of waves, and we speak of it having a cutting ‘knife’).
At the hollow part of the wave the particles move backwards with respect to the advance of the wave. This gave us the idea to use these opposing forces as a couple at opposite ends of a device to increase its displacement and to so make more power available.
Most of the power available arises from waves of 3m and less, so the improvement shown below was significant in movement towards commerciality.
Fig 8: LHS how the Buoyant Fulcrum pivots. RHS, the amplitude and bandwidth were dramatically tuned to take more from waves off Belmullet.
Importantly, SEAI’s Graham Brennan, formerly of Rolls-Royce, who had viewed many attempts at WECs, was on the spot. He suggested we park the Chuter immediately in favour of the very promising genesis of a new WEC that would harness such fins. A high-performing WEC was anticipated, suggesting a change of technology not due to failure, but to unexpected success.
Fig 9: Eite model with PTO, shown under test in tank. Jospa won the iMERC national innovation award for its “VEPPI “(Velocity Proportional Power Instrument) to measure its power output accurately.
So now we embarked on 'The Eite' (wing) and with it a purposed low inertia PTO suited to wave energy (Fig 4). All succeeded well in proof of concept with videos, data gathered, reports and electricity produced and measured by our new VEPPI instrument.
But storm clouds were gathering on two fronts. One, wave energy was rapidly losing commercial attraction. A series of ventures that were hyped up far too early, failed, having run through hundreds of millions of euro.
We had made all our models for test (typically at 1/20 or 1/25 scale supported by Froude factors well known to many engineers, to scale up) for a very small expenditure (less than 1/100th of the spend of a few leading companies), supported by SEAI, but to us wave energy was gradually becoming unfundable with little promise of being grid-competitive for a long time.
Outstanding UCD mechanical engineering students
On the Jospa front, our technical leader, Joss, had become seriously incapacitated. Our ability to get assistance – Dr Wm O’Connor, head of mechatronics in UCD, brought to us Simon O’Callaghan who did excellent work in modelling technical scenarios, and subsequently Claire Lambe, Irish Olympian oarswoman, who carried out a techno-economic assessment and greatly assisted in our workshop and tank testing, both outstanding UCD mechanical engineering students – that kept us advancing when help could not be otherwise engaged. Wave energy was less glamorous now.
We had experienced encouraging situations – a Swedish Chalmers University spin-off came to Cork to discuss a merger with us, the Spanish oil co Repsol asked us to enter a competition where we came within a hair’s breadth as also in a Horizon competition.
Most importantly, the management of Dunlop Oil & Marine, a sectoral leader to whom ITC manufacture was very suited, had proposed it to their owner the giant Conti Corp (then sales $53bn mainly in rubber products) and it went up the line until Conti decided on a major international job-shedding.
We were/are, I believe, the last standing of 13 Irish companies dedicated to wave energy. In our view, it was time for us to turn to real markets with competitive sales, not a hobby or eternally subsidised R&D.
That was the background we came from, and we saw it now appearing in front of us in another sector of wave energy that is less daunting technically and financially, and where our efforts showed us we could gain a significant advantage. We decided to investigate it, and to go for it if so indicated – to be described in our next article.
In the meantime, the OE Buoy, emanating from Matsuda of Mitsubishi and developed in Cork by promoters with the assistance of UCC Professor Tony Lewis and the head of LIR Dr Jimmy Murphy, stands out in wave energy leadership with a full-scale deployment with the backing of the US navy – good luck to them.
Author: Patrick Duffy, co-founder Jospa.