Now that we’ve all had time to see how the Rena disaster has played out, a number of later lessons, versus early lessons can be taken. Our marine infrastructure, after a slow start, is doing a plucky job in cleaning up the spilt oil and safely removing the rest. But as for removing the containers, we must wait patiently for the large marine crane from Singapore to arrive and – as for removing all traces of the Rena from Astrolabe Reef itself – that will be the magician’s trick we are all waiting to see!

What all this underlines is that marine disasters nearly always require very case-specific, carefully calculated plans to be worked through and co-ordinated. There’s nothing routine about anything to do with the Rena. But marine disaster co-ordinators in more advanced countries typically have more options – more pieces on the watery chessboard to move around – than they do here. That’s basically because those countries, like the USA, the UK, Sweden, Denmark, Holland and Singapore, have much larger and more sophisticated marine infrastructures than we do. They have significant navies, testing tanks, shipbuilding industries, industrial ports, dry-docks, floating cranes, tug boat fleets, and a menagerie of highly specialised ships, such as those dedicated to the offshore oil drilling industry. As a further bonus, the Europe-centred countries are all in much closer proximity than we are to any other country, so that any resource any one of them may urgently require can be quickly be hired – at competitive prices – from the others.

I can tell you first hand that brainstorming about wave energy is great fun. It produces much the same buzz you get from reading Jules Verne novels. Even my broad-brush Calculations page (have a play) paints a very optimistic picture. There is certainly a lot of energy in waves! Even so, wave power is fundamentally a tertiary effect. The primary source of energy is from the Sun. That generates the secondary source – wind – and that, in turn, eventually generates third-stage energy in the form of waves. Each stage results in a drop in efficiency. At the primary end, even though solar power has its own inefficiencies, costs and scores the occasional own-goal, it is becoming more and more attractive with every year that passes. At the secondary stage – wind power – prospects are also looking strong and might be even stronger if wind turbines were placed over the wind-swept sea, as they already are in many countries. Stronger again if the new generation of vertical axis turbines can shake off the bad reputation their disintegrating first generation ones left.

So, with all those thoughts and the Rena in mind, Let’s look at just how economically feasible the generation of electricity using ocean waves around the New Zealand coastline could ever really be. At this point, however, we must distinguish between the possible use of tides –  in Cook Strait or the Kaipara harbour for example – and the use of waves  from the open ocean to generate electricity. Tidal power certainly requires a strong marine infrastructure but its almost perfect predictability, coupled with its similarity to fresh water hydro power, at least enables costs to be accurately calculated.

A good take on the on-going world-wide effort on ocean wave power is the Wikipedia Wave Power article. Here we see an amazing collection of very  “Vernesque” devices. New Zealand has a few of its own but none is at full scale.

One full scale wave power device which has emerged is the Pelamis  which consists of three or more huge, semi-submerged cylindrical sections linked by hinged joints. As waves pass along the length of the machine, the sections move relative to one another. That motion is resisted by hydraulic cylinders which pump high pressure oil into tanks. That oil pressure can then turn electrical generators. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cable.

All of which sounds reasonable but let’s think about the length of this giant sea snake. At 180 meters, its nearly as long as the Rena (236 m). What would happen it broke loose from its moorings and ended up on the rocks of some remote West Coast beach? Even if it didn’t shed its own oil and could be repaired, how would it be towed back out to sea? If somehow salvers did succeed with that, to which large dry-dock would they tow it? This would likely be the West Coast, remember. And, aside from all that, what would the power cables be doing all this time? Would commercial divers be required to salvage and eventually re-connect them? And when would the service vessel be able to safely go there – when the waves subsided? But the position would have been chosen precisely for the waves being as large and as constant as possible.

Even in absence of accidents like the above, the routine maintenance would still involve many of the above factors – tug boats, dry docks and divers at a minimum and there is the fact that the West Coast is far from the National Grid. In that long journey, more of the power would be lost in transmission.

OK, I think you’ve got the idea, so let’s not even bother to add in the likely huge costs of the many and varied resource consents and related legalistic hurdles.The bottom line is that the net number of dollars per kilowatt from ocean wave power for New Zealand will probably never be competitive in a free, unsubsidised energy market.