This is a transcript of an episode of Public Address Science which was originally broadcast on Radio Live, 28th April 2007, 2 pm - 3 pm.
You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.
Theme music...
Voiceover:
What could be more pleasant than a day at the beach?
Well, practically anything as far as I'm concerned. I don't really enjoy sand in my underwear -- and I'm completely bored by lying on hot beach, and giving myself skin cancer.
What I do enjoy, however, is getting out and swimming in the ocean. And, in particular, thinking about ways to extract useful energy from the waves.
As a ball-park figure, New Zealand's total wave energy resource is around 2500 petajoules per annum. That's a lot of energy -- about five times more than all the energy produced or imported into New Zealand every year.
In practice, of course, it's only possible to exploit a small percentage of this energy. Firstly, because we can't surround New Zealand with an impenetrable barrier of wave energy converters. And, secondly, because the efficiency of any practical wave energy conversion system will be far less than 100 per cent.
Nevertheless, wave energy still represents a very significant renewable energy resource for this country -- and one that's actually more reliable and predictable than wind energy. What a shame that the potential of wave energy in New Zealand appears to have been completely ignored.
Well, actually, that's not entirely true.
You may never have heard of them, but Industrial Research Ltd (or IRL) is one of New Zealand's Crown Research Institutes. They've been given some spare change, and told to invent a machine that can extract useful energy from New Zealand's ocean wave resource. And, it turns out, that's exactly what they've done.
I visited energy engineer Alister Gardiner -- who heads the research team for IRL's wave energy programme.
Interviewer:
I'm now standing in IRL's Christchurch laboratories looking at their prototype wave energy device, which has been dubbed the 'Wave Wobbler'. There are two different parts to this device. One part is a large rectangular block about 6 metres long welded together out of steel sheets. It's rather dense and heavy-looking, and it reminds me a little of the monolith from 2001: A Space Odyssey except that it's painted bright yellow. A swing-arm protrudes from the top of this monolith, and is attached to a large rectangular float -- which is slightly smaller and much lighter-looking.
Alister, can you explain how this device generates electricity from ocean waves?
Alister Gardiner:
Well this, of course, is an experimental device -- but basically it's quite simple. The large monolithic hull you mentioned [floats] vertically in the water just below the waterline. The float sits horizontally on top of the water, and the motion of the waves oscillates the float up and down.
Interviewer:
Okay, so the monolith is sitting in the water [and] effectively it hardly moves at all. But the float follows the surface of the waves, and the difference in the motion enables you to generate electricity [via a suitable mechanism].
Alister Gardiner:
Fundamentally, yes. Although, of course, it's not quite as simple as that. There's some quite complex maths around getting the two parts to move together in a synergistic way.
Interviewer:
And you've obviously done quite a lot of modelling to explore that?
Alister Gardiner:
Yes, we spent two years developing some complex [mathematical] engineering models to develop the whole concept and come up with an optimized [design].
Interviewer:
So I know you've had this prototype in Lyttelton harbour, which only has tiny waves. In your further testing -- when you actually get it out into the
real ocean -- what sort of power output do you expect from it?
Alister Gardiner:
With the larger scale version which we'll be heading towards commercialization we're expecting round about 100 kilowatts. Which is enough power to keep round about a hundred houses going.
Interviewer:
Okay, right, it wouldn't just be one [machine] by itself -- you might have a hundred or more all moored together in a sort of a 'field' of wave generators?
Alister Gardiner:
Yes, that's right. And we estimate from our modelling that we'd probably get each individual device up to around about a megawatt ultimately. But they will even be larger still.
Interviewer:
So what sort of size are you expecting for that in terms of length and mass?
Alister Gardiner:
Well the 100 kilowatt version, which is really our first commercial focus, may weigh between 30 and 100 tonnes in total. So it's quite a substantial device -- although, of course, you only see a small portion of it above the surface.
Interviewer:
How long [i.e. the length of the device] would that be underneath the water?
Alister Gardiner:
It could be up to ten to 15 metres long.
Interviewer:
And so would you be using water as ballast -- or would it be made out of concrete, or steel, or something [equally] heavy to provide all that mass?
Alister Gardiner:
Yes, that's one of the secrets in fact. Most of the mass is taken up by water. So you don't have to actually tow it out [to the desired location]; you simply flood it when you get it there.
Interviewer:
On land it's actually quite a light-weight device, it's only when you put it into the sea that it [fills up with water and] becomes this very heavy machine?
Alister Gardiner:
Yes, you
might argue that it's a submerged yacht with a small float sitting at the top of it.
Naturally enough, IRL aren't the only company who are looking into wave energy devices. Research teams are working on a variety of different systems in countries all around the world.
The United Kingdom are investing hundred of millions of New Zealand dollars on their marine energy program, and British company Ocean Power Delivery are definitely leading the field in terms of development.
Their 'Pelamis' wave energy device is a truly huge machine. It measures 120 metres long, and floats on the surface of the sea like a gigantic snake.
It couldn't be more different from IRL's 'Wave Wobbler' device, and -- when we'd returned to his office -- I asked Alister Gardiner why the research team at IRL had chosen to take such a different path.
Alister Gardiner:
There's no question that Pelamis is the benchmark at the moment. But we feel that our concept of going for a point-absorber gives us more flexibility -- and, in theory, should provide a more cost-efficient device because of the lower use of materials. It's more flexible because we think we can make smaller devices, [which] could be used off-shore on remote islands at a lower cost.
Interviewer:
What are the comparative efficiencies of the devices -- do you have any sort of feel for that?
Alister Gardiner:
One can look at the Pelamis data sheets, and work out pretty quickly that their efficiency is relatively low -- perhaps just a few per cent. That has it's disadvantages in terms of the size of the device. We feel from our modelling that we can achieve a much higher efficiency than that. And so we've started with an inherent design that we think is cost efficient.
Another point, I guess, is that if a large portion of the device is below the water -- beneath the surface of the waves -- then there's better chance of it remaining viable and surviving storm conditions.
Interviewer:
Which is important when at least some of New Zealand's in the roaring forties, and it's really subject to some pretty horrific waves.
Alister Gardiner:
Exactly, yes. New Zealand is very fortunate in its wave energy resource.
Interviewer:
We're fortunate in wind, too. And we've seen recently a little bit of wind coming on to the market -- there are wind farms generating a very small amount of New Zealand's electricity. How long do you think it's going to be before we see something equivalent to that beginning to happen with wave energy?
Alister Gardiner:
We think it will happen a lot quicker.
I would expect
that by 2010 there will be a number of commercial (or pre-commercial) devices in the water from various suppliers. And, by 2015... maybe 2020... we'll certainly see quite substantial uptake of marine energy of various sorts.
Interviewer:
So that's actually really quickly.
Alister Gardiner:
You've only got to look at the energy crisis in the 80s, and so on, to see the massive involvement in wind energy. Now when the fuel prices came down that more or less stopped, which is the only reason it took maybe twenty years for wind energy to get to where it is today. If that research effort had continued we would have seen wind turbines and wind farms much earlier...
Interviewer:
That brings me to something else, which is whether rising energy prices are a threat to New Zealand or also something of an opportunity as well? What I'm thinking here is of Denmark. You talked about the oil crisis in the 70s, and [Denmark] responded by investing heavily in wind energy technology. And they've now become -- as a country -- the world's leading exporter of wind turbines. Is there a similar opportunity for New Zealand here in terms of marine energy?
Alister Gardiner:
There's no reason at all why we can't produce a technology that's competitive globally. And, as I've mentioned, we think that basic concepts that we're putting together are potentially globally competitive.
However New Zealand does need a supportive environment and an enthusiasm to capture this [opportunity]. And this is, of course, what happened in Denmark. There was a strong government support for a particular type of energy technology.
We certainly need that sort of involvement (I think) within New Zealand. Both from the energy companies -- who are obviously very keen on these technologies -- and probably government leadership
[as well], and obviously the manufacturing companies that will benefit down the track.
IRL have clearly come a very long way with their 'Wave Wobbler' device, but only time will tell whether New Zealand has the political and economic will to develop a domestic wave energy industry -- or whether, as with so many of our other innovative technologies, we'll be content to let the opportunity slip through our fingers.
Theme music...
- Read more about the WET-NZ wave energy converter.
- Read more about the Britain's Pelamis wave energy converter.