Posts by David Haywood
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Andrew Stevenson wrote:
Which is easier said then done...
Sure... if it was easy to do then it would have been done years ago...
Andrew Stevenson wrote:
It doesn't matter how wonderful a widget is, its got to prove itself for 10 to 20 years before serious money gets invested and larger scale operations commence.
Sure... that's extremely well understood by everyone involved. But that's no reason not to try to develop this sort of technology. (Do you work as an accountant for an electricity company, by the way -- this is exactly the sort of conversations I used to have with them when I was an energy engineer!).
The early wave energy research (in the 1950s and 1960s) was incredibly costly. Japan put itself off wave energy by building a few super-expensive systems that only survived a few days/weeks at sea.
But with recent advances in computer modelling this sort of expensive suck-it-and-see engineering has been greatly reduced. IRL have been 'testing' and optimizing their wave energy device for the last two years in a virtual environment based on real wave conditions.
Pelamis underwent similar development -- although they came up with a very different solution. Their device then passed extensive sea-trials in the North Sea.
At the moment, unfortunately, the cost of electricity produced by Pelamis would be far too high for New Zealand, but it is already economic in some countries. Portugal, for example, is in the final stages of constructing the world's first wave energy farm (based on Pelamis). Further wave farms (also based on Pelamis) are in the early stages of construction in Scotland and England.
Juha Saarinen wrote:
What happens if one of the large arrays break up?
You have, as Andrew suggests, a big problem. But I should emphasize here, that really -- engineers aren't a bunch of complete fuckwits. They have thought hard about these issues for many years. If a wave array breaks up they won't throw up their hands and say: "Oh, I never considered the possibility of that happening". They design in safety systems (quadruple redundancy, warning beacons, scuttling systems) that make this possibility as remote as possible, and -- if it occurs -- to have a safe failure option.
Frankly, the possibility of such an event is not a reason to give up on attempts to develop this sort of technology.
Yes, the development of wave energy devices is an extremely difficult engineering problem. But that means that it is also a huge opportunity.
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Juha Saarinen wrote:
... is the 100kW figure correct? That's the output of an average car engine if it's right. Expected a bit more.
Yes, that's for the first commercial-scale device that they're working on. They expect to be able to increase this to around 1 MW for later devices.
To put this figure into perspective, the Brooklyn wind turbine in Wellington is rated at 225 kW.
Comparisons with car engines are always a little unfair. A hundred kilowatts is actually a lot of power -- about 5000 energy-efficient light bulbs worth, or the maximum continuous power output of around 350 fit human beings.
In automotive terms, note that 100 kW would be the maximum output for a (large-ish) car, and the engine would wear out after only a few dozen hours at this output. A wind turbine or wave device can keep generating this power output for years on end -- and you never have to fill up the tank with petrol!
Note also that they expect to operate these devices in large "arrays" with a common electrical feed back to land. If you have an array of 100 x 1 MW devices then you're talking about a very sizable total power output.
Juha Saarinen wrote:
Second, these seem like fairly major structures. What's the "resource cost" in terms of energy and material to build wave generators, and to transport and maintain them? Is it worth it, basically?
The power density in waves is much higher than that from wind -- so the devices should theoretically be smaller than comparable wind turbines (note that wind turbines have large concrete foundations), and therefore would require less energy and material to build/transport. The energy pay-back period is expected to be only a couple of months.
So, yes, if you can build a cost-efficient and reliable wave energy device then it is definitely worth it.
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Steve Curtis wrote:
I wonder why you focus on 'Energy' but fail mention 'Power'.
Thanks for your comment, Steve.
I think your question may arise because you are confused about the terms energy and power.
Power is defined as energy per unit time. It's measured in Joules/second (aka Watts).
Energy is, of course, measured in Joules. A kWh is simply a special unit of energy used by electricity companies (where 1 kWh = 3.6 MJ).
In other words, the examples you give ("babbling brook, a rooftop baking under the sun, a gentle breeze, waves crashing on the shore") are all examples of both energy and power.
The examples that you claim are power ("8000 kWhr per year... 20kWhr per day) are, in fact, examples of energy.
You may be talking about the difference between exergy and energy -- but, even so, your statements are misguided with respect to the output of solar cells, which directly produce energy in the form of electricity (i.e. virtually 'pure' exergy).
Wikipedia may have some useful information for you in terms of energy, power, and exergy:
http://en.wikipedia.org/wiki/Energy
http://en.wikipedia.org/wiki/Power_%28physics%29
http://en.wikipedia.org/wiki/Exergy -
What's with New Zealand’s Wave Energy Technology (WET-NZ) programme? Find out in this week's episode of Public Address Science...
NOTE: A complete transcript of this episode is available here.
Further information:
-- Read more about the WET-NZ wave energy converter.
-- Read more about the UK's Pelamis wave energy converter.
-- Read more about wave energy in general in Wikipedia.
-- Visit a gigantic wave-powered musical instrument in Zadar, Croatia.
This episode of Public Address Science was originally broadcast on Radio Live, 28th April 2007, 2 pm - 3 pm.
An archive of all Public Address Science episodes can be found here.
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Andrew Stevenson wrote:
Batteries... don't forget the cost component
Fair point. Energy storage is certainly a major issue with all the 'flow type' renewable energy sources e.g. solar, wind, wave, and (perhaps to a lesser extent in NZ) tidal flow.
I was hoping to be able to cover this topic in the current series of PA science, but it might have to wait for next time.
a large reduction in cell cost still won't make it cost effective compared to grid supplied power
Interestingly, with regard to other 'balance of plant': it's anticipated that the price of grid-tied inverters will also drop significantly with larger production volumes. For new installations it looks like the Grätzel cells could be integrated into existing building components (window glass, roofing steel, etc), which would reduce the cost of additional structural items (e.g. mounting frames, etc).
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Judi:-
You're quite right! Unfortunately time didn't permit more than a quick overview of this technology.
Some interesting areas where other research groups have had promising results include forming these cells onto flexible surfaces -- which, for example, could be used as a coating for roofing steel.
Others researchers have been able to integrate Grätzel cells into window glass. This means that you could have the north-facing (in our hemisphere) windows of an office block completely covered in semi-transparent low-cost solar cells.
Both the above approaches would reduce the cost of these cells even further, since buildings (obviously) require both roofs and windows anyway -- so you effectively get most of the substrate and all of the mounting structure for free.
The other nice thing about the Grätzel dye cells is that -- unlike silicon solar cells -- they will work in dim light conditions (cloudy days, etc) to a certain extent. This means that in real sunlight conditions they will actually perform better (in comparison to conventional silicon cells) than their raw efficiency would suggest.
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What on earth is a Grätzel solar cell, and why is it so important? Find out in this week's episode of Public Address Science...
NOTE: A complete transcript of this episode is available here.
Further information:
-- Read more about Grätzel solar cells in Wikipedia.
-- Read more about solar cells in general in Wikipedia.
-- Read more about the Nanomaterials Research Centre at Massey University.
-- Read about Dyesol and Konarka, two companies who have already begun to manufacture Grätzel solar cells (using Ruthenium-based dyes) in small quantities.
This episode of Public Address Science was originally broadcast on Radio Live, 21th April 2007, 2 pm - 3 pm.
An archive of all Public Address Science episodes can be found here.
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Slarty wrote:
... what happened to Stacey? Were there really lots of little warts inside? What did they look like?
It's burned into my memory like it happened yesterday, Slarty. Teeny-weeny stalks of warty stuff waving gently from the centre of an enormous blister crater.
I think Stacey (not her real name) had the wart treated with LN2. At the time I gave her my medical opinion that the stalks were nothing more than the roots of the wart.
But, as I recall, Stacey had to repeat the treatment a whole bunch of times, so maybe she was correct in identifying them as "baby warts". Just waiting to turn into proper grown-up warts all over her hand.
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Nat Torkington wrote:
I represent the "Michael Laws Does Not Look Like A Vagina" society...
Reading your heartfelt message has really been an emotional journey for me, Nat. I'm so very, very, sorry to have caused you (or your worthy society) any offence. Where do I sign the apology?
Andrew Llewellyn wrote:
One day there's a knock on the door & it's Jason Gunn & Candy Lane...
What a terrifying imagination you've got, Andrew.
Not for a million dollars, mate...
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Riddley Walker wrote:
your... comments on Laws are accurate if not a little too forgiving. I had the same feeling for that short old guy who used to be on tv...
Fair point, Riddley. I found the whole thing so depressing that I admit to feeling rather sorry for Laws & Holmes. So I guess I pulled my punches a little when it came to describing their performances.
Actually, I was going to be even easier on Holmes, but then I remembered the unprovoked savaging he dished out to Vicki Hyde (NZ's best science writer, editor of ScitechDaily, and someone who's made a terrific contribution to the communication of science in this country).
But, even so, you're quite right. I was still rather soft on both Laws & Holmes.
So next time I write about Dancing with the Stars, I assure you, no more Mr Nice Guy from me.