by Russel Norman
The US is accelerating the dismantling of dams in light of their environmental impacts. It’s ten years since the dismantling of the 917 foot wide Edwards Dam on the Kennebec River in Maine. Something the American Rivers NGO and the New York Times have been celebrating. It was the first time a dam was removed for ecological reasons and the first time the water had flowed free in the Kennebec for 160 years.
In the ten years since, over 600 dams have been removed (75,000 dams over 6 foot high remain).
The removal of dams means that migratory or diadronous fish, such as sturgeon, salmon and bass, can once again move from the oceans up the rivers to breed.
In the US they have tried to overcome the ecological impacts of dams on salmon and trout by running breeding programs that dump millions of baby fish in the rivers downstream of the dams. But now the San Francisco Chronicle is reporting that these hatchery bred fish have high levels of genetic damage, tend to have low breeding rates and the salmon fishery has been closed on the west coast of the US for the last two seasons.
A further contributing factor is the demise of the Sacramento-San Joaquin Delta/San Francisco Bay estuary which is the migratory path and food bowl for the salmon. The extraction of up to 50% of the freshwater headed for the delta, to supply agriculture, industry and human drinking water, has also had a dramatic impact.
It’s possible that the hatchery bred fish are making things worse by interbreeding with the wild populations and passing on their dud genes. The only real solution is to fix the habitat.
There are lessons here for us.
Dams have made a significant contribution to hydro electric power generation, especially in NZ, and irrigation but they have major environmental impacts. They block migration, raise temperatures, reduce water levels, slow rivers, alter timing of flows, cut oxygen levels etc.
In NZ we have already dammed virtually all our large rivers. Our native fish and eels are migratory and dependent on wild rivers in order to survive. Native fish and eel populations are in decline due to the impact of dams and pollution. Trucking eels around dams doesn’t work that well and fish ladders have a poor record.
You’ve got to wonder why we are still having to fight proposals like the Mokihinui and the Wairau hydro projects when we should be learning from those who started damming well before we did and who are pulling some of them down.
Published in Environment & Resource Management by Russel Norman on Mon, July 6th, 2009
More posts by Russel Norman | more about Russel Norman
on the trolls and those who are unable to keep on topic
Ecological reasons are not the ONLY reasons they’re being dismantled, though, are they…
Token ‘we need dams to generate clean electricity’ point, done.
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This is rediculous, you can NOT compare NZ rivers to those in the USA, just like you greenies say we can not compare 1080 poison use in NZ to the USA.
Hydro is and must continue to be the most important generator of electricity in NZ, our climate and topography make it the responsible thing to do.
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Shunda – when you are on Kiwiblog, do you say, ‘you tories say’?
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No
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What’s the energy generated by those dams being replace by? Coal?
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“Native fish and eel populations are in decline due to the impact of dams and pollution. Trucking eels around dams doesn’t work that well and fish ladders have a poor record.”
I guess there are no fish or eels in our hydro lakes then?
There is probably 10 times as much biomass in the average dammed river in NZ.
Due to many NZ rivers being “flashy” Dams can actually stabilise the environment and sediment loading improving water quality and habitat for eels and other fish.
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Shunda (popular today!) I worked with the eel ‘trap and transfer’ programme on the Waiau river, hauling elvers up the face of the mararoa weir (the fish ladders didn’t work at all) and netting and relocating adult eels from the lakes down below the dams and away from the turbines that minced them, if the tried to get to the ocean under their own power. It’s a tragedy for the eels and a long term tragedy at that. Enormous numbers of breeding age eels have been destroyed and untold numbers of elvers have been unable to get to the lakes since the dams were installed. Those that are there are in many instances landlocked and there is no future in that.
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“Those that are there are in many instances landlocked and there is no future in that.”
Then how do you explain Lake Brunner on the West Coast? It is absoluteley teeming with biomass, and eels are a big part of it, and the lake is blocked off from the sea by the Arnold dam.
I understand the native Galaxid’s and eels use the lake like the sea and have a stable land locked population.
Are you sure that even with those eels that get killed in the Waiau turbines there is not a net gain of biomass in the hydro lakes?
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I don’t know the situation with Lake Brunner. Can the eels travel across land and get out to the sea, like they do at Ellesmere?
Never the less, land locked fishes, where once they did have access to the sea, will represent a loss to the wider environment, in that they won’t contribute to the oceanic environment the way they once did.
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“Can the eels travel across land and get out to the sea, like they do at Ellesmere?”
No its about 30km inland.
“Never the less, land locked fishes, where once they did have access to the sea, will represent a loss to the wider environment, in that they won’t contribute to the oceanic environment the way they once did.”
Well thats probably a fair point. I wonder whether a compromise is possible, perhaps the creation of artificial wetlands around hydro scheme’s would be a way to mitigate some of the environmental impact.
Don’t get me wrong greenfly, I think damming rivers like the Mokihinui is not acceptable, but pulling down existing dams? I think the clean energy they produce is just too valuable.
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Shunda – the dams being pulled down are less that 6 feet high. I don’t think anyone was eyeing up the Clyde.
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“Dams … have major environmental impacts. They block migration, raise temperatures, reduce water levels, slow rivers, alter timing of flows, cut oxygen levels etc.”
So is it the Green Party’s position that these negative impacts are worse than carbon emissions which is is the only available alternative?
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dbuckley – if tiny ‘micro-dams’ could be fitted into the veins in your body, providing you with the ability to work day and night without the need for sleep, how many of them would you have installed?
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Cities, farms, and all other forms of human organization inevitably impact the environment. Dams prevent floods and provide vital reserves of drinking water in the event of recurrent droughts, apart from generating electricity. It is possible to create shelters and reserves for people and wildlife affected by dams. Rivers without dams bring unending misery and keep communities in penury.
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Nuclear is an alternative.
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But it’s stupid.
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Rivers without dams bring unending misery and keep communities in penury.
Funny! Off-shore, are we drsbanerji? A continent perhaps?
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Owen, Barry Brook of Adeliade Uni’s Climate Change and Sustainability Research Institute is a leading proponent of integral fast reactors. He’s rather convincing. I think it’s time to take another look.
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How else do you generate low carbon footprint reliable power – if that is the aim?
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Owen, I think with good management, NZ can use the huge wind resources we have – mostly unexploited in the south in conjuntion with hydro. The need for nuclear isn’t all that great in NZ, compared to elsewhere where wind and hydro are comparatively limited in possibility.
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Hydro + increased efficiency + conservation
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drsbanerji Says:
July 6th, 2009 at 1:21 pm
> the environment. Dams prevent floods and provide vital reserves of drinking water in the event of recurrent droughts, apart from generating electricity.
The dams on the Clutha river seem to actually increase flooding. I think storage dams where the water level is allowed to drop a lot reduce flooding, but the water behind these dams is kept at a reasonably constant level for electricity generation, and that means that water level rise below the dam is greater because the river can’t hold much of the extra water by rising above the dam.
Also, flooding is not always a bad thing. Before the Aswan dam was built, the nile used to flood and deposit topsoil eorded from Ethiopia on the fields in Egypt. Now all that topsoil collects behind the dam, and the farmers have to spend more money on fertiliser.
Dams have both advantages and disadvantages, and the balance will be different for different rivers.
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# greenfly Says:
July 6th, 2009 at 2:16 pm
> Hydro + increased efficiency + conservation
+ tidal + wave + geothermal + passive solar design for buildings
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Geothermal is not carbon neutral kakikatea.
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# Shunda barunda Says:
July 6th, 2009 at 2:20 pm
> Geothermal is not carbon neutral kakikatea.
That depends on the technology. If all the fluid is piped back into the geothermal fields and only the heat is taken out of it, then it is carbon-neutral, clean and renewable.
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kahikatea – that’s a lot of plusses! Makes the nuclear suggestion look like a non-starter!
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Kahikatea, indeed. We might even undam a few rivers if we get all of that done.
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If one is going to include wave and tidal power, why not…hur, clean coal? I may be wrong, but all seem a rather long way off…
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Clean coal! Of course! I’ve heard there are extensive clean coal seams to be found under the Big Rock Candy mountain.
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I dont like ad hominem attacks but I need to use one now because its the truth of the matter and it needs to be said.
Many so-called environmentalists, GP folks amongst them, have this view that if they wish for some form of renewable energy other than the current hydro proposals, then it will appear, and all will be better in the world.
But, taking off the rose tinted spectacles, it is only proposals that ever make it to reality; ideas and wishful thinking are simply so much hot air.
So to oppose hydro at the moment means more thermal generation (or more use of existing thermal generation), so more carbon emissions.
When are you guys going to get a bit of Environmental understanding and support the reduction in the rate of increase of carbon emissions rather than supporting a certain increase? Just whining about it on the blog doesn’t cut the mustard.
Whose side are you guys on? How can you support a reducion in emissions target whilst simultaneously campaigning for more emissions?
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Wind power is not reliable and now is wave power and nor is tidal power (tidal power has the benefit of its unreliability being predictable but its potential is trivial)
When the wind speed through the blades drop by half the power output drops eightfold. That is a recipe for a massively unstable grid and although NZ has a lot of wind it is also highly unstable. Ask any yachty.
So after wind reaches about 12-15% of peak demand every megawatt has to backed up by another generator on standby and capable of rapid response.
That becomes the most expensive power in the world.
And every day as we become more dependent on electronic gear for intelligence and communication we demand more and more stable power – getting rid of the entropy becomes more and more important. It takes a couple of hundred watts “in the furnace” to deliver about one watt to your microprocesserr in usable form. We are no longer generating power to drive the satanic mills. We are now powering up electronic brains on which we depend heavily for the operation of the world we live in.
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Owen McShane Says:
July 7th, 2009 at 2:44 pm
> So after wind reaches about 12-15% of peak demand every megawatt has to backed up by another generator on standby and capable of rapid response.
this can be a problem if you have to use thermal power generation as the back-up. However, the most efficient back-up for wind power is hydro-power. That’s why some of the largest wind farms being proposed are for Central Otago – you’ve got existing hydro power stations nearby with huge capacity that can easily be used as back-up for wind power. Hydro-power stations are perfect for coming on at a moment’s notice to provide back-up for wind power.
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Are you sure its potential is trivial? I had heard there is potential in Cook Strait to generate masses of power.
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Owen McShane Says:
July 7th, 2009 at 2:44 pm
> Wind power is not reliable and now is wave power and nor is tidal power (tidal power has the benefit of its unreliability being predictable
Tidal power also has the advantage that the time of minimum flow at one part of the country is always a time of maximum flow in another part of the country. It doesn’t quite cancel out – when there’s no flow in Manukau Harbour there’s maximum flow in Lyttelton Harbour, but Lyttelton is a smaller harbour and has a smaller tidal range, so its flow will never be big enough to make up for the lack of flow in Manukau. But it all helps (though it does all make for more variation that the Waitaki power stations have to cancel out, because only they really can).
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Kahikatea – those harbours are a long way away and so you have a distribution porblem. IT is a pity NZ is not lying horizontally because then one harbour would kick in after another.
However, the only two tidal power stations generating reasonable amounts of power are in fact hydro dams placed across their harbours. We are not about to do that here. From memory the only tidal stations using under water turbines are experimental and generate power for a few houses. It is a savage environment and if you stack enough turbines to generate a decent amount of power wiithin a compact area they form a turbine back pressure wall and the water flows around the turbine farm rather than through the turbines.
So if you want a powerful tidal farm you must spread the turbines over a massive area. MY suspicion is that any money invested in the Kaipara scheme will end up in a Swiss bank account and never leave.
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And again, hydro is a useful back up for wind power and that is why we may be able to get to 12 – 15% of peak load from wind rather than the normal 8 – 10%.
(There is some dispute about these numbers but the principle is the same).
Certainly, any talk of 30% of our power from wind will require standby back up.
Physics.
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Owen McShane Says:
July 8th, 2009 at 11:18 am
> IT is a pity NZ is not lying horizontally because then one harbour would kick in after another.
broadly speaking, one harbour does kick in after another. There are some gaps in the sequence because harbours aren’t evenly distributed along the coastline.
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You mean like Cook Strait?
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Do you believe that shipping and massive underwater turbines mix – and in a high wind wave environment?
Also the bigger the area the bigger the distribution collection problem so the more cables. It is hard to think of a worse environment in which to generate electricity than below the saline sea.
Costs count.
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How deep is Cook Strait? I would guess the tidal tubines would be hundreds of metres below the ships.
Yeah it would be a tricky environment, but that would be balanced up against other means of power generation. To have renewable, non-polluting generation that is completely predictable are some huge advantages to weigh up with the cost disadvantages that you quite accurately describe.
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Re: decommissioning US dams: Most have been old and small (i.e., of no use and in some instances dangerous). It would be more instructive to know what level of net societal uses (and what types) have been lost/gained through decommissioning.
Re: nuclear energy: I’m not aware of any nation that has solved the waste stream problem. Aside from perhaps Iran and North Korea. MIT’s “Future of Nuclear Power” report is relevant here.
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15% of our peak load is about 25% of our average load, as our peaks are around 50% higher than our average. If we can even out our peaks and troughs then we will be able to use more of the wind generation when it is blowing. Good demand management will help with this, including such tricks as freezing water during off-peak times and using the ice for cooling at peak times instead of running air conditioning pumps.
We can also improve the utilisation of wind by taking advantage of spatial diversity – spreading out our wind farms so their peaks and troughs don’t coincide.
If that is not enough, we can use energy storage such as pumped hydro storage or on a smaller scale vanadium redox flow batteries, such as the ones they use on Kings Island. If battery electric vehicles become common, we may also be able to use some of their capacity to even out the supply and demand.
Trevor.
PS: You could add solar to kahikatea’s list, but don’t expect much since we are in the land of the long white cloud.
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From memory its 535 m at its deepest, I think NIWA has some good maps on their site…
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Owen – It isn’t necessary for the generators to actually create electricity down there, all they have to do is extract energy. Something hydraulic perhaps. Which would be my preferred solution as the point about electricity and salt water is IMHO, well taken. People who want to generate power out of wind and wave at SEA have to reckon with rust.
I spent enough time at sea to have a powerful appreciation of the power of rust.
Most tidal generation isn’t deep-water. Cook strait is a special case, it is using the two islands themselves as a dam, and the flow through the strait is pronounced and reliable and can be harnessed at depth.
I don’t like the likely costs of maintenance though. Probably would have to have the equivalent of a small drill-rig out there in the middle of the strait, just to keep the whole thing running reliably.
BJ
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One other thing about wind and tide… we can shift our work to match its rhythm sp as to use it better. Certainly not 100% but some things can be scheduled a bit differently to take advantage of the peaks and avoid the troughs. This would make the 9-5 into a 6 and 6 sort of shift, but it would avoid wasting available collectible energy.
respectfully
B J
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BJ,
Would non-rusting alloys or plastics not fit the job/ be too expensive? Could one use high-chromium alloys for the rotating joints and then coat the major components with rubber? Just something that occurs to me, I dont have the background to have any idea about its practicality.
I like the idea of using the batteries of electric cars as a sort of storage capacity or having them similar to hot water cylinders, decrease the amplitude. Could have excess go to pumped storage or the haber process for our non-electric vehicle fleet?
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One of the problems with storage of excess demand is that converting the electricity into the storage medium and then back out to electricity involves the loss of energy, compared to what BJ was pointing to with changing our use patterns.
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True, I am aware of the inefficency. But if we are generating excess to what we can resonably expect to use and in absence of use it woukd just be wasted then to utilise it inefficently is better than not utilising it at all. There are limits to how much we can expect people to shift their use patterns and the storage part is also relivant to wind generation. Both should be part of the soulution I think.
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It’s OK to consider building the tidal system in the strait. I am not saying it can’t be done. We put some damned big propellers on ships, and they turn and function for years and years.. the engineering to do that part is relatively well known and straightforward. Ships propellers are still made of bronze alloys. Sacrificial zinc is used to hold the worst corrosion at bay.
What is different is that in this case, they want to couple what are essentially large propellers (working backwards) to generators that are immersed in water. On a ship, there is a shaft-alley and the engine-room is kept dry.
Building a space like THAT down there is feasible/expensive Hence my preference for hydraulics running to the surface and driving the generator sets. That makes the electrical parts more maintainable than they would be at 200-300 meters and simplifies the maintenance issues a bit.
I don’t think the system would be on the bottom.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6M-4VM9KBY -5&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_sea rchStrId=954049979&_rerunOrigin=google&_acct=C000050221&_version=1&_ur lVersion=0&_userid=10&md5=879dc047a504202d277765464e1ae1f0
The only things on the bottom should be anchors or if the water isn’t real shallow, the legs of power platforms.
Maintaining the anchor chains and suspended propeller pods would be a big part of the maintenance. Keeping them dry internally… we know how to do that stuff. Submarines so it all the time.
Protecting the system from the odd whale will take some additional caging, Smaller fish won’t have a problem.
This is an engineering problem it is solvable. The expense of the maintenance means that this will not be CHEAP renewable power… and this is part of Owen’s consideration. The assumption that renewable=cheap isn’t valid.
One other thing, the nature of the ocean movement associated with the tide means that the N-S orientation of NZ is GOOD, not bad. It acts as a dam in the global flow. Bodies of water that are attached to the ocean at different points can have different timing for tides, even if separated by only a few NM of land.
http://www.linz.govt.nz/hydro/tidal-info/tidal-intro/nz-tides/index.as px
Auckland-Manukau have a 3.5 HOUR difference in time of high tide. Which should suggest something to someone.
respectfully
BJ
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BJ,
I just downloaded that study, rather large (lots of colourful pictures). From just a quick browse it looks like there are a good number of flats well away from cliffs and fairly deep. Though the canals where I suppose current based energy generation would be best look alittle risky. I havint read in enough depth to know the integrity of the slopes so I cant really make much of a risk judgement. I assume you dont have the subscriptions needed to download the PDF? I could send it if you desire, I doubt the journel snoops patrol this blog.
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The best return on investment for tidal flow power generation will be where the water flow rates are highest, which will be in areas of shallower water, such as on underwater ridge lines.
Plans I have seen from Neptune Power suggest bouyant generator modules which are moored using chains and which can be brought up to the surface for servicing by letting out the chains.
Tidal flow through Cook Strait peaks every 6 hours, so the generation troughs only last a few hours. A number of applications for electricity can cope with short periods without power, such as refrigeration units, so sensible demand management would allow a significant proportion of our power to be generated from tidal flow generation.
Trevor.
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Another renewable resource to add to kahikatea’s list is generation from biomass. This could be implemented by burning charcoal at Huntley instead of coal (or perhaps a mixture), or by adding cogeneration at institutions that need a significant amount of low temperature heat such as hospitals and retirement homes.
Trevor
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I think the advantage of tidal is that it can be used to replace expensive baseload generation from diesel plants and (in the future) from coal & gas that I think will become more and more expensive once we put a price on carbon.
We will probably need to get used to paying more for electricity in the future than we do now – no matter what method we use to generate it. Hence the advantages of improving energy efficiency through insulation etc.
What potential is there in NZ for further geothermal generation?
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The wiki page is interesting:
http://en.wikipedia.org/wiki/Cook_Strait
http://www.niwa.co.nz/our-science/natural-hazards/research-projects/al l/physical-hazards-affecting-coastal-margins-and-the-continental-shelf /news/m2mov
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Sapient
I don’t have the subscription, and I reckon Neptune can do the engineering. That sort of stuff is a specialized, difficult, full time job. If Neptune is doing pretty much what I expected them to do, I have to assume that they have some engineering staff and a reasonable knowledge of the situation. I would only look deeper into this if they weren’t doing what I expected.
Given that there is risk to the scheme from earthquakes, it makes sense to make the generation modules moored and buoyant.
The current will be strongest where it is most constrained.
Thanks Trevor
respectfully
BJ
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12GW…. holy heck that’s even more than what I had heard. Obviously I doubt you’d ever get close to generating that amount, but 1-2 GW would certainly help things. Could help retire Huntly Power Station for example.
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Bj,
I had thought that it would be strongist in the canals since they are both the deepist and the most constrained. Though admitedly I dont know the depth effects of tidal flow.
http://www.niwa.co.nz/__data/assets/image/0003/50493/ocean3_large.jpg
http://www.niwa.co.nz/our-science/natural-hazards/research-projects/al l/physical-hazards-affecting-coastal-margins-and-the-continental-shelf /news/cookmov
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There is still significant geothermal potential which could be exploited for generation, some of which is proceeding. Refer to
http://www.nzgeothermal.org.nz/elec_geo.html
On top of this, there is a large potential for low temperature geothermal energy to be used for water and space heating and some drying applications.
Trevor.
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The problem with wind is the rapid and unpredictable changes in output. Wave powered generation also has large changes in output power, but these are predictable a few days in advance and the output power changes much more slowly. This gives time for other generation to be started or stopped, making it much easier to handle.
New Zealand has some of the best wave and wind resources of any country – we should take advantage of this.
Trevor.
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Was chatting to a Director of Neptune recently.
S(he) tells me that all the engineering problems have been solved, and also the potential for ‘bykill’.
They can equal NZ’s current generation capacity from turbines in Cook Strait alone.
Sounds like an idea worth looking into to me…
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