Windmills for Hong Kong: Yes or no?

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If air-pollution is bad, steps towards reducing it should be good, right? I was very pleased to read that a project to build a wind farm (generating electricty from the wind) off Hong Kong's coast took a big step forward last week [1]. But in the same article I was surprised to read there is a local group organising petitions against building the wind farm.

The group is called the Association for Geoconservation. Their website lists their objections, and their homepage [2] shows what they believe the view from Clear Water Bay will look like once the windmills are built:

Dramatic stuff - but hold on a moment. See the island in the top left corner of the photo? That's Basalt island, whose highest point is 174m above sea level.

And those windmills, towering over the island? The tallest point (the tip of the blade when its pointing straight up) of the largest proposed windmill is only ... 150m above sea level [3]. (The red line in the photo is my guess at what 150m looks like at that distance). They've let photoshop and a strong imagination get the better of them.

It reminds me of a speech by Ed Miliband (the UK's secretary of state for energy and climate change) last month [4]:

"There's a big, big persuasion job we'll have to do on people: that the biggest threat to the countryside is not the wind turbines; it's climate change. … The truth is that a vocal minority has stopped them going ahead and the silent majority has not done enough to ensure they go ahead."

Here we're not even talking about windmills on the land, but windmills out to sea. Yes they will be visible, but nothing like as visible as the above photo makes out. And you know what? We'll get used to them very quickly. It won't stop us from hiking around Sai Kung and enjoying the view. And maybe with wind-generated electricity, that view will be just a little clearer.

MrB

References:

  1. CLP Gets Approval to Develop Hong Kong Wind Farm
  2. Website of Association for Geoconservation 
  3. Hong Kong offshore wind farm : Turbines
  4. Wind power: the silent majority must speak out, says Miliband

Comments

I really like this idea. The

I really like this idea. The people that are arguing against the windmills are exaggerating greatly.

What about typhoons though? are there any chances that the typhoons that Hong Kong face will tear those things apart and have windmill debris flying everywhere? I think chances of that happening are slim but I hope they put some thought into it.

seabed and turbines

once you move away from the islands the seabed gets very silty and muddy and most people who have any kind of marine knowledge know that many fish enjoy solid/rocky seabed in order to inhabit. The rock that is out there I would expect to be under many meters of mud and so I wonder how much marine life is there (not much thanks to this and a bunch of trawlers stirring up the bottom).

Personally, I think they will help attract fishlife to that area (albeit after a period of messy construction) acting as an artificial reef. This also has the added benefit of making the site (and, I expect a large surrounding area) un-trawlable, and would they will make a great dive site.

I'm all for it.

Typhoons & turbines

Chocolove, I can't find any mention of typhoons on their website, but I can't imagine you can design a large structure in Hong Kong without taking typhoons into account. There is a form to leave feedback / ask questions if you'd like to ask them for more information.

Phil, you might be interested in the Environmental Impact Assessment, which talks about the effects on marine life and fisheries in more detail. As you mention, they don't believe it's a very important site for fish: 'Uniform and exposed muddy seabed with no habitat diversity is unattractive to fish as a shelter or feeding area. (8.8.3.2)'

Looking at the proposed foundation, do you think there is any value in asking them to make it a more irregular shape? If it looked more like a christmas tree with articificial branches, would it increase the surface area, and so increase the reef effect?

Re: Typhoons & turbines

Hi there,

I guess it is pretty safe.  I have been looking at the sole turbine in Lamma since it was inaugurated.  Quite a few strong typhoons had come and gone and it is still there.  According the HKE, if the wind speed is up to a certain speed the turbine would be shutdown and secured.

But I still have a little bit of doubt of building such a wind farm close to the Pins.  They say the hexagon columner joints spreaded under the see out to the Pins and such joints are very fragile.  If they are going to build a wind farm there the foundation would have to be very deep.

Best Regards,

T

Typhoons - Turbines

I have limited success looking for structural design and considerations in the EIS.   But from looking at the diagram, I expect there will be a tremendous amount of bending moment at the joint between the substructure and the superstructure (credit goes to tngan).   It might be able to withstand severe storms including those of climate change, but what about metal fatigue over a period of decades with salt water action taken into consideration?

Re: Wind farm at sea

Hi there,

I remember seeing a documentary about a huge wind farm project in Europe, which also have a series of wind turbine being build at a certain distance from the shore.  I could not recall exactly which country it was, but it has to be one of the low countries.  You might be able to get further information about salt water action and turbine there.  I'll see if I could fetch something from discovery.com

Best Regards,

T

re: Wind Farm

T, there are some more comments about the foundations on the project's website. They say they will use a 'suction caisson'. In the following page the diagram shows the foundations don't reach down to the rock layer, so perhaps the condition of that rock is less important?

I'm not sure about the effects of sea-water on corrosion. You'd probably find some useful information by searching for information from the oil industry. They've been building metal structures in this environment for many years, so should have a good understanding of the problems.

regards, MrB

I've heard that wind turbines

I've heard that wind turbines are notoriously inefficient, and that they generate enough energy to heat a mug of coffee.  I can't find a source for this, or efficiency in general, but if it is anything other than an urban myth then Hong Kong would be foolish to build a wind farm.  Of course, if they are relying on the Typhoons to generate record levels of power then...lol!  Also, while the residents may get used to the look, the tourists may not.

Re: Suction caisson, would it work in so shallow water?

Hi there,

I did a casual search and found this piece of document.  I am not an engineer so I am not in the capacity to verify it.  In layman terms, I just don't understand how it works.  Anyway the document mentioned Suction caisson is quite common for drill platforms in areas with a depth of 1000m to 3000m.  I guess the great water pressure at that depth helps the ancorage quite a bit.  Hmm..... there is hardly anywhere place around Hong Kong with such depth, I would say.  Would it work in so shallow waters?  I wonder.

Best Regards,

T

 

Re: I've heard about wine turbines

Hi there,

There is already one smaller scale wind turbine in the Lamma Island up and running for about a few years.  I have an impression of reading a news clipping that ccording to Hong Kong Electric, if the wind speed exceeds a certain speed the wind turbine would be shutdown and seecured as extremely high wind speed would just damage the generator.  So using typhoons and the gale force to generate power is out of the question.

Best Regards,

T

Wind

I've got mixed feelings about windmills, I have to admit.

A couple of concerns that no doubt have been brought up in relation to the ones proposed in HK:

First, birds. Windmills are notorious for shredding birds in flight, and since HK is such a haven for migratory species, what will the potential impact (pun intended, unfortunately) turn out to be? Admittedly, the proposed wind farm is on the opposite side of HK from Mai Po and the main wetlands, but still . . . .

Second, I really don't think of Hong Kong as a windy place. There are lots of still days here -- especially in summer -- when those turbines will sit absolutely stationary. And whatever power they're counted on to generate will need to be compensated for by other power plants. In particular, I think about HK's hideous pre-typhoon days, when the air is stagnant, and demand for electricity for air conditioning peaks in the heat. Getting a workable balance of sources to support the grid under these conditions must be quite a trick.

On a related note, I've noticed that wind power has taken off big time in my ancestral homeland, as these two articles from the Atlantic magazine describe: part 1 and part 2. Iowa, I should note, is a fairly windy place, and it certainly doesn't have the world's most interesting landscape, so perhaps it's an ideal location for wind turbines. But it's interesting to note that the author of the pieces seems tacitly to approve of wind farms in Iowa, but firmly rejects the possibility of the same structures marring the landscape of her own childhood home in southern Indiana. You can look at the photos included in the articles, and see what you think . . . .

This NIMBY-ism (i.e. 'I like wind power, but Not In My Back Yard') has popped up quite frequently in discussions of wind power in the USA. The most famous case was of the Kennedys promoting wind power like crazy in their public politicizing, but then surreptitiously working to undermine plans to situate sea-bed turbines near Cape Cod, Nantucket and Martha's Vineyard, where they keep their holiday homes -- because they would spoil the view, of course.

Suction Caisson - Turbine

Thanks tngan for tracking down this technical paper.  I share your concerns.


Water pressure is proportional to the water depth:   P = Depth x Specific Weight of water.  At a depth of 1,000 feet, P = 1,000 ft x 62.4 pounds/cubic foot = 62,400 pounds/sq ft.  So, when water is pumped out, the maximum theoritical downward hydrostatic (water) force would approximate 20 million pounds acting on the caisson whose diameter is 20 ft, limited by the structural integrity of the caisson itself.  Actual load is expected to be less - not enough depth, leakage around the rim at seabed, pumpage capacity, etc.  An actual field test on the proposed site will give some answers.


As caisson/foundation failure could be the most difficult and expensive to repair and replace, this issue should be given a thorough consideration.   The  EIS could use more discussion on the geological and hydrographic settings, and seabed compositions at the site.

Windmills

Cups of coffee

My kettle is rated at 2,000W. The wind-farm is described as generating 200MW, or enough to run 100,000 kettles at the same time.

However it's not clear what's the average actual power generation they expect to get from the farm. Even if you only get 10% of that, it's still a lot of cups of coffee, but it would be good to know the number they are assuming, and then compare it with the actual results they get.

Typhoons

As T notes, the turbines are shut down if the winds are too strong. eg the Lamma Winds turbine quotes a cut-in wind speed of 3m/s, and a cut-out wind speed of 25 m/s.

Notorious bird shredders?

Not really. Britain's Royal Society for the Protection of Birds (RSBP) 'supports a significant growth in offshore and onshore wind power generation in the UK.' However the same page also notes that 'Poorly sited wind farms have caused some major bird casualties'.

So windmills don't suck birds to their destruction from far off locations, but they will do damage if they're in the wrong place. The RSPB say they object to around 7% of the hundreds of wind-farm proposals they review each year.

For the Hong Kong project, the EIA has a long section that discusses the effects on bird life. It concludes:

7.10.1.4  The impact assessment suggests that potential impacts on all birds resulting from construction and operation of the proposed wind farm will not be significant. The SNH model has been used and predicts negligible collision risk for all the most sensitive species in the Study Area based on their distribution and abundance information obtained from boat based field surveys. The significance of construction and operation impacts on avifauna is anticipated to be very low.

Windy enough?

Good question - closely related to the 'how much actual electricty can we expect'. I can't see it quoted in their documents, but let's make a rough guess.

  • Start with table 1 in Technical note #77, Wind Statistics in Hong Kong in Relation to Wind Power, from the HK Observatory. It gives the average wind speed for Waglan Island (I'll assume it has similar conditions to the wind farm site) as 6.7m/s. (Second only to Tai Mo Shan among the locations they monitored)
  • The project website uses the Vestas V90-3MW turbine as their example.
  • Page 3 of the Vestas brochure for that model gives a graph of power output for a given wind speed.
  • If we just use the average wind speed, that translates into an average power of around 500Kw throughout the year. I think it's going to be higher than that, but my maths isn't up to it! If you look at figure 17 in the HKO document, 6.7 is the average, but as power is proportional to the square of the wind speed, we'll get a lot more electricity from the higher wind speeds. 
  • So I'll make a rough guess that average power is 750KW through the year, or 25% of the stated maximum. For the whole wind farm, that would be 50MW.
  • Over a year, the wind farm will generate 365*2*50 = 438,000MWh (Megawatt -hours).
  • In 2008, Hong Kong consumed appx 147,000 terajoules of electricity, or 41,000,000 MWh
  • So the wind farm will generate around 1% of the electricty we consume.

That feels like I've just done a maths exam, so feel free to pick holes in my calculations and assumptions.

Iowa

The Economist again: 'a farmer in Iowa who gives up a tenth of a hectare (a quarter of an acre) of land might earn $10,000 a year from it (about 3% of the value of the electricty it produces). Planted with maize, the same land would yield a mere $300-worth of bioethanol.'

Suction Caisssons

I think the document titled 'SUCTION CAISSON ANCHORS - A BETTER OPTION FOR DEEP WATER APPLICATIONS' might be a bit misleading. I don't read it as 'Suction caisson works better in deep than shallow'. From the content of the document, it is closer to 'suction caissons are better than piling in deepwater'. The document goes on to quote the difficulties of piling in deep water.

It's still true that suction caissons benefit from the increased pressure in deep water, but I don't see anything there that suggests they face problems in shallow water.

CLP has performed loading testing of a suction caisson at the proposed project location.

Windmills

Thanks MrB for the responses to the issues raised by others and me.


"The foundation was left for 45 days and then removed.  During the
installation water quality sampling and video monitoring was carried out in order to verify the water quality modeling assumptions used in the EIA.  Building Department was also present to witness the tension test and verify the engineering design parameters - all of which met or exceeded design requirements."  As I am interested in the long-term performance and survivability (to withstand waves, winds, etc.)  of these caissons, I found some comfort in reading these conclusions. 
Your point about the technical paper is well taken.  If the water is shallow, the water pressure may not be strong enough to push the caisson deep into the seabed and in that case, larger but shallower caissons may be a solution.  I realize the EIS is not the right place to look for technical calculations.


The 200 MW is the installed capacity which is the maximum power the farm can generate if all the turbines are operating and at their peak efficiency given optimum wind conditions, and there are available transmission and market for it.  Even in a typical day, given your assumptions they can drive, as you say, many kettles.

Windmills

Thanks, MrB, for that comprehensive reply!

I had a look at the EIA section on the birds, and it's clear they've done a pretty comprensive job assessing the impact on pretty much all of the bird species in that area, so I agree this project seems acceptable on these grounds.

The capacity question still lingers, though, doesn't it? That is, places that use wind power have to find some way to meet peak demand without any contribution from the windmills, since they simply can't be counted on. So redundancy has to be built into the grid somewhere along the line, which isn't the most efficient scenario, but again to me seems acceptable if enough savings can be realized via the windmills.

I can also fully understand why many Iowa farmers find those yearly rental payments -- wait, I mean find those windmills -- downright handsome . . . .

OldTimer, I've seen it mentioned somewhere that the expected life span of windmills is 20-30 years. But I'm not sure if that refers to the rotors only, or to the whole setup, including the caissons. Has anyone else seen anything about this?

Windmills - life span

http://www.treehugger.com/files/2008/01/wind_turbine_lca.php


Thanks Mr. Tall, this site says the life span is about 20 years but I think on condition that it undergoes regular maintenance and some parts will have to be replaced due to wear-and-tear.  I can't imagine my car's alternator will last that long giving the time it is driven each day.  It says within the first year it can recover the energy used to make the unit; of course this depends on several factors.


The international hydropower plant on the St. Lawrence River virtually passes the entire riverflow which is the water from all the five Great Lakes, having an installed capacity of about 2,000 MW.  Although winds are not as reliable as river flow, this wind farm would make up, albeit small, for the lack of hydropower potential in Hong Kong.  This will boost the city's peak capacity, and allows more time for other generating stations to schedule their repairs/maintenance.

Windmills

OldTimer, good to see you back again. There's also a mention on the website for this project:

Design Life: Typical turbine design is 20-25 years

Mr Tall, At this early stage, I don't think the varying output from the wind farm will cause much of a problem. Take a look at this graph of the demand for electricity in the UK over a 24-hour period. You'll see several times where there are changes of over 5% in a given hour, and the current system is able to cope with them.

If the wind farm goes from rest to full output, based on the earlier estimates the local grid will need to cope with around 4% extra power supplied. In terms of how the grid handles it, it doesn't seem it would be much different from the demand dropping by 4%. I'm not sure how quickly wind speeds vary, but in general I think it would take at least an hour to go from calm to a 15m/s wind?

It will become an issue if the installed capacity for wind climbs to say 20-30% of total demand. I figure that problem will take care of itself though - if the power companies see that 'free' electricity is being thrown away on a regular basis, I believe they'll have a strong incentive to find a make better use of it.

Thanks for all the questions, they've made me learn more about this.

Windmills

I was interested to read the many and intelligent comments about the windfarm project and for now I am sitting on the fence on this issue. One big disadvantage to me is that these large windfarms look so ugly!

I think it would be of far more benefit to allow and encorage individuals to contribute more to power saving, but especially to power generation. Hong Kong is so far behind other countries in offering incentives, or even in allowing, individuals to generate their own solar or wind power.

If I understand it correctly the HK power suppliers will not allow one to feed into the grid. This makes the generation of electricity from solar or wind energy financially non viable for individuals.

Suction caisson

Actually the main strength to support a suction caisson in water does not depend on the depth of water, but the lateral friction resistance between the boady of suction caisson and the seabed it stands. When wind blows the turbine, the suction caisson foundation holds itself resistantly because the great friction between body and its touched surface. So the geotechnial sea statistics will be quite essentially important to decide if suction caisson is OK or not. Even in a shallow water, if we let suction caisson goes deeper, where the touching surface is enough, the suction caisson can be OK.

Pls take a look at a field test in Denmark: a suction caisson foundation a 2.3MW turbine stands in a basin condition where water are much shallow.

Windmills

Mike, thanks for your comment:

I think it would be of far more benefit to allow and encorage individuals to contribute more to power saving, but especially to power generation.

It would be good to see some numbers for this, to be able to compare the costs and benefits of allowing individuals to generate their own power, against those for the wind farm. Any ideas?

I'm guessing the potential for self-generated power are limited. eg In our case, we're on the 20th floor of an apartment block, so no opportunities for us to generate any power from wind or solar. Wouldn't that apply to the majority of people living in Hong Kong?

Alex, thanks for the clarifications about the way a suction caisson works. Any chance you can provide a link to information about the field test in Denmark please?

Regards, MrB

Windmills

Thanks for the comment Mr B. quote." I'm guessing the potential for self-generated power are limited." I am thinking not only of the many people who live in village houses in the New Territories (myself included), but even those in apartment blocks. Where there is a will there is a way! Surely the flat top roofs of apartment blocks would be an ideal site for individual or communal solar panels or wind generators. After all satellite dishes and TV antennas also go on roofs. It just needs owners and tenants to come to an agreement, and Government to encourage these facilities. With regard to power saving - What about insulation to prevent heat gain? Why does government not encourage insulated cladding to concrete walls and double glazing, as in most developed countries? As you say, some numbers to show the value of a moderate percentage saving in power consumption due to the combined effect of individual power generation and power saving through insulated buildings would be interesting. Mike

Link to Suction Caisson Test in Denmark

Mr. B,

http://www.gl-group.com/pdf/No12_Bakmar.pdf

You can download a presentation about the suction caisson test.

It looks good!

But applying this technique itself to a specific site is a little complicated, espcially in the case of large-scale commercial development. It needs geotechnical investigation, onsite design, heavy steel structure fabrication, sepcial foundation installation vessel, scouring protection, monitoring system, and an unique turbine installation vessel too.

Human's demand for more electricity power has already been updating for many years and it will keep its pace. The whole design of every industry chain and living style of people counts on power, which is transferred easily.

Personally I don't think we have a better energy solution for men living in apartments.

A windmill is an ideal solution to power Hongkong.

Windmills

Alex, thanks for the link.

But the document says their solution is still under development:

Statistically, 1 of 3 prototypes have failed so far. This clearly underlines the vulnerability of the concept.

The monopod bucket foundation will not be commercialized before we are completely confident that we are able to handle all risks successfully!

It's not clear if their concerns apply to all suction caissons, or just to their own design. Any ideas?


Mike,

"Surely the flat top roofs of apartment blocks would be an ideal site for individual or communal solar panels or wind generators."

Solar heating. I've already seen solar water heating panels on NT houses (see government leaflet), so they're already an option.

Solar electricity. Possibly, though I'd still like to see some more numbers on what their potential contribution is if they are widely adopted, and then if the take-up rate is lower.

Wind. I don't see a good future for this. From what I've read of small turbines that would run on a 3-storey rooftop, the small turbine and low wind speed means the returns are not attractive. On top of a multi-storey does mean there's more wind power available, but I think safety concerns will make it unlikely we'll see many of these.

"With regard to power saving - What about insulation to prevent heat gain? Why does government not encourage insulated cladding to concrete walls and double glazing, as in most developed countries?"

This is an attractive solution. Build a more efficient building, and you use less electrcity regardless of the inhabitants behaviour. The magic word is OTTV, or "overall thermal transfer value", which describes how easy it is for heat to pass into a building. So a well-insulated building will have a lower OTTV.

New buildings in Hong Kong do have to meet a standard for OTTV. But the regulation applies to 'commercial buildings and hotels.' As I've grumbled elsewhere, a strange quirk in our regulations ecourages bay windows in residential buildings, which are a bad choice if you're trying to minimise the OTTV.

Worth further investigation.

MrB

day of the LED

Hi!  I can't wait for the day when LED light bulbs are cheap and of high-quality, comparable to CFLs or incandescents in light output and color or better.  When they finally are easily accessible, everyone can do their part in conserving energy.  Just a bit of wishful thinking for, hopefully, not too long.

Windmills

Thanks Alex, I learn something new from this slide show.


When installed in the seabed supported by suitable material (local or additional), a suction caisson can stay in place plus supporting the windmill mounted on it.  I agree that the caisson will resist lateral (in the horizontal direction) movement, and skin friction with the seabed will also resist uplift movement of the caisson.


The term "suction caisson" is a bit misleading.  It refers a type of caisson which is driven into the seabed by suction action - removal of the air from inside the bucket thereby allowing the water pressure to press the bucket into the seabed.  Once the pumps are removed, the negative pressure inside the bucket will, over time, diminish when seawater seeps in from under to fill the void.  But we still call it a "suction" caisson.


It is interesting to note the buckling of the bucket skirt in the photo.  There are metal plates inside (roughtly every 30 degrees) so perhaps they might try to use more reinforcement.   I suggest the water pressure was not enough (not enough depth)  to drive the caisson downward and the negative air pressure exceeded the critical stage.


It appears then, that if the water is shallow and rocks may be present (about 40 feet in these examples), piling/hanmmering might be a better alternative.

Suction caisson

Frankly the application of suction caisson is uncertain as there are still many unsure technial issuses.  The failure of the test in the photo may be not caused by suction caisson itself but control of installation for the suction caisson. Obviously its deformation was clashed by the ship or crane or tool and generally the thickness of bucket also depends on negative pressure inside it generates when pumped,  the corrosion and tolerance designed. It must be have been enough. So I'd prefer assuming it's a failure of installation.

I also read some innovative idea regarding integrated installation of a whole offshore wind turbine, including the foundation, tower, turbine, blade and nacelle within one step. Specifically the foundation is a suction bucket. A crazy idea but interesting! If it goes well, the capex of wind farm must be lowered down greatly as we know the construction and installation cost owns 30% of the total cost. It relates too many techniques.

But seemingly there are just a few of us talking about this. No more guys concerns this. I'd like to propose the writter of this post shall make some ADs. lol.

Added benefits to windmills?

I'm still a bit dubious about the long-term utility of wind farms, but this article suggests that their presence may even benefit the marine ecosystems in which they're placed. Interesting stuff!