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Archive for the category “offshore”

“Assembling Offshore Wind-towers Onshore is Cheaper”

State of the art offshore installation. Can it really be done more economically than this?

The cheapest and fastest way to install an offshore wind turbine is to assemble it completely onshore first, including the monopile. That’s the outcome of research done by the University of Delaware. The method employed is to not work with a single large monopile ramed into the sea floor, but with several “buckets” that are suctioned into the sea floor at less depth and less acoustic impact for sea mammals. Starting base was a hypothetical large 1 GW offshore wind farm in the Delaware Wind Energy Area off Rehoboth Beach, Del., using the port near Delaware City and working with 10 MW turbines. Results: $1.6 billion less cost and only half the construction time.

[udel.edu] – Industrializing Offshore Wind Energy Development
[4coffshore.com] – Suction Bucket or Caisson Foundations
[offshorewind.biz] – University of Delaware

Read more…

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Hywind Scotland – the World’s First Floating Wind Farm Operational

Offshore wind no longer tied to shallow water, up to 800 m deep is workable.

How a Transition Piece is Made?

[smulders-projects.com]

Crane Aeolus Jack-Up Vessel Being Upgraded

Pictures from Schiedam harbor near Rotterdam. The 900 tons crane of the offshore wind jack-up vessel Aeolus is being replaced with a 1600 tons one to prepare the ship for installation of heavier 8 MW wind turbines. Investment volume 300 million euro. The ship is playing an important role in getting the planned 4.5 GW offshore wind capacity installed by 2020 (Germany 6.5 GW and UK 10 GW by 2020). The Aeolus is able top operate in water depths of up to 45 m. The crane adaption has to be made only 3 years after the ship was commissioned, illustrating the rapid pace with which the offshore wind sector is developing and subsequent price decline.

In 2016 the Dutch government was prepared to subsidize 12 cent/kWh, but Danish Dong offered to do it for 7.27 cent. Later Shell, Van Oord, Eneco and Mitsubishi/DGE were awarded the tender for Borssele III & IV for merely 5.45 c/kWh. In Germany tenders were awarded for wind parks to be built in 2024-2025 with no subsidy at all. Won’t be long until wind developers will be fighting over available offshore locations for the privilege of being allowed to build ever larger wind farms.

In 2017 technology has advanced to the tune that monopiles are installed with an 8 m diameter, 80 m long and weighing 1300 tons. Vestas and Siemens are building 8 MW turbines and the next steps towards 10-15 MW machines are being prepared. The Aeolus can install one foundation per day.

[heavyliftnews.com] – “Aeolus” of Van Oord being upgraded with stronger Crane
[maritiemnieuws.nl] – Huisman gaat voor 300 miljoen aan nieuwe kranen bouwen
[ayop.com] – Van Oord lays strong foundations for wind
[maritiemnederland.com] – Waar liggen de limieten in offshore wind?
[noordzeeloket.nl] – Noordzeeloket

Offshore Wind Energy 2017 Opening Video

Offshore Wind Energy 2017 conference was held on 6-8 June earlier this year in London.

[offshorewind2017.com] – Official site

2 GW Offshore Windpower Planned for British Columbia

DONG of Denmark did it again. After acquiring the 1.4GW Hornsea-UK project in the North Sea, they now will build an even bigger 2GW project off the West coast of Canada. For DONG this means an expansion beyond European borders and the Danish wind energy giant could ascend to become one of the global players in wind power that in a few decades will have replaced the mainly Anglo oil majors (“Seven Sisters”). European Seven Brothers, anyone?

[cleantechnica.com] – DONG Partners With NaiKun Wind Energy Group To Develop 2GW BC Offshore Wind Site
[4coffshore.com] – Naikun Haida Energy Field Offshore Wind Farm
[4coffshore.com] – Events on Naikun – Haida Energy Field
[deepresource] – DONG to Build World’s Largest Offshore Wind Park Hornsea-UK
[wikipedia.org] – Seven Sisters (oil companies)
[deepresource] – The Seven Brothers – Europe Taking Lead in US Offshore

DONG to Build World’s Largest Offshore Wind Park Hornsea-UK

DONG Energy of Denmark has won the bid for building the largest offshore wind park to date (1.4 GW), Hornsea-2 in the British part of the North Sea at a record low price guarantee of £57.50/MWh and is scheduled for completion in 2022. DONG is currently working on Hornsea-1 (1.2 GW), to be completed in 2020.

[wikipedia.org] – Hornsea Wind Farm
[cleantechnica.com] – UK Offshore Wind Now Cheaper Than Gas & Nuclear
[cleantechnica.com] – UK Renewable Energy Competitive Auction Yields Record Price Lows

Gasunie Joining North Sea Wind Power Hub Consortium

Earlier today the Dutch company Gasunie has joined the North Sea Wind Power Hub Consortium. The aim is to build an artificial “energy island” in the middle of the North Sea, where wind power to the tune of 100 GW will come together eventually and distributed to countries neighboring the North Sea. Furthermore the participating partners (Netherlands, Germany and Denmark) are serious about producing hydrogen and store it in empty gas fields under the North Sea.

dogger island map north sea

[nos.nl] – Nederlandse energiereuzen gaan wind- en zonne-energie opslaan
[infrasite.nl] – Gasunie treedt toe tot North Sea Wind Power Hub consortium
[wikipedia.org] – Gasunie
[tennet.eu] – Gasunie treedt toe tot North Sea Wind Power Hub
[renews.biz] – Gasunie backs island vision
[renewablesnow.com] – Gas grid operator joins North Sea wind hub concept
[arstechnica.com] – North Sea Wind Power Hub: A giant wind farm to power all of north Europe
[deepresource] – Important Step Taken Towards Energy Hub North Sea
[deepresource] – Power to gas

European Wind Energy Potential

The “raw technical potential” of wind power in Europe is enormous, if you keep in mind that in 2015 total EU electricity consumption was in the order of 3000 TWh. However in reality there are constraints, mostly of esthetical nature.

This study confirms that wind energy can play a major role in achieving the European renewable energy targets. As Table ES.1 makes apparent, the extent of wind energy resources in Europe is very considerable. Leaving aside some of the environmental, social and economic considerations, Europe’s raw wind energy potential is huge. Turbine technology projections suggest that it may be equivalent to almost 20 times energy demand in 2020.

Onshore, the environmental constraints considered appear to have limited impact on wind energy potential. When Natura 2000 and other designated areas are excluded, onshore technical potential decreased by just 13.7 % to 39000 TWh. However, social constraints, particularly concerns regarding the visual impact of wind farms, may further limit the onshore wind energy development.

Offshore, the environmental and social constraints applied have a larger impact on potential. Using only 4 % of the offshore area within 10 km from the coast and accounting for the restrictions imposed by shipping lane, gas and oil platforms, military areas, Natura 2000 areas etc. reduces the potential by more than 90 % (to 2800 TWh in 2020 and 3500 in 2030). When production costs are compared to the PRIMES baseline average electricity generation cost, the onshore potential for wind decreases to 9600 TWh in 2020, whereas offshore wind potential decreases to 2600 TWh. Despite being a small proportion of the total technical potential, the economically competitive wind energy potential still amounts to more than three times projected demand in 2020. However, high penetration levels of wind power will require major changes to the grid system i.e. at higher penetration levels additional extensions or upgrades both for the transmission and the distribution grid might be required to avoid congestion…

European wind speed data. Best places: North Sea, Baltic, British Isles.

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EROI of Offshore Wind Power [Continued]

Last juli we made a calculation regarding the EROI of wind power, making some assumptions regarding the weight of the wind tower, see link below.

Now we have more accurate data, coming from the implemented Gemini wind farm, consisting of 150 Siemens 4 MW wind turbines. One of these wind turbines weighs in total 1.347 ton max. Annual electricity production Gemini wind farm: 2.6 TWh. That would be 17,333 MWh per turbine annually or 47,487 kWh/turbine/day. We again apply 5555 kWh/ton energy cost in steel production or 7,483 MWh/turbine. Payback time in energy terms: 158 days. Assuming again the worst case scenario of having to transport iron ore from Australia to Europe: 1600 kWh/ton or another 1600 * 1347 = 2,155 MWh which corresponds to 2,155/17,333 = 45 days. Energy payback tower construction + transport iron ore from Australia: 203 days [*]. Assuming an economic life time of 30 years, we arrive at an EROI of 54.

Ignored is here is the energy cost of maintenance and installation. And then there is storage.

[*] – Note that after 30 years the energy to create a new turbine from the scrap steel of the old one is less than the energy required to create a wind tower + turbine from iron ore from Australia. There is no transport energy cost other than to bring the tower to a smelter in Europe and in general the energy cost to create steel from scrap metal is (much) lower than from ore. According to Wikipedia the energy required to produce 1 metric ton of steel from scrap metal in an arc furnace is merely 440 kWh/ton (theoretical minimum 300 kWh). It goes without saying that electricity from wind power and arc furnaces are a match made in heaven and can operate on moments when supply of electricity from power is high. In the link “EU Economic Papers” (p14) it is confirmed that the energy intensity of producing 1 ton of steel from ore is a factor of 10 more intensive than producing 1 ton of steel from scrap metal in an arc furnace. If you take this in account than it follows that the EROI of a wind tower produced from the scrap metal of a previous wind tower is in the order of 500-600 [**] rather than the values 54-60 we calculated for the “first generation” wind tower. In other words, the whole EROI discussion of wind energy is obsolete.

[**] That’s too optimistic. Here an older piece of information from 2008 concerning a 600 kW onshore wind turbine:

Embodied energy
Onshore wind turbine: 0,6MW, height = 50 m, rotor diameter = 40 m
Production 1900 GJ (embodied energy tower + nacelle)
Installation 495 GJ
Maintenance (20 year) 774 GJ
Total 3169 GJ generated energy
Annual electricity production 5015 GJ
Energy payback time 7-8 maanden
EROI 32

If we recycle the old turbine we will have a vastly reduced embodied energy for the 2nd generation machine. But we need energy for extraction and transporting the tower back onshore. With maintenance remaining unchanged we arrive at an EROI of 51 instead of 32. But not “500-600”. Note that this is for a very conservative 20 years life time. So far, to our knowledge two windfarms have been decommissioned, one in Denmark and one in The Netherlands, both functioned for 24 years and there is no reason to assume they could not have functioned for many additional years. If lifetime would increase to 40 years you achieve a doubling of EROI (ignoring maintenance).

[deepresource] – EROI of Offshore Wind
[geminiwindpark.nl] – Gemini wind park
[wikipedia.org] – Electric arc furnace
[ec.europa.eu] – EU Economic Papers
[energy.gov] – Theoretical Minimum Energies To Produce Steel

[steeloncall.info] Over the past half century energy intensity of crude steel production fell with 60%

[eia.gov] Over the coming 23 years energy intensity of steel production is expected to come down even further from 11 to 8 units or 27%.

Wind Shadow – The Fewer, the Better Cheer?

“Don’t take my breath away!”

The largest offshore windfarms to date have cost multi-billion euro’s. Wind Farm Layout Optimization Problem or WFLOP is an important consideration. Can we build random numbers of large wind turbines in the North Sea without harvesting substantial lower energy per turbine?

Gemini wind farm data: 150 turbines of 4 MW each, area 68 km2 or 0.453 km2/turbine, total weight heaviest wind tower 1.347 ton (monopile, transition piece, nacelle and rotor with blades), rotor diameter 130 m. Assuming a layout with square cells, this would correspond with a rib of 673 m or 5 rotor diameters (5D).

But for very large grids with a size much larger than the height of the atmosphere other rules of thumb apply:

For realistic cost ratios, we find that the optimal average turbine spacing may be considerably higher (∼ 15D) then conventionally used in current wind-farm implementations (∼ 7D).

[kuleuven.be] – Optimal turbine spacing in fully developed wind-farm boundary layers

If we were to expand the Gemini wind farm over the entire North Sea, in so far it is suitable for monopile construction (200,000 km2), we would arrive are a grid of squares with a rib of 15 * 130 m = 1950m or an area of 3.8 km2/turbine. Total turbine in the North Sea: 200,000/3.8 = 52,631 turbines of 4 MW each or 211 GW in total.

[researchgate.net] – The Wind Farm Layout Optimization Problem
[]hindawi.com] – Wind Turbine Placement Optimization (Monte Carlo Simulation)
[fenix.tecnico.ulisboa.pt] – Offshore Wind Farm Layout Optimization Regarding Wake Effects and Electrical Losses
[geminiwindpark.nl] – Gemini wind park feiten | cijfers
[youtube.com] – Berlin – Take My Breath Away

Gemini offshore wind farm in Dutch part North Sea

US Offshore Wind About to Take Off

Inspired by the success of offshore wind in the North Sea, prospects for offshore wind to take off in the North Atlantic and Gulf of Mexico look good.

This push may be enough to usher a multi-gigawatt surge in US offshore wind development, led by the first commercial wind farm off Block Island, Rhode Island, commissioned in December 2016. With well-capitalized and experienced offshore wind developers such as Dong Energy, Statoil and Iberdrola eager to demonstrate their 15 years of European offshore wind know-how, it is likely that positive offshore wind market forces can be sustained in the US in the upcoming years… there is a potential capacity for more than 14GW of offshore wind in sites already leased on the US outer continental shelf, which could spark investments of up to $50bn if fully developed.

[rechargenews.com] – Gulf of Mexico will benefit from coming wave of US offshore

Read more…

Sif – The Wind Tower Company

In February 2015 Port of Rotterdam and Sif Group met during an exhibition in Hamburg. In June of that year the two parties signed a contract for the construction of the 500 meter long assembly- and the 120 meter long coatinghall from Sif.

October 24, 2015 the first pile of the hall and in April 2016 the first pile of the deep sea quay was driven into the ground. The construction of the halls went smooth so the first cans and cones from Roermond were delivered in September for assembly. In December, the 200 meter deep deepsea quay was finished and in January 2017 the first load-out of monopiles took place.

Thanks to the excellent cooperation between the Port of Rotterdam and Sif Group we realized a new production facility in just 14 months. Through this production expansion Sif is perfectly equipped to produce 4-5 monopiles per week with a diameter up to 11 meters.

That would be 5 x 6 MW = 30 MW per week or 1.5 GW per year or 50 GW until 2050, when Europe needs to be fossil free. Companies like Sif exist in Germany, Denmark and Spain, see below for an overview of the European (=global) offshore wind foundation industry.

Current Dutch electricity production capacity is 28,7 GW. Assuming a capacity factor of 50% of North Sea offshore wind, this current Sif production capacity would suffice to achieve electricity independence for The Netherlands in 2050. The European monopile market in 2015 was 385 and 560 in 2016. In 2018, Sif alone will be able to produce ca. 250 monopiles. It is likely however that Sif will continue to expand far beyond that number in the coming years.

[sif-group.com] – Company site [Google Maps]
[sif-group.com] – Sif projects
[energieoverheid.nl] – Nederland heeft voorlopig genoeg elektriciteit beschikbaar
[sif-group.com] – De razendsnelle realisatie van Sif op de Maasvlakte 2
[ewea.org] – The European offshore wind industry – key trends and statistics 2015
[windeurope.org] – The European offshore wind industry 2016
[tube-tradefair.com] – FA 07 Monopiles – gigantic pipes for offshore wind farms

European offshore foundation market 2016

References to the producers listed in the diagram according to production capacity:

[de.wikipedia.org] – Erndtebrücker Eisenwerk, Erndtebrück, Germany [Google Maps]
[steelwind-nordenham.de] – Steelwind Nordenham, Germany [Google Maps]
[ambau.com] – Ambau, Mellensee, Germany [Google Maps]
[bladt.dk] – Bladt Industries, Aalborg, Denmark [Google Maps]
[navantia.es] – Navantia, Ría de Ferrol, Spain [Google Maps]

Read more…

Lowering Maintenance Cost – Energy Islands in the North Sea

On March 23, 2017 an agreement was signed for the development of an artificial energy island in the middle of the North Sea intended to ease maintenance effort to keep potentially tens of thousands of offshore wind turbines running and to distribute power to neighboring countries.


Energy Island to be built in the Dutch part of the Doggersbank. Because of Brexit, Britain is an unlikely candidate to host this island and in case of a hard-Brexit will go it alone anyway.

[independent.co.uk] – North Sea island: Danish, Dutch and German firms launch bid
[tennet.eu] – European Operators to develop North Sea Wind Power Hub
[arstechnica.com] – North Sea: A giant wind farm to power all of north Europe
[deingenieur.nl] – Gigantisch Stopcontact op Eiland Doggersbank

World’s First Offshore Windfarm Vindeby Decommissioned

Reason decommissioning: end of economic life
Installation date: 1991
Decommissioning date: March 2017
Turbines: 11 of 450 kW
Water depth: 4 m
Capacity factor: 22.1%
Installation cost: 10 million euro
Cumulative lifetime power: 243 GWh
Danish electricity price consumers: 30 cent/kWh
Turnover consumer price: 79 million euro

The capacity factor was extremely low. More recent Danish offshore wind farm typically have an average capacity factor of 41.5%

[wikipedia.org] – Vindeby Offshore Wind Farm
[Google Maps] – Vindeby, Denmark
[energynumbers.info] – Capacity factors at Danish offshore wind farms
[deepresource] – Nuon Dismantles Offshore Wind Farm in the Netherlands

Sandbank Offshore Wind Farm Cabling

After the wind tower monopiles are installed, they need to be connected with cables. In the video it is done by offshore wind cabling market leader VBMS.

[vbms.com] – VBMS (VolkerWessels Boskalis Marine Solutions), Papendrecht, the Netherlands
[vattenfall.com] – Offshore Wind Farm Sandbank
[4coffshore.com] – Sandbank Offshore Wind Farm

2-B Energy – Back To Two Blades

3-blade turbines have become the standard in present day wind energy development. The Dutch company 2-B Energy argues that for offshore, wind 2-blades could perhaps be a better design. First of all from a maintenance perspective: in case of a defect, nacelle and rotor can be lifted from the tower in one piece and brought to a maintenance location, onshore or nearby offshore. Furthermore the company claims to be able to realize lower production costs. A first 2-b wind turbine has meanwhile been installed in Eemshaven, in the North of the Netherlands, see video below. Installation rotor downwind and able to rotate freely around a vertical axis, ensuring automatic direction towards an orientation perpendicular to the wind flow. Dimension nacelle 17 m, large enough for a helicopter to be able to land on top of it. Gain: less material, easier maintenance. 2-B Energy is participating in the Methil offshore project off the coast of Scotland.

[2benergy.com] – Company site
[offshorewind.biz] – Forthwind Cleared to Install Two-Bladed Turbine Duo off Scotland
[wikipedia.org] – Methil Offshore Wind Farm

At [1:33] you can see the test-installation of the 2-B wind turbine in Eemshaven. Visually it is not a very attractive installation, but it is intended for offshore operation anyway.

EROI of Offshore Wind

There is a lot of confusion about the real value of the EROI of wind energy. Time for a back-of-an-envelope calculation.

By far the largest energy input in the construction of a wind turbine from iron ore is realized in the steel mill. How much energy does it take to produce 1 ton of steel? Here is an old Dutch study (1986) from the Energie Centrum Nederland:

[ecn.nl] – Energy Consumption For Steel Production

On p20 we see that the lowest value for steel production is ca 20 GJ/ton or 5555 kWh/ton. We can safely assume that in 2017 the amount of energy required is lower, but we will accept this figure anyway to be on the prudent conservative side.

A 6 MW offshore wind turbine has roughly the following weight distribution:

Part Weight [ton]
monopile 2200
tower 650
nacelle 350
Total 3300

Energy cost for the steel production: 3300 * 5555 = 18331500 kWh
In the North Sea this 6 MW wind turbine on average produces 144,000 kWh/day, see:

[deepresource] – Gold Mine North Sea

Payback time in energy terms therefore is: 18331500/144000 = 127 days

There are of course extra energy costs. Say you need to get the iron ore from Australia, the worst case in transport energy terms, from a Dutch perspective.

[withouthotair.com] – Sustainable Energy – without the hot air, David JC MacKay

This source claims a shipping transport cost for dry cargo: 0.08 kWh/ton-km

Australia-Rotterdam = 20,000 km, in other words: 1600 kWh/ton. Or 3300 * 1600 = 5280000 kWh for the entire wind turbine. Divide it again by the daily energy production of 144,000 kWh of our 6 MW turbine to arrive at 37 days extra work for the wind turbine to earn itself back.

Total energy payback time: 127 + 37 = 164 days.

In other words: the offshore wind turbine must work for less than half a year to “earn” itself back in energy terms.

The remaining items like rotor (3 * 25 ton), construction of the gear, generator, maritime handling, installation, etc, have far smaller energy cost. Add a 22 days (wet finger in the air) to conveniently arrive at exactly half a year.

Things get even better if it is realized that these days about 1/3 of the world’s steel production comes from scrap metal, which requires far less energy to turn into new steel than iron ore. If in the future the windturbine has arrived at end-of-life, you can reuse the steel of the old turbine. You don’t have to get the iron from Australia anymore and recycling of steel costs far less in energy terms than producing steel from ore.

Summarizing: assuming a very conservative [*] life cycle of 30 years for the turbine, EROI for our offshore 6 MW wind turbine is therefore 30/0.5 = 60 or higher.

[*] The Eiffel tower is around since 1887 or 130 years. Experts estimate that the tower can easily survive another 300 years. Likewise it is absurd to assume that an offshore wind tower will fall over after 30 years.

P.S. After writing this post we discovered this calculation by Jan-Pieter den Hollander:

[duurzaamgebouwd.nl] – Energiebalans van een windmolen

Embodied energy

Onshore wind turbine: 0,6MW, height = 50 m, rotor diameter = 40 m

Part Energy in GJ
Production 1900
Installation 495
Maintenance (20 year) 774
Total 3169

Generated energy

Energy yield per year: 5015 GJ
Energy payback time: 7-8 months

In essence a comparable value to ours. In the example of Jan-Pieter den Hollander we are dealing with an onshore machine with less yield than offshore. Although it must be said that in his calculation there are counter-intuitive high values for installation and maintenance. Perhaps we will update this post in the future to have look at those.

Offshore Wind in Japan

Youtube text: “A number of projects are under way around Japan’s coast to develop offshore wind power Japan has developed an advanced form of this platform that it expects will create demand in the rest of the world.

Sandbank Offshore Wind Farm Inaugurated

Map with all German offshore wind farms, planned, under construction or realized. Click to enlarge.

Swedish company Vattenfall completed the installation of the Sandbank offshore wind farm in the German part of the North Sea. The plant went operational on July 23. 288 MW worth of wind power was installed with 72 Siemens turbines. A Munich-based utility company Stadtwerke München also participated (49%). Investment volume 1.2 billion euro.

[vattenfall.com] – Offshore wind farm Sandbank now officially inaugurated
[4coffshore.com] – Sandbank Offshore Wind Farm

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