New figures show that the Anholt offshore wind farm in the Kattegat between Denmark and Sweden had an impressively high capacity factor of 50% last year. This is all the more impressive since, as Mike Parr, Director of energy consultancy PWR points out, 2014 was a year with unusually low wind speeds. In an average year the capacity factor would have been more like 75%. This means, writes Parr, that if just 10% of the Kattegat region were developed for offshore wind, it would deliver 40% more power than the proposed Hinckley nuclear power station at a lower cost. According to Parr, this presents an unique opportunity to Europe. He calls on policymakers in Brussels and elsewhere to ensure that it will not be lost.

Denmark is one of the few countries which publishes the monthly output of each wind turbine installed in the country both on and off-shore (www.ens.dk). Currently data is available up to November 2014.

Recently Denmark announced that wind power had produced close to 40% of the electricity used by the country in 2014. Furthermore,  the country is building up its off-shore wind fleet and has launched a tendering process for the construction of a “next generation” of off-shore farms both in the North Sea and in the Kattegat and adjoining waters.

The 400MW Anholt farm built in the course of 2012 and 2013 had its first full year of operation in 2014. This provides a chance to look at capacity factors (CFs) for an off-shore farm in a windy location (Kattegat), using modern off-shore wind turbines. The location “enjoys” wind conditions similar to the North Sea………or does it?

Dispatchable generation

At the moment, in broad terms Danish off-shore farms can be split into two groups: those built in the early 2000s and those built post 2009. There is a considerable difference in CFs between these two groups. Those built in the early 2000s – for example, Horns Rev I – have CFs around 25%. This contrasts with the Horns Rev II (209MW) wind farm which has CFs for the four years 2010 through to 2013 of 47, 50, 52 and 49% respectively. This wind farm is located in the North Sea off the west coast of Jutland.

Figures for the new Anholt farm (400MW) in the Kattegat are available for 11 months in 2014. This farm uses more modern and larger 3.6MW turbines. The average CF for the 11 months of 2014 was an impressive 50%.

This is equivalent to the 2010-2013 average for Horns Rev II. However, for the same 11 months in 2014 Horns Rev II had a capacity factor of only 32%, much lower than in the years before. The reason is that average wind speeds were well below average in 2014.

If we look at the month by month CF figures for both farms an interesting picture starts to emerge.

The CF figures (%) for Anholt for 11 months of 2014 are shown below. It is immediately obvious that there is a high degree of asymmetry, with very high CFs for winter months (when power demand in Northern Europe is high) and much lower CFs in summer (when power demand is correspondingly lower). The figures for January, February and November are striking. The WF is acting almost like dispatchable generation!

Equivalent figure for Horns Rev II are shown below. The upper figures are for 2014, the lower figures are for 2011. The figures for 2011 indicate that indeed 2014 was a low wind year. Each year since 2011 Horns Rev II has delivered CFs over the year in the range 49 to 55% suggesting that 2014 was anomalous by being quite low on average, during the summer months (i.e. at a time of low power demand).

There are two factors which can account for the difference in CFs between Anholt and Horns Rev II. One is the difference in the size of the machines: capacity (2.3 vs 3.6MW), rotor diameter (93 mtrs vs 120 mtrs), swept area (6792 m2 vs 11309 m2, i.e. almost twice the area for the 3.6MW machine compared to the 2.3MW machines) and in mast height (55m vs 81m). These size differences have an impact on output and CF.

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The other and probably key difference is average wind speed. The Kattegat, where Anholt is located, has average wind speeds of 14m/sec compared to around 10m/sec for Horns Rev II in the North Sea and by implication much of the Danish and German North sea sectors. This 40% difference in wind speeds is a key element. This is confirmed by the fact that the the CF performance of Anholt over the 11 months of 2014 is roughly 50% higher than Horns Rev II over the same period. This suggests that in an average year, when Horns Rev II is delivering 50% CF, Anholt, or other off-shore farms located in the Kattegat would deliver CFs around 75%! This starts to look like dispatchable generation.

The Kattegat

The Kattegat covers around 12,000 km2. The Anholt farm occupies roughly 80 km2. Water depth in much of the Kattegat rarely exceeds 20 mtrs on the Danish side.  Although the construction of the Anholt farm encountered problems due to “difficult” sub-sea terrain, nevertheless the relatively shallow depths coupled to very high average wind speeds and proximity to land suggests an attractive location for off-shore (near-shore?) farms.

It will be interesting to see if EU institutions are capable of even recognising the business opportunity offered by the Kattegat

Currently, with respect to the Kattegat proper, a single 200MW offshore farm is scheduled to be tendered near Saeby (Jutland opposite Byrum). If 10% of the Kattegat were developed, this would deliver around 6,000 MW of power with a CF of perhaps 75%. Expressed another way, and taking €3360/MW as the development cost (Anholt), this would deliver 4.5 GW (6 GW derated by 75%) at a cost of €18 billion. Re-expressing: this would deliver 40% more power than the proposed Hinkley nuclear station (3.2GW) in the UK at a lower cost of £55/MWh vs the £92.5 proposed for Hinkley. Furthermore £55/MW is close to UK wholesale prices and without the disposal problems associated with nuclear waste.

Who Pays – Who Benefits

The limitation on delivering 6 GW of off-shore “Kattegat-power” is likely to be the ability of the Danish population to support the subsidies a large-scale roll-out of off-shore farms might need. However, the very high CFs raise further questions with respect to the need for subsidies. One assumes that scale would deliver lower costs and thus the need for much lower support.

There is also the unresolved question of “who pays for the network reinforcements needed to carry away the power”? Denmark? Two possible candidates for Kattegat energy are Sweden (closing down its nuclear stations soon) and Germany – building (expensive) off-shore in the North Sea with lower CFs and costly HVDC connections.

Given the above it is unlikely that German off-shore power in the North Sea could compete with Danish “Kattegat-power”. This brings us to energy policy and the debate going on in Europe about “building renewable energy sources where conditions are best”. Discussions on this usually revolve around “wind in the north” and “solar PV in the south”, but as this example shows, the situation is more complex than that.

The Kattegat can clearly be considered a business opportunity – for Europe. The Kattegat and the adjoining waters offer a large-scale low-cost opportunity for off-shore wind. Expecting the Danes to pay for its development, when benefits are pan-European, seems unreasonable. Thus we arrive in the territory of the Energy Union, ENTSO-E’s ten year network development plan and the EU’s desire to be seen as a global leader in renewable energy.

In my previous article for Energy Post on UK capacity markets, I outlined the almost measureless inability of UK politicians and bureaucrats to develop energy policies that benefit a population as opposed to vested interests. In the same area, it will be interesting to see if EU institutions are capable of even recognising the business opportunity offered by the Kattegat (and other locations for high performance renewable energy sources), let alone grasping it. Perhaps they will produce a………policy paper. That’ll get things moving.

Editor’s Note

Mike Parr is Director of energy consultancy PWR. He previously worked for one of the UK’s distribution network operators as a systems engineer running their network Merseyside. He then moved into industrial engineering running the services (and energy saving activities) at Sony’s Bridgend TV plant. In the late 1990s he founded PWR Consultants which undertakes research in the area of climate change and renewables for clients which include a G7 country and global corporations.

His recent article on the UK capacity market scheme: “UK “capacity market” is not a market – it’s state aid (£1 billion/year)” is also very much worth reading.

Note that the website RenewEconomy reports that just recently the tender for the Horns Rev 3 offshore wind farm in Denmark was won by Vattenfall at a price of 10.31 eurocents per kWh, which compares to 14.07 eurocents for the Anholt park and to UK prices of more than 15 eurocents per kWh. In other words, costs here have come down by a third already. The European offshore wind industry has committed to bringing down costs of offshore wind by 40% around 2020.