New Technology Critical to Future of Offshore Wind Energy

Germany’s Siemens has handed over the first of a total of five commissioned North Sea grid connections, the BorWin2 offshore platform, to its customer TenneT, a German-Dutch transmission grid operator, for immediate commercial operation, the company announced in a press release on January 30. TenneT is one of the four Transmission System Operators (TSOs) that make up Germany’s well developed and intricately branched high voltage electricity grid. TenneT covers large parts of Germany from the southern German state of Bavaria – where Siemens has its corporate headquarters – all the way up north to the North Sea coastline. This is a significant development in the ‘High Voltage Direct Current Transmission’ (HVDC) market segment, in which Siemens is establishing itself as a technology leader with prior experience from projects in China and the UK. Siemens already holds the top position as offshore wind turbine supplier in terms of annual installations.

“This is the first offshore grid connection worldwide to take up commercial operation with efficient direct-current technology,” Jan Mrosik, CEO of the Siemens Energy Management Division said. Siemens explains why the use of HVDC transmission technology is especially critical for the integration of offshore wind energy into the national power grid.

“High-voltage direct-current (HVDC) transmission technology is used to ensure efficient transfer of the electrical energy to land: (…) Thanks to the Siemens high-voltage direct-current (HVDC) technology, transmission losses for each grid connection, including cable losses, are less than four percent. This Siemens HVDC technology is installed on the offshore platforms and in the land-based converter stations. The wind-based electricity is transmitted as alternating current [AC] to the converter platform, transformed into direct current [DC] and fed to the mainland via a subsea cable. The land-based station converts the direct current back into alternating current and feeds the electricity into the extra-high voltage grid. HVDC is the only efficient transmission solution for cable lengths of more than 80 kilometers. The HVDC Plus technology used by Siemens is less complex and extremely compact, making it predestined for use in sea-based applications. (…) [S]ystems equipped with HVDC Plus feature self-stabilization. As fluctuations in the grid must always be reckoned with for wind-based power generation, grid stability and reliability is enhanced considerably through the use of the Siemens HVDC Plus technology.”

How HVDC Transmission Technology Links Large-Scale Offshore Wind Installations to the Grid

Source: Siemens

Even though the installation of offshore wind turbines requires a substantially higher initial investment vis-à-vis onshore wind installations, the benefits are considerable and include higher levels of reliability, steadier yields in terms of more full-load hours compared to onshore wind power installations and, in this respect, a significantly higher yield per turbine. Note, it is the geographic location which guarantees that offshore wind turbines will have higher full-load hours due to obviously ‘better’ – at times – severe wind conditions (see Breaking Energy on wind energy and severe weather) at sea while additionally obtaining an advantage from bigger rotor diameters and higher hub heights than would be possible or allowable both onshore and further inland.

Average Turbine Configuration of Land-Based Wind Turbine Generators Installed in 2014 (For Comparison Purposes)

Source: Deutsche WindGuard; “Status of Land-Based Wind Energy Development in Germany 2014” report on behalf of German Wind Energy Association (BWE) and VDMA

Wind Power in Germany – Typical Annual Yields

All benefits above, however, used to inevitably come with a ‘cost’; namely, the ‘transport’ of energy over great distances leads to significant power (transmission) losses every time AC has to be converted to DC along the way. In this respect, the above new HVDC transmission technology represents a major advancement in terms of power transmission efficiency and thus is predestined to save large amounts of power by limiting necessary conversions and ‘cable losses’.

When higher voltage transmission losses are kept low, more electricity can be transmitted via the line to electricity customers. Again, the most efficient way of moving large amounts of electricity with minimal energy lost in transmission is high-voltage DC current. The one caveat here is that given the comparatively high costs of electrical conversion (from DC to AC), DC remains cost-effective only for long-distance transmission. Besides, the ideal placement of all transmission lines would be underground in order to protect the grid from severe weather and/or extreme temperature swings in both directions along the thermostat. This, however, often remains a matter of logistics and, above all, economic feasibility.

In Germany, offshore wind projects are far offshore due to landscape protection and higher wind yield. According to Siemens, “hardly any electricity is delivered [- that’s for underground or submarine cables -] when AC lines are 80 km or longer (The cable capacities absorb the usable electricity).”

Offshore Wind Installations in the North Sea

Source: Siemens

The following two charts provide evidence of the fact that in general offshore wind energy installations have moved further offshore into deeper waters over the years and that this trend is more than likely to continue with distances to shore increasing steadily given the projects already under construction, consented and planned. According to the EWEA, the average water depth of online offshore wind farms was 22.4 m and the average distance to shore for those projects was 32.9 km at the end of 2014.

Water Depth and Distance to Shore of Online, Under Construction and Consented Wind Installations (2014)

Source: The European Wind Energy Association (EWEA)

Water Depth, Distance to Shore and Size of Offshore Wind Installations under Construction during 2014 by Country

Source: The European Wind Energy Association (EWEA)

In light of the growing distances, connecting offshore wind power to the grid requires HVDC transmission links. Other advantages of HVDC transmission include:

1. 30-50% less transmission losses incurred vis-à-vis alternating current (AC) overhead lines.
2. Given the same width of the cable run, 30-40% more energy transmission possible than with conventional AC carrying overhead lines.
3. HVDC can prevent the transmission of faults between connected AC grids and thus prevent blackouts.
4. HVDC transmission technology tends to be more cost-effective than AC technology when using overhead transmission lines running past 600 km (375 miles).

According to the technical data sheet provided by Siemens, the BorWin2 offshore platform is “with an overall transmission capacity of 800 megawatts (MW) the world’s largest direct-current grid connection.” This transmission capacity translates into supplying about one million German households with electricity generated from wind power and proves that offshore wind energy is – at the very least to rural areas – able to deliver large-scale grid-supplied electricity. To better evaluate what a maximum transmission capacity of 800 megawatts means in the wind energy space, consider another fact from the EWEA report: “In 2012, the average size of connected offshore wind projects was 286 MW while in 2013 it was 485 MW. In 2014, it was 368 MW. This is the result of the completion in 2013 of the record breaking London Array (630 MW).”

So, what is the current state of wind power in the US, Europe and globally? And what is the outlook for wind energy in 2015 and 2016?

As reported by Breaking Energy, last week the Federal Energy Regulatory Commission (FERC) issued preliminary figures on 2014 US energy capacity additions and wind energy claimed the top spot among renewable energy sources with 4,080 MW, thereby growing substantially year-on-year but, as Pete Danko notes in his article, “that figure could well be updated upward.” In this respect, it is very important to note that the above wind power number is purely ‘land-based’ meaning that as of 2015 there is no offshore wind farm in the US. America’s first offshore wind installation – the 468 MW “Cape Wind” project – is slated for “construction in federal waters off the coast of Massachusetts in Nantucket Sound”, pending final approval which will coincide with the end of litigation by project opponents.

Across the pond, data gathered by the European Wind Energy Association (EWEA) – in a report entitled “The European Offshore Wind Industry – Key Trends and Statistics 2014” (January 2015) – show that in 2014 ”408 new offshore turbines were fully grid connected, adding 1,483 MW to the European system” with total installed capacity now standing “at 8,045 MW in 74 offshore wind farms in 11 European countries.” According to the report, 373 additional turbines are awaiting grid connection.

Justin Wilkes, EWEA’s Deputy CEO, suggested that “[o]ffshore wind will have a monumental part to play in the EU’s energy security drive as part of the European Energy Union but it is political determination that will help Europe unlock its offshore wind potential.” With this statement in mind, just imagine America’s potential for offshore wind installations. According to the report, the UK accounted for over half of all new installations (54.8 per cent) and Germany came in second with 35.7 per cent in 2014. But in 2015, Germany is ready to turn the tables on the UK, the current leader in new installations, with the installation of more offshore capacity.

“Germany is set to buck the trend this year [2015]. The UK has more installed offshore capacity than the rest of the world combined but this year shows that other countries in the EU are making serious investments in the sector,” Wilkes stressed. As for additions to German onshore capacity, the German Energy Blog cited interesting 2014 data from the German Engineering Federation (VDMA) and the German Wind Energy Association (BWE) showing that “new onshore wind power turbines with a total capacity of 4,750 MW were installed.”

Most importantly, the authors of the German Energy Blog note that “this exceeds the growth target of 2,500 MW net annually introduced with the amendment of the Renewable Energy Sources Act (EEG) that is effective since August 2014 (EEG 2014) by far.” All this only underscores that Germany seems to be betting big on wind power. So, Siemens’ HVDC transmission technology may not only be another crucial ingredient to push the “Energiewende” further along but could also allow for aggregating wind output over larger and distant areas thereby helping to smooth wind energy’s volatility, variability and unpredictability.

While EWEA data show that “12 offshore projects currently under construction will increase installed capacity by a further 2.9 GW, bringing Europe’s cumulative capacity to 10.9 GW by 2016,” the boom in wind energy is also increasingly becoming a global phenomenon. Deutsche Welle (DW) cites estimates from VDMA Power Systems that “around 44 GW of wind power worldwide was installed on land in 2014 – an increase of 31 percent from 2013.” As China remains the global leader in expanding wind power capacity, a strong push is also readily identifiable in “India, Canada, Brazil, South Africa, France and the United Kingdom,” according to DW citing the Word Wind Energy Association (WWEA).

To receive more information on this article, our Newsletter or find out more about what w3.windfair.net has to offer, please, do not hesitate to contact Trevor Sievert at ts@windfair.net.

Please don't forget to follow us on Twitter: w3.windfair.net on Twitter

w3.windfair.net is the largest international B2B internet platform in wind energy – ultimately designed for connecting wind energy enthusiasts and companies across the globe.