Before the power generated at an offshore wind farm is fed into the transmission grid, it is combined in an offshore transformer substation, like the Siemens’ Lillgrund offshore wind park substation. Voltage there is converted from 33 kV (or now 66 kV is sometimes used) to a transmission voltage of 138 kV by a 120-MVA power transformer. Platform equipment also includes medium-voltage switchgear, protection and control technology, and a service transformer for the substation. (Credit: Siemens AG)

Offshore substations — the systems that collect and export the power generated by turbines through specialized submarine cables — are an essential component of offshore wind farms, especially at large, multi-megawatt sites. These systems serve an important function: to stabilize and maximize the voltage of power generated offshore, reduce potential electrical losses, transmit electricity to shore, and do so in a manner that supplies the greatest return on investment.

But the wind industry is still young, and there is a long way to go before the development of offshore substation systems fully mature. Given that the typical cost breakdown for large-scale offshore wind installations includes 7.5% for platforms, cabling, substation equipment, and more, there is opportunity for greater cost-effectiveness and efficiency.

Sizing up substations
Early substations for offshore wind farms consisted of simple topside frames with basic modules installed on top or as a covered deck. These structures were intended to operate unmanned, and required few visits from personnel. In many cases, these substations weighed as little as 400 tons.

That’s not much compared to today’s more advanced structures that weigh upwards of 10,000 to about 22,000 tons. These substations are more fully developed, and consist of a topside or a deck installed on monopole or jacket structures. Options today include self-floating and self-installing structures that eliminate need for expensive marine lifts or cranes.

Over and above serving as an offshore power-converter station, a substation’s platform may be equipped with boat landings, a helicopter deck (yes, a helicopter deck), accommodations, and act as a logistics’ service base during installation and operation of an offshore wind farm. Not surprisingly, one of the greatest cost challenges to developing an offshore substation is the sheer size of the structure. Much like transporting and installing wind-turbine components offshore, careful logistical planning is key.

The two substations installed at what’s been dubbed “the world’s largest wind farm at sea,” the UK’s London Array offshore wind farm, required use of a 3,300-ton, lift-capacity floating crane just to maneuver the systems onto a foundation that’s 15 km from shore — undoubtedly a costly venture.

With an area of around 20 x 20 m, the substations are each 22-m high, and feature three levels of structural steel decks. They weigh in at 1,250 tons and are supported on transition pieces, connected to monopile foundations driven into the seabed. The substations let the wind farm operate more efficiently by transforming the energy generated from 33,000 to 150,000V, after which electricity is exported through cables 50-km long to an onshore substation.

Self-installing structures
One option for overcoming the size and cost challenges related to substation installation is a self-installing platform, a design used by ABB and Alstom Grid. Their floating and self-installing HVDC offshore substation was used to connect the 400-MW, MEG 1 offshore wind farm to the German high-voltage, direct current system.

Alstom’s GIS substations were installed on a platform at the Baltic Sea 2 offshore wind site. The platform was placed on a pre-installed jacket and brought out to the installation site where water depths reached 44 meters. The buoyant and self-erecting platform design enabled a high degree of flexibility and independency from crane ships for the transport and installation of the substation. The closed platform layout protects the electrical components from offshore conditions. (Credit: Alstom)

According to Alstom, the platform uses a “suction can” method to set the foundations to the seabed floor and is fully self-contained to protect electrical equipment. The method reduces cost, noise pollution, and is believed safer on the environment when compared to conventional options.

Siemens is also working on a more efficient installation system for offshore substations. The company’s WIPOS (wind-power offshore substation) is available in different options, including self-lifting, topside and jacket, and floating, all of which involve pre-fabricated sections with flexible configurations for ac and dc applications.

Much like, Alstom’s system, Siemens’ self-lifting platform can self-install to reduce the need, costs, and risks related to heavy lift vessels. In this configuration, the foundation is the substructure base frame, which connects to piles that are driven into the seabed. The topside includes a rectangular pontoon with customizable internal walls and decks. Self-jacking legs, attached to the topside, are immersed and then connected to the substructure base frame.

Operations & maintenance
Configuration of a substation, its access points, and storage areas for maintenance equipment are important when considering the design for use at an offshore wind farm. These factors impact how often a substation may require servicing and its accessibility. But the factors are also difficult to assess because of extreme weather conditions and vibrations an offshore substation must endure, so routine O&M is typically a guess.

Because maintaining anything offshore is more costly and hazardous to operators, there is an inherent risk of unexpected equipment breakdown if maintenance is not made simpler and more efficient. The wind industry is responding to these challenges several ways. For example, along with using condition-monitoring systems, the industry is planning more frequent maintenance visits to detect potential equipment failures early on. They are also starting to take notes. With more detailed records, wind technicians can identify issues and that insight provides for better future substation designs.

Transformers, for example, are an issue. They the use oil as electrical insulation and are made of thin steel making them susceptible to corrosion. To overcome this challenge, designers are working with gas-insulated transformers that are safer for personnel to deal with. Additionally, some substation designs are moving transformers indoors to help minimize exposure to the elements.

Standardization in substation safety and manufacturing is another topic gaining traction. If the industry can develop more consistent standards for substation designs and installation techniques, time and cost savings are bound to follow. But this takes time. To date, just over 20 substations for offshore wind farms have been built around the world.

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There, in the choppy Atlantic surf, a company called Deepwater Wind started building what will be America’s first offshore wind farm. The farm will have five wind turbines, each rising to twice the height of the Statue of Liberty. When completed in late 2016, they will generate a combined 30 MW and turn Block Island into the most powerful coastal enclave in the northeast (with apologies to the Hamptons).

But there’s more to the project. It is also the physical example of GE’s future following its acquisition of Alstom’s power and grid business, which closed earlier

A jacket foundation is set for a turbine off of Block Island. The turbines will be installed Spring or summer of 2016.

The Block Island farm brings together Alstom’s massive Haliade turbines, whose blade tips will reach 600 feet above the water, and GE’s innovative gearless permanent magnet generators that can produce 6 MW. The combination has the potential to transform the renewables business in the U.S. and abroad.

Until now, Europe has been the hub of wind innovation, says Bryan Martin, head of U.S. private equity at the financial firm D.E. Shaw. The company is financing the $290 million Deepwater farm, and Martin believes that bringing Alstom’s wind turbines and GE’s power generation technology under one roof will change the wind industry’s competitive landscape. “We’re very excited about GE’s acquisition of Alstom’s power businesses,” Martin says.“GE and Alstom getting together provides the first real competitor to Siemens” for offshore wind farms in Europe, Martin says.

The rotor of each Haliade turbine is nearly one-and-a-half times the length of a football field, or 150 meters. All that torque spins GE’s 6-MW direct drive permanent magnet generator. The design lets GE engineers eliminate the gearbox, reduce the number of moving parts, cut the need for maintenance, and lower the operating cost.

The generator weighs 150 tons and will sit 100 meters in the air. It’s split into three separate electrical circuits. Even if two circuits go offline, the turbine can still produce 2 MW on the remaining circuit. Low maintenance and redundancy are hugely important, especially for offshore installations, where treacherous waters and high wind can delay a repair trip for days or weeks.

Jeffrey Grybowski, chief executive of Deepwater, says the farm will power all of Block Island, which currently relies on expensive diesel fuel. The farm will also lower carbon emissions by an estimated 40,000 tons annually. It could also help cut electricity bills for Block Island residents by up to 40%. “Offshore wind can power much of the U.S. East Coast, not least in the Northeast, where the wind is strong and we need energy,” Grybowski says. “And we can employ lots of people doing it.”

The artist’s rendering hints at the size of the Haliade turbines. Their rotors will sport 150-m diameter and each unit will be capable of generating 6 MW for a total of 30 MW.

The Block Island farm will be the first offshore wind farm in the U.S. But the potential for U.S. offshore wind energy is massive — over 4,000 gigawatts (GW), which amounts to more than four times the nation’s annual electricity production, according to the U.S. Department of Energy. President Barack Obama’s Clean Power Plan has also increased interest in onshore and offshore wind energy, presenting a new opportunity for industry.

So far, a total of 47,000 onshore turbines have been installed in the U.S. wind market, where GE is a major player. The Alstom power and grid acquisition now gives it a stronger offshore offering and also one of the broadest and deepest renewables portfolios in the industry. The combined businesses will also have expanded project expertise and financing for power projects.

“Today offshore wind is a small market with big potential, and the Block Island project sits at the leading edge of innovation,” says Anders Soe Jensen, CEO of GE’s offshore wind unit. “We’re proud that GE will again be making energy history with the first American offshore wind farm.”

The farm will have five wind turbines, each rising to twice the height of the Statue of Liberty. When completed in late 2016, they will generate a combined 30 MW.

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The Alstom acquisition marks GE’s largest ever industrial deal.

GE has officially completed the acquisition of Alstom’s power and grid businesses, following regulatory approval of the deal in over 20 countries and regions. It is GE’s largest-ever industrial acquisition, and spans the EU, the U.S., China, India, Japan, and Brazil.

GE reached an agreement with Alstom in 2014 to purchase Alstom’s power and grid businesses for €12.35 billion.

Adjusting for the joint ventures announced in June 2014 (renewables, grid, and nuclear), changes in the deal structure, price adjustments for remedies, net cash at close, and including the effects of currency, the current purchase price is €9.7B (approximately $10.6B). This figure includes working capital of approximately €0.6B in October of this year.

GE expects the deal to generate $0.05 to $0.08 of earnings per share in 2016, and $0.15 to $0.20 of earnings per share by 2018. GE is targeting $3.0 billion in cost synergies in year five and strong deal returns.  The overall economics and strategic rationale remain the same as GE announced in April 2014.

“The completion of the Alstom power and grid acquisition is another significant step in GE’s transformation,” said Jeff Immelt, chairman and CEO, GE. “The complementary technology, global capability, installed base, and talent of Alstom will further our core industrial growth. We are open for business and ready to deliver one of the most comprehensive technology offerings in the energy sector for our customers.”

The GE and Alstom combination will benefit U.S. customers in New Jersey for the combined-cycle power plant, PSEG Sewaren (GE 7HA gas turbine + Alstom heat recovery steam generator). Among other global projects, GE and Alstom are also  preferred bidders for a combined-cycle plant project in Asia.

GE continues to execute its strategy to become a simpler, more focused company. In addition to the Alstom acquisition, GE is moving forward with several plans: the split-off of Synchrony Financial has commenced; the GE Capital exit strategy is ahead of plan with $126 billion of signed dispositions; the recent formation of GE Digital is consolidating all digital capabilities across the company to provide customers with the best industrial solutions and software; and GE is winning in the marketplace and delivering strong financial results.

GE
www.ge.com/investor

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