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Smart transformer design can help optimize offshore wind costs

Wind energy set a new record in Europe last October with wind sources providing nearly 25% of total electricity powering nearly 200 million households

Wind energy set a new record in Europe last month with wind sources providing nearly 25% of total electricity on October 28 – enough to power nearly 200 million households .

Year-on-year, the wind industry sets new production records and supplies more power than any other new energy source. But, only three percent of wind power is generated offshore – even though the more consistent winds out at sea would mean less wind farm downtime and therefore higher production.

The International Energy Agency says that offshore wind could produce 50 percent more electricity than onshore farms, making it the fastest-growing renewable energy sector in the world. So, why is the offshore segment still so small?

Simply put: the high risk and complexity of major projects on the sea results in billions of dollars of construction, operating and maintenance costs. Costs which would make offshore farms economically unviable if not for government subsidies. Costs which would otherwise get passed onto the consumer: you.

For renewable energies to truly become a preferred choice, costs have to be attractive for operators. Technology providers like ABB are looking at how they can contribute to these lower costs by designing better electrical system components, which could save millions over the lifetime of the wind farm.

One important component is the transformer – the device that transfers electrical energy between two or more circuits through electromagnetic induction. Transformers are used to step-up the voltage to a higher level to effectively transmit energy generated on an offshore platform substation to the onshore transmission and distribution grid.

Transformers are traditionally built with large quantities of steel, iron and copper. This makes them heavy. In this industry, the heavier it is, the bigger the cost because floating something massive on the open water isn’t easy or cheap.

In short, the viability of building an offshore wind platform hinges on how much weight and how much area space is involved. As offshore wind farms increase in size, the platform design becomes heavier and bigger. Investment costs surge and this challenges the industry’s goal of reducing the levelized cost of offshore wind energy (LCoE). LCoE is calculated as the net present value of the unit-cost of electricity over the lifetime of a generating asset, like a wind farm. Simply put, it is the average price that the generating asset must receive in a market in order to break even over its lifetime.

A lighter transformer could very well be key to reducing platform building costs and therefore the overall cost of generating offshore wind electricity. But only if this lighter design were still reliable.

It’s not just weight that matters. Transformers are tailor-made for each wind farm platform and the challenge is to design a device that achieves the most affordable and reliable performance within the limitations of each unique – and demanding – offshore environment, which includes weather patterns, mechanical and thermal stresses, as well as corrosive conditions.

The very intermittent nature of wind determines each transformer design. Variable winds lead to variations in the current flowing through the windings. This, in turn, leads to varying temperatures, causing wear and tear. Designers may need to allow for occasional overloading of the transformer.

Designers have to make tough choices between competing electrical and mechanical requirements. For example, a smaller core and windings within a transformer will reduce its weight but could also reduce its energy efficiency and the economic viability of the platform might require that the transformer meet a minimum energy efficiency target.

Of course we need to keep in mind that transformers are one of the many components within the offshore wind farm system – albeit an important one. Transformer designers have to consider the overall platform design and cost, as well as transportation offshore, and how their transformers fit into the bigger picture.

For all these reasons, ABB is striving to design transformers that can help drive the efficient and cost-effective growth of offshore wind and enable a stronger, smarter and greener grid.

Sources:

Wind Europe

Bloomberg

Related links:

Transformers for wind power

ABB at WindEurope 2017

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