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The new N163/5.X joins its sister model, the N149/5.X, which was announced earlier this year. 

It builds technologically on Nordex’s initial N149/4.0-4.5 turbine, first unveiled in 2017, which started serial production in March 2019.

"The two N149/4.0-4.5 prototypes performed well regarding actual versus calculated loads, power curve, sound and reliability performance," said Nordex vice-president for product strategy and sales support, Till Junge.

"We got to know this turbine well over the past year, and it gave us sufficient confidence to utilise available design reserves for the N163 and N149 5.X models," he said.

Both 5.X models share a largely unchanged mechanical high-speed geared layout with three-point gearbox support.

The higher rating was enabled by raising the generator voltage from 690V to 750V, using the latest insulated-gate bipolar transistor (IGBT) technology, and enhancing the cooling system.

"The retained DFIG-based electrical system, even at the enhanced 5MW-plus level, is fully capable of meeting all current and medium-term global grid demands," said Junge.

"This includes countries like Ireland and Australia, which have the strictest grid codes at present.

"Currently, a DFIG-based solution offers the most economical solution in Capex terms, draws from a large and mature global supply chain, and AEP performance still proves superior to full-converter equivalents,"  Junge added.

The 5.X hub has been enhanced for both variants, together with the pitch bearing and electrical pitch system. The load-based independent pitch control has been retained.

Single-piece blades

The 163-metre diameter rotor features newly developed glass- and carbon-fibre reinforced epoxy single-piece "lightweight" blades, dubbed NR81.5.

Their structural design builds on the NR74.5 series for the N149/4.0-4.5, and the shorter, earlier NR65.5 blades fitted to the N131/3000 range, introduced in 2013.

"The NR81.5 and NR74.5 blades partially share the same geometry, which, as a standardisation and cost-saving measure, can be produced in the same inner mould-sections, a concept we have already applied extensively on our AW3000 platform," said Junge.

"The tip sections are variable in length, similar to the blades for the AW series, and the inner and outer blade sections are, in a final production step, chemically bonded."

The rationale behind sticking to single-piece blades is that many of the key markets for the N163 can still be supplied with such huge components despite the transport and logistical complications.

Nordex seriously considered offering a segmented blade, but a comparative in-house review showed that single-piece blades of this size still offer substantial benefits in terms of loads, lifetime performance and costs.

The introduction of the N163/5.X does not automatically mean a phasing-out of the original N149/4.0-4.5, which enjoys brisk demand in a number of leading wind markets, Junge pointed out.

The flexible power-rating strategy, rapidly being adopted across the industry, is retained for both 5.X models.

Customers can choose between longer asset life by running the turbines with a modest output, or a shorter life at maximised output for higher revenue.

"Within power purchase agreement financing structures we see an increasing trend for maximising lifetime-based project net present value (NPV) by starting operation with the highest available power modes," said Junge.

"This yields maximum revenues in the initial years, then operators can switch to reduced power modes in the later stages to prolong operating lifetime.

"This wind asset operating strategy, enabled by the flexible rating approach, contributes to risk reduction too, because uncertainty increases in the longer terms," said Junge.

Nordex will certify the 5.X models for IEC S classification, and has decided not to provide a maximum rating yet. On sound performance, Junge stated a sound power level of 106.4dB(A) at 5.5MW.

The N163/5.X will initially be offered with hub heights ranging fron 118 to 164 metres, with several tubular steel and concrete/steel hybrid solutions available.

"What’s new is that the 5.X turbines will be available with 120-metre full concrete in-house developed towers," said Junge.

"This was an original Acciona “uåX˜äŠÊ˜·³Ç design for the AW3000 series, and it’s enjoying increasing global demand due to local content, construction and transport-logistical benefits."

The N163/5.X will yield up to 20% more energy than the N149/4.0-4.5, according to Junge.

The first prototype is planned for installation in the second half of 2020, with serial production starting in 2021.