The E-175 EP5 E1 flagship prototype, which was installed in late August, comes with a 175-metre rotor – one of Europe’s largest for onshore turbines – enabled by a new, slender 86-metre rotor blade that was developed and produced in house.
The E-175 EP5 E1 variant will be available with flexible power ratings of between 6.0MW and 6.3MW, but the prototype that will soon start spinning in the German state of North Rhine-Westphalia is 6.0MW, with specific power of 249W/m2.
“The rather modest 249–262W/m2 range makes this first E-175 EP5 model an ideal configuration for specific conditions, including grid-constrained projects and low-wind sites in Germany,” says Jörg Scholle, chief technology officer at Enercon, as we meet just a few days after prototype completion.
“The turbine is now in the commissioning phase, which will be followed by field-testing and technology validation,” he adds, noting that ramp-up is planned for the first quarter of next year.
Scholle confirms that there has been “overwhelming market interest” in the company’s new flagship model, which he says implies that the planned production volume for 2025 is sold out already.
Enercon is in concrete negotiations with customers for numerous projects for the next 24 months – and there are also further enquiries, including from more international customers, he adds.
Model variants
The E1 prototype is installed on a standard hybrid concrete-steel tower with 162-metre hub height supplied by German market leader Max Bögl. The largest available tower has a height of 175 metres.
Enercon further offers tubular steel towers, while an in-house hybrid steel tower (HST) comprising a wide-base bolted steel bottom section and tubular upper sections is also being evaluated as a possible future option.
Enercon refers to the E-175 EP5 E1 variant as its ‘basic model’. It is visually distinct from the upcoming E2 variant thanks to a single-piece inner-rotor permanent magnet generator (PMG) with an outer diameter of just over six metres. The E-175 EP5 E2 will by contrast feature a much larger PMG with a 10-metre outer diameter (see below).
Main enhancements
The E1 generator configuration is essentially an enhancement of the 5.56MW E-160 EP5 E3’s PMG unit, but with an optimised cooling system. This is necessary to compensate for a combination of increased rating and reduced rotor/generator speed, whereby the extra heat generated must be dissipated to ensure sound temperature management and a guaranteed 25-year service life.
Besides the new rotor and blades, another novel feature of the E-175 EP5 E1 is a self-supporting containerised E-nacelle concept which, in addition, incorporates newly developed modular power converters and a new control system.
These latter two components are already incorporated in the 4.26MW E-138 EP3 E3 E-nacelles. They are being carried over to the E-175 EP5 E1, but with additional converter modules due to its higher rating.
“The new customised converters are more efficient and more reliable than the previous offering,” Scholle says. “The containerised E-nacelle concept represents our ‘one box for all’ philosophy for achieving a standardised lean manufacturing solution,” he adds, noting that the E-138 EP3 E3 still features the initial E-nacelle concept consisting of a space frame and cladding. “This will be changed into the containerised variant in future,” he explains.
Logistics challenge
Another topic we discussed is the logistics of road transport – one of the biggest overall challenges in preparing the E-175 EP5 E1 prototype for installation, and of crucial importance once the giant enters volume production.
Currently, the dimensions of E-160 generators and the substantially shorter E-160 blades, measuring approximately 78.5 metres, already feature in the top two of Enercon’s road transport difficulties, and this is reflected in the permitting process too.
Scholle explains that obtaining permits is easier and faster in wind markets with a higher degree of digitalisation. “With the E-175 EP5 we have to be even more creative, especially for transporting the blades,” he elaborates.
In Germany, this involves the option of using barges to transport blades, as a back-up alternative to roads. “But this is dependent on available and suitable waterways infrastructure,” he points out.
“Prototype installation finally turned out to be a smooth process through careful preparation at crucial levels, including an evaluation of all transport-related logistical issues. Each of them is now an integral part of our masterplan.”
Enercon’s road transport logistics experts drove an 86-metre E-175 EP5 blade with a blade transporter from Cuxhaven, where blades arrive by ship from the company’s blade plant in Portugal to Leipzig and vice versa.
These trials involved remote-controlled rotor blade adapter vehicles with blade tilting capabilities and especially deployed for complex ‘last-mile’ stretches in urban and forested areas or mountainous roads, Scholle explains.
“Our overall goal was the thorough testing, validation and detailed mapping of many different routes, and turning these into a representative blueprint that could act as a reference tool,” he adds.
Novel blade installation tool
Scholle moves on to highlight the features of a novel single-blade installation gripper stabilising tool that Enercon redeployed for the E-175 EP5 E1.
The tool was first successfully tried, tested and validated at complex sites in Germany and Chile. Its overall concept solution consists of two essential parts supplementing each other and forming a full system that offers multiple benefits.
The first element is a novel blade gripper tool developed by German specialist Ematec. Like conventional blade-hoisting devices, it lifts individual blades to their required elevation at around a turbine’s hub height. 
In addition, this gripper enables varying blade angles during installation, while previously blades could only be mounted with the blade in a horizontal position.
“This first key element is merged with a second novel element,” Scholle explains. “Two ducted propeller sub-assemblies provide the gripper with blade stabilising and positioning capabilities as well.”
Scholle says that Enercon developed this second element of the overall solution in cooperation with external specialist Seasight Solutions. “The individual propeller units are mounted to the left hand side and right hand side of the gripper tool respectively, and align with the blade’s length axis when the gripper is attached to it.”
Another major benefit he highlights is that the tool removes the need for hub rotating tools, resulting in less specialist equipment being required. This in turn contributes to the introduction of lean practices whenever possible and feasible – from manufacture and assembly down to transport and installation logistics.
Hub rotation
The usage of hub rotating tools was previously necessary to rotate the hub to a fresh blade mounting position each time, so that a matching pitch bearing and blade would directly face each other.
The above procedure was inherently linked to Enercon’s direct-drive turbines, which unlike geared equivalents cannot be rotated via the drivetrain and thereby use the generator as a drive motor.
With this novel and versatile gripper tool solution, the hub can now be rotated to its next position via the gravity mass of each freshly mounted blade.
“The third benefit is the elimination of ‘classic’ blade guiding ropes, which allows a reduced working space footprint around each individual turbine position,” Scholle says. “The new method is easier, safer and faster. And because less manpower is required, it also saves on labour costs.”
Implementing changes
Several major planned changes inside Enercon’s mechatronics centre of excellence, which were discussed during my visit earlier this year, have now been implemented.
They include the inauguration of a second moving line for mixed-model E-nacelle assembly, and a division of the production lines into main lines and pre-assembly areas.
The pre-assembly areas will produce separate component modules and feed them into the main lines. This makes it possible to untangle the complexities of production lines and ensure precise and efficient production timing.
E-nacelles for the E-160 EP5 E3 and the E-138 EP3 E3 are now produced at these lines, plus some final units for the E-115 EP3 E4 being phased out, according to Scholle.
“We also created a central area in between the two lines dedicated to the supply of parts in predetermined quantities for each turbine being produced,” he adds.
Serial robotised hub production has been implemented in parallel. Still on a trial run earlier this year, it offers huge time savings compared with the previous manual mounting of hundreds of studs in each hub.
“Robots also mount the pitch bearings, place the nuts, and then torque these to the required values,” Scholle explains, noting that the new assembly line design in the mechatronics centre of excellence achieves both faster throughput times and higher output numbers.
Expanding volumes
The next step within the expanding E-nacelle production volume at the two lines is to add the E-175 EP5 E1 next year.
The ramping-up of the E-138 EP3 E3, for which a type certificate award will be announced at WindEnergy Hamburg later this week, is somewhat slower than previously anticipated.
The main reason for the delay, according to Scholle, is the ongoing strong demand for its predecessor E-138 EP3 E2 ‘compact nacelle’ model – which has more than 840 units in operation – in various key markets. The E2 variant is assembled on a separate line.
“We will soon switch completely from using overhead cranes to automated guided vehicles (AGVs) for moving E-nacelle sub-assemblies to their new takt-time position,” School adds. “This is essential as we continuously increase E-nacelle output volumes. The cranes are then redeployed to moving main components and parts to predetermined places along the assembly lines”, he concludes.
The prototype of Enercon’s second E-175 EP5 E2 model variant is planned for the first quarter of 2025. Once completed, this will represent another leap in technology, this time through a generator swap to the groundbreaking horizontally split, 10-metre outer-rotor PMG design introduced in August 2023.
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