Are prefabricated foundations the future for onshore sites?

Utility Enel has completed what is claimed to be the first fully prefabricated wind-turbine foundation to be installed in Spain.

The prefabricated foundation can be installed in a single day with a much smaller crew (pic: Artepref)
The prefabricated foundation can be installed in a single day with a much smaller crew (pic: Artepref)

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Rather than the six weeks it typically takes to construct a standard foundation, the prefabricated units "can be laid in just one day," according to the foundation's manufacturer, Artepref Renovables.

The 400-tonne units require specialised transportation and crane but slash onsite workforce needs "by around 90%," Artepref claims.

A second day is needed to tighten the steel "tendons" criss-crossing the concrete mass before the turbine can be mounted.

Another advantage Artepref points to is the controlled factory environment its product is made in, "enabling a standardised process" and ensuring a "validated" foundation system arrives on site.

In contrast to the drawn-out conventional method for laying turbine foundations, the company claims its solution also "eliminates uncertainties related to concrete setting, variable environmental conditions and the continual supervision and quality controls needed onsite".

The demonstrator foundation at Enel Green Power’s Los Llanos project in Burgos province will have a Vestas 2.2MW turbine on it. 

Its completion marks over a decade of development since Artepref received international patent accreditation for the solution in 2009.

The firm already produced 7,500 concrete pedestals for solar heliostats for the 150MW Noor III concentrated solar power plant in Morocco.

Ready-made future

The advent of prefabricated solutions for wind-turbine foundations "is now inexorable", said Ramón López, director of Spain-based Esteyco Energía, which makesa partially prefabricated foundation.

Esteyco says it has built 115 foundations, with another 250 under development or construction across the globe.

The growing trend in power auctions for wind is pushing down returns on the megawatt-hour, said López, and developers are increasingly concerned about extending wind-plant lifespans and raising tower heights to tap higher wind speeds.

To bear the extra turbine loads, typical reinforced concrete foundation volumes are growing from 450 cubic metres to nearly 1,000m3.

To avoid increasing foundation volumes, Esteyco has developed a brace system consisting of diagonal precast concrete supports surrounding the upper and lower slabs of the foundation, reducing overall concrete volumes.

One foundation can be built every one or two days using a 120-200-tonne crane, according to López.

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