Wind generators

SCHWING truck-mounted concrete pumps used for pouring extensive wind generator foundations

Already in 2010 Germany was no. 3 regarding the electricity output from wind generators. If the planned energy turnaround is to be successful, it will be necessary in the future to harness the power of the wind to an even higher degree. More than 50 % of the electricity demand could thus be generated by onshore wind power stations. This scheme would require however the enlargement of the preferred windfarm sites and larger wind turbines. A study by the “Fraunhofer Institut für Windenergie und Energiesystemtechnik” has in principle confirmed the feasibility of developing 2 % of the German territory for wind energy projects as already demanded by the “Bundesverband Windenergie”.

This form of regenerative energy has been experiencing a new boom since the passing of the new wind energy decree. It is planned to increase the current share of electricity generated by wind power from 4 to 15 % by 2020. Already today, between 40 and 50% of the net electricity consumption in the German laender Saxony-Anhalt, Mecklenburg-Vorpommern, Schleswig-Holstein and Brandenburg is generated by wind power stations.

The company ENERCON is a pioneer in the construction of wind power stations and their integration into the power grid. The focus here is on considerable higher nominal outputs of the generators and thus on greater heights of the rotor hubs. The rated output of the plants has risen in the last few years from 600 kW to 7,500 kW and the height of the rotor hubs from 45 m to 136 m. In order to make the foundations fit for withstanding all the higher static and dynamic loads, their volumes had to be enlarged accordingly. These heavy-duty foundations require nowadays up to four times as much concrete as the foundations 10 years ago.

The company BEZ from Zahna specializes in the construction of foundations for wind power stations for which it can fall back on more than ten years of experience. Manager Rene Zachey is proud on the fast rising number of more than 1000 foundations built : “This is only the beginning” he says, “for in northern states of Germany the demolition of older windmills has just begun in order to install more powerful generators.” In addition, the construction of these plants is significantly sped up in the remaining states, too. The deconstruction of the older plants is carried out by blasting up the existing foundations. Many smaller plants are thus being successively replaced by fewer, but bigger ones.

For the concrete placing operations, the company BEZ cooperates primarily with the Brandenburg-based concrete pumping service Arno´s GmbH from Werder-Leest who uses its three SCHWING truck-mounted concrete pumps. The latest acquisition is an S 39 SX which meets the ever-increasing requirements of larger foundations. Arno’s managing director Keller appreciates the advantages of the four-section roll-and-fold boom of this pump which has proved its worth during more than 10 years already in his smaller concrete pumps from SCHWING.

Of particular importance for this work, however, are the advantageous reaching distances of the boom of this machine. With 34.70 m, SCHWING’s truck-mounted concrete pump S 39 SX has the longest boom on a three-axle truck chassis according to European standards. The total length of less than 12 m and a weight of less than 26 t make special permissions by the competent authorities unnecessary. The innovative SX-H outrigger system which requires considerably less space for the installation and shorter set-up times moreover offers the possibility of equipping the machine with a long-stroke pumpkit.

The stroking length of 2.50 m permits reducing the switching cycles by up to 23 % for the same concrete output. In combination with the SCHWING-typical Rock valve this means lower wear and lower operating costs for the user.