HAW-Hamburg: Research projects

back

A motivation for multi-rotors is the so-called square-cube law. To simplify, it can be said that the mass of a rotor and therefore also the costs increase cubically with the rotor size. However, the swept rotor area and therefore the yield only increase quadratically. This problem can be evaded by combining the same swept rotor area from many smaller rotors.

The aim of the sub-project X-Multirotor was to investigate multi-rotor concepts with a total rated output of 20 MW and to compare their levelised costs of energy (LCoE) with that of a single turbine with an equivalent output. Multirotors consist of several rotors that are connected to each other and to the tower via a supporting frame (spaceframe). The connection was assumed to be a fixed/floating bearing combination in order to transfer the rotor loads well into the tower and also to enable the entire multi-rotor structure to track the wind. Concept analyses were carried out in which the number and arrangement of the rotors, but also geometric design parameters such as the spaceframe depth or fixed bearing position and thus also the tower height, were varied.

Results

Selected findings from X-Multirotor are:

A spaceframe depth of 10-13% of the spaceframe width leads to an optimal force flow and therefore low costs.
A fixed bearing position and thus tower height relatively in the centre of the spaceframe, viewed over the height, leads to minimal costs for the tower and spaceframe.
Stability (buckling) is a design driver, as almost all spaceframe connecting elements that are under a compressive load must be re-dimensioned for buckling after the strength dimensioning.
Due to the so-called load averaging, more rotors have a positive effect on the dimensioning based on the fatigue strength.
The operating phase of multi-rotors and thus the Operational Expenditures (OPEX) are currently still relatively unclear and are being investigated in the follow-up project X-Multirotor - Design for Maintenance (DfM).
Alternative wind tracking concepts for multirotors, such as yaw by pitch, are possible and have been demonstrated in two simulation environments.
Multi-rotors show great potential for reducing the LCoE.

The results from the X-Multirotor sub-project are being applied and further developed in the sub-project X-Multirotor DfM.

A more detailed presentation of the results of X-Multirotor can be found in the final report of the sub-project.

Project Team:

Sven Störtenbecker

Project Leader

Prof. Peter Dalhoff

Duration

11/2017 - 06/2022

Budget

676.600 €

In cooperation with

Siemens Gamesa

Funding

Federal Ministry of Education and Research

Unit

CC4E - Competence Center for Renewable Energies and Energy Efficiency

Contact

Prof. Peter Dalhoff

Professor für Windtechnik

Department of Mechanical Engineering and Production Management

peter.dalhoff (at) haw-hamburg (dot) de

Stellv. Leiter CC4E

Competence Center Erneuerbare Energien und Energieeffizienz

T +49 40 428 75-8674

peter.dalhoff (at) haw-hamburg (dot) de