The reduction of the Levelised Cost of Electricity (LCoE) in wind energy, and offshore in particular, is among the main objectives of research in the academia nowadays, and a demanding task as well. Offshore wind farms are capital intensive investments and lowering uncertainties and costs throughout design, planning, installation and operational phases will offer cheaper electricity production and a more competitive nature against fossil fuel powered energy. Of course, a big part of the total cost of a wind farm is the wind turbines themselves. Innovations in the design and manufacturing processes are always welcome in order to further advance within the learning curve of the technology and achieve efficient economies of scale. Furthermore, the blades of the wind turbine rotor are its most important component because they express the most basic operation of the turbine, aerodynamics and energy capture. Yet they pose structural challenges. There are efforts to maximise energy output while keeping their mass low, which should subsequently drive down secondary costs. Additionally, another important factor is the increase of energy output in the farm level that can lead to a larger cost reduction. This thesis aims to investigate the performance and feasibility of lightweight, low power density rotors. This investigation is made by acquiring a performance baseline with the reference rotor of the 10 MW INNWIND machine and comparing it with the proposed alternative rotor designs by means of parametrical modifications. The reference machine rotor radius is 89.166 m, with a blade mass of 41.7 tn and a rated power output of 10 MW operating at an optimal lambda of 7.5. All the new designs include an increase in rotor radius to 103 m. They also include differences in operational parameters such as rated rotational speed, blade slenderness and tip speed, while rated power stays the same. These designs result in different blade masses and allocation of energy production...