Renewable energy generation sector has grown rapidly over the past decade with expanding investments in relation to increasing political and public support, as well as technological maturation. This review aims to provide the reader with the recent technological developments in the field, while analyzing the state-of-the-art to identify the major overarching technological trends. The collected information indicates that the main maturation directions for emerging renewable technologies are towards harnessing new untapped sources of renewables and combining the energy generation with additional value creation for more versatile and effective land, infrastructure or labor usage. The overarching concept is clear: generating more economic or environmental value with less investment. The three main emerging technological trends were identified as the development of means for: distributed small-scale generation, large-scale land versatility, and accessing marine renewables. Agrivoltaics, floating PV and floating wind were identified as maturing technologies with high deployment that are heading towards becoming industrial de facto standard practices. The overall technological development, and the possibility of adding new, previously unexploited sources of energy, combined with distributed generation possibilities and novel high versatility co-location applications will likely result in an increased rate of deployment of renewable energy technologies in the coming decade.

Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC electromagnetic material properties are presented, showing comparable results to conventional and other 3D-printed, high-grade, soft magnetic materials. The magnetization of 1.5 T was achieved at 1800 A/m, exhibiting a maximum relative permeability of 28,900 and hysteresis losses of 0.61 (1 T) and 1.7 (1.5 T) W/kg. A clear trend of total core loss reduction at 50 Hz was observed in relation to the segregation of the specimen cross-sectional topology. The lowest 50 Hz total core losses were measured for the toroidal specimen with four internal air gaps annealed at 1200 °C, exhibiting a total core loss of 1.2 (1 T) and 5.5 (1.5 T) W/kg. This is equal to an 860% total core loss reduction at 1 T and a 510% loss reduction at 1.5 T magnetization compared to solid bulk-printed material. Based on the findings, the advantages and disadvantages of printed air-gapped material internal structures are discussed in detail.

Samples from FeSi4 powder were fabricated with a low power selective laser melting (SLM) system using a laser re-melting strategy. The sample material was characterized through magnetic measurements. The study showed excellent DC magnetic properties, comparable to commercial and other 3D printed soft ferromagnetic materials from the literature at low (1 T) magnetization. Empirical total core losses were segregated into hysteresis, eddy and excessive losses via the subtraction of finite element method (FEM) simulated eddy current losses and hysteresis losses measured at quasi-static conditions. Hysteresis losses were found to decrease from 3.65 to 0.95 W/kg (1 T, 50 Hz) after the annealing. Both empirical and FEM results confirm considerable eddy currents generated in the printed bulk toroidal sample, which increase dramatically at high material saturation after annealing. These losses could potentially be reduced by using partitioned material internal structure realized by printed airgaps. Similarly, with regard to the samples characterized in this study, the substantially increased core losses induced by material oversaturation due to reduced filling factor may present a challenge in realizing 3D printed electrical machines with comparable performance to established 2D laminated designs.

3D printing or additive manufacturing (AM) technology is considered an essential component of the Industry 4.0 revolution due to its improved capabilities over traditional manufacturing systems, facilitating the shift towards next generation smart factories. The three-dimensional fabrication freedom also suggests a new epoch in the design of electrical machines, as the process can finally be liberated from the constraints of 2D laminations. Despite the multi-material nature of 3D printing electrical machines, due to the availability and maturity of dedicated metal printing systems, most of the research and development on the field is concentrated on material optimization and rapid prototyping on these systems. In this paper we present the challenges of 3D printing electrical machines with current manufacturing systems and solutions offered by different authors. Challenges of selective laser melting (SLM) fabrication are discussed in greater detail due to its recognition and popularity in the electrical machine community.

Over the past decade, additive manufacturing (AM) of functional electromagnetic components has grown into a promising new area of research. Not only does AM allow for unparalleled in-house prototyping speed and flexibility, but it also introduces a completely new set of design rules for obtaining optimized component shapes. Up to date, relatively few functional electromagnetic components or devices have actually been printed, and fewer still actually characterized or compared in terms of performance. This work describes the completion process of a prototype induction motor with fully 3D printed electrical steel cores, from design to printing, post-processing, assembling, and performance evaluation. This work aims to establish a baseline for further optimization and to map the design and production process of a fully functional electrical machine for future reference. The output of the finished motor was measured at 68 W (0.5 Nm) at 34% energy efficiency. This is roughly 2/3 of the efficiency of conventional machines of the same size and type. Further optimization steps for the 3D printed material and core design are proposed to obtain higher motor performance.

Additive manufacturing (AM) is a key technology for advancing many fields, including electrical machines. It offers unparalleled design freedom together with low material waste and fast prototyping, which is why it has become to focus of many researchers. For electrical machines, AM allows the production of designs with optimized mechanical, electromagnetic and thermal parameters. This paper attempts to give the reader an overview of the existing research and thermal solutions which have been realized with the use of AM. These include novel heat sink and heat exchanger designs, solutions for cooling the machine windings directly, and additively manufactured hollow windings. Some solutions such as heat pipes, which have been produced with AM but not used to cool electrical machines, are also discussed, as these are used in conventional designs and will certainly be used for additively manufactured electrical machines in the future.