Global warming concern is pushing aviation to introduce innovative technologies for greener flights, since aviation stakeholders committed to ambitious targets of reducing global net aviation carbon emissions by 50% by 2050 compared to 2005. Hybrid-electric propulsion is one of the solutions proposed to reach this ambitious goal. The introduction of such solution opens new opportunities and originates new challenges as well, such as the need for dedicated thermal management systems (TMS) to cool-down electric machines. European Union has co-funded ORCHESTRA(Optimised electric network aRCHitEctures and SysTems for moRe-electric Aircraft) Project to design new technologies allowing 10% efficiency increase and 25% weight reduction of electric power system (EPS) compared to state-of-the-art. Within ORCHESTRA Project, Skylife developed a Dual Active Bridge (DAB) bi-directional modular converter to manage the power transfer between Kilo-Voltage Direct Current (kVDC) bus (1-3kV) and High Voltage Direct Current (HVDC) bus (540V). 

Consortia: University of Nottingham (coordinator), Leonardo, Safran Electrical & Power, Safran, C.I.R.A, Fraunhofer, Aeromechs, AIT (Austrian Institute of Technology), BSIM, Skylife Engineering, VR Aviation Safety Partnership

Introduction

On-board aircraft power demand is continuously increasing, due to both the introduction of new onboard systems requiring additional power, and since the concern related to aviation impact on global warming is increasing, pushing towards aircraft electrification. In particular, the Intergovernmental Panel on Climate Change has set the target of at least 50% reduction of carbon dioxide (CO2) emissions by 2050. However, it is expected that global CO2 emissions produced by mobility sector will increase of 80% by the end of 2050. 

According to ICAO, about 20% of the foreseen increase should be produced by aviation. Thus, to meet overall mobility emission reduction targets, the Advisory Council for Aeronautics Research in Europe (ACARE) has defined the Flightpath 2050, according to which it is expected a reduction of 75% in CO2 and 90% in Nitrogen Oxides (NO) emissions.

These ambitious goals can be achieved by introducing new aircraft configurations and/or disruptive technologies, such as hybrid/electric propulsion for aircraft, changing the paradigm of current aviation market, which is still based on the use of jet engines introduced in 1950s.

The introduction of hybrid/electric power-plants opens new potentialities, but also new challenges to be faced. One of the main challenges to solve is the way to dissipate heat produced by hybrid/electric power-plant components: such systems cannot use conventional techniques applied in current aircraft and have strict thermal constraints to be met. Thus, detailed studies of TMS are needed to unleash the potentialities of hybrid/electric propulsion system.

European Union (EU) has co-funded the ORCHESTRA Project [5] with the aim to design new technologies allowing 10% efficiency increase and 25% weight reduction of electric power system (EPS) compared to state-of-the-art.

In this paper the design of a novel bidirectional modular converter to manage the power transfer between kVDC bus (1-3kV) and HVDC bus (540V) of the multi-Mega Watt (MW) architecture of a future Much More Electric Aircraft (M2EA) is proposed. The selected topology for this equipment is a DAB. Then, the design of an optimized TMS for the thermal control of the DAB is shown, including the feasibility study of SMA to improve off-design performance.

Bi-directional 1-3kV/540 converter for Multi-Megawatt Topology

The power converter designed for this project has one main characteristic to consider: the high voltage input, whether 1 kV or 3 kV. Usually, for that voltage level, the most typical solutions include IGBT (Insulated Gate Bipolar Transistor) modules as semiconductors, for their high voltage withstanding capability, and high current capability. However, in this case, the converter’s size and weight are also critical, and that is the reason that motivated the increasing of switching frequency, making imperative the use of faster devices like SiC MosFETs (Silicon Carbide Metal-OxideSemiconductor Field-Effect Transistors), with good voltage withstand and current capability.

The chosen topology for the DC/DC converter was the Dual-Active Bridge converter. This choice was based on the main characteristics of this topology: bi-directional power flow, high efficiency, voltage regulation, galvanic isolation, reduced harmonics and modularity. This last characteristic was the one that allowed the use of the converter in different modular configurations to work at an input voltage of 1 kV or 3 kV. When the input voltage is 1 kV, the converters have their input connected in parallel in what is called IPOP (Input Parallel, Output Parallel). When the input voltage is 3 kV their input is connected in series, in what is called ISOP (Input Series, Output Parallel). Both connections are represented bellow.

Electrical design

The design of the converters was made to reach the characteristics presented bellow:

• Nominal Power: 70kW
• Nominal Voltage kVDC: 1kV
• Nominal Voltage HVDC: 540V
• Topology: Dual-active bridge

Reference: Diego Giuseppe Romano, Salvatore Ameduri, Antonio Carozza, Bernardino Galasso, Gianluca Marinaro, Edson Lima Junior Manuel Lagares, Carmen Bejarano Espada, María Dolores Jiménez Sánchez (2024),  Development of a bi-directional modular converter and its thermal management system for a future much more electric aircraft, International Conference on More Electric Aircraf, France

This project has received Horizon 2020 funding under the European Union's Horizon 2020 research and innovation program under grant agreement number 101006771.

Skylife Engineering participa en el diseño y desarrollo de un nuevo sistema de recarga ultrarrápida para vehículos eléctricos, que dispondrá de estaciones modulares basadas en criterios de sostenibilidad para reducir el impacto sobre el medio ambiente.

El proyecto ZEUS, subvencionado por el CDTI y financiado por la Unión Europea a través de fondos NextGenerationEU con un importe de unos 3 millones de euros,  se lleva a cabo a través del consorcio liderado por WallBox Chargers S. L., junto con Skylife Engineering S. L., Bold Valuable Technology Spain S. L. y Tekniatest Solutions S. A.

El nuevo sistema de recarga eléctrica modular y ultrarrápido en el que trabaja ZEUS alcanza potencias de carga de hasta 350 kW buscando, además, ser más sostenible. En este sentido, contará con un sistema de baterías integradas que serán alimentadas por fuentes de energía renovable. Con estas estaciones de carga (VE) se conseguirá amortiguar un pico de potencia en la demanda eléctrica, una ventaja diferenciadora, al tener en cuenta la previsión de expansión del parque de vehículos eléctricos a corto plazo y la limitada estructura de red eléctrica estatal.

La actividad de Skylife Engineering, con sede en el Parque Científico y Tecnológico Cartuja, en Sevilla, se basa en la innovación para la implementación de alta tecnología con impacto positivo. La compañía está especializada en ingeniería aeroespacial, donde dispone de una destacada trayectoria de más de 10 años. Asimismo, desarrolla innovación tecnológica con soluciones aplicadas a otros sectores, como el de la energía, la salud o la educación.

La empresa andaluza, nacida con una clara conexión con la Universidad de Sevilla, cuenta entre sus clientes con grandes multinacionales presentes en todo el mundo, para las cuales desarrolla tanto software como hardware. Su equipo humano, formado en su mayoría por profesionales de la Ingeniería con diversas especialidades, mantiene un firme compromiso con valores como la sostenibilidad.

During the last century, energy production has been supplied, predominantly, by power plants based on fossil fuels. However, for some years the harmful effects on the environment of this source of energy production have caused the awakening of a collective awareness of the need to seek alternative sources for energy generation. In this process, it is renewable energy sources such as solar or wind power that are leading the change. However, the dependence on climatic conditions of these energy sources makes it difficult to achieve a 100% renewable system applicable anywhere on the planet. It is at this point that the need to search for a different and alternative energy source that functions as a central system that complements and completes energy production from renewable sources is born. Nuclear fusion energy emerges in this context as a promising solution that makes it possible to achieve a sustainable society, without the consumption of fossil fuels, the emission of greenhouse gases or highly polluting radioactive waste.

What is fusion energy?

Fusion energy seeks to harness the energy emitted during the fusion of light atomic nuclei. When two such particles merge, the resulting nucleus is slightly lighter than the original ones. The difference, however, does not disappear, but is converted into energy. The truly amazing thing is that this minimal loss of mass translates into a huge amount of energy. This is the reason why there are so many private companies and public entities launched to conquer fusion energy.

To understand a little more the theory of this energy source we have to refer to physics. There are three states of matter: solid, liquid, and gas. But if we keep subjecting a gas to extremely high temperatures, it turns into plasma. In this state, electrons are separated from atoms. When an atom lacks electrons orbiting around the nucleus, it is said to be ionized and is called an ion. Thus, plasma is composed of ions and free electrons. In this state, scientists can stimulate ions to collide with each other, fuse together, and release energy. This is where the creation and operation of the Tokamak comes into play.

What is the Tokamak and how does it work?

Research on nuclear fusion issues is advancing rapidly towards the creation of a commercial and industrial solution that allows the enormous amounts of energy produced by this new and clean energy source to be exploited. One of the most advanced devices is known as the Tokamak, where strong magnetic fields create and confine a plasma in a donut-shaped container where the fusion reaction is achieved.

What is the role of power supplies in all of this?

Power supplies are one of the most important and critical elements of creating a Tokamak. Keeping plasmas stable in order to extract energy is difficult. They are chaotic, extremely hot, and prone to turbulence and other instabilities. Understanding, modeling, and controlling plasma is extremely complex, but researchers have made great strides by using magnetic confinement devices to manipulate plasmas. The magnetic fields are induced by coils, which need to be powered by specific forms of current controlled by their power supplies.

Due to the high currents required in tokamaks, power systems are a demanding part of the design. Most of the relevant tokamaks use thyristor-based and grid-connected or flywheel-based systems, although new trends are leading us towards flexible, modular power supplies based on supercapacitors and Insulated Gate Bipolar Transistors (IGBTs).

Skylife, creators of the power supplies of the Tokamak SMART of the University of Seville

A new Tokamak device for the purpose of fusion energy research, called SMART (SMall Aspect Ratio Tokamak, small aspect ratio tokamak), is being designed at the University of Seville.

Skylife Engineering, in its commitment to sustainability and complex and innovative projects, participates in this project with its line of Power Electronics in charge of the design and manufacture of the magnetic field coils, the microwave system and the power supply system.

The coil system is made up of 3 subsystems, designed to generate and control the flow of plasma inside the vacuum chamber. In total, more than 3000 kg of high conductivity copper will be available.

The 6 kW microwave system operating at 2.45 GHz acts as a booster in the plasma generation process inside the vacuum chamber. The power supply system consists of 5 pieces of equipment to generate a magnetic pulse in the coil system that will form and control the plasma flow in the vacuum chamber.

The electrical pulses will be generated by banks of supercapacitors, with the possibility of being charged with domestic electrical current.

The objective is the installation of a compact spherical tokamak, unique in Spain, which is a world benchmark in the development of magnetic confinement fusion.