Despite what many may believe, the aviation sector's contribution to overall CO₂ emissions represents a relatively small share. Even so, it is clear that sustainability and efforts to reduce the environmental impact of all economic sectors are, and should be, a global objective. And these efforts include decarbonisation.
For various reasons, aviation is one of the most difficult sectors to decarbonise. For this reason, for some years now, a number of initiatives have been promoted. solutions to help reduce the use of fossil fuels. An important part of these efforts focuses on the use of alternative energy sources, including sustainable aviation fuels (SAF), but also on increasing efficiency and reducing the energy demand of aircraft. In essence, this is about further electrification of aircraft.
The aim is to to enhance the aircraft design hybrid or electricThis is particularly true, at least in the short term, as a solution for short- and medium-range flights. This is certainly a feasible mission, but it is not without its challenges. various challenges.
Seeking solutions for the decarbonisation of the aviation sector
Personally, whenever I hear any expression with the word "electrification" in it, I think of the scene in Jurassic Park with the 10,000 V wire fence around the T-Rex enclosure, where we all saw it coming that someone would be electrocuted... Although, in reality, the famous scene with the boy on the fence can be considered a failure that no electrical engineer would have accepted, as there was no earth faulty shunt to close the circuit.
Possible script flaws aside, the trend for the past 20 to 25 years, especially in the automotive world, and with the aim of contributing to decarbonisation of the economy, it is a progressively increase electrificationThe stresses on the vehicles are also reduced. But why?
We will try to explain it in a simple way through the well-known formula of Ohm's law, and its corollaries in the form of power:
The first formula, the Ohm's Lawexpresses that voltage (V) and current (I) are proportional to a constant (R) commonly known as resistance. This Law can be used both for DC circuits (DC or Direct Current), as well as alternating (AC or Alternate Current). The second formula is simply the multiplication of both variables to see the quadratic dependence of voltage and current on power (twice the voltage, or current, gives four times the power).
It can be seen that if we want to increase the power delivered by the electrical system (battery) of our car, we have two options: O we increase V (voltage), or we increase I (current)R is the load or resistance of our system, and is constant for a given car and conditions.
Between increasing V or increasing I, there are some pros and cons that make engineers opt for one or the other alternative. Roughly speakingThe disadvantage of increasing V is that the conductors and sub-circuits need to be better insulated to prevent arcing or voltage discharges to the vehicle chassis, while increasing I has the disadvantage that the effective cross-section of the conductors needs to be increased in order to carry the higher current that has to reach the sub-systems.
This is where the synergies between the aeronautical world and the automotive worldThe ultimate aim of electrification in the very short term is to save fuel by carrying less weight, and to reduce the weight of the vehicle. in the medium and long term, we want to be fuel-free in order to decarbonise our planet and reduce our carbon footprint as much as possible..
Challenges in vehicle electrification for decarbonisation
Circuits at higher voltages than the classic 12 V that we found (and still find for the starter circuit) in our combustion or hybrid vehicles, fall short for this purpose. And that is why the automotive industry started to mobilise to look for an optimum between the battery pack to be installed, the required insulation, the resulting operating voltages and the required inverters or inverters needed to switch from AC to DC during the charging, discharging and regenerative braking process.
| Although the aeronautics industry uses automotive industry concepts for electrification, some essential elements, such as inverters, will need to be redesigned to reach voltages of 900 Vdc or higher, thanks to advances in GaN and SiC. |
Many manufacturers placed this optimum point at around 400 V for electric vehicles (hybrid, plug-in hybrid or fully electric), since Silicon (Si) and IGBTs (Insulated Gate Bipolar Transistor) technology was well established thanks to previous work on soft starters for single and three-phase motors for HVAC (High Voltage Alternate Current) present in various industrial machines. The problem started when 100 km of autonomy was not enough, or a full charge in less than 1 hour was not achievable.
This is the birth of the batteries of higher voltages to achieve greater autonomy, accompanied by other types of technology that can no longer be based on Silicon alone, but on Silicon Carbide (SiC) and Gallium Nitride (GaN).which enable electronic developers to work in the 400 - 900 V range with high efficienciesThis is understood as low heat dissipation in the delivery of the battery to the vehicle's electric motors, as well as high efficiency in the Wall Mount charger that will deliver power from the domestic mains to the battery for recharging when plugged in.
Figure 1. Si, IGBT, SiC and GaN comparison (from Pnt Power .com)
We won't go into too much detail about why SiC or GaN can work at higher voltages than Si, but we can comment that the main explanation is that they are devices that are referred to as WBG (Wide BandGap). This higher value in SiC and GaN to pass an electron from the valence band to the conduction band is what makes it possible for them to have higher breakdown voltages and, therefore, to work at higher voltages than Si alone.
Decarbonisation of the aviation sector through electrification
And what is happening in the aeronautical world? Quite simply, the same thing that happened in the automotive world 24 years ago: We want hybrid or electric aircraft to help us decarbonise and reduce our CO2 by route. The challenge is that the power required to make a light aircraft fly is not comparable to that required to make a car roll.
Particular features of electrification in aviation
For this decarbonisation of the aviation sector to be effective, i.e. for aircraft to be truly electrified without losing functionality and profitability, it will presumably be necessary to promote the innovation in various development pathways, including:
- New battery technologies (higher energy density per cubic centimetre and lower weight)
- New materials for distribution
- Improving the electrical insulation.
- And of course, increase the current values of "typical" aircraft stressesThe voltage is usually 28 V DC, and 115 V AC at 400 Hz.
Again, the aviation industry will be able to take the concepts that the automotive industry has developed for the decarbonisation of its vehicles, adapting and improving them for electric aviation according to its boundary constraints. But what does seem clear is that, to electrify aircraft, it will be necessary to design new inverters in the range 250 - 600 VdcThe first stages (hybrid aircraft) bleed this inversion of the engines at 115 Vac @ 400 Hz, complying with all applicable aeronautical regulations (DO-160, MIL-STD-704, etc.), and then move on to a all-electric model aircraft, perhaps at a voltage in excess of 900 Vdc, where SiC technology has to be researched and polished as it was done decades ago with Si-based technology.
Companies such as AERTEC We are now ready to design and realise this new future that the decarbonisation of the aviation sector is leading to. Will you join us?
