What does a more sustainable aviation look like? Electrical machines and devices might be our future – both in the air and on the ground.
Sustainability in Aviation: Clean & electrical Aircraft & GSE
Over the past four months, the global pandemic has utterly dominated the news cycle. It has spread out into all walks of life, and is the epicenter of all attention, and the aviation industry has actually been a pretty large part of that news cycle, with airlines around the world shutting down for weeks on end. Well, there is still a world outside of COVID-19, and technology continues to advance. We are going to have a look at what is going on in the world of sustainable aviation, clean aircraft, and clean ground support equipment.
Making sustainability happen in aviation: How Feasible is the Completely Clean Aircraft?
The question of the feasibility of a completely clean, i.e., electric aircraft is a totally valid question to pose. The amount of electrical power necessary to propel a jet airliner is absolutely enormous, somewhere in the ballpark of the power necessary to power two thousand residential houses.
The interesting thing about electrical aircraft is that the movement is – not necessarily for sustainability reasons – quite old, not new at all. In fact, the very first recorded electric aircraft goes all the way back to 8 October 1883, when Gaston Tissandier flew an electric powered airship. Even more remarkable was the Austro-Hungarian Petróczy-Kármán-Žurovec PKZ-1 helicopter which flew on an electric motor in 1917!
Electric aircraft are a wonderful concept, largely for two reasons: internal combustion engines are laborious and extremely expensive to maintain, and they burn enormous quantities of fuel. The latter is particularly true of turbine engines, where fuel burn is considerably higher than that of reciprocating engines. Electric motors are immensely less complicated than any internal combustion engine, and have an incredible advantage in terms of power curve.
Of course, if it sounds too good to be true, it probably is too good to be true. An electric motor is tremendously efficient, but, the electric motor must be powered by a reliable source of energy. The solution is large cell batteries, which are very reliable but only afford a very short duration in the air, at least as of right now. magniX, a company specializing in repowering commercial commuter aircraft with electrical power propulsion, is one of the pioneers in sustainable aviation.
The limiting factor as of now is not power; the electric motor used in the magniX Cessna Caravan produces 750shp. Electric motors produce tremendous power to weight, actually, making the motor itself an excellent contender for aviation use. The issue is endurance. Our present battery technology allows for approximately 100 miles of travel in an aircraft, which is about 45 minutes of flight time in an eCaravan. This doesn’t seem like a whole lot, but it is important to recognize that the vast majority of commercial flights are less than 500 miles.
Some pundits speculate that battery technology is going to continue to advance at a rate which it has grown in the past, which would put our battery technology and capacity far beyond what it is now in a decade. But this might not be an accurate assessment at all; the current crop of lithium ion batteries took 40 years to get the technology where it is now.
Battery storage is not the only issue at hand here. Commercial aircraft have distinct needs in terms of power settings. Takeoffs and initial climb require tremendous amounts of energy, which is the phase of flight which requires the vast majority of energy. In an internal combustion aircraft, this is where a huge amount of fuel is burned; the remainder of the flights requires very little energy to sustain inertia in flight. The issue with modern batteries isn’t as much to do with their ability to provide adequate power during cruise settings as it does with the ability to meter electrical flow at the extreme power levels required for the aircraft to take off. The fuel cell supplying fuel to a traditional engine is only limited by the amount of fuel which can flow through the applicable fuel line, so it is essentially limitless. But electrical current is not the same as gravity-fed fuel, and this does pose an issue, among quite a few other significant concerns.
Another valid concern is the effects of weight on an aircraft. As a traditional aircraft cruises, it continuously burns fuel, which also creates a more efficient aircraft the longer it remains aloft. But a completely electrical aircraft weighs the exact same upon landing as it does on takeoff. This is not much of an issue in, say, a converted Cessna. But an airliner is a completely different matter; there are very specific windows of which an aircraft much operate in, and landing weights figure highly into this equation.
The Verdict on Electric Airplanes
Inconclusive at best, especially in regards to airliners. The potential of a small air-taxi does certainly make some sense, in places where each leg may only be 50-75 miles where a turbine engine may very likely burn hundreds of dollars of fuel, whereas the electric engines would cost less than a cheeseburger value meal. This is already being rolled out, and it does make sense. But airliners leave a lot more questions than answers. It is not just about weight; it is about potential energy. Jet fuel releases far more energy than electrical power per pound, which is going to be the one of the biggest hurdles to the entire process because as we all know in the industry, weight is everything to an aircraft. So as of right now, we can confidently state that there are likely a few applications where it may work, but in the near future it is safe to expect that Jet A will still be the fuel of choice for air travel.
No sustainable aviation without Electrical Ground Support Equipment
The services market, on the other hand, seems ripe for transitioning to electrical power. Many pieces of GSE are ideally suited for electrical power, with a fair amount of it making the switch quite some time ago.
Many of the burdens which complicate the process of electrically powered aircraft pose no encumbrance to ground service vehicles, which do not require enormous amounts of energy for a specific phase of movement. Instead, electrically powered GSE, tugs in particular, are models of consistent, even use of power. They generally never travel more than a mile from their charging dock, often just a matter of yards or meters at a time. This sort of idling, slow environment is terrible on internal combustion GSE, but is great for electric power.
The environmental impact is felt on the micro level on the cargo and parking ramps. Workers are subjected to fumes all day long when GSE is diesel or gasoline powered, which gets old really fast. It leads to headaches, fatigue, and sometimes nausea. This is particularly true for workers in hangars, where tugs frequently come in and out. The tugs come and go, but the fumes do not necessarily follow suit. An electric tugs is a breath of fresh air for those working in these conditions.
The other, highly tangible value of transitioning to an electric fleet of GSE is fuel. Industrial diesels in this horsepower range burn around five to six gallons per hour. At a median price per gallon of $2.43, this comes out to $12.15 per hour, per piece of equipment. That amounts to $291.60 for a full 24 hour work cycle, which is reasonable to expect at a busy airport. If an airline operates five tugs around the clock, they are going to spend just shy of $1,500 per day in fuel to operate their fleet of tugs.
Fueling an electric GSE is a stark contrast; the average cost per kilowatt hour (kWh) is a mear twelve cents, meaning a 40kWh unit costs around $4.80 to charge. While aircraft tugs are not all that well covered in media, comparable warehousing equipment is easy to find data on. Forklifts, which are very comparable in size and output, generally require one charge per shift, three in a 24 hours workday, which comes out to $14.40 per day, per machine. Multiply that by the same five vehicles, and you are at a whopping $43.20 to fuel the aircraft tug fleet.
This is all based around very simple math; electricity does vary in cost depending on the time of day, but $0.12 is the average cost across the board. Even if you were to double that figure, it would be a mere fraction the cost of diesel.
The last topic we’ll just briefly touch on is noise pollution. Noise pollution causes fatigue, plain and simple. It hampers communication in environments which are wholly dependent on good communication for safety sake. Electric GSE is completely quiet, removing a layer of noise pollution which is good for everyone on the jobsite.
Conclusion to sustainability in aviation and electrical aircraft
It is far too soon to really know just how effective an electric fleet of aircraft might be; the technology for electric jets is still a long way off. However, there is validity in the movement to repower turbine aircraft used for short-haul taxi service. Right now the distance limit is around 100 miles on average, which is a very small footprint but there are services which this may be ample for like outfitters in the bush where the distances are short via air but very long on the ground. GSE is a market that is ready to embrace the technology now and will reap immediate and very real savings for those who choose to take the plunge and try an electric towbarless tug.