When Aviation with its AAM concept enters Public Transportation along side and at level with current Land-based Public Transportation, many eVTOL developers and infrastructure planners have forgotten to include the important minority of disabled passengers.

As an upcoming add-on mode of daily public transportation to the total grid of existing modes of daily public transportation like busses, trains, trams, metro's, taxi's, ferries etc., AAM (Advanced Air Mobility) is meant to like current modes of public transportation to include all users, all citizens, all visitors etc., wanting and needing the services that AAM will provide in an integrated MaaS system; Moving people from A to B in an easy to use and seamless and comfortable way.

In most developed countries, public transportation has therefore for decades adapted to include access for those users who are not as fortunate as the majority; being able to walk freely and enter/exit public transportation with little to no assistance.

Users with disabilities who for example have difficulties to walk without a walker or a cane or who might need a wheelchair on a daily basis, by for example developing low-floor busses, trams and trains, making it relatively easier for such user to enter and exit those modes of public transportation.

Even buildings with public access has to follow certain building codes/regulations such as providing easy access for disabled people with items like ramps, elevators for buildings with multiple levels, dedicated disability parking spots near an entrance etc..

 

But not Aviation

Though Aviation has avoided and not adapted their aircrafts nor many of their services in the same manner and to the same standard as other public modes of public transportation has, as the documentary from VICE News below tells.

To date, unless a jet bridge is used to enter/exit an airliner, it is very difficult for a wheelchair user to enter/exit even a large aircraft.

The difficulties goes as well for the staff that has to literally physically bend over in such a manner that it can take a toll on their back and without the proper tools, one day maybe make them disabled as well.

Without a jet bridge, often the user either has to be carried physically onboard or a truck with a lift used in the same manner to load bulk cargo has to be used ... not very easy, quick, seamless nor comfortable nor gracefully handled compared to how other modes of land-based public transportation can handle this group of users.

"Eighty percent of the wheelchair community does not fly because of a risk to their physical selves or a loss of their wheelchair due to damage" - President of All Wheels Up, Michele Erwin

 

Hands-On experience

Having for the past two decades as a helicopter pilot flown sightseeing tours and OnDemand flights for several more or less disabled passengers in a small helicopter with a little door entrance - and seen family members ending in a wheelchair primarily due to lack of proper tools lifting/moving by hand other disabled patients and what impact that does to their and their family's life quality, I have on first hand seen these issues and effects it has.

There can be reasons (or excuses) for current procedures and lack of proper tools, such as usually a flight is a longer trip and not done on an everyday basis for most people, so the entrance/exit of an aircraft might not seem to be such a big issue, when only used on a couple of occasions a year. Or an aircraft has to have a certain design or shape to function what it does best, fly at high altitudes with pressurized cabins.

Though it looks more like excuses than technical reasons, because there are small and large airplanes with pressurized cabins designed with entrance like a private jet BUT also with a big door for easy access for cargo, bulk luggage - or a wheel chair such as the Pilatus PC12, proving that even a small airplane can be designed to have space for a large door and with a simple genius tool in hand, making it relatively simple, easy, comfortable and respectful to enter/exit an airplane in a wheelchair, as this video below shows.

 

Get up to standard

If the goal for AAM and the eVTOL, eSTOL and eCTOL aircrafts being developed is to integrate into the grid of existing daily use of public transportation in as a strong, seamless way and easy to use for the disabled users as todays land- and sea-based modes of public transportation has been able to offer for decades, and with regulators breathing down the aviation industries neck with possible upcoming legislations to ease access for passengers with disabilities onboard public accessible aircrafts, it is incomprehensible that so few aircraft designers and developers have designed their brand new aircrafts with a mindset how on a daily basis to include easy access for disabled users, knowing (or they should know) that the general public demand from politicians and governments has changed land- and sea-based public transportation to include disabled users easy access to daily usage of public transportation and public infrastructure.

Aircraft designers designing aircrafts for daily public transportation needs to get up to standard where ground-based public transportation has been at for decades, like:

• Include a big sliding door like many helicopters has such as the Airbus H125/H130 or a big door such as the Pilatus PC12.
• Preferable design with high-wings for easy un-interrupted access to/from and around the cabin.
• For multi-rotor eVTOL design, not having rotors/propellers at knee height.
• Not designing the entrance to the cabin ONLY with a small private jet like a door staircase.
• Not designing the entrance to/from the cabin above the wing on a low-wing aircraft.

At Copenhagen Helicopter, easy access for passengers with disabilities is one of the main characters we evaluate and grade if a certain aircraft design used for daily public transportation, has a place and a business case in the public space of transportation. Those designs who don't have this, we expect have little chance to become publicly accepted despite how good in other terms the aircraft might be otherwise.

No other form of transportation trains, buses, boats, forces you to give up your mobility device when you board. The same should be true for airlines. pic.twitter.com/XkmcEwaHCH

— Secretary Pete Buttigieg (@SecretaryPete) October 31, 2022

 

Nearly 2 percent need wheelchairs

Nearly 2 percent of the worlds population need the use of a wheelchair to get around in their daily life. With approx. 7,8 billion people on this planet, that equates to approx. 140 million people around the world.

Today there are 4 million wheelchair users in the USA, spending approx. 17 billion USD annually on travel expenses. Similarly number is the same for wheelchair users in Europe.

Add to that percentage those who need a walker or a cane, that would benefit greatly with a design giving easy physical access to enter and exit an aircraft.

 

Bad for business not to be inclusive

As an operator to be accepted by the public integrated in the grid of public transportation and the future of MaaS, if not operating an aircraft suitable designed to accommodate disabled passengers like other modes of public transportation does today, we at Copenhagen Helicopter know by experience from other modes of transportation it can be bad for that operators business and for example risk loosing out to competitors for winning possible public routes.

Just like with other modes of public transportation, the turn-around- or midway stop-time for AAM is to be kept at a very minimum of merely a very few minutes to utilize the aircraft most efficiently and not to delay other passengers onboard continuous journey.

On top of that, consider that often there will be no other staff at a Vertipad other than the single pilot flying the aircraft to assist the disabled passenger - and in the future, no pilot will be there when the aircrafts goes fully autonomous, just like the Metro is in Copenhagen, demanding the disabled passenger being able to enter/exit the aircraft more or less on their own, which require a design making that possible.

 

Technical solutions exist

Technical solutions can be made to accommodate disabled passengers. As the work, studies and support made by the organization All Wheels Up shows.

And we know because just like an operator figured out how to make a cost-effective and mobile wheelchair lift for the Pilatus PC12 aircraft for the need of a specific user, at Copenhagen Helicopter we designed a cost-effective lift to be stowed away onboard for use in most helicopters and some small airplanes we expect to test later this year.

Because in that part of aviation of pleasure flights, if not lifted manually by staff, lifts for disabled passengers are bulky and non-mobile as the video above shows and why should a wheelchair user not be allowed out on excursions where the helicopter lands during a sightseeing tour, when all the other non-disabled passengers can and technical solutions can solve it ?

Aviation faces a triple crisis; Climate + Energy + Financial, that it must address and adapt to for not loosing its competitiveness in a world facing the most disruptive time period in modern time in the foundational sectors of Energy, Transport, Information, Food and Materials.

Aviation is a highly Energy dependent business, it is what turns our engines on the aircrafts and makes flights possible. The true future of Green sustainable Aviation holds a range of Green energy supply solutions, each more suitable than others for different segments.

But current strategy largely embrace a "one-fuel-fits-all" mindset called Power-to-X based on Hydrogen, a mindset Aviation has been used to for over a century in the fossil fuel age. But data shows that legacy mindset will likely render Aviation less competitive, if it only stick to that same old strategy.

This article is not about slandering Hydrogen nor Power-to-X, we have nothing for nor against Hydrogen, we have no stake in either energy supply solution, we only seek the best, cleanest and cheapest solutions based on data. By reference to independent experts, we will show why Green Hydrogen will be more expensive for decades than other Hydrogen solutions and especially much more expensive where Battery-Electric and Hybrid power can be used as a cheaper, better and cleaner solution.

Green Hydrogen is promoted as the cheap clean fuel of the future, but why hasn't the Energy Sector then already started cleaning up the current Grey & Black CO2 emitting Hydrogen production and converted it to Green Hydrogen. It will require world-wide up to 130.000 wind turbines to do so, providing all the incentives and scale the business need to prove that their business-plan making Green Hydrogen competitive is true.

By: John Martin Winther Andersen

Aviation is feeling the impact of current climate debates like "flygskam" (Flight Shame), France banned flights that can be taken by train or bus within 2,5 hours of travel time and a Danish politician wants to ban flights that a train can do within 12 (twelve) hours of travel time, an idea that seems to have an origin from the year 2020 by others.

Aviation is a large energy consumer, so energy is a very big part of Aviations cost, so when Aviation decides to transit away from fossil fuels as current energy source to new Green sources of energy, Aviation need to look at the entire energy production(s) and supply-chain(s) it then choose to rely on in the future.

Because the choice(s) we do today of tomorrows energy will dictate how we design and use our aircrafts, its infrastructure and our services, the choice(s) we make today at this cross road is very important for making Aviation Green, Affordable and Competitive for decades to come. We must analyze the choice(s) thoroughly with an open mind, not only thinking about how we did it yesterday, but if other ways are better include them to continue securing a sound future for Aviation.

Aviation focus on Power-to-X because it technically fits into its legacy supply-chain & legacy aircrafts. But history and data indicate Power-to-X fuel will be more expensive than other Green alternatives and possibly fossil fuels. How will that keep Aviation Competitive, Green and Sound at the same time ?

To date Aviation has at large bet on Hydrogen and its derivative "sister" Power-to-X as the replacement away from fossil fuel, a bet that also seems to need public money to support its goal.

The Alternatives

Before going through Hydrogens pros and cons as a replacement for fossil fuel, let's go through the Alternatives that also can make aircrafts fly sustainable.

• Battery-Electric
• A hybrid combination of Battery-Electric and SAF for extended range
• SAF (Sustainable Aviation Fuel) made from sustainable Bio-mass

Above chart shows how efficient the end result is from the same 100% of electricity produced at the wind turbine (or solar cell etc.) when it has gone through all the different steps and processes to finally deliver what is left of the initial electricity at the propeller, for example using Direct Electrification (first column) shows that out of 100% energy produced at the wind turbine, 77% is left to turn the propeller so only a loss of 23% of energy. And 81% efficiency is expected by year 2050.

Battery-Electric

The chart shows that Battery-Electric (Direct Electrification) is the most energy efficient way to use electricity from sustainable sources like wind turbines, solar-cells, hydro and nuclear to turn an aircrafts propellers, fans or rotors. Simplified said it uses 3-5x less energy from the sustainable sources to deliver the same amount of energy at the propeller than Hydrogen or Power-to-X, meaning Hydrogen and Power-to-X uses 3-5x more wind-turbines, solar-cells etc. than Battery-Electric.

Today batteries capacity (specific-energy) can power cars, medium sized trucks and busses, coastal ships and small sports airplanes, but their specific-energy is yet not sufficient for what Aviation needs to power larger commercial aircrafts.

As mentioned in our July article "Hydrogen - To Be or Not To Be", historic data for many decades shows that batteries specific-energy on average increases 5-8% per year, in later years closer to 8% than 5%. It is therefore simple to establish a projection when batteries can be expected to have a high enough specific-energy to power commercial sized aircrafts for airliners for a certain distance.

For example according to ACS approx. 650 km distance, equivalent for a Copenhagen to Stockholm, Oslo, Prague or Amsterdam route, is battery-wise plausible by year 2030 in the smaller Regional sized aircraft like CRJ's and ATR's, and by year 2036 a 1.000 km route in a narrow-body like Airbus 220/320 and Boeing 737 from Copenhagen to Paris, London, Munich, Zurich etc. is battery-wise plausible.

Distances beyond 1.000 km will follow as evolution in battery capacity continue, though long-haul especially in wide-body aircrafts like crossing the Atlantic or Pacific, is not expected with pure Battery-Electric aircrafts in any foreseeable decades. Unless we change the way we travel, for example if one travel with Iceland Air over the Atlantic, one stop on Iceland for a couple of hours or so or have a stay over if one so choose, before continuing the travel.

Splitting one large journey into several shorter trips could make pure Battery-Electric aircrafts possible even on longer journeys, making time to recharge at each stop. And if you are traveling for holiday, why the rush then ? - have a break, stretch your legs, relax and enjoy an airports lounge, services and local cuisines or a short onshore excursion before continuing your journey, something like an electrified airborn cruise ship experience.

Hybrid combination of Battery-Electric and SAF

Though the plausible fuel-efficient and most cost-effective alternative mode of flying for many long-haul flights will be a hybrid powertrain solution, meaning a combination of Battery-Electric for take-off and landings and relatively small(er) turbine(s) engines using SAF Bio-fuel for the en-route part to power the electric motors turning the propellers/fans, only utilizing the turbine engines at their optimum designed conditions (altitude, temperatures, workload etc.) for lowest fuel consumption as possible, but also to keep local CO2 and NOx pollutions during take-offs, landings and taxi at airports to zero.

SAF (Sustainable Aviation Fuel) Bio-mass

Truly sustainable SAF made from waste products and other left over bio masses is a good alternative to fossil fuels, since it is CO2 neutral meaning the CO2 it emit comes from sources that has already taken the CO2 out of the worlds air, it demands no renewable power to produce energy and can use current logistics and storage, but it is a limited resource because there is only so much land and so much amount of waste it can be made from without for example clearing extra land like fragile jungles, rainforests etc. for additional farmland to produce crops for fuel or taking food from those who really need the food to live or survive on, so unfortunately we can not swap all the worlds current fossil fuel usage 1:1 with SAF if its going to be done in a sustainable, responsible and human way.

SAF Bio-fuel should therefore be reserved for those applications and routes, where there really is no other practical option to replace fossil fuel, like on one-stop long-haul flights.

Other environmental impacts

An often forgotten environmental topic in the debate of what new energy source Aviation should rely on in the future to become CO2 neutral, is noise.

In regards of noise, the different propulsion methods can be divided into two groups, the ones that burn stuff (combustion engines) to create propulsion vs. those two that does not, i.e. Electrification and Fuel-Cell. To date the amount of data on noise difference between combustion engines and electric motors on larger commercial aircrafts is limited, especially with a comparison on the same type of airframe, but there is no doubt there is a significant difference when removing from the equation the part that has a noisy combustion in its powertrain.

magniX has in corporation with operator Harbour Air, converted one of their turboprop de Havilland Beaver DHC-2T airplanes, that used a PT6 Turboprop engine running on fossil fuel, a type of engine used on many Regional commuter aircrafts. The difference was significant, ranging from 16-22 dBA lower noise emissions using electric motor instead of combustion engine, especially at take-off a 20,8 dBA decrease in noise. This significant difference shall at large be expected to be the same on other turboprop aircraft converted to electrification.

What the difference will be between a modern Turbofan Jet engine used on all larger modern commercial aircrafts from Airbus and Boeing vs. the same airframe with electric Turbofans is still unanswered, but knowing the noisy part is the combustion part and that 70-80% of the propulsion of a modern Turbofan Jet happens from the large fan, that essential is a shrouded propeller, and 20-30% from the hot exhaust of the Jet engine itself, and on a Turboprop engine the portion of hot exhaust propulsion vs. propeller is even less, the decrease of noise of an electrified Turbofan engine on an airplane taking off should be expected to be even greater than 20 dBA (> 100x).

The fact that electric powered aircrafts emit a lot less noise than its counterpart using some sort of combustion engine, needs to be addressed as well for the sake of the neighbouring community to an airport and airfield and the employees working there.

In addition to local noise from aircraft operations, in our collected search for the best new energy solutions for Aviation, we also need to address and include local emissions produced from combustion engines on an aircraft, because no matter what their fuel is produced from, if its fossil fuel or Green Power-to-X that on a global scale has zero effect on climate change because it has taken CO2 out of the air and pared it with Hydrogen to create Power-to-X, locally it is still felt as emissions in and around the airport neighbouring communities with the side-effects it can create like respiratory disorders etc..

Beside fossil fuel and Power-to-X both locally emit CO2, little attention has been given that no matter if we burn fossil fuel or Hydrogen or Power-to-X, they all three produce some level of NOx emissions. Electrification and Fuel-Cell powertrain does neither of this, no local CO2 no NOx emissions.

In addition to environmental concerns, battery-powered aircrafts does not create contrails and though still not fully understood by experts it is suspected to count for over half of aviations entire climate impacts.

Finally, recycling batteries is today technically possible for up to 95% of the batteries materials, so the materials can be used again in for example manufacturing new batteries. But recycling batteries need to be at large scale to make recycling a viable business and competitive vs. digging out new raw materials.

Below a simplified technical comparison between current fossil fuel and the alternatives in Hydrogen (and Fuel-Cell), Power-to-X, SAF (Bio Fuel) and Electrification.

So what are some of the problems with Hydrogen and its "sister" Power-to-X as a fuel especially in a triple-crises as Aviation and everybody else finds themselves in ?

• Hydrogen has an extremely low Energy Density, meaning it occupy a massive amount of space, making it in Aviation impractical to use. Power-to-X does not have this issue.
• Hydrogen or Power-to-X require approx. 3x to 5x more renewable energy than Battery-Electric powered aircrafts, meaning 3x to 5x more wind-turbines, solar cells etc. is needed to produce its type of energy, meaning 3x to 5x higher electricity cost than Battery-Electric, making it non-competitive when Electrification can work in the same market, route etc..
• Hydrogen or Power-to-X has no proven track record of being commercially viable at scale in contrast to Battery-Electric. Hydrogen and Power-to-X are known technologies for many decades but never proven itself commercially viable as a fuel.
• Hydrogen is the worlds smallest atom, i.e. it's highly difficult to storage and especially transport at scale, it wants to escape any containment even through many solid materials. It has to be kept under high pressure or cooled down below -253 degree celsius to become a liquid. Power-to-X does not have this issue.
• Despite lobbyism, heavy subsidizing, marketing and hypes since the 90's, Hydrogen has never taken off at scale in any form of transportation. Grid-Electric, Battery-Electric and Hybrid powered solutions has always won over Hydrogen.
• Hydrogen and Power-to-X produce local emissions / pollutions and noise when burned, i.e. combustion engines of any kind.
• If Hydrogen accidentally starts as a fire, it is in daylight colorless, smokeless, odorless and highly explosive with potential large blast-radius if out of control. Power-to-X does not have these issues and no more dangerous than other carbon-based fuels.
• If the business case for Green Hydrogen is good and sound, for sure we would have already seen the worlds Energy companies stopped producing the worlds current need of 94 mill. tons per year Hydrogen as CO2 emitting Grey and Black Hydrogen and replaced it with Green Hydrogen. The incentives and scale is for sure there, requiring up to 130.000 wind turbines. Yet we have seen no move from the worlds Energy companies, cleaning that up first before heavily promoting Hydrogen as a fuel.

Below we describe in more details the apparent and upcoming issues, challenges etc. with using Hydrogen as a fuel.

What is Hydrogen and how is it produced

It is important to understand that Hydrogen is not an energy source, but an energy carrier. Difference is that Hydrogen is not found on earth as a stand-alone substance, it is attached to something else like water (H2O) or methane gas (CH4).

"Hydrogen is not an energy source, but an energy carrier."

This means a an external energy source like electricity or heat needs to be applied to the substance that Hydrogen is a part of to separate the Hydrogen from the substance, so as a carrier it can carry energy, for example by splitting it away from water via electrolysis or as it's done in 99% of today's production of Hydrogen, which is Grey (natural gas) or Black (coal), run through a 700-1.000 degress celsius steam heat reforming process splitting it from Natural Gas (i.e. methane gas), both processes with huge energy losses and consumptions in the process as a result.

Hydrogen is not just Hydrogen

To evaluate a potential transit to a future of Hydrogen, we need to understand the different processes future Hydrogen comes from. As mentioned above Hydrogen comes mainly from two different sources, one is Green and made from electricity from only renewable sources like wind-turbines, solar-cells, hydro and nuclear plus water. The other source of future Hydrogen is Blue and Grey, which both are made from Natural Gas (i.e. fossil fuel), which contain 70-90% Methane Gas.

".. The total amount of fugitive methane from oil and gas industry as emissions is something like the equivalent of the total carbon footprint of Europe .." - Professor David Cebon, University of Cambridge

Difference on Blue and Grey Hydrogen is that Blue storage (or it try to) its CO2 emissions in the ground or such like, where Grey releases its CO2 into the atmosphere in the production process, being dirtier than Blue. Though according to experts it is doubtful that Blue Hydrogen will ever work or happen at scale due to its cost and not at least 20 years track record of not reaching its many set goals and promises around the world.

Due to how the global Oil & Gas industry mishandle Natural Gas many places around the world in an non-environmentally unsafe matter letting a lot of leaks happen, due to Oil & Gas is not very regulated many places around the world and due to Oil & Gas industry should have no trust left in the public after half a century of denying, lying and delaying climate actions, Green Hydrogen must be advanced instead of Blue and Grey.

Lately cost of producing Green Hydrogen has beaten Grey and Blue, but not so much because Green Hydrogen has become significantly cheaper, but because of the crisis with Russia & Ukraine cutting out Natural Gas from Russia by political tools for the time being. In a post-Russia/Ukraine crisis, unless real tax on emissions that can be felt on Grey Hydrogen happens to parity the cost of its more expensive Green alternative until Green Hydrogen hopefully by 2050 or so can match cost of Blue and Grey Hydrogen, it would be financially natural to expect a return of the order of Hydrogen cost to Grey as the cheapest, then Blue and Green battling as no. 2, leaving Green somewhat stranded due to current cost before it can be scaled up over the next decades.

The world already produce wast amount of Hydrogen, but it's not Green

A topic that somewhat slipped the public discussions of producing Green Hydrogen for all sorts of new purposes replacing fossil fuels in the future incl. for Aviation, is that 94 mill. tons of Hydrogen is already produced today world-wide per year, emitting 830 mill. tons of carbon per year and rising, of which 99% is made by Natural Gas or Coal as Grey or Black Hydrogen, the most polluting types of Hydrogen.

"Before we position hydrogen as the solution to climate change, we first have to deal with hydrogen as a problem in climate change" - Bloomberg NEF analyst, Michael Liebreich

Producing these 94 mill. tons Hydrogen from Green Hydrogen instead of yesterdays, todays and tomorrows Grey and Black Hydrogen requires 143% of all the wind and solar installed globally to date. Figures from other independent renowned experts we have consulted puts it at at least 200% of all the wind and solar installed globally in 2019.

200% of all global wind and solar equates to 130.000 wind turbines on Horns Rev 3

Even if offshore wind-turbines in two decades from now become an average size of 15 MW, turning the worlds current Grey to Green Hydrogen still need approx. 70.000 wind-turbines of 15 MW capacity each.

One has to wonder why hasn't the global energy sector yet swapped the current 94 mill. tons fossil fuel based Hydrogen produced per year for use like fertilizer with Green Hydrogen, if Green Hydrogen at scale is an affordable and competitive alternative. The incentives certainly seems to be there at scale and an easy opportunity for the energy business to prove the world that their business case is sound.

Green Hydrogen as a fuel

Hydrogen as an energy source for transportation has an extremely poor energy-density compared to its fossil fuel competitor it wants to replace, that is Jet A1 for Aviation. It's a topic we looked into in details with consultancy from independent experts in the field like h2sciencecoalition. Calculations shows to replace the fossil fuel (Jet A1) sold in Aviation just in Denmark with Power-to-X based on Green Hydrogen, we need up to 1.500 offshore wind turbines, which will be for the first decades be costly making Green Hydrogen in competition to Grey or Blue Hydrogen, unless carbon taxes are set in place to parity the cost of producing Green Hydrogen.

Adding emission tax on Grey Hydrogen to parity cost of Green Hydrogen, only excludes the Grey. It doesn't lower the cost of Green Hydrogen to be competitive with other non-Hydrogen non-emission Green energy sources, like solar-wind-batteries.

According to independent experts like h2sciencecoalition, replacing all fossil fuel usage in aviation from the EU, requires 81.000 - 96.300 km2 surface area filled with wind turbines depending on type of aircraft engines it replaces, just to deliver enough green electricity to produce Hydrogen for EU's aviation sector.

96.300 km2 is 2x the size of Denmark landmass covered with wind-turbines.

In addition to the wast amount of wind-turbines, many independent experts disregard usage of Hydrogen with Fuel-Cells, both due to the great difficulties of handling and adapting current infrastructure and aircrafts to Hydrogen, and due to it has been tried, hyped, lobbied and subsidized several times in the past in other modes of transportation and failed to scale up each time, i.e. busses, trucks, cars etc.

To replace 2% of the kerosene used in EU, needs 5.000 wind-turbines. Meaning, replacing 100% of kerosene used in EU, largely used for fuel in Aviation, needs 250.000 wind-turbines in EU.

If we are to replace all the 100% of kerosene we use in the EU, where a large part goes to producing Jet fuel, it requires 250.000 wind-turbines, according to DW (2% = 5.000 wind-turbines). In the record year of 2021 for installing wind-turbines all over the EU, onshore and offshore all together, equates to approx. 1.700 wind-turbines installed all over the EU in 2021. If we are to install 250.000 wind-turbines all over the EU, land and ocean just for replacing kerosene with Power-to-X, with this pace the last of the 250.000 wind-turbines will not be installed until around year 2170, or approx. 147 years from now, plus in that period pretty much nobody else gets to have wind-turbines installed for other uses if capacity is occupied for this demand.

We mention these examples of massive amount of needed wind-turbines for usage of a singular purpose, to visualize by sheer numbers the apparent unrealistic amount of wind-turbines needed just for a single business such as transportation needs for using Hydrogen or Power-to-X as a fuel. At eVTOL.dk we have tried to make sense in those who advocate for usage of Hydrogen and Power-to-X for several different purposes especially as a fuel, but can not find it based on the data and history we have found.

We have to realize and act upon that renewable energy production is a scarce resource and will be for many decades to come, meaning there seems to be no realistic surplus at scale of renewable energy to use on things like Hydrogen for fuel, where it takes 3-5x more energy from the wind-turbines than pure Electric-Battery propulsion. The sources are scarce.

Start using Green Hydrogen where it's really needed first

On top of the 94 mill. tons of Grey Hydrogen produced today, which is needed to produce important things like fertilizer to help feed the +7 billions of people on this earth, renewable energy resources also need to replace all other current fossil fuel spendings like Power Plants on Gas and Coal, it could be done with for example grid connected Sand batteries for District Heating and Industrial needs, or heat pumps housing, not to forget the sometimes questionable Biomass as fuel, before being wasted on any Green Hydrogen for transportation, wasting up to 80% of the produced renewable energy.

For transportation incl. Aviation in a time of both financial, energy and climate crisis at the same time, we have to be smart and prioritize where we use the scarce amount of Green Energy we have now and we can afford and have time/capacity to build in the next couple of decades to come. The solutions are easy to find, direct electrification like on trains and many trucks, battery-electric or hybrid-biofuel propulsion, where ever each solution is most suitable. These solutions are much more energy efficient, using a fraction of renewable energy produced compared to Hydrogen and its "sister" Power-to-X.

Focus and Fundings

Unfortunately focus and fundings among Aviations legacy companies, suppliers, lobby-organizations etc. are mainly on solutions that fits into their "old world" of aviation by advocating Hydrogen and Power-to-X as a replacement to current delivery and usage of fossil fuel.

It is a shame with little to no focus and fundings on Battery-Electric as an energy source in Aviation. Because where it can be used in a few years on more and more commercial routes as batteries evolves, beside being much more energy efficient than Hydrogen and Power-to-X, meaning demanding a lot fever of the scarce amount of wind-turbines and solar cell plants able to detach sooner from fossil fuels on more and more routes than Hydrogen and Power-to-X, delivering zero local polluting and a lot less noisy, just like many other disruptions according to our survey there are possible extra positive purposes going Battery-Electric in for example rural locations with small airports and vertiports on the country side, where the unused surface of a small airport/vertiport with solar cells of such place can supply the needed electricity to the expected amount of charging and departure of Battery-Electric aircrafts plus delivering a possible surplus of local produced green energy to the local grid for example as a peak-plant for the local community.

A successful climate action plan is no longer just about the rapid build out of wind turbines and the phasing out of coal plants. It is about deploying all the solutions we have within the right sectors, ensuring that we tap into all expertise available to guide these decisions - H2 Hydrogen Science Coalition

UP TO 1.500 HUGE WINDMILLS NEEDED IN DENMARK TO COVER DANISH AVIATION's NEED ON PtX FUEL.

Foreword: This is a longer article, so if you just want the conclusion of this article, please see the chart below from Bloomberg NEF Michael Liebreich what Green Hydrogen is best at and what it probably or mostly likely can not compete with in terms of other and cost-wise more favorable Green energy sources.

By: John Martin Winther Andersen

In a recent article the Danish Aviation sector mentioned they would in contrast to its Scandinavian siblings in Sweden and Norway, focus on Power-to-X (PtX), or Electrofuel and later Hydrogen to replace the current usage of fossil fuel (Jet A1) in domestic and short-haul routes, in contrast to Norway and Sweden that believes more in electric powered aircrafts, despite they initially have shorter range but that opens up for other routes.

At eVTOL.dk we have no biased relation to either Hydrogen, its derived child PtX/electrofuel or to SAF (Biomass) or battery-powered aircrafts or any other green energy source for that matter. All we want as an environmentally responsible company, is that we choose what ever energy source is the best for a given task, need, problem etc., meaning it has to be the cheapest solution to be able to outcompete fossil-fuel energy (Jet A1 in Aviation) on free open market terms, but a solution that at the same time favor the environment by being really CO2 neutral and not just offsetting its emissions, because as we have documented when the consumer purchase a flight ticket, price is the dominant factor no matter if the energy used to propel the aircraft is green, grey, blue or black, where the last three (grey, blue and black) are all based on fossil fuels, and that offsetting emissions does not in general work in real life.

Today we all know that we have to decarbonize our way of living. As mentioned previously, according to United Nations; ".. We should reduce greenhouse gas emissions because if we don't, it's going to get really bad .." and ".. There is a brief and rapidly closing window to secure a liveable future on the planet ..".

The large fossil-fuel companies that produces the products that emit a majority of the total CO2, have known about their products environmental impact since 1977 and since tried to control the narrative for decades in for example putting the "choice" and later blame on the consumer of using their products.

Get sued if we don't uphold our promises

This decade old blame tactics used by fossil-fuel companies have lately caught up with todays reality with the landmark case in Holland, where fossil-fuel company Shell lost in court for not having done enough to adhere to policies of cutting down emissions and ordered by court to do so. A court ruling we believe our own industry, Aviation, need to take notice of since IATA has claimed Aviation will be Net-zero in 2050, because if a fossil-fuel company can be ruled for not doing enough for the environment in accordance to set targets despite it is the customers who actively emit the majority of the CO2, we as an industry should expect to be held up to the same level of standards we put out to do what we claim we will do for the environment, or we believe we could risk future court rulings will rule against us.

So when the Danish Aviation sector goes another way than our two sibling-countries, it made us wonder if Denmark despite being a minority out of three countries, found a better way or reason than the other two and digged into the pros and cons of choosing Hydrogen or Hydrogen-derived fuels such as PtX/Electrofuel instead of SAF (Biomass) and battery powered energy.

Is Hydrogen at large the savior for Aviation ?

Hydrogen is at normal temperatures a gas and the most abundant element in the universe, but on earth it's usually not found naturally alone but attached to other elements like water, methane etc.. It is also the smallest element hence it's more difficult than other elements to keep from leaking out through its containment materials (tanks, pipes, joints, couplings, sealings etc.).

We look at two ways to storage Hydrogen.

1. As a gas under pressure at ambient temperatures in a pressurized tank.
2. Liquified kept below -253 degrees celsius temperature in cryogenic tanks.

Liquified Hydrogen is what Aviation most likely plan to use, as liquid Hydrogen has a higher amount of energy per unit volume than as a gas, and space also matters in an airplane. Hydrogen as a liquid has a boiling temperature at -252,9 degrees celsius, meaning it has to be cooled down to at least -253 degrees celsius in special cryogenic tanks or it will boil into a gas.

Compared to Jet A1, Hydrogen as a fuel no matter if its a gas or a liquid has a very little energy per volume (liter), 0,5-1,4 kWh/liter depending on the pressure it's under in the tank or 2,3 kWh/liter as liquified Hydrogen. In contrast Jet A1 has 9,6 kWh/liter, so a factor of 4-19x, meaning the same energy needed for a specific flight of Hydrogen used in the same type of engine, occupies 4-19x more space in the airplane, meaning a need of much larger fuel tanks than current Jet A1 require.

Note: If the airplane used propellers instead of a turbofan and use fuel-cell technology instead of a turboprop engine to power the propeller, up to an approx. 20% efficiency comes into the hydrogen powered aircraft favor. But subtracting 20% from a 4-19x factor still leaves a huge factor difference in favor of Jet A1. This is to say we recognize there is a smaller efficiency factor for Hydrogen + fuel-cell technology, but in this article we exclude it to keep it as simple as we can.

On top of the very little energy per volume in contrast to Jet A1, current aircrafts has all or the wast majority of their Jet A1 fuel in its wings. By design that is a great idea, because the wing then lifts the weight of the fuel where the fuel is. This demands less needed structure in the aircraft at the joints of its wings and the fuselage. As Lecturer in Airplane Performance, Bernard Dijk van from the independent organization, Hydrogen Science Coalition, explain in this video and follows up with why promises from a Hydrogen cryogenics tank developer are not valid in real life:

Unless we start flying in aircraft designs something like the Airbus Beluga cargo airplane converted to passengers with space for pressurized or liquified Hydrogen in its hump, or radical new airplane designs comes to market like for example flying wings concepts that might be able to storage some Hydrogen tanks in the wings structure, then flying on Hydrogen in current airplane designs already face serious challenges and limitations, that likely can not cost-wise compete with using fossil-fuel or maybe not even the more-expensive-than-Jet-A1, SAF (Biomass), which both fuel types can go into the wings (or battery on light/regional- and short-haul flight), as shown on Michael Liebreich chart above.

Additional challenges using Hydrogen

The following issues and concerns in the daily operation of a Hydrogen powered aircraft need considerations for an overall assessment of pros & cons:

• New Infrastructure: To deliver Hydrogen from windmill/solar cell -> electrolysis plant -> truck or long distance Hydrogen (new) pipeline -> airport cryogenic tank facility -> airport Hydrogen fueling system -> airplane, a new infrastructure is needed.
• Low Energy/Volume: Due to Liquid Hydrogen's much lower energy per volume (4-19x less than Jet A1), a larger nozzle should be expected to refuel airplanes, if turn-around times are to be kept at current level, meaning probably a heavier fueling system that no single man/woman can handle alone and therefore likely has to be fully or partially automated.
• Regularly Spillage: To fuel an airplane with Liquid Hydrogen, if using the proven Thompson coupling one have to purge the pipes first with Helium due to its even lower boiling point than Hydrogen, because practically no Oxygen like from the air are allowed into the cryogenics tanks or pipes. But Helium is not recycled in this matter and is a scarce nearly finite resource on earth and also used for other and important purposes like cooling magnets in MRI scanners, computer business etc.. If the clean-break coupling though not expected used before year 2050 is used instead of the Thompson coupling, usage of Helium is avoided but there will be a small spillage per refueling process of an airplane of up to 0,5 dl of Hydrogen that vent into the atmosphere. Hydrogen itself is a bad Greenhouse Gas, in short term it is up to 100x more potent than equal amount of CO2.
• Daily Loss: Even the largest Cryogenics tank depletes from 0,2% per day or more of its liquid Hydrogen into a gas and from there into the atmosphere, since it's hard to expect that every tank facility at every large and small airport has an expensive Claude cycle plant to recapture and liquify it back, meaning it went out daily a gas 100x more potent than equal amount of CO2. The smaller the cryogenics tank, the higher percentage we can expect it to deplete of up to a couple of percentage of its volume per day.
• Explosive and Safety: In contrast to Jet A1 or its equivalent SAF that "just" burns if heated enough or under enough pressure, Hydrogen if out of control is rather explosive and can ignite with even just small amount of heat or energy. We have to consider that accidents and incidents sometimes happens where there are humans involved, so to mitigate that and to keep the Swiss Cheese model in use in regards of avoiding accidents and incidents, several measures must be implemented to make sure no single or a few human and/or technical faults can turn Hydrogen into an inferno in an aircraft.
• Planning: If other countries does not implement the same availability of Hydrogen as Denmark claim it will, what effect and limitations does it put on the operator in regards of refueling, planning for alternative airports etc. ?

The challenges of Hydrogen's very low energy per volume and the other challenges mentioned, can be avoided if we instead of fueling Pressurized or Liquid Hydrogen on an aircraft designed to fly on Hydrogen, convert Hydrogen into Power to Liquid (PtL) with CO2 capture. Then it will be more/less as easy to handle as current Jet A1 and SAF (Biomass).

But there is a catch converting Hydrogen into Power to Liquid, more about that later.

Producing the renewable energy to make Hydrogen

If we are to produce and use Liquid Hydrogen instead of fossil fuel in our aircrafts, we have to produce the energy needed from renewable sources, like wind-turbines and solar cells, and not as it is done in 99% of the cases today, where it's made of fossil fuels. But how much energy do we need from wind-turbines alone to do this ? - let us crunch some numbers.

In 2019, that is pre-COVID19 when the world was still normal travel-wise, Denmark used/sold 1.3 billion liters of Jet A1 fossil-fuel. An amount we shall expect increase by an average of approx. 3% per year as need for air travel historically increases year on year (except in unusual times like pandemics, major wars and conflicts etc.). Meaning if we continue to fly on liquid fuels as today, we shall expect a need of Jet A1 or an equal substitute of it in year 2030 of 1,7 billion liters, year 2040 of 2,2 billion liters and year 2050 of 3 billion liters.

Note: This subject can for many be a bit complex, so to simplify the understanding we have excluded the possible small single-digit percentage efficiency that Hydrogen can have over Jet A1 in form of its lighter weight as mentioned in Mr. Bernards video, because several factors alter that small efficiency from a single-digit percentage at best to near nil at worst, factors like size of aircraft, needed range / loaded fuel quantity etc.. We recognize there can be one, but in the grand picture in this article, it doesn't make much of a difference.

So how much electricity does the used/sold Jet A1 equates to ?

• 1,3 billion liters Jet A1 = 12,5 billion kWh using 9,6 kWh/liter
• 12,5 billion kWh = 12,5 tWh

But we need more than the 12,5 tWh of energy from the windmills to produce enough Liquid Hydrogen or alternatively (PtL) to swap out all Jet A1 usage in Denmark, because there is a major loss converting electricity into something like Hydrogen through an Electrolysis process, storage it as a gas or liquid or if we want to turn it into a PtL fuel.

Above chart from Transport & Environment shows a 32% loss turning electricity into gaseous Hydrogen under pressure (100% - 68% = 32%). According to the renowned expert, chemical engineer Paul Martin from the independent group Hydrogen Science Coalition, even with the best technology available only a 63% efficiency should be expected. So we will work with both numbers in this article to satisfy most readers, because as we stated in the beginning, we at eVTOL.dk have no favorite in what source of energy to use, as long as it is the cheapest AND really green alternative to fossil fuels.

This mean with approx. 3% increase of air travel per year post-C19, we will need the following amount of renewable electricity produced at the wind-turbines/solar cells to produce just the Hydrogen for Hydrogen powered aircrafts, if they come to market like Airbus has announced they are working on;

• 16,3 tWh liquid Hydrogen Year 2030 = 24,0 - 25,9 tWh wind-turbine energy produced
• 21,1 tWh liquid Hydrogen Year 2040 = 31,0 - 33,5 tWh wind-turbine energy produced
• 28,8 tWh liquid Hydrogen Year 2050 = 42,4 - 45,7 tWh wind-turbine energy produced

Note: To simplify it, we have not included the power needed to run these new electrolysis facilities, infrastructure, cooling of the cryogenic tanks etc. - and the likely min. 0,2% or more boil off loss of Liquid Hydrogen every day from its cryogenics tanks until the Liquid Hydrogen is used. So total power needed produced at the wind-turbines are even greater.

In comparison to make the number more tangible for people outside this business:

• Denmark as a whole country used approx. 35 tWh in 2019.
• All windmills in Denmark, land- and offshore, produced 16,14 tWh in 2019.
• Horns Rev 3 windmill park 49 new 8,3 MW mills produce from 2019 approx. 1,7 tWh.

Producing PtX fuel

To avoid all the issues handling liquid Hydrogen and the risk associated with it as mentioned above and because there is no Hydrogen powered aircrafts (yet), what will the energy need look like if we instead produced PtL fuels that can more/less work as it in the current aircrafts ?

The answer is quite simple. The chart above shows a 45% loss of energy producing Power-to-Liquid (PtL). According to chemical engineer Paul Martin we are more likely in a real world looking at a loss of 70%, in other words if we are to swap out all Jet A1 with PtL fuel, we need from the wind-turbines / solar cells the following;

• 16,3 tWh liquid PtL in Year 2030 = 29,6 - 54,3 tWh renewable energy produced
• 21,1 tWh liquid PtL in Year 2040 = 38,4 - 70,3 tWh renewable energy produced
• 28,8 tWh liquid PtL in Year 2050 = 52,4 - 96,0 tWh renewable energy produced

Note: To simplify it, we have not included the power needed to run these new electrolysis facilities, CO2 capture facilities which is said to be significant, infrastructure, etc.. So total power needed produced at the wind-turbines are even greater.

A LOT of windmills

Bottom line, according to our survey and calculations, to swap all the Jet A1 used/sold in Denmark out with PtL in the years and decades to come, we need to just for this relatively small business that "Danish Aviation" relatively speaking is compared to all other business in Denmark added together, either:

• Produce today up to the same amount or more of electricity as the whole country consumes today.
• By year 2030 have raised and installed 17-32x the amount of wind-turbines parks the size of Horns Rev 3, equivalent to 833 - 1.568 MHI Vestas 8,0 MW wind-turbines.
• Use 60-110% of the total offshore wind-turbines capacity of the 49,5 tWh in 2030 the government has announced it will boost it up to.
• Denmark announced along with EU, Germany, Holland and Belgium that by the year 2050, 10.000 of the largest windmills will be raised in the North Sea delivering 150GW yearly, whereas nearly 2.500 is expected on Danish soil (approx. 37GW). Using a friendly 4,3 tWh / GW capacity factor that gives approx. 160 tWh. Meaning in year 2050 Danish Aviation will need approx. 33-60% of the energy produced out of the approx. 2.500 largest wind-turbines = 825 - 1.500 of the largest wind-turbines in 2050.

What we have illustrated here is, that according to our research, sources and calculations, even with the most Hydrogen-friendly data, Danish Aviation need over 800 wind-turbines just for Danish Aviation, and probably up to approx. 1.500 wind-turbines.

Bottom line: It's a massive waste of green energy producing Hydrogen let alone PtL.

In contrast for delivering the same amount of energy (or horsepower) at an aircrafts propeller or fan, battery powered aircrafts only need 13-30% of the produced wind-turbine electricity compared to PtL powered aircrafts, due to a lot less loss of energy in transmission, battery storage and that electric motors are A LOT more energy efficient than combustion powered engines. In other words, where ever a battery-electric aircraft can fly instead of combustion powered aircrafts, that route would only need 15-30% of the amount of wind-turbines. That is significant less amount of wind-turbines needed for battery-electric aircrafts, somewhere between 200-250 wind-turbines. Still a lot, so maybe we should also look into other green energy sources beside wind-turbines and solar cells ?..

"But batteries don't cut it and there isn't enough Biofuel, therefore we need PtL"

That is a statements that pops up regularly, especially about batteries. Sure batteries are not able to deliver enough energy per weight today to give any commercial plane a decent range, but the development is going fast.

We made this chart to roughly illustrate with past and current battery technology in cars, how fast it has gone since the first Tesla Roadster car in 2008 hit the market and kicked the automobile industry into electric gear, through the first Model S, then Model 3 and then the announced level of 400-500 Wh/kg in 2025 by other car manufactures and made a trend line where it looks like we are heading.

Note: there is a 400-450 Wh/kg battery on the market now for use in the space industry, so getting to 400-500 Wh/kg in cars by 2025 seems no longer just to be words.

Several other battery technologies with other material or chemical combinations than current types are under development, for example Lithium-air where a Japanese consortium has established a density of 500 Wh/kg. Lithium-air has a theoretical density of over 1.000 Wh/kg, so plausible good margin for further development just with this type. And other combinations of materials and chemicals are in the works for even higher energy density in the future to come.

Having consulted people who study and follow battery development for a living, they nodded that this scenario reaching approx. 800 Wh/kg by around year 2035 looked plausible. We can't tell the future, but so far batteries track record, projections and professionals in the industry seems to agree it is heading that direction.

What we also find interesting with an 800 Wh/kg energy density in batteries is as we have mentioned in this previous article, that approx. 50% of all flights, not measured by distance, but 50% of the number of all flights can then be flown on battery-powered aircrafts alone with no need of any fuel being burned, hence emitting no CO2 or any other gasses at the airport or to the airports local community (and likely less noisy as well). Being able to reduce emissions and noise locally like at an airport and to the airports local community, we find that important.

In addition to environment issues, battery-powered aircrafts does not create contrails, which is suspected to count for over half of aviations entire climate impacts.

According to this Forbes article, we just need to reach approx. 5-600 Wh/kg to be able to start flying regional with reference to this source / illustration, which follow very well the previous source of reaching approx. 800 Wh/kg, which then starts entering the narrow body airplanes domain (ex. Airbus A220/320, Boeing 737 etc.) up to 600 Nm short-haul routes.

Hybrid-electric solutions

Another interesting alternative we find not mentioned a lot in our traditional part of aviation, is hybrid-electric solutions as in having a combination of batteries and a gas-turbine engine using SAF (Biomass) that powers a generator, that parallel with the batteries can power the electric motor(s)/propeller(s) on the aircraft and/or charge the batteries en-route, so landing just like takeoff can be done on pure battery power with the gas-turbine turned off, i.e. no local emissions at the airport. Data on one of the eVTOL/eSTOL projects in the making shows us compared to a traditional turboprop airplane of similarly size, the hybrid aircraft while traveling at approx. same speed and at a same given altitude en-route, its fuel-flow is only approx. 40% of the traditional turboprop airplane.

Rolls-Royce seems to agree there is a market in hybrid-electric solutions, since they announced recently their program to support that need.

The hybrid-electric solutions is also useful to get some eVTOL/eSTOL quicker into a larger market than with pure battery powered solutions, until batteries in the near future will get a high enough energy-density per weight, so pure battery powered journeys can be done even further and not limited to approx. sub-150 miles ranges as the limitations are with current battery technology with eVTOL and a bit further for eSTOL aircrafts.

If we can conclude that producing Hydrogen or PtL for aviation is a waste of capital and green energy, due to SAF (Biomass) at some point will become a scarce resource, maybe we can lower the consumption of SAF (Biomass) by developing hybrid-electric aircrafts instead of trying to fly on Hydrogen and limit usage of SAF (Biomass) where batteries are not sufficient yet.

Ending words

Topics not covered in this article we looked into but kept out for simplicity reasons, but topics that should have considerations as well;

• Environmental impact: How recyclable are wind-turbines materials after their 20-30 years life ?
• Environmental impact: What influence does that many wind-turbines have to the atmosphere in term of for example change of windspeeds and precipitation on short and long distances from the wind-turbine farm ?
• Capital expenditure, private and public.
• Environmental impact: How recyclable are todays and futures batteries ?

We are aware of this article is in contrast of much of the current broad agenda in believing a lot in PtX and Hydrogen as a fuel. If you find faulty sources we refer to or miscalculated numbers, please let us know.

But if we have not quoted sources incorrect or done poor calculations, we believe it is obvious as it is for several other independent experts with many years of knowledge in their respective field, that Hydrogen is not the great savior for aviation. For that there are better alternatives that makes a lot more sense, i.e. battery and hybrid (battery + SAF) on short haul and SAF from bio-sources on long haul.

And if there is not enough bio-based SAF for all long haul flights, maybe some of the passengers for example those going on holidays where time is not as important, could book flights that are shorter or flights with technical stops underway to give time to for example recharge the aircrafts batteries and give the passengers time to stretch their legs and have a short break, just like you can when flying transatlantic with Icelandair via Iceland - or like in the old times when piston-prop planes didn't have to range to go non-stop over long distances they had stops underway.