Department of Department of Mechanical Mechanical Engineering Engineering

Powertrain & Vehicle PowertrainLow & Vehicle-Carbon Aviation – How can this be achieved? Research Centre Research Centre

Dr James Turner Professor of Engines and Energy Systems University of Bath, UK Niels Bohr

“Prediction is very difficult, especially if it's about the future.” Overview of Presentation

Downsized engines . The historical link between aviation and automotive Our need to change . The growth in transportation energy The need for high energy fuel in aviation . Pure and the problem with everything else Some options for decarbonizing fuel in aviation . , nuclear, Another (blue sky) way . ZELTA Carbon-neutral liquid fuels . Decarbonizing practical fuels Concluding remarks Downsized, Boosted Engines – the Link

Aviation pursued engine boosting to maintain power at altitude and then to increase specific output significantly Many of the engine technologies now employed in road vehicle engines effectively came from aviation via racing . Twin-spark ignition 1923 Halford . Double overhead cams (DOHC) Special Engine . Four valves per cylinder (4vpc) 4vpc, DOHC 6-cylinder The first turbocharged . Supercharging (then turbocharging) car engine . High octane fuels . Direct injection (DI) . Water injection (‘ADI’) Major Frank Halford designed all of de Havilland’s Major Halford was engines and all of the Napier H-engines, as well as being President of the fundamental in the successful development of the gas RAeS in 1951 turbine (with ‘straight-through’ combustion chambers) Automotive Engines are Architecturally-Frozen Aero Engines…

It could be argued that the template for the modern automotive engine was actually laid down by Napier in 1916 with the Lion . 4vpc, DOHC, narrow valve angle and a single cam cover . 101 years old Then general automotive engineering followed aero engine technology after a 10-20 year delay… However, in the 1940s/50s the gas turbine comprehensively broke this delayed take-up link . …And the automotive industry never adopted the sleeve valve as a result Consequently the modern automotive engine shares Napier Lion much in common with the Rolls-Royce Merlin, Daimler- Benz 601 and Allison V-1710 . Effectively it’s architecturally frozen at 85 years old Potential Transfer of Automotive Technology Back to Aviation

It has been attempted to use an automotive engine in light aviation before – the Porsche Flugmotor PFM 3200 . Development started in 1981 . 212-241 bhp Modern downsized, boosted, DI automotive engines are light, reliable and fuel efficient, and their control systems may well be more reliable than current light avionics . Due to on-board diagnostics requirements There are now several all-aluminium 2.0 litre DI engines which deliver 200-350 bhp . Is this an option worth persuing? This would be going full circle on engines… UK Transport Energy Consumption by Mode, 1970-2014

Air transport represents a particular problem: How do you fully decarbonize an aircraft?

Air

Water

Road

Rail

Taken from: Energy Consumption in the UK (2015), DECC Change in UK Transport Energy Consumption, 1970-2014

Long-range aircraft present a significant problem

Even hybrid aircraft propulsion systems can only Air

reduce CO2 while there is fossil carbon in the fuel % Water

Road Air: +320 Air:

Rail

Taken from: Energy Consumption in the UK (2015), DECC UK Road Transport Energy by Type of Vehicle, 1970-2014

2008: Beginning of

Simple: let’s just electrify the private road transportation fleet EU CO2 legislation

Consumption of road transport is ‘only’ 40 Mtoe…

Cars 1 Mtoe = 41.87 PJ (41.87 x 1015 J)… This is a continuous output of 1.33 GW over a year – more than a good-sized nuclear power station (~ 1 GW)

HGVs

LGVs Buses Motorcycles

Taken from: Energy Consumption in the UK (2015), DECC UK Transport Energy Consumption by Mode, 2014

 53 x 1 GW nuclear The total design power of the two power stations Hinkley Point C reactors is 3.2 GW 16.5 Hinkley Point Cs For perspective, in 2014 the average UK electrical power demand was 34.4 GW (or only half the total transport demand) Peak demand in 2015 was  52.7 GW

To date, the only practical energy 5.3 Hinkley Point Cs system for transport has been fossil oil  17 x 1 GW nuclear power stations Which, because we have developed fuel supply together with transportation, has developed symbiotically with it

By my reckoning, we pump oil at a rate of 7.4% of the flow of Niagara Falls…

Taken from: Energy Consumption in the UK (2015), DECC Long-Range Aircraft Battery Sizing Calculation

At take-off, a Boeing 787-9 has 50.7 tonnes of fuel on board for a 9000 km . This is 605 MWh of energy (2.18 x 106 MJ) To convert to electric propulsion, we should allow an approximate factor of two to allow for increased electric machine efficiency versus thermal engines . Implies energy at take-off for the electric version is 302.5 MWh (1.09 x 106 MJ) • Or 3000 Tesla Model S P100D batteries (which are 700 kg each…) Using 150-250 Wh/kg as a cell energy density, this gives a battery mass of 1210-2017 tonnes (cell level) Calculation courtesy of Current 787-9 fully-laden take-off Dr Richard Pearson, BP weight is 253 tonnes . Battery will be 5-8 times heavier At 1.4 MW it would take 216 hours (9 days) to fully charge it… Plainly, this isn’t going to work! On-Board Energy Density: Batteries v Everything…

HTA 30 aviation Diesel/Kerosene really 25 Road Gasoline needs to transport be here Rider: at 20 could E85 automotive happily scale : live here M85 15 Ethanol Liquid (cryogenic) H2 = 70.8 kg/m3 H is hardly 2 Kerosene (jet fuel) = better than Methanol 10 840 kg/m3 batteries Liquid H2 (or 11.8 times greater)

5 700 bar H2 200 bar

This makes them really expensive and heavy Net volumetric energy density / [MJ/l] / density energy volumetric Net 0 Compared to liquid fuels batteries don’t really get off the origin… Batteries 0 5 10 15 20 25 30 35 40 Net gravimetric energy density / [MJ/kg] Courtesy Lotus Engineering How do you Decarbonize Aviation?

General Electric

Ammonia (NH3) and X211 turbojet: Hydrazine (N2H4) have also nuclear core (!) been researched, as has…

Hydrogen Uranium Oxide

Requirement to carry significant energy makes liquid hydrogen viable here NERVA Nuclear Rocket Engine Carbon-Neutral Ammonia

Battlefield Mobile Compact 82% of power to Reactor electrolysis

What could possibly go wrong?

32.7% efficient in terms of HHV Allison PD-81 Ammonia Taken from RRHT Allison Branch Research Engine Newsletter, November 2011 Can Hydrogen Work? (1)

Liquid hydrogen has historically been investgated by the Lockheed Skunk Works and Pratt & Whitney – Project ‘Suntan’ . Hydrogen was considered attractive because of its high lower heating value and the fact that a lot of energy would have to be carried

Suntan performed preliminary design work and P&W built a liquid H2 engine . The 304 . But the idea was dropped because of the problem of difficulties in hydrogen storage The concept was rescoped and became the SR-71

Pratt & Whitney 304 ‘Suntan’ engine Taken from: “Advanced Engine Development at Pratt & Whitney” by Mulready, R.C. Can Hydrogen Work? (2)

Recently the EU-funded ‘Cryoplane’ project investigated the use of liquid hydrogen to fuel long-range passenger aircraft . Combustion tests using hydrogen were conducted to establish engine control limits Investigations into global warming potential were conducted

. H2 was found to significantly better than kerosene . Water is a too, but if the hydrogen cycle is closed then this is not an issue – as long as ‘green’ hydrogen from e.g. electrolysis is used Unfortunately the requirement for a Note impact of large particular shape of tank – torospherical – torospherical tanks meant that the concept was not viable There is also the need to derive lift from the fuel energy in heavier-than-air aircraft

6 For the 787-9: 2.18 x 10 MJ = 18 tonnes of H2 Which occupies 254.2 m3 c.f. 60.4 m3 of kerosene – 4.2 times greater Cryoplane ZELTA – Zero Emission Lighter-Than-Air

If the requirement for high-speed aerodynamic efficiency and the need to carry the energy to generate lift can be removed, an interesting possibility arises… A preliminary design study has been conducted at the University of Bath . Suggests that a 100-tonne payload, 100 knot with sufficient range to fly from Cardington to San Francisco could be built and fuelled using liquid hydrogen Note: would be the lifting gas, not hydrogen! . Exhaust ballast recovery and fuel cells to generate electricity and supply potable water would also be incorporated

LH2 Tank ZELTA

Richardson, A., ‘Study of design factors for rigid for long- range, high-payload operation with zero in use carbon emissions’ Returning to the Actual Problem…

The real problem with transport is that we operate the vehicles on fossil fuels . Economically-affordable engines do not have to use such fuels: both Diesel and Ford made their engines run on biofuels – we then made them run on fossil fuels instead But there is no shortage of carbon-free energy . We just need to find a means to convert it to a form usable in existing vehicles Solving the Problem…

A pragmatic solution would be to use renewable energy to synthesize drop-in alternatives to the fuels we use now

These are known as ‘Carbon-Neutral Liquid Fuels’, ‘Electrofuels’ or ‘Synthetic Fuels’ Solving the Problem: the Sustainable Methanol-Based Cycle

Feed stocks are water, air Energy in Hydrogen from and renewable energy electrolysis of water: 1 H O  H + O 2 2 2 2 The price of these feed stocks is free and a high- value product is made

Carbon out Methanol synthesis: Provides the economic Synthetic CO 2 + 3H2  C H3 OH + H2 O hydrocarbons From Lackner, K.,‘Options for and products driver to decarbonize and Capturing Carbon Dioxide CO2 consumption from the Air’, May 2008 a valuable buffer for Fuel use: renewable energy 3 CH OH + O Direct air 3 2 2 capture

of CO2  CO 2 + 2H2 O

Carbon in CO2 from fossil fuel burning Atmospheric CO 2 power plants Gasoline, diesel and kerosene CO2 emission can also be synthesized from AdaptedAdapted from Olah fromet al., The Olah Methanol et Economy al., these feed stocks – with an ‘The Methanol Economy’ energy penalty (c. 8% point)

Courtesy Lotus Engineering Available Upstream Energy…

Source: Dr Wolfgang Warnecke, Shell, SAE PF&L, Baltimore, USA, October 2016 Available Upstream Energy…

The average solar load in deserts is 1000 W/m2 Therefore, assuming 20% solar panel efficiency, 12 hour days, and 50% land area utilization, it would take 16000 km2 (a square of 127 km sides) to power the entire European road transport fleet (400 GW) . This is only <0.2% of the area of the Sahara ‘A Gas Tank in the Sky’

CO2 is being extracted from the atmosphere now . In space ships and submarines . Done to provide a breathable atmosphere aboard Using demonstrated performance, it is possible to synthesize methanol at 45% process efficiency (based on the HHV) . The biggest energy input –  80% – is the 60 electrolysis of water to get the hydrogen 55 Values achieved in needed 50 practice to date

. The other  20% is the CO2 extraction and 45

overhead to make hydrogen storable 40

UK DfT has consulted on synthetic fuels (and 35 30

continue to do so) / [%] efficiency Electricity-to-tank Thermodynamic limit is 20 kJ/mol CO2 California ARB has just published draft standards 25 0 100 200 300 400 500 600 700 800 900 1000 Energy for CO2 extraction / [kJ/kmol CO2] Example of Direct Air Capture: Climeworks

Climeworks, a spin-out from ETH Zurich, is one company that has built and is

operating functioning ‘direct air capture’ CO2 extraction equipment already

It has set itself the goal of capturing 1% of global CO2 emissions by 2025 . Has a 50 tonne p.a. DAC plant operating at the moment . Is now building a 900 t.p.a. commercial plant to open next year

. 900 t.p.a. is equivalent to the CO2 produced by 40 people or 150 cars

The CO2 will be sold to food companies but the aim is to close the fuel cycle . Is already in partnership with Audi So Who Is Actually Doing This?...

Many researchers are showing the feasibility of the approach, among them: George Olah’s group at University of Southern California

. Direct conversion of atmospheric-concentration CO2 to methanol with virtually no catalyst degradation, at 79% conversion rate Harvard University group showing the ‘Bionic Leaf’ UC Berkeley with their ‘Solar-to-Fuel’ system The EU are funding the ‘Sun-to-Liquid’ project to decarbonize aviation

. The project will be making aviation-grade kerosene directly from CO2, water and solar thermal energy in a pilot plant using thermolysis driven by a heliostat Sunfire with Climeworks – building a full synthesis system in Norway

. DAC of CO2 in a commercial pilot plant using hydroelectricity to make 10,000 litres /year of ‘blue crude’ to go into conventional petroleum refineries . Sunfire, like Climeworks, also have a relationship with Audi The University of Bath – in the initial stages of feasibility project for gasoline …And What Might These Plants Look Like?

Illustrations courtesy of the Institution of Mechanical Engineers Concluding Remarks

Aviation and automotive engineering are closely linked historically . Especially in the area of light aircraft . Modern automotive engine fuel-consumption technology could be applied to

aviation to reduce CO2 output from light aircraft . Could also use proven three-way catalysis to improve gaseous emissions Long-range aircraft present a significant problem . The most practical way to use hydrogen might be to use it for propulsion in airships… Not as a lifting gas! However, for practical applications, the fuel itself needs to be decarbonized

This is really the only way to fully eliminate CO2 emissions from aviation . The technology exists to do this now

This would provide a means to monetize the direct air capture of CO2 The technology of electrofuels could then migrate to fuels for surface transport . Making it a disruptive technology for electric vehicles THANK YOU FOR LISTENING

For further information on Direct Air Capture of CO2 and Electrofuels see also: http://loker.usc.edu/methanolecon.html http://www.climeworks.com/ http://www.sun-to-liquid.eu/ http://www.sunfire.de/en/company/press/detail/first-commercial-plant-for-the- production-of-blue-crude-planned-in-norway https://www.arb.ca.gov/fuels/lcfs/lcfs.htm