Reaction Engines ZAS0036
Written evidence from Reaction Engines
Introduction - Reaction Engines
Reaction Engines (RE) is a private UK-company founded to develop air-breathing rocket engine (SABRE) technology for the space and aerospace domain. The thermal management capability developed through SABRE has found additional purpose in optimising the efficiency of energy intensive applications and processes across a large number of industries – the unique technology advances the capability to capture, manage and recycle heat energy in transformative ways. As a result, RE can play a vital role in supporting sustainable aviation/marine and has already undertaken significant exploration about how best to deploy this capability within the sectors. Accordingly, RE submit the following in response to the Environmental Committee’s paper.
Executive Summary
Ammonia systems appear to provide a balanced near-term solution to the challenge facing the aviation/marine industry. This is due to the combination of a) significant harmful emission reduction. b) relatively minor vehicle/engine modifications required c) existing infrastructure conformity. It is recommended that this option be pursued through Government funded programmes such as to accelerate the exploration and adoption of such systems.
Hydrogen fuels such as ‘Pure Hydrogen’ combustion and Fuel-Cells can also provide a strong alterative to incumbent technology however further development is likely required that will not satisfy the near-term imperative around sustainably aviation and shipping. Use of novel systems to thermally manage new and existing systems shows great promise. It is recommended these also be considered via Government funding.
Drop-in alternatives (SAF) that attempt to replicate existing aviation/marine fuels and avoid vehicle/engine modification will not provide enough benefit to meet the long-term Government ambition around sustainability and net-zero. They may provide a short-term respite, whilst other zero-carbon alternatives are brought to the line and should be treated accordingly.
How close are zero carbon fuels to commercialisation for aviation / shipping? How effective will the Jet Zero Council be in catalysing zero emissions technologies? What role should transitional fuels such as alternative hydrocarbon fuels play?
Ammonia is a zero-carbon fuel, and has a well-established global supply chain, including regulation for road transport, storage, and transfer (all developed to support the chemicals and fertiliser industries which are huge consumers of ammonia). However, most of today’s Ammonia is formed by steam reformation of methane, which is itself a carbon-emitting process. In the future more countries with suitable climates and geographies will shift their focus to solar or wind-based electrolysis of water to produce hydrogen (eg Saudi Arabia, Australia). Ammonia is a suitable carrier to allow global distribution of the hydrogen, significantly less complex and inherently safer than transporting cryogenic liquid hydrogen. Ammonia can either be decomposed at storage depots to create hydrogen for local distribution or can be used directly as a fuel if technology is used either to partially decompose (“crack”) it to liberate some hydrogen or it is mixed with a second fuel to promote combustion. Either system can be embodied into the combustion system of ships or aircraft power generation systems. A major advantage of ammonia compared to hydrogen is that it is quicker, simpler and cheaper to implement. For example, an ammonia fuelled airliner could be developed as a new variant of an existing airliner for EIS in the early 2030s, whereas a hydrogen fuelled airliner would be a brand-new development with an EIS in the 2040s.
The Jet Zero Council’s acceptance of Sustainable/Synthetic Aviation Fuel (SAF) as part of the solution to decarbonising aviation without setting a target time to phase out carbon-based fuels entirely will not provide the optimum environment for the development of zero-emissions technologies. The ultimate goal should be to phase out all carbon-emitting fuels, regardless of whether the carbon they emit is captured from the atmosphere earlier in the cycle or offset by Carbon Capture and Storage. Whilst zero emission fuels will not be available in sufficient volumes and aircraft capable of conducting long-haul flights with zero emissions will not be developed in time to deliver net-zero targets without use of SAF, the strategy should still set a hard target for phasing out entirely of carbon fuels. In doing so the UK would put itself in a strong position to encourage inward investment in zero emission transport and take a lead role in developing the underpinning technology, regulation, and supply chain.
What new technologies are there to reduce emissions from aircraft / shipping vessels and how close to commercialisation are they?
Current maritime and aircraft propulsion systems lose substantial amounts of energy as waste heat. Until recently, capture and recycling of that heat through technologies such as intercooling, recuperation, and waste heat recovery wasn’t viable or economic for aircraft or ships due to the extra complexity, weight and volume required for such systems. However recent developments in heat exchanger technology and new thermal cycles such as (for example) Supercritical CO2 now make feasible the capture and recycling/conversion of waste heat throughout the engine cycle to increase thermal efficiency.
Hydrogen-powered fuel cells are seen as one of the primary candidate technologies for zero-emission aviation, albeit currently only to replace short and medium range flights (due to the volumetric power density of hydrogen and the need to store it in pressurised tanks, thereby precluding the use of the wing as a fuel tank as is done with current aircraft). However, fuel cells typically run at 60% efficiency or less, with the remainder of the energy in the fuel being transformed into waste heat. Thermal management is therefore rapidly emerging as one of the key issues to solve to make zero emission aviation viable. Derived from the UK Space Agencies’ investment in the SABRE space propulsion system, Reaction Engines now has a suite of thermal management technologies which have the required properties of being super-lightweight, highly power dense, and capable of operating in the demanding conditions inside an engine, aircraft or ship to unlock the integration of such systems into commercially viable aircraft designs.
Ammonia is a potential zero CO2 emission fuel. Reaction Engines in conjunction with Science & Technology Facilities Council (STFC) is developing compact and lightweight ammonia cracker technology to aid ammonia combustion (otherwise an additional combustion ‘promoter’ fuel is required, typically hydrogen). Their first demonstrator is currently in manufacture and will be showcased at COP26 in November.
Hydrogen is also a zero CO2 emission fuel however its storage is problematic. It can either be stored as a high pressure gas (which results in large, heavy fuel tanks) or as a cryogenic liquid (which is better suited to long range aircraft but requires technically complex handling systems). Reaction Engines has a background in this technology from their hydrogen fuelled SABRE engine programme, particularly heat exchangers and hydrogen combustors both of which are currently on test.
How should the Government’s net zero aviation strategy support UK industry in the development and uptake of technologies, fuels and infrastructure to deliver net zero shipping and aviation?
Through schemes such as FlyZero and other competitions and programmes, the Government should seek out and fund technologies which make radical steps towards enabling zero emission operations of aircraft and ships. Both industries are very conservative and without strong funding encouragement will adopt incremental solutions which will not meet the climate change imperative. Technologies which offer a step change, such as using Ammonia as a fuel for both aircraft and ships, or completely novel thermal management solutions will be required if the Net-Zero targets are to be met, but government support funding will be required to accelerate those technologies to the point where they become commercially viable on a like for like comparison with their carbon-emitting counterparts.
Safety will of course remain paramount in future maritime and aviation transport, so the UK must take a lead on providing a regulatory environment which enables the safe use of technology and solutions which are substantially different from today. For example, Ammonia is currently not a strong contender as a fuel in aviation due to its toxicity when compared to kerosene. However, a supportive regulatory regime could find ways of maintaining safety levels with Ammonia on board and enable an earlier adoption of a zero emission fuel than waiting for a new aircraft design suitable for liquid hydrogen as a fuel.
September 2021