Applications & Pathways

Hydrogen (H2 ) is currently a highly attractive fuel for internal combustion engines (ICEs) owing to the prospects of potentially near-zero emissions. However the production emissions and cost of H2 fuel necessitate substantial improvements in ICE thermal efficiency. This work aims to investigate a potential implementation of H2 combustion in a highly efficient double compression-expansion engine (DCEE). DICI nonpremixed H2 combustion mode is used for its superior characteristics as concluded in previous studies. The analysis is performed using a 1D GT-Power software package where different variants of the DICI H2 and diesel combustion cycles obtained experimentally and numerically (3D CFD) are imposed in the combustion cylinder of the DCEE. The results show that the low jet momentum free jet mixing dominated variants of the DICI H2 combustion concept are preferred owing to the lower heat transfer losses and relaxed requirements on the fuel injection system. Insulation of the expander and removal of the intercooling improve the engine efficiency by 1.3 and 0.5 %-points respectively but the latter leads to elevated temperatures in the high-pressure tank which makes the selection of its materials harder but allows the use of cheaper oxidation catalysts. The results also show that the DCEE performance is insensitive to combustion cylinder temperatures making it potentially suitable for other high-octane fuels such as methane methanol ammonia etc. Finally a brake thermal efficiency of 56 % is achieved with H2 combustion around 1 %-point higher than with diesel. Further efficiency improvements are also possible with a fully optimized H2 combustion system.

This work investigates the cost-efficient integration of renewable hydrogen into steelworks for the production of methane and methanol as an efficient way to decarbonize the steel industry. Three case studies that utilize a mixture of steelworks off-gases (blast furnace gas coke oven gas and basic oxygen furnace gas) which differ on the amount of used off-gases as well as on the end product (methane and/or methanol) are analyzed and evaluated in terms of their economic performance. The most influential cost factors are identified and sensitivity analyses are conducted for different operating and economic parameters. Renewable hydrogen produced by PEM electrolysis is the most expensive component in this scheme and responsible for over 80% of the total costs. Progress in the hydrogen economy (lower electrolyzer capital costs improved electrolyzer efficiency and lower electricity prices) is necessary to establish this technology in the future.

A comprehensive investigation on diesel pilot spray ignited methane-hydrogen (CH₄–H₂) combustion tri-fuel combustion (TF) is performed in a single-cylinder compression ignition (CI) engine. The experiments provide a detailed analysis of the effect of H₂ concentration (based on mole fraction M_H2) and charge-air temperature (Tair) on the ignition behavior combustion stability cycle-to-cycle (CCV) and engine performance. The results indicate that adding H₂ from 0 to 60% shortens the ignition delay time (IDT) and combustion duration (based on CA90) up to 33% and 45% respectively. Thereby H₂ helps to increase the indicated thermal efficiency (ITE) by as much as 10%. Furthermore to gain an insight into the combustion stability and CCV the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) methodologies are applied to estimate the combustion stability and CCV of the TF combustion process. The results reveal that the pressure oscillation can be reduced up to 4 dB/Hz and the CCV by 50% when M_H2 < 60% and Tair < 55 °C. However when M_H2 > 60% and Tair > 40 °C abnormal combustion and knocking are observed.

Although recent studies have shown the possibility of running ‘standard’ spark-ignition engines with 6 pure ammonia the operating range remains limited mainly due to the unfavorable characteristics of 7 ammonia for premixed combustion and often requires the addition of a complementary fuel such as H2 8 to extend it. As the best way to add H2 is to crack ammonia directly on-board this paper focuses on 9 the impact of the upstream cracking level of ammonia on the performance and emissions of a single 10 cylinder spark ignition engine. Experiments were performed over several equivalence ratios 11 dissociation rates and load conditions. It is confirmed that only a slight rate of ammonia dissociation 12 (10%) upstream of the combustion considerably enhances the engine's operating range thanks to a 13 better combustion stability. In terms of pollutant emissions the partial dissociation of ammonia 14 especially for slightly lean mixtures induces a very clear trade-off between high NOx and high 15 unburned ammonia level for high and low ammonia dissociation rates respectively. Therefore 16 cracking NH3 does not only improve the operating range of ammonia-fueled spark ignition engines but 17 can also help to reduce NH3. However to reach the same engine output work higher ammonia fuel 18 consumption will be necessary since the global system efficiency is lower using fuel dissociation. In 19 addition the global warming effect is increased with dissociation level since a higher level of N2O is 20 generated by the hydrogen contribution.

In this paper the broader perspective of green hydrogen (H2) supply and refueling systems for aircraft is provided as an enabling technology brick for more climate friendly H2-powered aviation. For this two H2 demand scenarios at exemplary airports are determined for 2050. Then general requirements for liquid hydrogen (LH2) refueling setups in an airport environment are derived and techno-economic models for LH2 storage liquefaction and transportation to the aircraft are designed. Finally a cost tradeoff study is undertaken for the design of the LH2 setup including LH2 refueling trucks and a LH2 pipeline and hydrant system. It is found that for airports with less than 125 ktLH2 annual demand a LH2 refueling truck setup is the more economic choice. At airports with higher annual LH2 demands a LH2 pipeline & hydrant system can lead to slight cost reductions and enable safer and faster refueling. However in all demand scenarios the refueling system costs only mark 3 to 4% of the total supply costs of LH2. The latter are dominated by the costs for green H2 produced offsite followed by the costs for liquefaction of H2 at an airport. While cost reducing scaling effects are likely to be achieved for H2 liquefaction plants other component capacities would already be designed at maximum capacities for medium-sized airports. Furthermore with annual LH2 demands of 100 ktLH2 and more medium and larger airports could take a special H2 hub role by 2050 dominating regional H2 consumption. Finally technology demonstrators are required to reduce uncertainty around major techno-economic parameters such as the investment costs for LH2 pipeline & hydrant systems.

The decarbonisation of waterborne transport is arguably the biggest challenge faced by the maritime industry presently. By 2050 the International Maritime Organization (IMO) aims to reduce greenhouse gas emissions from the shipping industry by 50% compared to 2008 with a vision to phase out fossil fuels by the end of the century as a matter of urgency. To meet such targets action must be taken immediately to address the barriers to adopt the various clean shipping options currently at different technological maturity levels. Green hydrogen as an alternative fuel presents an attractive solution to meet future targets from international bodies and is seen as a viable contributor within a future clean shipping vision. The cost of hydrogen fuel—in the shortterm at least—is higher compared to conventional fuel; therefore energy-saving devices (ESDs) for ships are more important than ever as implementation of rules and regulations restrict the use of fossil fuels while promoting zero-emission technology. However existing and emerging ESDs in standalone/combination for traditional fossil fuel driven vessels have not been researched to assess their compatibility for hydrogen-powered ships which present new challenges and considerations within their design and operation. Therefore this review aims to bridge that gap by firstly identifying the new challenges that a hydrogen-powered propulsion system brings forth and then reviewing the quantitative energy saving capability and qualitive additional benefits of individual existing and emerging ESDs in standalone and combination with recommendations for the most applicable ESD combinations with hydrogen-powered waterborne transport presented to maximise energy saving and minimise the negative impact on the propulsion system components. In summary the most compatible combination ESDs for hydrogen will depend largely on factors such as vessel types routes propulsion operation etc. However the mitigation of load fluctuations commonly encountered during a vessels operation was viewed to be a primary area of interest as it can have a negative impact on hydrogen propulsion system components such as the fuel cell; therefore the ESD combination that can maximise energy savings as well as minimise the fluctuating loads experienced would be viewed as the most compatible with hydrogen-powered waterborne transport.

We analyze the use of hydrogen as a fuel for the automotive industry with the aim of decarbonizing the economy. Hydrogen is a suitable option for avoiding pollutant gas emissions developing environmentally friendly technologies replacing fossil fuels with clean renewable energies and complying with the Paris Agreement and Glasgow resolutions. In this sense renewable energies such as wind solar photovoltaic geothermal biomass etc. can be used to produce the necessary hydrogen to power vehicles. In this way the entire process from hydrogen production to its consumption as fuel will be 100% clean. If we are to meet future energy demands it is necessary to forecast the amount of hydrogen needed taking into account the facilities currently available and new ones that will be required for its generation storage and distribution. This paper presents a process for optimizing hydrogen production for the automotive industry that considers the amount of hydrogen needed the type of facilities from which it will be produced how the different sources of production are to be combined to achieve a competitive product and the potential environmental impacts of each energy source. It can serve as a frame of reference for the various actors in the hydropower and automotive industries so that more efficient designs can be planned for the gradual introduction of hydrogen fuel cell vehicles (HFCVs). The methodology implemented in this paper sets an optimization problem for minimizing energy production costs and reducing environmental impacts according to the source of energy production. The EU framework with respect to the decarbonization of the economy the percentages of the different types of energy sources used and the non-polluting vehicle fleet in the automotive sector will be considered.

‘A System For All Seasons’ analyses Britain’s electricity generation and consumption trends concluding that the country’s wind and solar farms will have enough spare electricity generated in spring and summer when demand is lower to produce green hydrogen to the equivalent capacity of 25 Hinkley Point C nuclear power plants.

The hydrogen stored would provide the same amount of energy needed for every person in the UK to charge a Tesla Model S electric vehicle more than 21 times in the autumn and winter months when energy demand is highest creating a clean energy buffer that avoids having to manage limited energy supplies on the international markets.

Crucially the research finds that the UK has enough capacity to store the hydrogen in a combination of salt caverns and disused oil and gas fields in the North Sea as well other locations to meet this demand.

The research also finds that using renewable hydrogen will help reduce the total number of wind farms needed in 2050 by more than 75% because it will ensure electricity generated by Britain’s wind farms is used as efficiently as possible by avoiding surplus electricity going to waste.

‘A System For All Seasons’ finds that:

• Britain’s wind and solar farms could generate between 60-80GW of renewable hydrogen - the equivalent capacity of 25 Hinkley Point C nuclear power plants - from spare renewable electricity generated in the spring and summer months between May and October each year.
• Running the energy system this way will reduce the need for the total electricity generating capacity of UK wind farms from 500-600GW by 2050 down to 140-190GW – a reduction of up to 76%.
• It would mean Great Britain would be using spare renewable electricity that would otherwise go to waste to produce green hydrogen. Under the alternative scenario additional wind farms would need to be built to accommodate for autumn and wind energy demand peaks but be left unused during other times of the year.
• With 140-190GW of wind generation capacity 115 to 140TWh of green hydrogen would be stored – enough energy for every person in the UK to charge a Tesla Model S more than 21 times.
• The potential storage volume from Britain’s salt fields ranges from >1TWh up to 30TWh. For disused oil and gas fields the potential storage volume for individual sites ranges from ~1TWh up to 330TWh.

This is a time of enormous change for the gas industry as the UK and the world at large attempts to meet the challenges of decarbonisation in the face of climate change. Hydrogen is expected to play a vital role in achieving the government’s commitment of eliminating the UK’s contribution to climate change by 2050 with the industry creating up to 8000 jobs by 2030 and potentially unlocking up to 100000 jobs by the middle of the century. But despite the UK government’s huge ambitions hydrogen is just one piece of the puzzle and it will be necessary to seek solutions that bring the whole energy system together – including not just heat for buildings but hard-to decarbonise areas such as manufacturing road transport aviation and shipping. Here we bring you just a taste of some of the amazing work taking place across the energy sector to understand this fuel more clearly to comprehend its strengths and limitations and to integrate it into our current energy infrastructure. We hope you enjoy this special publication.

An existing diesel engine was fitted with a common rail direct injection (CRDi) facility to inject fuel at higher pressure in CRDi mode. In the current work rotating blades were incorporated in the piston cavity to enhance turbulence. Pilot fuels used are diesel and biodiesel of Ceiba pentandra oil (BCPO) with hydrogen supply during the suction stroke. Performance evaluation and emission tests for CRDi mode were carried out under different loading conditions. In the first part of the work maximum possible hydrogen substitution without knocking was reported at an injection timing of 15◦ before top dead center (bTDC). In the second part of the work fuel injection pressure (IP) was varied with maximum hydrogen fuel substitution. Then in the third part of the work exhaust gas recirculation (EGR) was varied to study the nitrogen oxides (NOx) generated. At 900 bar HC emissions in the CRDi engine were reduced by 18.5% and CO emissions were reduced by 17% relative to the CI mode. NOx emissions from the CRDi engine were decreased by 28% relative to the CI engine mode. At 20% EGR lowered the BTE by 14.2% and reduced hydrocarbons nitrogen oxide and carbon monoxide by 6.3% 30.5% and 9% respectively compared to the CI mode of operation.