Publications

The report calls for a focus on new advanced alternative fuels in particular synthetic kerosene (efuels) which have the capacity to substantially reduce emissions and be scaled up to meet the fuel demands of the sector.

For aviation to reach zero emissions sustainable advanced fuels are needed to replace fossil kerosene currently used by the sector. The European Green Deal (EGD) includes a legislative proposal which would bring about a long overdue development and uptake of such fuels for the sector that legislative proposal is now being developed under the EU’s ReFuelEU initiative. However this initiative will only succeed if its support is limited to those fuels which can truly deliver emission reductions and which can be scaled up sustainably to meet the demand from the aviation sector. The paper recommends how such objectives can be achieved.

The ReFuelEU proposal should focus on these fuels with an ambitious programme combining mandates with financial support so that Europe's aviation sector is put on a pathway to net zero emissions.

Link to document download on Transport & Environment Website

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets delivering low carbon heat and power decarbonising industry and more recently its ability to facilitate the net removal of CO₂ from the atmosphere. However despite this broad consensus and its technical maturity CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus in this paper we review the current state-of-the-art of CO₂ capture transport utilisation and storage from a multi-scale perspective moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS) and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

There are multiple references to sample cleaning methods prior to hydrogen content determination or hydrogen spectroscopy analysis but there is still no unified criteria; different authors use their own “know-how” to perform this task. The aim of this paper is to solve or at least clarify this issue. In this work the most commonly used sample cleaning methods are compared. Then five different methodologies are applied on certified hydrogen content calibration pins and on high strength steel concrete-prestressing strands and the three main situations regarding hydrogen content in the microstructural net (non-charged charged and charged and uncharged) are studied. It was concluded that the HCl solution C-3.5 cleaning method recommended by ASTM G1 introduces large amounts of hydrogen in the samples; but can be useful for eliminating superficial oxides if necessary. The rest of the methods had similar results; but the more complete ones that involve ultrasounds and last longer than 8 min are not appropriated when important diffusion may occur on the samples during their application. Simple methods that involve acetone or trichloroethylene and last around 1 min are preferable for almost all situations as these are faster easier and cheaper. As a final recommendation as trichloroethylene is toxic the simple acetone method is in general the most convenient one for regular hydrogen content analysis.

Overview of advances in the technology of solid state hydrogen storage methods applying different kinds of novel materials is provided. Metallic and intermetallic hydrides complex chemical hydride nanostructured carbon materials metal-doped carbon nanotubes metal-organic frameworks (MOFs) metal-doped metal organic frameworks covalent organic frameworks (COFs) and clathrates solid state hydrogen storage techniques are discussed. The studies on their hydrogen storage properties are in progress towards positive direction. Nevertheless it is believed that these novel materials will offer far-reaching solutions to the onboard hydrogen storage problems in near future. The review begins with the deficiencies of current energy economy and discusses the various aspects of implementation of hydrogen energy based economy.

Efficient and robust control strategies can greatly contribute to the reliability of fuel cell systems and a stable output voltage is a key criterion for evaluating a fuel cell system's reliability as a power source. In this study a polymer electrolyte fuel cell (PEFC) system model is developed and its performances under different operating conditions are studied. Then two different novel controllers—a proportional integral derivative (PID) controller and a model predictive control (MPC) controller—are proposed and applied in the PEFC system to control its output voltage at a desired value by regulating the hydrogen and air flow rates at the same time which features a multi‐input and single‐output control problem. Simulation results demonstrate that the developed PEFC system model is qualified to capture the system's behaviour. And both the developed PID and MPC controllers are effective at controlling the PEFC system's output voltage. While the MPC controller presents superior performance with faster response and smaller overshoot. The proposed MPC controller can be easily employed in various control applications for fuel cell systems.

Premature delamination failure characterized by the white structure flaking (WSF) or the white etching crack (WEC) often occurs in rolling element bearings and it deteriorates the durability of bearing substantially. It is known that this failure is caused by shear-mode (Mode II and Mode III) crack growth in conjunction with evolution and invasion of hydrogen into material during operation. To ensure the structural integrity associated with rolling element bearing it is important to clarify the effect of hydrogen on the shear-mode fatigue crack growth behavior near the threshold level.<br/>In our previous study the effect of hydrogen on the shear-mode fatigue crack growth behavior in a bearing steel of JIS SUJ2 was examined near the threshold level. Consequently it was shown that the threshold stress intensity factor (SIF) range for shear-mode fatigue crack growth decreased significantly by action of hydrogen. However the investigation was made only for a crack with a surface length of about 900 mm. To thoroughly understand the critical condition for delamination failure it is important to investigate the crack size dependency of the threshold level for a shear-mode small fatigue crack in the presence of hydrogen. In the present study correspondingly the threshold SIF ranges for a shear-mode crack with different length were additionally measured in the same material by using a novel technique that enables continuous charging of hydrogen in a specimen during long-term fatigue test. Then a clear reduction in crack growth rate and a crack size dependency of the threshold SIF range were observed under the environmental condition of continuous hydrogen charging.

With the increase in renewable energy connected to the grid new challenges arise due to its variable supply of power. Therefore it is crucial to develop new methods of storing energy. Hydrogen can fulfil the role of energy storage and even act as an energy carrier since it has a much higher energetic density than batteries and can be easily stored. Considering that the offshore wind sector is facing significant growth and technical advances hydrogen has the potential to be combined with offshore wind energy to aid in overcoming disadvantages such as the high installation cost of electrical transmission systems and transmission losses. This paper aims to outline and discuss the main features of the integration of hydrogen solutions in offshore wind power and to offer a literature review of the current state of hydrogen production from offshore wind. The paper provides a summary of the technologies involved in hydrogen production along with an analysis of two possible hydrogen producing systems from offshore wind energy. The analysis covers the system components including hydrogen storage the system configuration (i.e. offshore vs. onshore electrolyzer) and the potential uses of hydrogen e.g. Power to Mobility Power to Power and Power to Gas.

Tension-compression fatigue tests were performed on two types of Ni-based superalloy 718 with different microstructures to which small artificial defects of various shapes and sizes were introduced. Similar tests were also conducted on hydrogen-charged specimens with defects with a solute hydrogen content ranging from 26.3 to 91.0 mass ppm. In the non-charged specimens in particular the fatigue strength susceptibility to defects varied significantly according to the type of microstructural morphology i.e. a smaller grain size made the alloy more vulnerable to defects. The fatigue limit as a small-crack threshold was successfully predicted using the √area parameter model. Depending on the size of defects the fatigue limit was calculated in relation to three phases: (i) harmless-defect regime (ii) small-crack regime and (iii) large-crack regime. Such a classification enabled comprehensive fatigue limit evaluation in a wide array of defects taking into consideration (a) the defect size over a range of small crack and large crack and (b) the characteristics of the matrix represented by grain size and hardness. In addition the effect of defects and hydrogen on fatigue strength will be comprehensively discussed based on a series of experimental results.

The susceptibility of high strength ferritic steels to hydrogen-assisted fracture in hydrogen gas is usually evaluated by mechanical testing in high-pressure hydrogen gas or testing in air after pre-charging the specimens with hydrogen. We have used this second methodology conventionally known as internal hydrogen. Samples were pre-charged in an autoclave under 195 bar of pure hydrogen at 450ºC for 21 hours.<br/>Different chromium-molybdenum steels submitted to diverse quenching and tempering heat treatments were employed. Diverse specimens were also used: small cylindrical samples to measure hydrogen contents and the kinetics of hydrogen egression at room temperature tensile specimens notched tensile specimens with a sharp notch and also compact fracture toughness specimens. Fractographic examination in SEM was finally performed in order to know the way hydrogen modify fracture micromechanisms.<br/>The presence of hydrogen barely affects the conventional tensile properties of the steels but it clearly alters their notched tensile strength and fracture toughness. This is due to the strong effect that stress triaxiality (dependent also on the steel yield strength) has on the accumulation of hydrogen on the notch/crack front region being the displacement rate used in the test another important variable to be controlled due to its influence on hydrogen diffusion to the embrittled process zone. Moreover the modification of fracture micromechanisms was finally determined being ductile (initiation growth and coalescence of microvoids) in the absence of hydrogen and brittle and intergranular under the material conditions of maximum embrittlement.

Heating and cooling accounts for almost half of global energy consumption. With most of this relying fossil fuels however it contributes heavily to greenhouse gas emissions and air pollution. In parts of the world lacking modern energy access meanwhile inefficient biomass use for cooking also harms people’s health damages the environment and reduces social well-being.



The transition to renewable-based energy-efficient heating and cooling could follow several possible pathways depending on energy demand resource availability and the needs and priorities of each country or region. Broad options include electrification with renewable power renewable-based gases (including “green” hydrogen) sustainable bioenergy use and the direct use of solar and geothermal heat.



This report developed jointly by the International Renewable Energy Agency (IRENA) the International Energy Agency (IEA) and the Renewable Energy Policy Network for the 21st Century (REN21) outlines the infrastructure and policies needed with each transition pathway. This edition focused on renewable-based heating and cooling follows a broader initial study Renewable Energy Policies in a Time of Transition (IRENA IEA and REN21 2018).



The shift to renewables for heating and cooling requires enabling infrastructure (e.g. gas grids district heating and cooling networks) as well as various combinations of deployment integrating and enabling policies. The policy framework can demonstrate a country’s commitment to the energy transition level the playing field with fossil fuels and create the necessary enabling conditions to attract investments.



Along with highlighting country experiences and best practices the study identifies barriers and highlights policy options for renewable heating and cooling.



Key recommendations include:

• Setting specific targets and developing an integrated long-term plan for the decarbonisation of heating and cooling in all end-uses including buildings industry and cooking and productive uses in areas with limited energy access.
• Creating a level playing field by phasing out fossil-fuel subsidies and introducing other fiscal policies to internalise environmental and socio-economic costs.
• Combining the electrification of heating and cooling with increasingly cost-competitive renewable power generation scaling up solar and wind use and boosting system flexibility via energy storage heat pumps and efficient electric appliances.
• Harnessing existing gas networks to accommodate renewable gases such as biogas and green hydrogen.
• Introducing standards certification and testing policies to promote the sustainable use of biomass combining efficient systems and bioenergy solutions such as pellets briquettes bioethanol or anaerobic digestion.
• Reducing investment risks for geothermal exploration and scaling up direct use of geothermal heat.
• Improving district heating and cooling networks through energy efficiency measures and the integration of low-temperature solar thermal geothermal and other renewable-based heat sources.
• Supporting clean cooking and introducing renewable-based food drying in areas lacking energy access with a combination of financing mechanisms capacity building and quality standards aimed at improving livelihoods and maximising socio-economic benefits.