Germany

Climate and energy policies are tools used to steer the development of a sustainable economy supplied by equally sustainable energy systems. End-users should plan their investments accounting for future policies such as incentives for system-oriented consumption emission prices and hydrogen economy to ensure long-term competitiveness. In this work the utilization of variable renewable energy and flexibility potentials in a case study of an an aggregate industry is investigated. An energy concept considering PV and battery expansion flexible production fuel cell electric trucks (FCEV) and hydrogen production is proposed and analysed under expected techno-economic conditions and policies of 2030 using an energy system optimization model. Under this concept total costs and emissions are reduced by 14% and 70% respectively compared to the business-as-usual system. The main benefit of PV investment is the lowered electricity procurement. Flexibility from schedule manufacturing and hydrogen production increases not only the self-consumption of PV generation from 51% to 80% but also the optimal PV capacity by 41%. Despite the expected cost reduction and efficiency improvement FCEV is still not competitive to diesel trucks due to higher investment and fuel prices i.e. its adoption increases the costs by 8%. However this is resolved when hydrogen can be produced from own surplus electricity generation. Our findings reveal synergistic effects between different potentials and the importance of enabling local business models e.g. regional hydrogen production and storage services. The SWOT analysis of the proposed concept shows that the pursuit of sustainability via new technologies entails new opportunities and risks. Lastly end-users and policymakers are advised to plan their investments and supports towards integration of multiple application consumption sectors and infrastructure.

Germany’s energy transition known as ‘Energiewende’ was always very progressive. However it came technically to a halt at the question of large-scale seasonal energy storage for wind and solar which was not available. At the end of the 2000s we combined our knowledge of both electrical and process engineering imitated nature by copying photosynthesis and developed Power-to-Gas by combining water electrolysis with CO2 -methanation to convert water and CO2 together with wind and solar power to synthetic natural gas. Storing green energy by coupling the electricity with the gas sector using its vast TWh-scale storage facility was the solution for the biggest energy problem of our time. This was the first concept that created the term ‘sector coupling’ or ‘sectoral integration’. We first implemented demo sites presented our work in research industry and ministries and applied it in many macroeconomic studies. It was an initial idea that inspired others to rethink electricity as well as eFuels as an energy source and energy carrier. We developed the concept further to include Power-to-Liquid Power-to-Chemicals and other ways to ‘convert’ electricity into molecules and climate-neutral feedstocks and named it ‘Power-to-X’ at the beginning of the 2010s.

Since the 1970s hydrogen has been considered as a possible energy carrier for the storage of renewable energy. The main focus has been on addressing the ultimate challenge: developing an environmentally friendly successor for gasoline. This very ambitious goal has not yet been fully reached as discussed in this review but a range of new lightweight hydrogen-containing materials has been discovered with fascinating properties. State-of-the-art and future perspectives for hydrogen-containing solids will be discussed with a focus on metal borohydrides which reveal significant structural flexibility and may have a range of new interesting properties combined with very high hydrogen densities.

Tensile and fatigue tests were performed on an AA2198 aluminum alloy in the T851 condition in ambient air and liquid hydrogen (LH2). All fatigue tests were performed under load control at a frequency of 20 Hz and a stress ratio of R=0.1. The Gecks-Och-Function [1] was fitted on the measured cyclic lifetimes.<br/><br/>The tensile strength in LH2 was measured to be 46 % higher compared to the value determined at ambient conditions and the fatigue limit was increased by approximately 60 %. Both S-N curves show a distinct S-shape but also significant differences. Under LH2 environment the transition from LCF- to HCF-region as well as the transition to the fatigue limit is shifted to higher cyclic lifetimes compared to ambient test results. The investigation of the crack surfaces showed distinct differences between ambient and LH2 conditions. These observed differences are important factors in the fatigue behavior change.

The ultrafine-grained (UFG) duplex microstructure of medium-Mn steel consists of a considerable amount of austenite and ferrite/martensite achieving an extraordinary balance of mechanical properties and alloying cost. In the present work two heat treatment routes were performed on a cold-rolled medium-Mn steel Fe-12Mn-3Al-0.05C (wt.%) to achieve comparable mechanical properties with different microstructural morphologies. One heat treatment was merely austenite-reverted-transformation (ART) annealing and the other one was a successive combination of austenitization (AUS) and ART annealing. The distinct responses to hydrogen ingression were characterized and discussed. The UFG martensite colonies produced by the AUS + ART process were found to be detrimental to ductility regardless of the amount of hydrogen which is likely attributed to the reduced lattice bonding strength according to the H-enhanced decohesion (HEDE) mechanism. With an increase in the hydrogen amount the mixed microstructure (granular + lamellar) in the ART specimen revealed a clear embrittlement transition with the possible contribution of HEDE and H-enhanced localized plasticity (HELP) mechanisms.

Our contribution demonstrates that hydrogen storage in stationary Liquid Organic Hydrogen Carrier (LOHC) systems becomes much simpler and significantly more efficient if both the LOHC hydrogenation and the LOHC dehydrogenation reaction are carried out in the same reactor using the same catalyst. The finding that the typical dehydrogenation catalyst for hydrogen release from perhydro dibenzyltoluene (H18-DBT) Pt on alumina turns into a highly active and very selective dibenzyltoluene hydrogenation catalyst at temperatures above 220 °C paves the way for our new hydrogen storage concept. Herein hydrogenation of H0-DBT and dehydrogenation of H18-DBT is carried out at the same elevated temperature between 290 and 310 °C with hydrogen pressure being the only variable for shifting the equilibrium between hydrogen loading and release. We demonstrate that the heat of hydrogenation can be provided at a temperature level suitable for effective dehydrogenation catalysis. Combined with a heat storage device of appropriate capacity or a high pressure steam system this heat could be used for dehydrogenation.

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.

The chemical and petrochemical sector relies on fossil fuels and feedstocks and is a major source of carbon dioxide (CO2 ) emissions. The techno-economic potential of 20 decarbonisation options is assessed. While previous analyses focus on the production processes this analysis covers the full product life cycle CO2 emissions. The analysis elaborates the carbon accounting complexity that results from the non-energy use of fossil fuels and highlights the importance of strategies that consider the carbon stored in synthetic organic products—an aspect that warrants more attention in long-term energy scenarios and strategies. Average mitigation costs in the sector would amount to 64 United States dollars (USD) per tonne of CO2 for full decarbonisation in 2050. The rapidly declining renewables cost is one main cause for this low-cost estimate. Renewable energy supply solutions in combination with electrification account for 40% of total emissions reductions. Annual biomass use grows to 1.3 gigatonnes; green hydrogen electrolyser capacity grows to 2435 gigawatts and recycling rates increase six-fold while product demand is reduced by a third compared to the reference case. CO2 capture storage and use equals 30% of the total decarbonisation effort (1.49 gigatonnes per year) where about one-third of the captured CO2 is of biogenic origin. Circular economy concepts including recycling account for 16% while energy efficiency accounts for 12% of the decarbonisation needed. Achieving full decarbonisation in this sector will increase energy and feedstock costs by more than 35%. The analysis shows the importance of renewables-based solutions accounting for more than half of the total emissions reduction potential which was higher than previous estimates.

In the near future the challenges to reduce the economic and social dependency on fossil fuels must be faced increasingly. A sustainable and efficient energy supply based on renewable energies enables large-scale applications of electro-fuels for e.g. the transport sector. The high gravimetric energy density makes liquefied hydrogen a reasonable candidate for energy storage in a light-weight application such as aviation. Current aircraft structures are designed to accommodate jet fuel and gas turbines allowing a limited retrofitting only. New designs such as the blended-wing-body enable a more flexible integration of new storage technologies and energy converters e.g. cryogenic hydrogen tanks and fuel cells. Against this background a tank-design model is formulated which considers geometrical mechanical and thermal aspects as well as specific mission profiles while considering a power supply by a fuel cell. This design approach enables the determination of required tank mass and storage density respectively. A new evaluation value is defined including the vented hydrogen mass throughout the flight enabling more transparent insights on mass shares. Subsequently a systematic approach in tank partitioning leads to associated compromises regarding the tank weight. The analysis shows that cryogenic hydrogen tanks are highly competitive with kerosene tanks in terms of overall mass which is further improved by the use of a fuel cell.

Underground hydrogen storage is a potential way to balance seasonal fluctuations in energy production from renewable energies. The risks of hydrogen storage in depleted gas fields include the conversion of hydrogen to CH4(g) and H2S(g) due to microbial activity gas–water–rock interactions in the reservoir and cap rock which are connected with porosity changes and the loss of aqueous hydrogen by diffusion through the cap rock brine. These risks lead to loss of hydrogen and thus to a loss of energy. A hydrogeochemical modeling approach is developed to analyze these risks and to understand the basic hydrogeochemical mechanisms of hydrogen storage over storage times at the reservoir scale. The one-dimensional diffusive mass transport model is based on equilibrium reactions for gas–water–rock interactions and kinetic reactions for sulfate reduction and methanogenesis. The modeling code is PHREEQC (pH-REdox-EQuilibrium written in the C programming language). The parameters that influence the hydrogen loss are identified. Crucial parameters are the amount of available electron acceptors the storage time and the kinetic rate constants. Hydrogen storage causes a slight decrease in porosity of the reservoir rock. Loss of aqueous hydrogen by diffusion is minimal. A wide range of conditions for optimized hydrogen storage in depleted gas fields is identified.