Publications

Hydrogen generated during core meltdown accidents in nuclear reactors can cause serious threat to the structural integrity of the containment and safe operation of nuclear power plants. The study of hydrogen release and mixing within the containments is an important area of safety research as hydrogen released during such accidents in nuclear power plants can lead to hydrogen explosions and catastrophic consequences. A small scale experimental setup called the AERB-IIT Madras Hydrogen Mixing Studies (AIHMS) facility is setup at IIT Madras to study the distribution of hydrogen subsequent to release as a jet followed by its response to various wall thermal conditions. The present paper gives details of the design fabrication and instrumentation of the AIHMS facility and a comparison of features of the facility with respect to other facilities existing for hydrogen mitigation studies. Then it gives details of the experiments conducted and the results of the preliminary experiments on concentration build-up as a result of injection of gases (air and helium) and effect of thermally induced natural convection on gas mixing performed in this experimental facility.

The hourly operation of Thermal Hydrogen electricity markets is modelled. The economic values for all applicable chemical commodities are quantified (syngas ammonia methanol and oxygen) and an hourly electricity model is constructed to mimic the dispatch of key technologies: bi-directional power plants dual-fuel heating systems and plug-in fuel-cell hybrid electric vehicles. The operation of key technologies determines hourly electricity prices and an optimization model adjusts the capacity to minimize electricity prices yet allow all generators to recover costs. We examine 12 cost scenarios for renewables nuclear and natural gas; the results demonstrate emissionsfree ‘energy-only’ electricity markets whose supply is largely dominated by renewables. The economic outcome is made possible in part by seizing the full supply-chain value from electrolysis (both hydrogen and oxygen) which allows an increased willingness to pay for (renewable) electricity. The wholesale electricity prices average $25–$45/ MWh or just slightly higher than the assumed levelized cost of renewable energy. This implies very competitive electricity prices particularly given the lack of need for ‘scarcity’ pricing capacity markets dedicated electricity storage or underutilized electric transmission and distribution capacity.

Global warming and fossil fuel depletion have necessitated alternative sources of energy. Biomass is a promising fuel source because it is renewable and can be carbon negative even without carbon capture and storage. This study considers biomass as a clean renewable source for transportation fuels. An Aspen Plus process simulation model was built of a biomass gasification biorefinery with Fischer-Tropsch (FT) synthesis of liquid fuels. A GaBi life cycle assessment model was also built to determine the environmental impacts using a cradle-to-grave approach. Three different product pathways were considered: Fischer-Tropsch synthetic diesel hydrogen and electricity. An offgas autothermal reformer with a recycle loop was used to increase FT product yield. Different configurations and combinations of biorefinery products are considered. The thermal efficiency and cost of production of the FT liquid fuels are analyzed using the Aspen Plus process model. The greenhouse gas emissions profitability and mileage per kg biomass were compared. The mileage traveled per kilogram biomass was calculated using modern (2019-2021) diesel electric and hydrogen fuel cell vehicles. The overall thermal efficiency was found to be between 20-41% for FT fuels production between 58-61% for hydrogen production and around 25-26% for electricity production for this biorefinery. The lowest production costs were found to be $3.171/gal of FT diesel ($24.304/GJ) $1.860/kg of H2 ($15.779/GJ) and 13.332¢/kWh for electricity ($37.034/GJ). All configurations except one had net negative carbon emissions over the life cycle of the biomass. This is because carbon is absorbed in the trees initially and some of the carbon is sequestered in ash and unconverted char from the gasification process furthermore co-producing electricity while making transportation fuel offsets even more carbon emissions. Compared to current market rates for diesel hydrogen and electricity the most profitable biorefinery product is shown to be hydrogen while also having net negative carbon emissions. FT diesel can also be profitable but with a slimmer profit margin (not considering government credits) and still having net negative carbon emissions. However our biorefinery could not compete with current commercial electricity prices in the US. As oil hydrogen and electricity prices continue to change the economics of the biorefinery and the choice product will change as well. For our current biorefinery model hydrogen seems to be the most promising product choice for profit while staying carbon negative while FT diesel is the best choice for sequestering the most carbon and still being profitable. All code and data are given.

For the general public to use hydrogen as a vehicle fuel they must be able to handle hydrogen with the same degree of confidence as conventional liquid and gaseous fuels. The hazards associated with jet releases from accidental leaks in a vehicle-refuelling environment must be considered if hydrogen is stored and used as a high-pressure gas since a jet release can result in a fire or explosion. This paper describes the work done by us in modelling some of the consequences of accidental releases of hydrogen implemented in our Fire Explosion Release Dispersion (FRED) software. The new dispersion model is validated against experimental data available in the open literature. The model predictions of hydrogen gas concentration as a function of distance are in good agreement with experiments. In addition FRED has been used to model the consequence of the bursting of a vessel containing compressed hydrogen. The results obtained from FRED i.e. overpressure as a function of distance match well in comparison to experiments. Overall it is concluded that FRED can model the consequences of an accidental release of hydrogen and the blast waves generated from bursting of vessel containing compressed hydrogen

A palladium (Pd) doped mesoporous titanium dioxide (TiO2) photocatalyst was used to produce hydrogen (H2) via water splitting under both near‐UV and visible light. Experiments were carried out in the Photo‐CREC Water‐II Reactor (PCW‐II) using a 0.25 wt% Pd‐TiO2 photocatalyst initial pH = 4 and 2.0 v/v% ethanol as an organic scavenger. After 6 h of near‐UV irradiation this photocatalyst yielded 113 cm3 STP of hydrogen (H2). Furthermore after 1 h of near‐UV photoreduc‐ tion followed by 5 h of visible light the 0.25 wt% Pd‐TiO2 photocatalyst yielded 5.25 cm3 STP of H2. The same photocatalyst photoreduced for 24 h under near‐UV and subsequently exposed to 5 h of visible light yielded 29 cm3 STP of H2. It was observed that the promoted redox reactions led to the production of hydrogen and by‐products such as methane ethane ethylene acetaldehyde carbon monoxide carbon dioxide and hydrogen peroxide. These redox reactions could be modeled using an “in series‐parallel” reaction network and Langmuir Hinshelwood based kinetics. The proposed rate equations were validated using statistical analysis for the experimental data and calculated kinetic parameters. Furthermore Quantum yields (QYୌ%) based on the H produced were also established at promising levels: (a) 34.8% under near‐UV light and 1.00 g L−1 photocatalyst concen‐ tration; (b) 8.8% under visible light and 0.15 g L−1. photocatalyst concentration following 24 h of near‐UV.

In August 2020 Germany and Ukraine launched an energy partnership that includes the development of a hydrogen economy. Ukraine has vast renewable energy resources for “green” hydrogen production and a gas transmission system for transportation instead of Russian natural gas. Based on estimates by Hydrogen Europe Ukraine can install 8000 MW of total electrolyser capacity by 2030. For these reasons Ukraine is among the EU’s priority partners concerning clean hydrogen according to the EU Hydrogen strategy. Germany plans to reach climate neutrality by 2045 and “green” hydrogen plays an important role in achieving this target. However according to the National Hydrogen Strategy of Germany local production of “green” hydrogen will not cover all internal demand in Germany. For this reason Germany considers importing hydrogen from Ukraine. To govern the production and import of “green” hydrogen Germany and Ukraine shall introduce legal regulations the initial analysis of which is covered in this study. Based on observation and comparison this paper presents and compares approaches while exploring the current stage and further perspectives for legal regulation of hydrogen in Germany and Ukraine. This research identifies opportunities in hydrogen production to improve the flexibility of the Ukrainian power system. This is an important issue for Ukrainian energy security. In the meantime hydrogen can be a driver for decarbonisation according to the initial plans of Germany and it may also have positive impact on the operation of Germany’s energy system with a high share of renewables.

Radiative heat fluxes from small to medium-scale hydrogen jet flames (<10 m) compare favorably to theoretical predictions provided the product species thermal emittance and optical flame thickness are corrected for. However recent heat flux measurements from two large-scale horizontally orientated hydrogen flames (17.4 and 45.9 m respectively) revealed that current methods underpredicted the flame radiant fraction by 40% or more. Newly developed weighted source flame radiation models have demonstrated substantial improvement in the heat flux predictions particularly in the near-field and allow for a sensible way to correct potential ground surface reflective irradiance. These updated methods are still constrained by the fact that the flame is assumed to have a linear trajectory despite buoyancy effects that can result in significant flame deformation. The current paper discusses a method to predict flame centerline trajectories via a one-dimensional flame integral model which enables optimized placement of source emitters for weighted multi-source heat flux prediction methods. Flame shape prediction from choked releases was evaluated against flame envelope imaging and found to depend heavily on the notional nozzle model formulation used to compute the density weighted effective nozzle diameter. Nonetheless substantial improvement in the prediction of downstream radiative heat flux values occurred when emitter placement was corrected by the flame integral model regardless of the notional nozzle model formulation used.

Hydrogen embrittlement (HE) together with the hydrogen transport behaviour in hydrogen-charged type 304 stainless steel was investigated by combined tension and outgassing experiments. The hydrogen release rate and HE of hydrogen-charged 304 specimens increase with the hydrogen pressure for hydrogen-charging (or hydrogen content) and almost no HE is observed below the hydrogen content of 8.5 mass ppm. Baking at 433 K for 48 h can eliminate HE of the hydrogen-charged 304 specimen while removing the surface layer will restore HE which indicates that hydrogen in the surface layer plays the primary role in HE. Scanning electron microscopy (SEM) and scanning tunnel microscopy (STM) observations show that particles attributed to the strain-induced α′ martensite formation break away from the matrix and the small holes form during deformation on the specimen surface. With increasing strain the connection among small holes along {111} slip planes of austenite will cause crack initiation on the surface and then the hydrogen induced crack propagates from the surface to interior.

Energy–structure–function (ESF) maps can aid the targeted discovery of porous molecular crystals by predicting the stable crystalline arrangements along with their functions of interest. Here we compute ESF maps for a series of rigid molecules that comprise either a triptycene or a spiro-biphenyl core functionalized with six different hydrogen-bonding moieties. We show that the positioning of the hydrogen-bonding sites as well as their number has a profound influence on the shape of the resulting ESF maps revealing promising structure–function spaces for future experiments. We also demonstrate a simple and general approach to representing and inspecting the high-dimensional data of an ESF map enabling an efficient navigation of the ESF data to identify ‘landmark’ structures that are energetically favourable or functionally interesting. This is a step toward the automated analysis of ESF maps an important goal for closed-loop autonomous searches for molecular crystals with useful functions.

In order to achieve a high level of safety while using hydrogen as a vehicle fuel the possible hazards must be estimated. Especially hydrogen release tests with defined ignition represent a very important way to characterize the basics of hydrogen combustion in a potential accident. So ICT participated on a hydrogen jet release campaign at HSL (Buxton) in 2008 to deploy their measurement techniques and evaluation methods to visualize jets ignition and subsequent flames. The following paper shows the application of high speed cinematography in combination with image processing techniques the Background Oriented Schlieren (BOS) and a difference method to visualize the shape of hydrogen jet. In addition these methods were also used to observe ignition and combustion zone after defined initiation. In addition the combustion zone was recorded by a fast spectral radiometer and a highspeed-IR-camera. The IR-camera was synchronized with a rotating filter wheel to generate four different motion pictures at 100Hz each on a defined spectral range. The results of this preliminary evaluation provide some detailed information that might be used for improving model predictions.