Ireland

The importance of the energy transition and the role of green hydrogen in facilitating this transition cannot be denied. Therefore it is crucial to pay close attention to and thoroughly understand hydrogen storage which is a critical aspect of the hydrogen supply chain. In this comprehensive review paper we have undertaken the task of categorising and evaluating various hydrogen storage technologies across three different scales. These scales include small-scale and laboratory-based methods such as metal-based hydrides physical adsorbents and liquid organic hydrogen carriers. Also we explore medium and large-scale approaches like compressed gaseous hydrogen liquid cryogenic hydrogen and cryocompressed hydrogen. Lastly we delve into very large-scale options such as salt caverns aquifers depleted gas/oil reservoirs abandoned mines and hard rock caverns. We have thoroughly examined each storage technology from technical and maturity perspectives as well as considering its techno-economic viability. It is worth noting that development has been ongoing for each storage mechanism; however numerous technical and economic challenges persist in most areas. Particularly the cost per kilogramme of hydrogen for most current technologies demands careful consideration. It is recommended that small-scale hydrogen storage technologies such as metal hydrides (e.g. MgH2 LiBH4) need ongoing research to enhance their performance. Physical adsorbents have limited capacity except for activated carbon. Some liquid organic hydrogen carriers (LCOHs) are suitable for medium-scale storage in the near term. Ammonia-borane (AB) with its high gravimetric and volumetric properties is a promising choice for medium-scale storage pending effective dehydrogenation. It shows potential as a hydrogen carrier due to its high storage capacity stability and solubility surpassing DOE targets for storage capabilities. Medium-scale storage utilising compressed gas cylinders and advancements in liquefied and cryocompressed hydrogen storage requires cost reduction measures and a strategic supply chain. Large-scale storage options include salt caverns aquifers and depleted gas/oil reservoirs with salt caverns offering pure hydrogen need further technoeconomic analysis and deployment projects to mature but storage costs are reasonable ranging mostly from €0.25/kg to €1.5/kg for location specific large-scale options.

As the global market develops for green hydrogen and ammonia derived from renewable electricity the bulk transmission of hydrogen and ammonia from production areas to demand-intensive consumption areas will increase. Repurposing existing infrastructure may be economically and technically feasible but increases in supply and demand will necessitate new developments. Bulk transmission of hydrogen and ammonia may be effected by dedicated pipelines or liquefied fuel tankers. Transmission of electricity using HVDC lines to directly power electrolysers producing hydrogen near the demand markets is another option. This paper presents and validates detailed cost models for newly-built dedicated offshore transmission methods for green hydrogen and ammonia and carries out a techno-economic comparison over a range of transmission distances and production volumes. New pipelines are economical for short distances while new HVDC interconnectors are suited to medium-large transmission capacities over a wide range of distances and liquefied gas tankers are best for long distances.

Many countries especially those with a high energy demand but insufficient renewable resources are currently investigating the role that imported low carbon hydrogen may play in meeting future energy requirements and emission reduction targets. A future hydrogen economy is uncertain and predicated on reduced price of hydrogen delivered to customers. Current hydrogen production steam reforming of natural gas or coal gasification is co-located to its end-use as a chemical feedstock. Large-scale multi-source value chains of hydrogen needed to support its use for energy are still at concept phase. This research investigates the combination of technical and economic factors which will determine the viability and competitiveness of two competing large scale renewable hydrogen value chains via ammonia and liquid hydrogen. Using a techno-economic model an evaluation of whether green hydrogen exports to Germany from countries with low-cost renewable electricity production but high-costs of storage distribution and transport will be economically competitive with domestic renewable hydrogen production is conducted. The model developed in Python calculates costs and energy losses for each step in the value chain. This includes production from an optimised combination of solar and/or wind generation capacity optimised storage requirements conversion to ammonia or liquid hydrogen distribution shipping and reconversion. The model can easily be applied to any scenario by changing the inputs and was used to compare export from Chile Namibia and Morocco with production in Germany using a 1 GW electrolyser and 2030 cost scenario in each case.

The use of aluminum-based products is widespread and growing particularly in industries such as automotive food packaging and construction. Obtaining aluminum is expensive and energy-intensive making the recycling of existing products essential for economic and environmental viability. This work explores the potential of using green hydrogen as a replacement for natural gas in the smelting and refining furnaces in aluminum recycling facilities. The adoption of green hydrogen has the potential to curtail approximately 4.54 Ktons/year of CO2 emissions rendering it a sustainable and economically advantageous solution. The work evaluates the economic viability of a case study through assessing the Net Present Value (NPV) and the Internal Rate of Return (IRR). Furthermore it is employed single- and multi-parameter sensitivity analyses to obtain insight on the most relevant conditions to achieve economic viability. Results demonstrate that integrating on-site green hydrogen generation yields a favorable NPV of €57370 an IRR of 9.83% and a 19.63-year payback period. The primary factors influencing NPV are the initial electricity consumption stack and the H2 price.

The development of green hydrogen can provide a welcome boost in energy security particularly for island nations that may be reliant on energy imports or intermittent renewables as part of their energy transition. However the expansion of a green hydrogen economy may have social environmental and economic impacts on tourism-reliant islands which may not be accounted for using typical market assessments. In this study focus groups and an online choice experiment survey are conducted with recent international tourists to Mallorca Spain to elicit preferences for green hydrogen infrastructure including the visual and biodiversity impacts potential for export and the value for the provision of additional local and tourism benefits. The results indicate generally positive attitudes to the development of green hydrogen in Mallorca however respondents indicate significant disutility associated with high visual impact of green hydrogen infrastructure with the exception of respondents that have previous experience with hydrogen transport. In general respondents favour policies that do not negatively impact biodiversity value restrictions on exports to enhance energy security on the island and are willing to pay to support green hydrogen development in Mallorca which provides benefits to tourism and local residents.