Croatia

In this age of human civilization there is a need for more efficient cleaner and renewable energy as opposed to that provided by nonrenewable sources such as coal and oil. In this sense hydrogen energy has been proven to be a better choice. In this paper a portable graphite crucible metal smelting furnace was used to prepare ten multi-element aluminum alloy ingots with different components. The microstructure and phase composition of the ingots and reaction products were analyzed by X-ray diffraction (XRD) scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The reaction was carried out in a constant temperature water bath furnace at 60°C and the hydrogen production performance of the multi-element aluminum alloys in different proportions was compared by the drainage gas collection method. The experimental results show that the as-cast microstructure of Al–Ga–In–Sn aluminum alloy is composed of a solid solution of Al and part of Ga and a second phase of In3Sn. After the hydrolysis reaction the products were dried at 150°C and then analyzed by XRD. The products were mainly composed of AlOOH and In3Sn. Alloys with different compositions react at the same hydrolysis temperature and the hydrogen production performance is related to the ratio of low-melting-point metal elements. By comparing two different ratios of Ga–In–Sn (GIS) the hydrogen production capacity and production rate when the ratio is 6:3:1 are generally higher than those when the ratio is 7:2:1. The second phase content affects the hydrogen production performance.

Fuel starvation is a major cause of anode corrosion in low temperature polymer electrolyte fuel cells. The fuel cell start-up is a critical step as hydrogen may not yet be evenly distributed in the active area leading to local starvation. The present work investigates the hydrogen distribution and risk for starvation during start-up and after nitrogen purge by extending an existing computational fluid dynamic model to capture transient behavior. The results of the numerical model are compared with detailed experimental analysis on a 25 cm2 triple serpentine flow field with good agreement in all aspects and a required time step size of 1 s. This is two to three orders of magnitude larger than the time steps used by other works resulting in reasonably quick calculation times (e.g. 3 min calculation time for 1 s of experimental testing time using a 2 million element mesh).

Based on the energy strategy of the Republic of Kosovo from 2017–2026 the increase in the integration of renewable energy sources (RES) in the national energy system was aimed at. However the hydrogen potential was not mentioned. In this work a roadmap toward the introduction of hydrogen in the energy system with the main focus on the transportation sector through three phases is proposed. In the first phase (until 2024) the integration of hydrogen in the transportation sector produced via water electrolysis from the grid electricity with the increase of up to a 0.5% share of fuel cell vehicles is intended. In the second phase (2025–2030) the hydrogen integration in the transportation sector is increased by including renewable hydrogen where the share of fuel cell electric vehicles (FCEVs) will be around 4% while in the third phase (2031–2050) around an 8% share of FCEVs in the transportation was planned. The technical and environmental analysis of hydrogen integration is focused on both the impact of hydrogen in the decarbonization of the transportation sector and the energy system. To model the Kosovo energy system the hourly deterministic EnergyPLAN model was used. This research describes the methodology based on EnergyPLAN modeling that can be used for any energy system to provide a clear path of RES and hydrogen implementation needed to achieve a zero-emission goal which was also set by various other countries. The predicted decrease in GHG emissions from 8 Mt in the referent year 2017 amounts to 7 Mt at the end of the first phase 2024 and 4.4 Mt at the end of the second phase 2030 to achieve 0 Mt by 2050. In order to achieve it the required amount of hydrogen by 2030 resulted in 31840 kg/year and by 2050 around 89731 kg/year. The results show the concrete impact of hydrogen on transport system stabilization and its influence on greenhouse gas (GHG) emissions reduction.

With the restructuring of the power system household-level end users are becoming more prominent participants by integrating renewable energy sources and smart devices and becoming flexible prosumers. The use of microgrids is a way of aggregating local end users into a single entity and catering for the consumption needs of shareholders. Various microgrid architectures are the result of the local energy community following different decarbonisation strategies and are frequently not optimised in terms of size technology or other influential factors for energy systems. This paper discusses the operational and planning aspects of three different microgrid setups looking at them as individual market participants within a local electricity market. This kind of implementation enables mutual trade between microgrids without additional charges where they can provide flexibility and balance for one another. The developed models take into account multiple uncertainties arising from photovoltaic production day-ahead electricity prices and electricity load. A total number of nine case studies and sensitivity analyses are presented from daily operation to the annual planning perspective. The systematic study of different microgrid setups operational principles/goals and cooperation mechanisms provides a clear understanding of operational and planning benefits: the electrification strategy of decarbonising microgrids outperforms gas and hydrogen technologies by a significant margin. The value of coupling different types of multi-energy microgrids with the goal of joint market participation was not proven to be better on a yearly level compared to the operation of same technology-type microgrids. Additional analyses focus on introducing distribution and transmission fees to an MG cooperation model and allow us to come to the conclusion of there being a minor impact on the overall operation.

The application of newly available technologies in the green maritime sector is difficult due to conflicting requirements and the inter-relation of different ecological technological and economical parameters. The governments incentivize radical reductions in harmful emissions as an overall priority. If the politics do not change the continuous implementation of stricter government regulations for reducing emissions will eventually result in the mandatory use of what we currently consider alternative fuels. Immediate application of radically different strategies would significantly increase the economic costs of maritime transport thus jeopardizing its greatest benefit: the transport of massive quantities of freight at the lowest cost. Increased maritime transport costs would immediately disrupt the global economy as seen recently during the COVID-19 pandemic. For this reason the industry has shifted towards a gradual decrease in emissions through the implementation of “better” transitional solutions until alternative fuels eventually become low-cost fuels. Since this topic is very broad and interdisciplinary our systematic overview gives insight into the state-of-the-art available technologies in green maritime transport with a focus on the following subjects: (i) alternative fuels; (ii) hybrid propulsion systems and hydrogen technologies; (iii) the benefits of digitalization in the maritime sector aimed at increasing vessel efficiency; (iv) hull drag reduction technologies; and (v) carbon capture technologies. This paper outlines the challenges advantages and disadvantages of their implementation. The results of this analysis elucidate the current technologies’ readiness levels and their expected development over the coming years.

Contrary to microgrids (MGs) for which grid code or legislative support are lacking in the majority of cases energy communities (ECs) are one of the cornerstones of the energy transition backed up by the EU’s regulatory framework. The main difference is that unlike MGs ECs grow and develop organically through citizen involvement and investments in the existing low-voltage (LV) distribution networks. They are not planned and built from scratch as closed distribution systems that are independent of distribution system operator plans as assumed in the existing literature. An additional benefit of ECs could be the ability to transition into island mode contributing to the resilience of power networks. To this end this paper proposes a three-stage framework for analyzing the islanding capabilities of ECs. The framework is utilized to comprehensively assess and compare the islanding capabilities of ECs whose organic development is based upon three potential energy vectors: electricity gas and hydrogen. Detailed dynamic simulations clearly show that only fully electrified ECs inherently have adequate islanding capabilities without the need for curtailment or additional investments.

This paper reviews state-of-the-art developments in hydrogen energy systems which integrate fuel cells with metal hydride-based hydrogen storage. The 187 reference papers included in this review provide an overview of all major publications in the field as well as recent work by several of the authors of the review. The review contains four parts. The first part gives an overview of the existing types of fuel cells and outlines the potential of using metal hydride stores as a source of hydrogen fuel. The second part of the review considers the suitability and optimisation of different metal hydrides based on their energy efficient thermal integration with fuel cells. The performances of metal hydrides are considered from the viewpoint of the reversible heat driven interaction of the metal hydrides with gaseous H2. Efficiencies of hydrogen and heat exchange in hydrogen stores to control H2 charge/discharge flow rates are the focus of the third section of the review and are considered together with metal hydride – fuel cell system integration issues and the corresponding engineering solutions. Finally the last section of the review describes specific hydrogen-fuelled systems presented in the available reference data.

This paper presents a new economic profitability model for a power-to-gas plant producing green hydrogen at the site of an existing wind power plant injected into the gas grid. The model is based on a 42 MW wind power plant for which an optimal electrolyzer of 10 MW was calculated based on the 2500 equivalent full load hours per year and the projection of electricity prices. The model is calculated on an hourly level for all variables of the 25 years of the model. With the calculated breakeven electricity price of 74.23 EUR/MWh and the price of green hydrogen production of 99.44 EUR/MWh in 2045 the wind power plant would produce 22410 MWh of green hydrogen from 31% of its total electricity production. Green hydrogen injected into the gas system would reduce the level of CO2 emissions by 4482 tons. However with the projected prices of natural gas and electricity the wind power plant would cover only 20% of the income generated by the electricity delivered to the grid by producing green hydrogen. By calculating different scenarios in the model the authors concluded that the introduction of a premium subsidy model is necessary to accelerate deployment of electrolyzers at the site of an existing wind power plant in order to increase the wind farm profitability.