Bulgaria

A viable hydrogen economy has thus far been hampered by the lack of an inexpensive and convenient hydrogen storage solution meeting all requirements especially in the areas of long hauls and delivery infrastructure. Current approaches require high pressure and/or complex heat management systems to achieve acceptable storage densities. Herein we present a manganese hydride molecular sieve that can be readily synthesized from inexpensive precursors and demonstrates a reversible excess adsorption performance of 10.5 wt% and 197 kgH₂ m^-3 at 120 bar at ambient temperature with no loss of activity after 54 cycles. Inelastic neutron scattering and computational studies confirm Kubas binding as the principal mechanism. The thermodynamically neutral adsorption process allows for a simple system without the need for heat management using moderate pressure as a toggle. A storage material with these properties will allow the DOE system targets for storage and delivery to be achieved providing a practical alternative to incumbents such as 700 bar systems which generally provide volumetric storage values of 40 kgH₂ m^-3 or less while retaining advantages over batteries such as fill time and energy density. Reasonable estimates for production costs and loss of performance due to system implementation project total energy storage costs roughly 5 times cheaper than those for 700 bar tanks potentially opening doors for increased adoption of hydrogen as an energy vector.

A promising method of energy storage is the combination of hydrogen and compressed-air energy storage (CAES) systems. CAES systems are divided into diabatic adiabatic and isothermal cycles. In the diabatic cycle thermal energy after air compression is discharged into the environment and the scheme implies the use of organic fuel. Taking into account the prospects of the decarbonization of the energy industry it is advisable to replace natural gas in the diabatic CAES scheme with hydrogen obtained by electrolysis using power-to-gas technology. In this article the SENECA-1A project is considered as a high-power hybrid unit using hydrogen instead of natural gas. The results show that while keeping the 214 MW turbines powered the transition to hydrogen reduces carbon dioxide emissions from 8.8 to 0.0 kg/s while the formation of water vapor will increase from 17.6 to 27.4 kg/s. It is shown that the adiabatic CAES SENECA-1A mode compared to the diabatic has 0.0 carbon dioxide and water vapor emission with relatively higher efficiency (71.5 vs. 62.1%). At the same time the main advantage of the diabatic CAES is the possibility to produce more power in the turbine block (214 vs. 131.6 MW) having fewer capital costs. Thus choosing the technology is a subject of complex technical economic and ecological study.

The article presents the results of an experimental study on the influence of hydrogen as gaseous fuel on the combustion process parameters of a single-cylinder diesel engine operating in dual-fuel mode. The study is conducted at an average engine speed of n = 2000 min⁻ 1 four engine load levels and two different diesel fuel injection timing angles. Indicator diagrams are recorded for each operating mode at varying hydrogen mass fractions in the total fuel supplied to the engine. The data from the indicator diagrams are processed using a developed software that enables the determination of combustion process parameters. The analysis of the experimental results focuses on changes in cylinder temperature the coefficients of total and active heat release the rate of heat release the duration of the combustion process phases and other parameters as a function of the hydrogen mass fraction in the total fuel mixture.

Hydrogen is a prospective energy carrier because there are practically no gaseous emissions of greenhouse gases in the atmosphere during its use as a fuel. The great benefit of hydrogen being a practically inexhaustible carbon-free fuel makes it an attractive alternative to fossil fuels. I.e. there is a circular process of energy recovery and use. Another big advantage of hydrogen as a fuel is its high energy content per unit mass compared to fossil fuels. Nowadays hydrogen is broadly used as fuel in transport including fuel cell applications as a raw material in industry and as an energy carrier for energy storage. The mass exploitation of hydrogen in energy production and industry poses some important challenges. First there is a high price for its production compared to the price of most fossil fuels. Next the adopted traditional methods for hydrogen production like water splitting by electrolysis and methane reforming lead to the additional charging of the atmosphere with carbon dioxide which is a greenhouse gas. This fact prompts the use of renewable energy sources for electrolytic hydrogen production like solar and wind energy hydropower etc. An important step in reducing the price of hydrogen as a fuel is the optimal design of supply chains for its production distribution and use. Another group of challenges hindering broad hydrogen utilization are storage and safety. We discuss some of the obstacles to broad hydrogen application and argue that they should be overcome by new production and storage technologies. The present review summarizes the new achievements in hydrogen application production and storage. The approach of optimization of supply chains for hydrogen production and distribution is considered too.

Electrolysis utilizing renewable electricity is an environmentally friendly non-polluting and sustainable method of hydrogen production. Seawater is the most desirable and inexpensive electrolyte for this process to achieve commercial acceptance compared to competing hydrogen production technologies. We reviewed metal–organic frameworks as possible electrocatalysts for hydrogen production by seawater electrolysis. Metal–organic frameworks are interesting for seawater electrolysis due to their large surface area tunable permeability and ease of functional processing which makes them extremely suitable for obtaining modifiable electrode structures. Here we discussed the development of metal– organic framework-based electrocatalysts as multifunctional materials with applications for alkaline PEM and direct seawater electrolysis for hydrogen production. Their advantages and disadvantages were examined in search of a pathway to a successful and sustainable technology for developing electrode materials to produce hydrogen from seawater.