Iran, Islamic Republic of

The concerns over food security and protein scarcity driven by population increase and higher standards of living have pushed scientists toward finding new protein sources. A considerable proportion of resources and agricultural lands are currently dedicated to proteinaceous feed production to raise livestock and poultry for human consumption. The 1st generation of microbial protein (MP) came into the market as land-independent proteinaceous feed for livestock and aquaculture. However MP may be a less sustainable alternative to conventional feeds such as soybean meal and fishmeal because this technology currently requires natural gas and synthetic chemicals. These challenges have directed researchers toward the production of 2nd generation MP by integrating renewable energies anaerobic digestion nutrient recovery biogas cleaning and upgrading carbon-capture technologies and fermentation. The fermentation of methane-oxidizing bacteria (MOB) and hydrogen-oxidizing bacteria (HOB) i.e. two protein rich microorganisms has shown a great potential on the one hand to upcycle effluents from anaerobic digestion into protein rich biomass and on the other hand to be coupled to renewable energy systems under the concept of Power-to-X. This work compares various production routes for 2nd generation MP by reviewing the latest studies conducted in this context and introducing the state-of-the-art technologies hoping that the findings can accelerate and facilitate upscaling of MP production. The results show that 2nd generation MP depends on the expansion of renewable energies. In countries with high penetration of renewable electricity such as Nordic countries off-peak surplus electricity can be used within MP-industry by supplying electrolytic H2 which is the driving factor for both MOB and HOB-based MP production. However nutrient recovery technologies are the heart of the 2nd generation MP industry as they determine the process costs and quality of the final product. Although huge attempts have been made to date in this context some bottlenecks such as immature nutrient recovery technologies less efficient fermenters with insufficient gas-to-liquid transfer and costly electrolytic hydrogen production and storage have hindered the scale up of MP production. Furthermore further research into techno-economic feasibility and life cycle assessment (LCA) of coupled technologies is still needed to identify key points for improvement and thereby secure a sustainable production system.

The demand for fossil fuels is increasing because of globalization and rising energy demands. As a result many nations are exploring alternative energy sources and hydrogen is an efficient and practical alternative fuel. In the transportation industry the development of hydrogen-powered cars aims to maximize fuel efficiency and significantly reduce exhaust gas emission and concentration. The impact of using hydrogen as a supplementary fuel for spark ignition (SI) and compression ignition (CI) engines on engine performance and gas emissions was investigated in this study. By adding hydrogen as a fuel in internal combustion engines the torque power and brake thermal efficiency of the engines decrease while their brake-specific fuel consumption increase. This study suggests that using hydrogen will reduce the emissions of CO UHC CO2 and soot; however NOx emission is expected to increase. Due to the reduction of environmental pollutants for most engines and the related environmental benefits hydrogen fuel is a clean and sustainable energy source and its use should be expanded.

Hydrogen produced by solar and other clean energy sources is an essential alternative to fossil fuels. In this study a commercial alkaline electrolyzer with different cell numbers and electrode areas are simulated for different pressure temperature thermal resistance and electrical current. This alkaline electrolyzer is considered unsteady in simulations and different parameters such as temperature are obtained in terms of time. The obtained results are compared with similar results in the literature and good agreement is observed. Various characteristics of this alkaline electrolyzer as thermoneutral voltage faraday efficiency and cell voltage are calculated and displayed. The outlet heat rate and generated heat rate are obtained as well. The pressure and the temperature in the simulations are between 1 and 100 bar and between 300 and 360 Kelvin respectively. The results show that the equilibrium temperature is reached 2-3 hours after the time when the Alkaline electrolyzer starts to work.

The price of constructing hydrogen generation units is very high and sometimes it is not possible to build them in the desired location so the transfer of hydrogen from the hydrogen generation system to the units that need it is justified. Since the storage of hydrogen gas needs a large volume and its transportation is very complex so if hydrogen is stored in liquid form this problem can be resolved. In transporting liquid hydrogen (LH2) over long distances owing to heat transfer to the environment the LH2 vaporizes forming boil-off gas (BOG). Herein in lieu of only reliquifying the BOG this study proposes and assesses a system employing the BOG partially as feed for a novel liquefaction process and also the remaining utilized in a proton exchange membrane fuel cell (PEMFC) to generate power. Using the cold energy of the onsite liquid oxygen utility of the LH2 cargo vessel the mixed refrigerant liquefaction cycle is further cooled down. In this regard by using 130 kg/h BOG as input 60.37 kg/h of liquid hydrogen is produced and the rest enters PEMFC with 552.7 kg/h oxygen to produce 1592 kW of power. The total thermal efficiency of the integrated system and electrical efficiency of the PEMFC is 83.18% and 68.76% respectively. Regarding the liquefaction cycle its specific power consumption (SPC) and coefficient of performance (COP) were achieved at 3.203 kWh/kgLH2 and 0.1876 respectively. The results of exergy analysis show that the exergy destruction of the whole system is 937.4 kW and also its exergy efficiency is calculated to be 58.38%. Exergoeconomic and Markov analyses have also been applied to the integrated system. Also by changing the important parameters of PEMFC its optimal performance has been extracted.

Hydrogen production by microalgae is a promising technology to achieve sustainable and clean energy. Among various photosynthetic microalgae able to produce hydrogen Chlamydomonas reinhardtii is a model organism widely used to study hydrogen production. Oxygen produced by photosynthesis activity of microalgae has an inhibitory effect on both expression and activity of hydrogenases which are responsible for hydrogen production. Chlamydomonas can reach anoxia and produce hydrogen at low light intensity. Here the effect of bacteria co-cultivation on hydrogen produced by Chlamydomonas at low light intensity was studied. Results indicated that however co-culturing Escherichia coli Pseudomonas stutzeri and Pseudomonas putida reduced the growth of Chlamydomonas it enhanced hydrogen production up to 24% 46% and 32% respectively due to higher respiration rate in the bioreactors at low light intensity. Chlamydomonas could grow properly in presence of an unknown bacterial consortium and hydrogen evolution improved up to 56% in these co-cultures.

Hydrogen as a clean fuel and a new energy source can be produced by various methods. One of these common and economical methods of hydrogen production is hydrocarbon vapor modification. This research studies hydrogen production using a propane steam reforming process inside a high temperature heat exchanger. The application of this high temperature heat exchanger in the path of the power supply line is a fuel cell stack unit to supply the required hydrogen of the device. The heat exchanger consists of a set of cylindrical tubes housed inside a packed-bed called a reformer. The energy required to perform the reaction is supplied through these tubes in which high temperature gas is injected and the heat exchanger is insulated to prevent energy loss. The results show that at maximum temperature and velocity of hot gases (900 K and 1.5 m s−1 ) complete consumption of propane can be observed before the outlet of the reformer. Also in the mentioned conditions the maximum hydrogen production (above 92%) is obtained. The best permeability under which the system can perform best is 1×10−9 m2.

Transformers are generally considered to be the costliest assets in a power network. The lifetime of a transformer is mainly attributable to the condition of its solid insulation which in turn is measured and described according to the degree of polymerization (DP) of the cellulose. Since the determination of the DP index is complex and time-consuming and requires the transformer to be taken out of service utilities prefer indirect and non-invasive methods of determining the DP based on the byproduct of cellulose aging. This paper analyzes solid insulation degradation by measuring the furan concentration recently introduced methanol and dissolved gases like carbon oxides and hydrogen in the insulating oil. A group of service-aged distribution transformers were selected for practical investigation based on oil samples and different kinds of tests. Based on the maintenance and planning strategy of the power utility and a weighted combination of measured chemical indicators a neural network was also developed to categorize the state of the transformer in certain classes. The method proved to be able to improve the diagnostic capability of chemical indicators thus providing power utilities with more reliable maintenance tools and avoiding catastrophic failure of transformers.

In this paper a multifunctional energy system (MES) is proposed for recovering energy from the extra of coke oven gas (COG) which is usually flared or vented out as a waste stream in coke making plants. The proposed system consists of a pressure swing adsorption (PSA) unit for extracting some of the hydrogen from COG a gas turbine for producing heat and power from PSA offgas and a heat recovery steam generator (HRSG) for generating the steam required by the plant's processes. o assess the performance of the system practically simulations are carried out on the basis of the design and operational conditions of Zarand Coke Making Plant in Iran. The results indicate that by utilizing about 4.39 tons of COG per hour 6.5 MW of net electric power can be approximately produced by the gas turbine which can supply the coke making plant's total electrical power demand. Furthermore through recovering heat from gas turbine's exhaust close to 57% of the plant's steam demand can be supplied by the HRSG unit. It is also found that around 350 kilograms per hour of nearly pure hydrogen (99.9% purity) at 200 bar can be produced by the PSA unit. According to the sensitivity analysis results if the hydrogen content of the coke oven gas decreases by about 10% the gross power output of the gas turbine also declines by around 5.2% due to the reduction of LHV of the PSA offgas. Moreover economic evaluation of the system shows that the payback period of the investment which is estimated at 36.1 M$ is about 5.5 years. The net present value (NPV) and internal rate of return on investment (ROI) are calculated to be 17.6% and 43.3 M$ respectively.

Biogas is one of the most important sources of renewable energy and hydrogen production which needs upgrading to be functional. In this study two methods of biogas upgrading from organic parts of municipal waste were investigated. For biogas upgrading this article used a 3E analysis and simulated cryogenic separation and chemical scrubbing. The primary goal was to compare thermoeconomic indices and create hydrogen by reforming biomethane. The exergy analysis revealed that the compressor of the refrigerant and recovery column of MEA contributed the most exergy loss in the cryogenic separation and chemical scrubbing. The total exergy efficiency of cryogenic separation and chemical scrubbing was 85% and 84%. The energy analysis revealed a 2.07% lower energy efficiency for chemical scrubbing. The capital energy and total annual costs of chemical absorption were 56.51 26.33 and 54.44 percent lower than those of cryogenic separation respectively indicating that this technology is more economically feasible. Moreover because the thermodynamic efficiencies of the two methods were comparable the chemical absorption method was adopted for hydrogen production. The biomethane steam reforming was simulated and the results indicated that this method required an energy consumption of 90.48 MJ kgH2 . The hydrogen production intensity equaled 1.98 kmoleH2 kmolebiogas via a 79.92% methane conversion.

A technical–economic assessment was carried out in this study to determine the possibilities for wind and solar power generation in Afghanistan’s Helmand province. The results showed that most of the province has a solar irradiance of over 400 W/m2 and also showed that wind and solar power generated in the province can be up to twice as cheap as the official price of renewable power in Afghanistan. The most suitable site for solar and hydrogen production was found to be Laškar Gah where solar and hydrogen can be produced at a cost of 0.066 $/kWh and 2.1496 $/kg-H ¯ 2 respectively. In terms of wind power production and hydrogen production from wind the most suitable site was Sang¯ın where wind power and hydrogen could be produced at costs of 0.057 $/kWh and 1.4527 $/kg-H2 respectively. Despite the high potential of wind and solar energy in the Helmand province the most suitable place in this region to produce hydrogen from wind/solar energy was evaluated from technical economic and environmental perspectives with the Multi-Criteria DecisionMaking (MCDM) method. The Stepwise Weight Assessment Ratio Analysis (SWARA) method was used for weighting criteria and the Weighted Aggregated Sum Product Assessment (WASPAS) method was used to prioritize locations. The results show that Sang¯ın is the most suitable place for the construction of a wind hydrogen power plant and Laškar Gah is the most suitable place for the ¯ construction of a solar hydrogen power plant.