Hydrogen and ammonia as a primary fuel-A critical review of production technologies, diesel engine applications, and challenges

Renewable energy resources have been recognized as one of the promising sources of energy to meet the current energy demand without affecting the environment. Hydrogen and ammonia fuels are being explored as sustainable energy sources to replace fossil fuels. Green fuels have gained profound attention due to their environmentally friendly nature and human health concerns. Although these fuels are sustainable on a laboratory scale, implementing them on a commercial scale is still in the early stages of development. Numerous studies have reported the effectiveness of hydrogen and ammonia in diesel engines as efficient energy carriers. However, although previous research shed light on these fuels, their economic viability is still a concern. This review provides an in-depth analysis of hydrogen and ammonia production methods. Additionally, the effect of blends on diesel engines was determined by comparing the obtained data through performance, combustion, and emission characteristics. Parameters such as brake thermal efficiency, brake-specific fuel consumption, exhaust gas temperature, heat release rate, in-cylinder pressure, carbon monoxide, carbon dioxide, hydrocarbon, nitrogen oxides, and particulate matter were observed. The effects of noise and vibration resulting from the addition of hydrogen, ammonia, and biodiesel blends were also discussed in detail. Increasing the concentration of hydrogen and ammonia increases the formation of pollutants and reduces brake thermal efficiency. On the other hand, increasing the concentration of biodiesel decreases pollutants such as CO, HC, and CO2, but there is an increase in NOx. Based on the findings, it is evident that hydrogen and ammonia can be effective sources of energy to replace fossil fuels, and their production methods and usage need to be further optimized to achieve economic and societal benefits.