Clean Energy for Tomorrow: Towards Zero Emission and Carbon Free Future: A Review

Fuel cell technology using hydrogen energy is an advanced green energy technology for the future use. This is green, sustainable, clean and very environmental friendly. Green house gases emission from industrial activities has been proven beyond doubt as the main cause of global warming and climate changes. The finite world energy supply that consists nearly 90% of fossil fuel which is depleted; an energy crisis because of widening fossil fuel production and demand gaps. Many nations responded to anticipate energy crisis by diversifying their fuel resources to include renewable and alternative energy and developing green energy technology for the future. Despite political announcements on renewable energy, fossil fuels will continue to dominate energy resources for some time to come and carbon emission will increase but global nuclear energy expansion is uncertain because of international tensions and general public fears of another Chemobyl or Fogoshima disasters or a nuclear terrorist attack. Biofuels are plagued by the conflict between crops for fuel and crops for food and there is a shift of interest towards crop biomass wastes. The further expansion of hydrogen energy is constrained by costs and safety in hydrogen transport and storage. Fuel cell research and development has shifted from older AFC, PAFC and MCFC whose entry into the market were stalled by intractable operational and durability problems, to more promising PEMFC, DMFC and SOFC. A new type of fuel cell, the microbial fuel cell (MFC) is also gaining some attention because of sustainable way of simultaneously reducing BOD and COD of wastewater and provide power; combined wastewater treatment and power (CWTP). The main thrust in PEMFC research and development is cost reduction of membrane and electrocatalyst by substitution of cheap and more efficient organic-inorganic nanocomposite membranes and nanoinorganic electrocatalyst as well as lower electrocatalyst loading and cost reduction of bipolar plate by material reformulation with nanomaterials for injection or compression molding. In addition, cost reduction can also be achieved by reduction of system complexity using non-hydrated or self-hydrated membranes that eliminate water management sub-system and CO tolerant anodes that eliminate CO removal of reform ate hydrogen feed. PEMFC system efficiency can be further enhanced by better design of flow field in bipolar plates and fuel and air manifold in the stack as well as through process optimization using process system engineering tools. The main thrust of SOFC research and development is reduction of its operational temperature by replacement with low temperature electrolytes, anodes and cathodes. Future DMFC development focuses on methanol crossover reduction, desired water management and low manufacturing costs. Also for future development on MBC focuses on understanding the electron transfer mechanism and redox reactions in cells and developing more efficient nanostructured electrodes and cell immobilization. The main objective in hydrogen production from liquid fuels are in the development of low temperature auto-thermal steam reforming catalysts, purification of reformate hydrogen through pressure swing adsorption and membrane processes as well as membrane reactors and higher hydrogen storage capacity in carbon nano-tubes and other nanostructures. The main focus on sustainable hydrogen production is photolysis of water into hydrogen and oxygen in solar photovoltaic-electrolyzer system, direct solar photoelectrochemical reactors and solar photobiological fermentors.