Abstract
Hydrogen is currently emerging as a second energy carrier, which will pave the way to sustainable energy systems. It is environmentally friendly, versatile, and has great potential in stationary and mobile power generation systems. A great deal of R&D work is conducted worldwide to utilize hydrogen as a new energy source in district heating, power utilities, and transportation sectors. In particular, the transportation sector is going through an era of rapid change towards the use of more renewable energy resources, pollution-free fuels, and the introduction of new automotive technologies. Hydrogen fueled vehicles based on fuel cells along with new technologies such as electric and hybrid vehicles offer an alternative to fossil fuels based transportation means. Hydrogen can be produced in virtually unlimited quantities from renewable resources, thus it is an important key to sustainable growth in power generation and transportation systems. Water electrolysis is the only hydrogen production process that does not involve fossil fuels if the required electric power is non-fossil in origin. Plasma catalytic reforming uses thermal plasma to produce hydrogen-rich gas from a broad range of light and heavy hydrocarbons. Plasma reformers provide highly controllable electrical heating of ionized gases, thus result in high power density and accelerate reaction kinetics. They are compact and low weight, and yield high conversion efficiencies. Wind power is an emerging technology with great potential for electricity generation. At favorable wind sites, it is fully competitive with fossil fuel and nuclear generation. Wind power is an intermittent electricity generator and does not provide power on an as needed basis. The variability of wind speed at any given site is a crucial factor in wind energy implementation. Due to the variation and intermittence of wind speed, wind energy assessment is subject to some degree of uncertainty due to the stochastic nature of wind flow.
This paper presents an assessment of the techno-economic viability of two novel hydrogen technologies, namely High Temperature Electrolysis (HTE) of steam and Plasma Catalytic Reforming (PCR) of natural gas using cheap off-peak electricity from wind power. Both technologies operate at high temperatures and are electricity intensive processes, which are characterized by high power density, high conversion efficiencies, and fast response time. Wind power is the main source of renewable energy, while biomass or natural gas is used as a source for clean and cheap thermal energy. By conducting the electrolysis process in the vapor phase, high current densities in the range of 0.4 A/cm2 can be applied due to improved reaction kinetics and lower polarization losses. This will result in reducing the electrical energy requirement by 36 %, and increase overall thermal efficiencies to 40-50%. The high power density results in low specific power consumption (2 kWh/kg H2) for the PCR. The major uncertainties involved are wind speed variation, and feedstock prices. The assessment includes hydrogen production, primary energy demands, capital cost estimates, storage, and distribution.. The cost of produced hydrogen reflects the variation and intermittence effects of wind energy. The economic evaluation also reveals that competitive hydrogen costs could be achieved at large-scale production using cheap off-peak electricity while taking into account by-product credits. Costs of hydrogen liquefaction, storage and distribution significantly contribute to the total cost of the produced hydrogen. Cost estimations of the novel hydrogen processes yield comparable results. However, the PCR process showed lower total capital investment (TCI) and hydrogen production costs per GJ H2 compared to the HTE process. Both processes suffer from problems related to material selection and high temperature operations.