In recent years, bicycle sharing systems have been increasingly promoted in our society as an environmentally friendly mode of transportation. In this study, we discuss the bike sharing system in terms of the mitigation of eco-burden and/or biomass energy use (e.g., sewage sludge). Here, biomass energy use indicates that the bicycle's fuel cell (FC) system is powered by H2 from the biomass. In other words, the bicycle is assisted with an FC and H2 storage as an alternative to the conventional Li-ion battery. Note that the H2 fuel is purified through the fermentation process and metal hydrides (MHs) are used for storing H2. In our study, we selected Sendai city as the model area. Our objective was to estimate the eco-burdens of our proposed bicycle using life cycle assessment methodology. We estimated the environmental impacts of the bicycles in the target area, considering their FC performance over a period of 10 years. Consequently, bicycle sharing using FC bicycles can reduce abiotic depletion potential by 15% and global warming potential by 10% compared to conventional bicycle sharing systems.

Hydrogen is an alternative fuel that is currently being used in fuel cell (FC) applications. This study focuses on electric-assisted bicycles (electric bicycles) powered by FCs and aims to determine the configuration of an FC system based on power demand. Metal hydrides (MHs) were used in the investigation to facilitate the containment of FC systems with improved hydrogen storage capacity. The flow performance was evaluated in our previous study; thus, here we focused on understanding the hydrogen flow characteristics from storage and the weight gain of the cartridge. Through experiments performed on existing electric-assisted bicycles, the relationship between the load weight and the power demand was evaluated. Furthermore, the power capacity of Li-ion batteries and FC systems was compared. No loss in performance was observed up to an additional payload weight of 8 kg. Combining the FC unit with an auxiliary battery offers up to 6.81× benefits with a significant weight capacity (8 kg). It is inferred that the current MH tank design does not support the required amount of hydrogen. The hydrogen flow could be supported by the exhaust heat of the FC to the MH.

No abstract

This study evaluated the use of a fuel-cell-assisted bicycle (H-bike) in bicycle sharing. Two pertinent issues arise. First, the number of start-stops and distance traveled lead to power consumption levels so high that they exceed those of households. Second, the H-bikes are 3 kg heavier than conventional bicycles. Reduction in rolling resistance due to increased tire pressures may afford a solution to these problems. The purpose of this study was to investigate whether increasing the tire pressure can reduce the amount of energy consumed and eliminate the impact of increased weight. Energy consumption was evaluated with a bicycle-riding experiment; the net impact of increased weight on energy consumption and the environment following the spike in tire pressure was assessed.Life-cycle assessment was performed using the CML model to estimate the abiotic resource depletion potential (ADP) and the global warming potential (GWP). Results showed that increasing the tire pressure reduced fuel consumption in bicycle-sharing systems by more than 10%. The 3-kg weight gain did not affect energy consumption, and the ADP and GWP were approximately 10% and 20% lower for the H-bike. Thus, H-bikes have more environmental benefits than conventional bicycles, and considering tire pressure in bicycle sharing makes sense.

Metal hydride is an alloy that reversibly reacts with hydrogen gas. Because it has low hydrogen storage pressure, it can contribute to the abatement of compression power in the hydrogen charging process. Despite this fact, owing to the exothermic reaction in its charging process, a longer hydrogen charging time is required.As a countermeasure to this problem, a cooling process for the metal hydride bed is necessary to enhance the reaction rate of the hydrogen charging process. Considering this background, in this study, an energy consumption comparison between metal hydride and compressed hydrogen (conventional) is conducted. In addition, a mathematical model of the hydrogen charging process is developed to estimate the effect of the metal hydride cooling process on the hydrogen charging time. The mathematical model is validated by comparison with experimental results and used to simulate different cooling conditions (outside temperature: 233, 253, 273, and 298 K).It was found that metal hydride could reduce the compression power compared to compressed hydrogen (maximum reduction of 7.57 kwh/kg-H 2) and reduce the hydrogen charging time by removing reaction heat from the metal hydride tank (886 s at outside temperature 233 K, 1902 s at 273 K).