Development of Synthetic Jet Air Blower for Air-breathing PEM Fuel Cell
This paper presents a synthetic jet air blower actuated by PZT for air blowing for air-breathing micro PEM fuel cell. The several factors to affect the performance of air-breathing PEM fuel cell such as air flow rate, opening ratio and cathode open type in the cathode side were studied. Especially, an air flow rate is critical condition to improve its performance. In this paper, we developed a synthetic jet air blower to supply a high stoichiometric air flow. The synthetic jet mechanism is a zero mass flux device that converts electrical energy into the momentum. The synthetic jet actuation is usually generated by a traditional PZT actuator, which consists of a small cylindrical cavity, in/outlet channel and PZT diaphragms. The flow rate of the fabricated synthetic jet air blower was 400cc/min at 550Hz and its power consumption was very low under 0.3W. The proposed air-breathing PEM fuel cell which installed synthetic jet air blower was higher performance and stability during continuous operation than the air-breathing fuel cell without auxiliary device to supply the air. The results showed that the maximum power density was 188mW/cm at 400mA/cm. This maximum power density and durability were improved more than 40% and 20%, respectively. Keywords— Air-breathing PEM fuel cell, Synthetic jet air blower, Opening ratio, Power consumption.
A Self-Breathing Proton-Exchange-Membrane Fuel-Cell Pack With Optimal Design and Microfabrication
An entire set of silicon-based microtechnologies is developed for a high-performance H$ _2/$air self-breathing microproton-exchange-membrane fuel-cell ($mu$PEMFC) pack. For improving the performance of the silicon-based$mu$PEMFC, microflow-fields together with the electrodes at the cathode and the anode are optimally designed. For simplifying the microfabrication, a bulk-micromachining process is developed for fabricating both the cathode and the anode. Besides that the optimally designed flow-fields and electrodes are accurate fabricated, both the cathodes and the anodes can be fabricated in a same wafer with identical process. Optimized packaging conditions, such as the compression ratio and the current-collecting layer for the membrane electrode assembly (MEA), are experimentally obtained for both high fuel-cell performance and reliable silicon micropackaging. Attributed to the optimized design and the precise microfabrication, the peak power-density of the self-breathing$mu$PEMFC is measured as high as 141.0–147.2 mW/cm$^-2$. For adapting the output voltage to handheld electronic systems, a thin-pad planar configuration is designed for the$mu$PEMFC pack that consists of six single cells connected in series. The planar-configured self-breathing$mu$PEMFC pack is micropackaged on a silicon-micromachined base-chip, with the specific power as high as 271 mW/cm$^3$measured. Experimental results demonstrate that the fuel cells can reliably work under normal environmental temperature and humidity. 1200-h continuing power supply of the$mu$PEMFC pack is performed, resulting in stable output of about 3 V.1643
Impacts of climate and land use changes on flood risk management for the Schijn River, Belgium
Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry.