Vulnerability assessment of two Adriatic mixed beaches for potential oil spill events

Oil still represents the most adopted source of energy for several human activities and goods production. Its extraction, transport and storage frequently occur across the sea and affect the largest ports all over the world. These actions have an environmental cost which can affect the marine environment at several levels among which the coastline is one of the most vulnerable. The NOAA (National Oceanic and Atmospheric Administration) in 2002 established the ESI guidelines (Environmental Sensitivity Index) in order to create vulnerability maps of the coastline for oil spill emergencies. Here it is presented an assessment of the vulnerability index for two Adriatic beaches (Portonovo and Sirolo) located in the Conero Headland which is one of the most congested areas for oil transportation due to the close port of Ancona. The aim of the work is to understand the specific role of coastal morphodynamics on the vulnerability assessment for oil spill events on mixed beaches. Portonovo and Sirolo are two mixed sand and gravel beaches (MSG) where sediment ranges from medium sand to cobble and boulders with a prevalent pebble fraction especially in Portonovo. Sediments are made of limestone and marl originated by cliff erosion which is the only sediment source of the beaches. The average tidal range at spring tide is 0.5 m. The dominant winds come from NE and SE, which correspond also to the main directions of storms. The wave heights are between 0.25 m and 2 m for most of the time. Topographic surveys of the beach surface and sediment sampling were undertaken in April 2015 in order to characterize the two beaches from a geomorphic and sedimentological point of view. Portonovo can be considered a borderline case between levels 5 and 6 of oil spill vulnerability given the larger quantity of gravel which increase the potential permeability of oil within the sediment wedge. Sirolo can be classified as lower vulnerability (5) because is a better defined mixed sand and gravel beach due to the larger sand fraction. The northern part of Sirolo, which is mainly comprised of cobbles and where the shoreline is almost in touch with the rocky cliff, is classifiable as the lowest vulnerability (1C). The burial entity of sediments can reach high depths (1 to 1.5 m), with several orders of storm berms on top. In normal conditions of wave motion the entity of burial is 25-30 cm in Portonovo (field tested) and up to 16 cm in Sirolo (formula derived). The temporal sequence of storms is also important: given the bimodal direction of storms in the Adriatic (NE and SE) consistent shoreline rotation of beaches has been already demonstrated [15; 17]. The high dynamism of beach topography and surface sediments is highlighted by obstructing structures that occupy and limit the beach in Portonovo where the entity of burial and sediment transport is higher. Despite the NOAA (2002) classification for oil spill vulnerability covers a wide range of environments and consider several aspects [23], an improvement is still needed focused on the geomorphic changes that mixed beach can experience in short periods of time

Design of 500 W Class SOFC Stack with Homogeneous Cell Performance

Our planar SOFC stacking technology uses unprofiled metallic interconnects (MIC) and thin cells of tape cast anode supported YSZ. The key element is the gas diffusion layer (GDL) between cell and MIC, which consists of so-called SOFConnex™. Using square cells with internal manifolds, 0.5 W/cm2 stack power density (800°C) can be obtained on short stacks. However, this open design configuration limits the assembly of large stacks and the durability of operation, owing to postcombustion and redox cycling occurring at unprotected cell edges. A new design, inspired from modeling work and the adaptability of the SOFConnex™ GDL, led to oblong-shaped cells, assembled in a closed stack casing with external air manifolding and fuel recovery manifolding, avoiding postcombustion. While stack power density in both designs remains similar, the operation at increased fuel utilization has become more stable in the 2nd design. Furthermore, a correlation of performance homogeneity during stack testing was drawn to assembly quality control. A 36-cell stack in dilute H2 at 800°C achieved 625 Wel (28% LHV efficiency, 0.35 W/cm2) under continuous polarisation, with all 6 clusters of 6 cells showing coincident i-V-output

Impact of Materials and Design on Solid Oxide Fuel Cell Stack Operation

Planar SOFC stack technology based on a unique concept (SOFConnex™) uses structured gas distribution layers between unprofiled metal sheet interconnects and thin Ni-YSZ anode supported electrolyte cells. The layers are flexible both in material and designand allow to implement new configurations relatively simply; manifolding can be internal, external, or combined. Together with thin stack components, independent of the supplier, the SOFConnex™ stacking approach allows compact planar assembly with low cost potential and adequate power density. Different cell and flow designs have been realized. With a basic flow configuration, short stacks (50 cm2 cell active area) were assembled and tested, power density at 800°C reaching 0.5 W/cm2 at 0.7 V average cell voltage (1.5 kWe /L, 0.36 cm2 area specific resistance), for 65% fuel utilization and 35% lower heating value electrical efficiency. Short stacks were thermally cycled and operated with both hydrogen and syngas. Degradation was essentially Ohmic(confirmed from impedance spectroscopy on stacks) and at first mainly due to the cathode-electrolyte interfacial reaction, performance loss was subsequently strongly reduced after cathode replacement. Using multiple voltage probes with additional interconnects allowed to separately monitor current collection losses during polarization. With an improved design in terms of sealing, postcombustion control and flow field, stacks up to 1 kWe have been operated

Local current measurement in a solid oxide fuel cell repeat element

A planar solid oxide fuel cell repeating unit, 50 cm2 in total active electrode size, consisting of an anode supported electrolyte cell bearing two 7 mm holes for fuel and air injection, and contacted to two dense metal current collector plates via gas distribution layers, was constructed with the aim of measuring local current densities rather than the integral current over the full area. The cathode side was entirely segmented (i.e. cathode layer, gas distribution layer, metal current collector plate) into 8 galvanically separated parts of ca. 6.5 cm2 each, with own current and potential leads

Modeling and experimental validation of solid oxide fuel cell materials and stacks

Results on solid oxide fuel cell stacks tested at 800° C with H2 fuel and using planar Ni-zirconia anode supported cells, 80x80x0.2 mm in size, are presented. Modeling and numerical simulation is used to interpret observed results and develop improved designs. Where neccessary, the models are calibrated with additional experimental data. Emphasis is placed on the critical issue of nickel anode reoxidation, related to the fuel flow field. Consideration is also given to gradients of temperature and current density developing over the cells and predicted by the models; local current density could be validated by measurement. Flow distribution within stacks is also illustrated by both experimental and modeling results

Compact 100 W stacks using thin components of anode supported cells and metal interconnects

Progress on anode supported cell stacks (SOFCONNEX design, 50 m2 per cell) is presented. A 6-cell stack and a 8 cell-stack were mounted and tested with hydrogen fuel at 800 degre C, yielding 100 W el and 140 W el, corresponding to a power density of 1kW el/L (0.34 W/cm2). Fuel utilisation was 50% and electrical efficiency 25%. A one-cell stack delivered 0.4 W/cm 2 at 70% fuel utilisation and 33 % electrical efficiency, and showed a performance increase over its 450 h test period. Another one-cell stack was monitored and variable conditions (20-50 % fuel utilisation, 0.2-0.5 A/cm 2) for 5500 h including several thermal cycles, with -5%/1000 h degradatio

Swiss SOFC Integration Activities: Stacks, Systems, and Applications

Solid Oxide Fuel Cell (SOFC) application development is very well represented in Switzerland by two companies. Sulzer Hexis AG is one of the world leaders in the commercialization of SOFC systems for single family houses. A smaller company, HTceramix, is active in novel processing routes for cells and in innovative stack designs. This article first presents the benefits of implementing SOFC in selected applications and markets. Then the current state-of-the-art in stacking is described for both Swiss stack designs, looking at power density, and electrical efficiency. It is remarkable that both stacks currently exhibit a unique characteristic in SOFC design: the absence of side sealing, which permits to significantly simplify the stack assembly and thus improve its reliability. Finally, the two generations of SOFC systems produced by Sulzer Hexis are presented. The HXS 1000 Premiere preseries system is evaluated on the basis of the extended demonstration program currently underway where 110 systems are in operation in single family houses and public buildings. The near-series system is then introduced with respect to the identified needs in reduction of investment and operating costs as well as size and weight