O presente estudo modificou o modelo parabólico da forma em planta de equilíbrio de Medellín et al., 2009, proposto para praias de enseada com desembocaduras, incorporando um parâmetro relacionado à dinâmica costeira, que seria o volume de areia necessário para formar a praia emersa próxima à desembocadura. Foram escolhidas 27 desembocaduras na costa brasileira e obtidos parâmetros da dinâmica costeira e estuarina, através de imagens do Googleearth e dados de ondas e marés astronômicas dos programas SMC-TOOLS e WXTide32, respectivamente. O modelo parabólico foi aplicado e não se ajustou adequadamente, com diferenças com relação à linha de costa de 20-40m até 80m. Logo, foi realizada sua adaptação à costa brasileira, apresentando uma moderada a baixa dispersão dos coeficientes A e B de 77 % e 64%, respectivamente. Sua validação apresentou ajuste bom a satisfatório, com diferenças médias de 5m até máximas de 15m com relação à linha de costa. Posteriormente, foi realizada a modificação do modelo parabólico que minimizou a dispersão dos coeficientes A e B com um ajuste de 98 % e 81%, respectivamente. Sua validação apresentou um ajuste excelente a bom, com diferenças médias de 3-5m até máximas de 10m com relação à linha de costa. / This study modified the equilibrium plan form formulations proposed by Medellín et al., (2009) to embayments beachs with inlets, by incorporating a parameter related to coastal dynamics, that would be the volume of sand required to build the aerial beach close to the inlet. For this study 27 embayments beaches with inlets were chosen on the Brazilian coast and obtained parameters of dynamics coastal and estuarine, through GoogleEarth images and waves and astronomical tide datas series by the SMC-TOOLS and WXTide32 programs, respectively. The Medellín parabolic model was applied and did not fit properly, with differences regarding the shoreline of 20-40m up to maximum of 80m. Therefore, their adaptation to the Brazilian coast was carried out, which showed a moderate to low dispersion of the coefficients A and B of 77% and 64%, respectively. Their validation showed good to satisfactory fit, with mean differences regarding the shoreline of 5m up to maximum of 15m. Subsequently, the modification of the parabolic model was carried out which minimized the dispersion of the coefficients A and B with a fit of 98% and 81%, respectively. Their validation showed an excellent to good fit, with mean differences regarding the shoreline of 3-5m up to maximum of 10m.

O presente estudo modificou o modelo parabólico da forma em planta de equilíbrio de Medellín et al., 2009, proposto para praias de enseada com desembocaduras, incorporando um parâmetro relacionado à dinâmica costeira, que seria o volume de areia necessário para formar a praia emersa próxima à desembocadura. Foram escolhidas 27 desembocaduras na costa brasileira e obtidos parâmetros da dinâmica costeira e estuarina, através de imagens do Googleearth e dados de ondas e marés astronômicas dos programas SMC-TOOLS e WXTide32, respectivamente. O modelo parabólico foi aplicado e não se ajustou adequadamente, com diferenças com relação à linha de costa de 20-40m até 80m. Logo, foi realizada sua adaptação à costa brasileira, apresentando uma moderada a baixa dispersão dos coeficientes A e B de 77 % e 64%, respectivamente. Sua validação apresentou ajuste bom a satisfatório, com diferenças médias de 5m até máximas de 15m com relação à linha de costa. Posteriormente, foi realizada a modificação do modelo parabólico que minimizou a dispersão dos coeficientes A e B com um ajuste de 98 % e 81%, respectivamente. Sua validação apresentou um ajuste excelente a bom, com diferenças médias de 3-5m até máximas de 10m com relação à linha de costa. / This study modified the equilibrium plan form formulations proposed by Medellín et al., (2009) to embayments beachs with inlets, by incorporating a parameter related to coastal dynamics, that would be the volume of sand required to build the aerial beach close to the inlet. For this study 27 embayments beaches with inlets were chosen on the Brazilian coast and obtained parameters of dynamics coastal and estuarine, through GoogleEarth images and waves and astronomical tide datas series by the SMC-TOOLS and WXTide32 programs, respectively. The Medellín parabolic model was applied and did not fit properly, with differences regarding the shoreline of 20-40m up to maximum of 80m. Therefore, their adaptation to the Brazilian coast was carried out, which showed a moderate to low dispersion of the coefficients A and B of 77% and 64%, respectively. Their validation showed good to satisfactory fit, with mean differences regarding the shoreline of 5m up to maximum of 15m. Subsequently, the modification of the parabolic model was carried out which minimized the dispersion of the coefficients A and B with a fit of 98% and 81%, respectively. Their validation showed an excellent to good fit, with mean differences regarding the shoreline of 3-5m up to maximum of 10m.

Maritime transportation emits about 3% of global greenhouse gas, International Maritime Organization (IMO) aims to reduce shipping’s emissions by 50% with respect to 2008 levels. Proton exchange membrane fuel cells (PEMFCs) are considered among the most promising clean technologies for decarbonizing the maritime sector. One of the challenges for commercial application of PEMFCs is their limited durability. The purpose of this thesis was to assess the most significant degradation mechanisms and operating conditions of the PEMFC in marine applications, including membrane and catalyst layer degradation during idle, start-stop cycles, and dynamic load cycles, and to build a model to forecast the lifetime.A semi-empirical approach was developed to evaluate the PEMFC lifetime through a 2D COMSOL model. The model takes into account the empirical relationships for membrane conductivity loss and electrochemical surface area (ECSA) decay as functions of cycling numbers, aging process, and idling time. The 2D model has been validated with the experimental data in the literature and are also compared with a previous 1D model. The polarization curves show the voltage output against current density, lifetime is evaluated using a 10% voltage reduction criterion at the current density 0.6 A/cm2.An improved ECSA degradation model with variable load levels increases the lifetime of the ferry in Case 5 from 5500 hours to 7500 hours. Load cycling and idling cause the most severe degradation, but the impact can be reduced by a hybrid system with battery supplement and onshore charging. The lifetime of the ferry in Case 5 has been significantly further improved from 7500 hours to 22500 hours, which is comparable to the 20000-hour lifetime of commercial products for marine applications. Furthermore, membrane thickness effect analysis showed that fuel cells with thinner membranes (such as NR211) have better performance before degradation due to higher proton conductivity, but degrade faster during load cycling due to hydrogen crossover. The results of this research can be extended to help optimize fuel cell, stack and power system designs to avoid worst-case operating conditions and thereby limit fuel cell degradation. / Sjötransporter släpper ut cirka 3% av de globala växthusgaserna, International Maritime Organization (IMO) har som mål att minska sjöfartens utsläpp med 50 % jämfört med 2008 års nivåer. PEM-bränsleceller anses vara bland de mest lovande rena teknikerna för att minska koldioxidutsläppen i den maritima sektorn. En av utmaningarna för kommersiell användning av PEM-bränsleceller är deras begränsade hållbarhet. Syftet med denna avhandling var att bedöma de viktigaste nedbrytningsmekanismerna och driftsförhållandena för PEM-bränsleceller i marina applikationer, inklusive nedbrytning av membran och katalysatorskikt under tomgång, start-stopp-cykler och dynamiska belastningscykler, och att bygga en modell för att förutsäga livslängd.En semi-empirisk metod utvecklades för att utvärdera PEMFC:s livslängd genom en 2D COMSOL-modell. Modellen tar hänsyn till de empiriska sambanden för membrankonduktivitetsförlust och den elektrokemisk ytareans (ECSA) sönderfall som funktioner av cyklingstal, åldrandeprocess och tomgångstid. 2D-modellen har validerats med experimentella data i litteraturen och jämförs även med en tidigare 1D-modell. Polarisationskurvorna visar utspänningen mot strömtätheten, livslängden utvärderas med ett 10 % spänningsreduktionskriterium vid strömtätheten 0.6 A/cm2.En förbättrad modell för nedbrytning av elektrokemisk yta med varierande lastnivåer ökar färjans livslängd i fall 5 från 5500 timmar till 7500 timmar. Lastcykling och tomgång orsakar den allvarligaste försämringen, men påverkan kan minskas genom ett hybridsystem med batteritillägg och landladdning. Färjans livslängd i fall 5 har förbättrats avsevärt ytterligare från 7500 timmar till 22500 timmar, vilket är jämförbart med 20000 timmars livslängd för kommersiella produkter för marina applikationer. Vidare visade membrantjocklekseffektanalys att bränsleceller med tunnare membran (som NR211) har bättre prestanda före nedbrytning på grund av högre protonledningsförmåga, men bryts ned snabbare under belastningscykler på grund av väteövergång. Resultaten av denna forskning kan utökas för att hjälpa till att optimera designen av bränsleceller, stack och kraftsystem för att undvika värsta driftsförhållanden och därigenom begränsa nedbrytningen av bränsleceller.