• Energy Research

Most previous studies show that inclement weather increases the risk of road users being involved in a traffic crash. However, some authors have demonstrated a little or even an opposite effect, observed both on crash frequency and severity. In urban roads, where a greater number of conflict points and heavier traffic represent a higher exposure to risk, the potential increase of crash risk caused by adverse weather deserves a special attention. This study investigates the impact of meteorological conditions on the frequency of road crashes in urban environment, using the city of Porto, Portugal as a case study. The weather effects were analyzed for different types of crashes: single-vehicle, multi-vehicle, property-damage-only, and injury crashes. The methodology is based on negative binomial and Poisson models with random parameters, considering the influence of daily precipitation and mean temperature, as well as the lagged effects of the precipitation accumulated during the previous month. The results show that rainy days are more prone to the occurrence of road crashes, although the past precipitation may attenuate such effect. Temperatures below 10 °C are associated with higher crash frequencies, complying with the impacts of precipitation in the context of the Portuguese climate characteristics.

For being densely populated and urbanized, and for concentrating high-value economic activities, estuarine regions have an increased energy demand, which boosts the claim for new, efficient, renewable, and safe energy production. Among these technologies, hydrokinetic energy conversion systems are potentially well-suited for estuaries. However, in the actual context of climate change, it is important to know how changes in mean sea level may affect hydrokinetic energy production. This work proposes a methodology to assess the hydrokinetic energy potential for future scenarios using numerical hydrodynamic modeling techniques. Applied to the Douro estuary, several scenarios considering present conditions, as well as medium (2050) and long-term (2100) predictions under different Shared Socioeconomic Pathways are proposed. The results revealed that the studied region maintains a high dependence on freshwater discharge until 2100, although tidal oscillation is also significantly perceived in the entire estuary. Overall, hydrokinetic power potential will not increase with the mean sea level rise and will instead be considerably lower. Therefore, a decline in the kinetic energy available for exploitation is expected with increasing CO2 emissions, along with the associated intensification of sea level rise. Results reinforce the need to perform local studies to evaluate future trends in hydrokinetic energy production. This research was supported by the Strategic Funding UIDB/04423/2020 and UIDP/04423/2020 through national funds provided by FCT – Foundation for Science and Technology and European Regional Development Fund (ERDF), and by the project EsCo-Ensembles (PTDC/ECI-EGC/30877/2017), co-financed by NORTE 2020, Portugal 2020, and the European Union through the ERDF, and by FCT through national funds. The authors would like to thank the Instituto Hidrográfico, EDP Energias de Portugal and the projects ECOIS (POCTI/CTA/48461/2002), RAIA (0313-RAIA-1-E), RAIA. co (0520-RAIA CO-1-E), RAIA tec (0688-RAIA TEC-1-P), ECORISK (NORTE 07 0124-FEDER-000054) and INNOVMAR/ECOSERVICES (NORTE 01 0145-FEDER-000035) for the data provided.

Abstract Influenced by both marine and river flows, estuaries can present a high potential for hydrokinetic energy exploitation. In this study, the hydrokinetic energy production in the Douro estuary was evaluated through hydrodynamic numerical modelling. The model analysed the tide and river flow, reproduced the combined effects of these two factors on the main current velocity patterns, and identified the estuarine locations with the highest potential for energy exploitation. Given the river’s high variability caused by the precipitation patterns in the hydrographic basin area and the river’s torrential regime, several discharge scenarios were explored, combining spring and neap tides, and high and low river flows. The results revealed that the region with the highest potential is located in the upper part of the estuary, where the highest-velocity currents were achieved for mid-ebb tide conditions and strong river flows. It was also found that tides reinforce the hydrokinetic energy production during ebb tide, although they are not strong enough to produce high values of hydrokinetic energy, being the river flow the main forcing. This work demonstrates the relevance of choosing parametrized magnitudes that are not dependent on a specific equipment, as well as the importance of a proper characterization of the estuarine hydrodynamic patterns needed to optimize the hydrokinetic energy exploitation.

Numerous offshore wave energy converter (WEC) designs have been invented; however, none has achieved full commercialization so far. The primary obstacle impeding WEC commercialization is the elevated levelized cost of energy (LCOE). Consequently, there exists a pressing need to innovate and swiftly diminish the LCOE. A critical challenge faced by WECs is their susceptibility to extreme wave loads during storms. Promising concepts must demonstrate robust design features to ensure resilience in adverse conditions, while maintaining efficiency in harnessing power under normal sea states. It is anticipated that the initial commercial endeavors will concentrate on near-shore WEC technologies due to the cost advantages associated with proximity to the coastline, facilitating more affordable power transmission and maintenance. In response, this manuscript proposes a pioneering near-shore WEC concept designed with a survivability mode that is engineered to mitigate wave loads during severe sea conditions. Moreover, prior investigations have highlighted favorable resonance properties of this novel concept, enhancing wave power extraction during recurrent energetic sea states. This study employs numerical and physical modelling techniques to evaluate wave loads on the proposed WEC. The results indicate a remarkable 65% reduction in wave loads on the moving floater of the WEC during a range of sea states under the implemented survivability mode.

Estuaries are areas that are vulnerable to the impacts of climate change. Understanding how these impacts affect these complex environments and their uses is essential. This paper presents a work based on an analytical solution and 2DH and 3D versions of the Delft3D numerical model to simulate the Minho River estuary and its saline wedge length under climate change projections. Temperature observations at several locations in the estuary region were selected to determine which model better simulated the temperature patterns. Specific simulations were performed for the observation periods. Sixteen numerical model scenarios were proposed, considering a varying tide, different river flows, and several SLR projections based on the RCP4.5 and RCP8.5 for 2050 and 2100. The analytical solution was also calibrated using the numerical model solutions. The results show that although there is no relevant stratification, there was a difference in both models in which in the worst climate change scenario, the length of the saline intrusion increased up to 28 km in the 2DH model and 30 km in the 3D model. It was concluded that the 3D model results were more precise, but both configurations can provide insights into how the saline intrusion will be affected. Additionally, the excellent agreement between the analytical solution and the results of the numerical models allowed us to consider the analytical solution a helpful tool for practical applications. It was demonstrated that freshwater discharges and bed slopes are the most critical drivers for the saline intrusion length in the Minho River estuary as they have more impact than the increase in sea level. Therefore, flow regulation can be an excellent way to control saline intrusion in the future.

In the current context of climate change, understanding the effects of the changing conditions on estuaries is of utmost importance to protect populations and ecosystems. Given the diversity of impacts depending on the region, there is a need for local and dedicated studies to understand and mitigate the risks. Numerical models can provide forecasts of extreme floods and sea-level rise (SLR). However, they can present inaccuracies. In this work, the ensemble technique was applied to improve the numerical modeling forecasting for estuaries by considering scenarios of extreme river flow discharges (EFDs) and SLR scenarios for 2050 and 2100. The simulations were performed for two different estuarine regions in northern Portugal, and the superensemble was constructed with the results of two different numerical models. The results differed per estuary, highlighting the importance of a local approach. For the Douro estuary dynamics, the results showed that for the EFD, the effects of the SLR were not noticeable, indicating that, in this estuary, the river component was more important than the maritime component. In contrast, the Minho estuary dynamics were found to be affected by the SLR along the whole estuarine region, indicating a maritime influence and a worsening of the flood conditions for future scenarios.