• Energy Research
• 11. Sustainability close

Le secteur des transports traverse une transition rapide vers les véhicules électriques afin de minimiser notre dépendance aux combustibles fossiles et de réduire les émissions de CO2. Cela se produit également dans le secteur du transport de marchandises, avec un déploiement rapide des camions électriques. Ce document propose que le remplacement des camions diesel par des camions électriques ait lieu d'abord sur les itinéraires où la cargaison est livrée d'un endroit à une altitude plus élevée à un endroit à une altitude plus basse. De cette façon, le système de freinage à récupération du camion peut recharger complètement la batterie du camion. Cet article étudie des scénarios où les camions électriques pourraient fonctionner indéfiniment sans électricité du réseau pour charger leurs batteries. Ce concept a été nommé camion électrique à mouvement perpétuel (PMET). Les résultats montrent qu'avec une pente moyenne de 5 %, une vitesse de 60 km/h, le poids de la cargaison doit être au moins 1,32 fois le poids du camion, ce qui permet d'atteindre la PMET. Le PMET est une alternative intéressante pour réduire la demande d'électricité et accroître la durabilité du secteur des transports. El sector del transporte está pasando por una rápida transición a los vehículos eléctricos para minimizar nuestra dependencia de los combustibles fósiles y reducir las emisiones de CO2. Esto también está sucediendo en el sector del transporte de carga, con un rápido despliegue de camiones eléctricos. Este documento propone que el reemplazo de camiones diésel por camiones eléctricos debe ocurrir primero en rutas donde la carga se entrega desde un lugar con mayor altitud a un lugar con menor altitud. De esta manera, el sistema de frenado regenerativo del camión puede recargar completamente la batería del camión. Este documento investiga escenarios en los que los camiones eléctricos podrían operar indefinidamente sin electricidad de la red para cargar sus baterías. Este concepto se denominó camión eléctrico de movimiento perpetuo (PMET). Los resultados muestran que con una pendiente media de la carretera del 5%, velocidad de 60 km/h, el peso de la carga debe ser al menos 1.32 veces el peso del camión, se puede lograr PMET. El PMET es una alternativa interesante para reducir la demanda eléctrica y aumentar la sostenibilidad del sector del transporte. The transportation sector is going through a rapid transition to electric vehicles to minimize our reliance on fossil fuels and reduce CO2 emissions. This is also happening in the cargo transport sector, with a rapid deployment of electric trucks. This paper proposes that the replacement of diesel trucks with electric trucks should first happen on routes where cargo is delivered from a location with a higher altitude to a location with a lower altitude. This way, the regenerative braking system of the truck can completely recharge the truck's battery. This paper investigates scenarios where electric trucks could operate indefinitely without grid electricity to charge their batteries. This concept was named perpetual motion electric truck (PMET). Results show that with an average road slope of 5 %, 60 km/h speed, the weight of the cargo should be at least 1.32 times the weight of the truck, PMET can be achieved. PMET is an interesting alternative to reduce electricity demand and increase the sustainability of the transport sector. يمر قطاع النقل بمرحلة انتقال سريعة إلى السيارات الكهربائية لتقليل اعتمادنا على الوقود الأحفوري وتقليل انبعاثات ثاني أكسيد الكربون. ويحدث هذا أيضًا في قطاع نقل البضائع، مع الانتشار السريع للشاحنات الكهربائية. تقترح هذه الورقة أن يتم استبدال شاحنات الديزل بالشاحنات الكهربائية أولاً على الطرق التي يتم فيها تسليم البضائع من موقع ذي ارتفاع أعلى إلى موقع ذي ارتفاع أقل. وبهذه الطريقة، يمكن لنظام الكبح المتجدد للشاحنة إعادة شحن بطارية الشاحنة بالكامل. تبحث هذه الورقة في السيناريوهات التي يمكن أن تعمل فيها الشاحنات الكهربائية إلى أجل غير مسمى بدون كهرباء الشبكة لشحن بطارياتها. أطلق على هذا المفهوم اسم الشاحنة الكهربائية ذات الحركة الدائمة (PMET). تظهر النتائج أنه مع متوسط انحدار الطريق بنسبة 5 ٪، وسرعة 60 كم/ساعة، يجب أن يكون وزن الحمولة 1.32 مرة على الأقل من وزن الشاحنة، ويمكن تحقيق PMET. تعد PMET بديلاً مثيرًا للاهتمام لتقليل الطلب على الكهرباء وزيادة استدامة قطاع النقل.

AbstractWater scarcity brings tremendous challenges to achieving sustainable development of water resources, food, and energy security, as these sectors are often in competition, especially during drought. Overcoming these challenges requires balancing trade-offs between sectors and improving resilience to drought impacts. An under-appreciated factor in managing the water-food-energy (WFE) nexus is the increased value of solar and wind energy (SWE). Here we develop a trade-off frontier framework to quantify the water sustainability value of SWE through a case study in California. We identify development pathways that optimize the economic value of water in competition for energy and food production while ensuring sustainable use of groundwater. Our results indicate that in the long term, SWE penetration creates beneficial feedback for the WFE nexus: SWE enhances drought resilience and benefits groundwater sustainability, and in turn, maintaining groundwater at a sustainable level increases the added value of SWE to energy and food production.

Abstract Population growth, economic development, and dietary changes have drastically increased the demand for food and water. The resulting expansion of irrigated agriculture into semi-arid areas with limited precipitation and surface water has greatly increased the dependence of irrigated crops on groundwater withdrawal. Also, the increasing number of people living in mega-cities without access to clean surface water or piped drinking water has drastically increased urban groundwater use. The result of these trends has been the steady increase of the use of non-renewable groundwater resources and associated high rates of aquifer depletion around the globe. We present a comprehensive review of the state-of-the-art in research on non-renewable groundwater use and groundwater depletion. We start with a section defining the concepts of non-renewable groundwater, fossil groundwater and groundwater depletion and place these concepts in a hydrogeological perspective. We pay particular attention to the interaction between groundwater withdrawal, recharge and surface water which is critical to understanding sustainable groundwater withdrawal. We provide an overview of methods that have been used to estimate groundwater depletion, followed by an extensive review of global and regional depletion estimates, the adverse impacts of groundwater depletion and the hydroeconomics of groundwater use. We end this review with an outlook for future research based on main research gaps and challenges identified. This review shows that both the estimates of current depletion rates and the future availability of non-renewable groundwater are highly uncertain and that considerable data and research challenges need to be overcome if we hope to reduce this uncertainty in the near future.

AbstractIn this study, we examine the spatial and temporal characteristics of water stress in China for the historical (1971–2010) and the future (2021–2050) periods using a multimodel simulation approach. Three water stress indices (WSIs), that is, the ratios of water withdrawals to locally generated runoff (WSIR), to natural streamflow (WSIQ), and to natural streamflow minus upstream consumptive water withdrawals (WSIC), are used for the assessment. At the basin level, WSIR estimates generally match the reported data and indicate severe water stress in most northern basins. At the grid cell level, the WSIs show distinct spatial patterns of water stress wherein WSIR (WSIQ) estimates higher (lower) water stress compared to WSIC. Based on the WSIC estimates, 368 million people (nearly one third of the total population) are affected by severe water stress annually during the historical period, while WSIR and WSIQ suggest 595 and 340 million, respectively. Future projections of WSIC indicate that more than 600 million people (43% of the total) might be affected by severe water stress, and half of China's land area would be exposed to stress. The found aggravating water stress conditions could be partly attributed to the elevated future water withdrawals. This study emphasizes the necessity of considering explicit upstream and downstream relations with respect to both water availability and water use in water stress assessment and calls for more attention to increasing levels of water stress in China in the coming decades.

For the next decade, the global water crisis remains the risk of highest concern, and ranks ahead of climate change, extreme weather events, food crises and social instability. Across the globe, nearly one in ten people is without access to an improved drinking water source. Least Developed Countries (LDCs) especially in sub-Saharan Africa (SSA) are the most affected, having disproportionately more of the global population without access to clean water than other major regions. Population growth, changing lifestyles, increasing pollution and accelerating urbanization will continue to widen the gap between the demand for water and available supply especially in urban areas, and disproportionately affect informal settlements, where the majority of SSA's urban population resides. Distribution and allocation of water will be affected by climate-induced water stresses, poor institutions, ineffective governance, and weak political will to address scarcity and mediate uncertainties in future supply. While attempts have been made by many scientists to examine different dimensions of water scarcity and urban population dynamics, there are few comprehensive reviews, especially focused on the particular situation in Sub-Saharan Africa. This paper contributes to interdisciplinary understanding of urban water supply by distilling and integrating relevant empirical knowledge on urban dynamics and water issues in SSA, focusing on progress made and associated challenges. It then points out future research directions including the need to understand how alternatives to centralized water policies may help deliver sustainable water supply to cities and informal settlements in the region.

The maritime shipping sector is a major contributor to CO2 emissions and this figure is expected to rise in coming decades. With the intent of reducing emissions from this sector, this research proposes the utilization of the jet stream to transport a combination of cargo and hydrogen, using airships or balloons at altitudes of 10–20 km. The jet streams flow in the mid-latitudes predominantly in a west–east direction, reaching an average wind speed of 165 km/h. Using this combination of high wind speeds and reliable direction, hydrogen-filled airships or balloons could carry hydrogen with a lower fuel requirement and shorter travel time compared to conventional shipping. Jet streams at different altitudes in the atmosphere were used to identify the most appropriate circular routes for global airship travel. Round-the-world trips would take 16 days in the Northern Hemisphere and 14 in the Southern Hemisphere. Hydrogen transport via the jet stream, due to its lower energy consumption and shorter cargo delivery time, access to cities far from the coast, could be a competitive alternative to maritime shipping and liquefied hydrogen tankers in the development of a sustainable future hydrogen economy. Keywords: Jet stream, Airships, Balloons, Hydrogen, Cargo, Shipping, Hydrogen economy

Target 6.4 of the recently adopted Sustainable Development Goals (SDGs) deals with the reduction of water scarcity. To monitor progress towards this target, two indicators are used: Indicator 6.4.1 measuring water use efficiency and 6.4.2 measuring the level of water stress (WS). This paper aims to identify whether the currently proposed indicator 6.4.2 considers the different elements that need to be accounted for in a WS indicator. WS indicators compare water use with water availability. We identify seven essential elements: 1) both gross and net water abstraction (or withdrawal) provide important information to understand WS; 2) WS indicators need to incorporate environmental flow requirements (EFR); 3) temporal and 4) spatial disaggregation is required in a WS assessment; 5) both renewable surface water and groundwater resources, including their interaction, need to be accounted for as renewable water availability; 6) alternative available water resources need to be accounted for as well, like fossil groundwater and desalinated water; 7) WS indicators need to account for water storage in reservoirs, water recycling and managed aquifer recharge. Indicator 6.4.2 considers many of these elements, but there is need for improvement. It is recommended that WS is measured based on net abstraction as well, in addition to currently only measuring WS based on gross abstraction. It does incorporate EFR. Temporal and spatial disaggregation is indeed defined as a goal in more advanced monitoring levels, in which it is also called for a differentiation between surface and groundwater resources. However, regarding element 6 and 7 there are some shortcomings for which we provide recommendations. In addition, indicator 6.4.2 is only one indicator, which monitors blue WS, but does not give information on green or green-blue water scarcity or on water quality. Within the SDG indicator framework, some of these topics are covered with other indicators.