• Energy Research
• 2021-2025close
• 7. Clean energy close
• 11. Sustainability close
• 2. Zero hunger close
• University of Oxford close

Here, we investigate how stochasticity and age-dependence in energy dynamics influence maternal allocation in iteroparous females. We develop a state-dependent model to calculate the optimal maternal allocation strategy with respect to maternal age and energy reserves, focusing on allocation in a single offspring at a time. We introduce stochasticity in energetic costs– in terms of the amount of energy required to forage successfully and individual differences in metabolism – and in feeding success. We systematically assess how allocation is influenced by age-dependence in energetic costs, feeding success, energy intake per successful feeding attempt, and environmentally-driven mortality. First, using stochastic dynamic programming, we calculate the optimal amount of reserves M that mothers allocate to each offspring depending on their own reserves R and age A. The optimal life history strategy is then the set of allocation decisions M(R, A) over the whole lifespan which maximizes the total reproductive success of distant descendants. Second, we simulated the life histories of 1000 mothers following the optimisation strategy and the reserves at the start of adulthood R1, the distribution of which was determined, the distribution of which was determined using an iterative procedure as described . For each individual, we calculated maternal allocation Mt, maternal reserves Rt, and relative allocation Mt⁄Rt at each time period t. The relative allocation helps us to understand how resources are partitioned between mother and offspring. Third, we consider how the optimal strategy varies when there is age-dependence in resource acquisition, energetic costs and survival. Specifically, we include varying scenarios with an age-dependent increase or a decrease with age in energetic costs (c_t), feeding success (q_t), energy intake per successful feeding attempt (y_t), and environmentally-driven extrinsic mortality rate (d_t) (Table 2). We consider the age-dependence of parameters one at a time or in pairs, altering the slope, intercept, or asymptote of the age-dependence (linear or asymptotic function). Our aim is to identify whether the observed reproductive senescence can arise from optimal maternal allocation. As such, we do not impose a decline in selection in later life as all offspring are equally valuable at all ages (for a given maternal allocation), and there are no mutations. For each scenario, we run the backward iteration process with these age-dependent functions, obtain the allocation strategy, and simulate the life history of 1000 individuals based on the novel strategy. We then fit quadratic and linear models to the reproduction of these 1000 individuals using the lme function, nlme package in R. For these models, the response variable is the maternal allocation Mt and explanatory variables are the time period t and t2 (for the quadratic fit only), with individual identity as a random term. We use likelihood ratio tests to compare linear and quadratic models using the anova function (package nlme) with the maximum-likelihood method. If the comparison is significant (p-value <0.05), we considered the quadratic model to have a better fit, otherwise the linear model is considered more parsimonious. We were particularly interested in identifying scenarios where the fit was quadratic with a negative quadratic term. For each scenario, the pseudo R2 conditional value (proportion of variance explained by the fixed and random terms, accounting for individual identity) is calculated to assess the goodness-of-fit of the lme model, on a scale from 0 to 1, using the “r.squared” function, package gabtool. All calculations and coding are done in R. Iteroparous parents face a trade-off between allocating current resources to reproduction versus maximizing survival to produce further offspring. Optimal allocation varies across age, and follows a hump-shaped pattern across diverse taxa, including mammals, birds and invertebrates. This non-linear allocation pattern lacks a general theoretical explanation, potentially because most studies focus on offspring number rather than quality and do not incorporate uncertainty or age-dependence in energy intake or costs. Here, we develop a life history model of maternal allocation in iteroparous animals. We identify the optimal allocation strategy in response to stochasticity when energetic costs, feeding success, energy intake, and environmentally-driven mortality risk are age-dependent. As a case study, we use tsetse, a viviparous insect that produces one offspring per reproductive attempt and relies on an uncertain food supply of vertebrate blood. Diverse scenarios generate a hump-shaped allocation: when energetic costs and energy intake increase with age; and also when energy intake decreases, and energetic costs increase or decrease. Feeding success and mortality risk have little influence on age-dependence in allocation. We conclude that ubiquitous evidence for age-dependence in these influential traits can explain the prevalence of non-linear maternal allocation across diverse taxonomic groups.

Project: Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets - These data have been generated as part of the internationally-coordinated Coupled Model Intercomparison Project Phase 6 (CMIP6; see also GMD Special Issue: http://www.geosci-model-dev.net/special_issue590.html). The simulation data provides a basis for climate research designed to answer fundamental science questions and serves as resource for authors of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR6). CMIP6 is a project coordinated by the Working Group on Coupled Modelling (WGCM) as part of the World Climate Research Programme (WCRP). Phase 6 builds on previous phases executed under the leadership of the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and relies on the Earth System Grid Federation (ESGF) and the Centre for Environmental Data Analysis (CEDA) along with numerous related activities for implementation. The original data is hosted and partially replicated on a federated collection of data nodes, and most of the data relied on by the IPCC is being archived for long-term preservation at the IPCC Data Distribution Centre (IPCC DDC) hosted by the German Climate Computing Center (DKRZ). The project includes simulations from about 120 global climate models and around 45 institutions and organizations worldwide. Summary: These data include the subset used by IPCC AR6 WGI authors of the datasets originally published in ESGF for 'CMIP6.AerChemMIP.HAMMOZ-Consortium.MPI-ESM-1-2-HAM' with the full Data Reference Syntax following the template 'mip_era.activity_id.institution_id.source_id.experiment_id.member_id.table_id.variable_id.grid_label.version'. The MPI-ESM1.2-HAM climate model, released in 2017, includes the following components: aerosol: HAM2.3, atmos: ECHAM6.3 (spectral T63; 192 x 96 longitude/latitude; 47 levels; top level 0.01 hPa), atmosChem: sulfur chemistry (unnamed), land: JSBACH 3.20, ocean: MPIOM1.63 (bipolar GR1.5, approximately 1.5deg; 256 x 220 longitude/latitude; 40 levels; top grid cell 0-12 m), ocnBgchem: HAMOCC6, seaIce: unnamed (thermodynamic (Semtner zero-layer) dynamic (Hibler 79) sea ice model). The model was run by the ETH Zurich, Switzerland; Max Planck Institut fur Meteorologie, Germany; Forschungszentrum Julich, Germany; University of Oxford, UK; Finnish Meteorological Institute, Finland; Leibniz Institute for Tropospheric Research, Germany; Center for Climate Systems Modeling (C2SM) at ETH Zurich, Switzerland (HAMMOZ-Consortium) in native nominal resolutions: aerosol: 250 km, atmos: 250 km, atmosChem: 250 km, land: 250 km, ocean: 250 km, ocnBgchem: 250 km, seaIce: 250 km.

Project: Coupled Model Intercomparison Project Phase 6 (CMIP6) datasets - These data have been generated as part of the internationally-coordinated Coupled Model Intercomparison Project Phase 6 (CMIP6; see also GMD Special Issue: http://www.geosci-model-dev.net/special_issue590.html). The simulation data provides a basis for climate research designed to answer fundamental science questions and serves as resource for authors of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR6). CMIP6 is a project coordinated by the Working Group on Coupled Modelling (WGCM) as part of the World Climate Research Programme (WCRP). Phase 6 builds on previous phases executed under the leadership of the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and relies on the Earth System Grid Federation (ESGF) and the Centre for Environmental Data Analysis (CEDA) along with numerous related activities for implementation. The original data is hosted and partially replicated on a federated collection of data nodes, and most of the data relied on by the IPCC is being archived for long-term preservation at the IPCC Data Distribution Centre (IPCC DDC) hosted by the German Climate Computing Center (DKRZ). The project includes simulations from about 120 global climate models and around 45 institutions and organizations worldwide. Summary: These data include the subset used by IPCC AR6 WGI authors of the datasets originally published in ESGF for 'CMIP6.CMIP.HAMMOZ-Consortium.MPI-ESM-1-2-HAM.historical' with the full Data Reference Syntax following the template 'mip_era.activity_id.institution_id.source_id.experiment_id.member_id.table_id.variable_id.grid_label.version'. The MPI-ESM1.2-HAM climate model, released in 2017, includes the following components: aerosol: HAM2.3, atmos: ECHAM6.3 (spectral T63; 192 x 96 longitude/latitude; 47 levels; top level 0.01 hPa), atmosChem: sulfur chemistry (unnamed), land: JSBACH 3.20, ocean: MPIOM1.63 (bipolar GR1.5, approximately 1.5deg; 256 x 220 longitude/latitude; 40 levels; top grid cell 0-12 m), ocnBgchem: HAMOCC6, seaIce: unnamed (thermodynamic (Semtner zero-layer) dynamic (Hibler 79) sea ice model). The model was run by the ETH Zurich, Switzerland; Max Planck Institut fur Meteorologie, Germany; Forschungszentrum Julich, Germany; University of Oxford, UK; Finnish Meteorological Institute, Finland; Leibniz Institute for Tropospheric Research, Germany; Center for Climate Systems Modeling (C2SM) at ETH Zurich, Switzerland (HAMMOZ-Consortium) in native nominal resolutions: aerosol: 250 km, atmos: 250 km, atmosChem: 250 km, land: 250 km, ocean: 250 km, ocnBgchem: 250 km, seaIce: 250 km.

Nearly three billion people in low- and middle-income countries (LMICs) rely on polluting fuels, resulting in millions of avoidable deaths annually. Polluting fuels also emit short-lived climate forcers and greenhouse gases (GHGs). Liquefied petroleum gas (LPG) and grid-based electricity are scalable alternatives to polluting fuels but have raised climate and health concerns. Here, we compare emissions and climate impacts of a business-as-usual household cooking fuel trajectory to four large-scale transitions to gas and/or grid electricity in 77 LMICs. We account for upstream and end-use emissions from gas and electric cooking, assuming electrical grids evolve according to the 2022 World Energy Outlook’s “Stated Policies” Scenario. We input the emissions into a reduced-complexity climate model to estimate radiative forcing and temperature changes associated with each scenario. We find full transitions to LPG and/or electricity decrease emissions from both well-mixed GHG and short-lived climate forcers, resulting in a roughly 5 millikelvin global temperature reduction by 2040. Transitions to LPG and/or electricity also reduce annual emissions of PM2.5 by over 6 Mt (99%) by 2040, which would substantially lower health risks from Household Air Pollution. Primary input data was collected from the following sources: Baseline household fuel choices - WHO household energy database (https://www.nature.com/articles/s41467-021-26036-x) End-use emissions - US EPA lifecycle assessment of household fuels (https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=339679&Lab=NRMRL&simplesearch=0&showcriteria=2&sortby=pubDate&timstype=Published+Report&datebeginpublishedpresented) Upstream emissions - Argonne National Labs GREET Model (https://greet.es.anl.gov/index.php) Current and future population estimates - UNECA (http://data.un.org/Explorer.aspx?d=EDATA) Input data was processed by defining household fuel choice scenarios, estimating national household fuel consumption based on these scenarios, and applying fuel-specific emission factors to create country-specific emission pathways. These emission pathways were input into the FaIR model (https://zenodo.org/record/5513022#.Yt_jfHbMLb0) which generated additional data for each scenario including time series of pollution concentrations, radiative forcing, and temperature changes. All data is provided in CSV format. Nothing proprietary is required. 

De nouveaux systèmes de refroidissement renouvelables sont nécessaires dans le monde entier pour répondre à la demande croissante de refroidissement. Cette étude propose et démontre une nouvelle intégration du refroidissement par absorption solaire avec le stockage de chaleur latente afin de maximiser l'utilisation de l'énergie renouvelable pour le refroidissement dans des climats extrêmement chauds. Une analyse paramétrique a été réalisée dans TRNSYS pour identifier les paramètres critiques pour un dimensionnement optimal liés à la taille du champ solaire, au volume du réservoir, à l'isolation du réservoir, au point de consigne de chauffage auxiliaire et à l'angle d'inclinaison du collecteur. De plus, l'intégration a été comparée à un système de refroidissement par absorption solaire conventionnel utilisant un stockage de chaleur sensible (un réservoir d'eau chaude) et un système de refroidissement par compression de vapeur électrique. Les résultats montrent qu'une taille de champ solaire de 1,5 m2/kWc, un volume de réservoir de stockage de chaleur latente de 30 L/m2, une isolation adéquate inférieure à 0,8 W/m2.K et des températures de consigne appropriées pour la chaudière auxiliaire fournissent les performances optimales pour maximiser la fraction solaire. Par rapport au refroidissement par absorption solaire conventionnel, l'étude démontre comment le matériau à changement de phase (PCM) a augmenté la fraction solaire de 4,2 % (de 70,3 à 74,5 %) en raison d'une température stable plus élevée et de pertes de réservoir plus faibles (réduites de 44 %). En outre, malgré le coût d'investissement initial plus élevé du système de refroidissement solaire à base de PCM proposé par rapport au système de refroidissement par compression de vapeur, les résultats soulignent que le coût du cycle de vie est beaucoup plus faible dans les climats extrêmement chauds. Après 25 ans, le coût du cycle de vie a été réduit de 34 % par rapport à la compression de vapeur et de 9 % par rapport à un système de refroidissement solaire conventionnel. Par rapport à la technologie de réfrigérant à compression de vapeur, le système proposé peut économiser 31,6 % d'énergie primaire et 1 222 kg de CO2eq par an. Cette recherche fournit des informations précieuses sur la conception et l'intégration optimales du refroidissement renouvelable pour les applications résidentielles dans les régions extrêmement chaudes. Se requieren nuevos sistemas de refrigeración renovables en todo el mundo para hacer frente a la creciente demanda de refrigeración. Este estudio propone y demuestra una nueva integración de la refrigeración por absorción solar con el almacenamiento de calor latente para maximizar el uso de energía renovable para la refrigeración en climas extremadamente cálidos. Se realizó un análisis paramétrico en TRNSYS para identificar los parámetros críticos para el dimensionamiento óptimo relacionados con el tamaño del campo solar, el volumen del tanque, el aislamiento del tanque, el punto de ajuste de la calefacción auxiliar y el ángulo de inclinación del colector. Además, la integración se comparó con un sistema de enfriamiento por absorción impulsado por energía solar convencional que utiliza almacenamiento de calor sensible (un tanque de agua caliente) y un sistema de enfriamiento por compresión de vapor impulsado por electricidad. Los resultados muestran que un tamaño del campo solar de 1,5 m2/kWc, un volumen del tanque de almacenamiento de calor latente de 30 L/m2, un aislamiento adecuado por debajo de 0,8 W/m2.K y temperaturas de consigna adecuadas para la caldera auxiliar proporcionan el rendimiento óptimo para maximizar la fracción solar. En comparación con el enfriamiento por absorción solar convencional, el estudio demuestra cómo el material de cambio de fase (PCM) aumentó la fracción solar en un 4,2 % (de 70,3 a 74,5 %) debido a una mayor temperatura estable y menores pérdidas del tanque (reducidas en un 44 %). Además, a pesar del mayor coste de inversión inicial del sistema de refrigeración solar basado en PCM propuesto en comparación con el sistema de refrigeración por compresión de vapor, los hallazgos destacan que el coste del ciclo de vida es mucho menor en climas extremadamente cálidos. Después de 25 años, el coste del ciclo de vida se redujo en un 34 % en comparación con la compresión de vapor y en un 9 % en comparación con un sistema de refrigeración convencional impulsado por energía solar. En comparación con la tecnología de refrigerante por compresión de vapor, el sistema propuesto puede ahorrar el 31,6 % de la energía primaria y 1222 kgCO2eq al año. Esta investigación proporciona información valiosa sobre el diseño y la integración óptimos de la refrigeración renovable para aplicaciones residenciales en regiones extremadamente calurosas. Novel renewable cooling systems are required worldwide to address the growing demand for cooling. This study proposes and demonstrates a novel integration of solar-driven absorption cooling with latent heat storage to maximise the use of renewable energy for cooling in extremely hot climates. A parametric analysis was performed in TRNSYS to identify the critical parameters for optimal sizing related to the solar field size, tank volume, tank insulation, auxiliary heating set point, and collector tilt angle. Moreover, the integration was compared with a conventional solar-driven absorption cooling system using sensible heat storage (a hot water tank) and an electric-driven vapour compression cooling system. The results show that a solar field size of 1.5 m2/kWc, a latent heat storage tank volume of 30 L/m2, adequate insulation below 0.8 W/m2.K, and appropriate set-point temperatures for the auxiliary boiler provide the optimal performance to maximise the solar fraction. Compared with conventional solar-driven absorption cooling, the study demonstrates how the phase change material (PCM) increased the solar fraction by 4.2 % (from 70.3 to 74.5 %) due to higher stable temperature and lower tank losses (reduced by 44 %). In addition, despite the higher initial investment cost of the proposed PCM-based solar-driven cooling system compared to the vapour compression cooling system, the findings highlight that the life cycle cost is much lower in extremely hot climates. After 25 years, the life cycle cost was lowered by 34 % compared to vapour compression and by 9 % compared to a conventional solar-driven cooling system. Compared to vapour compression refrigerant technology, the proposed system can save 31.6 % of primary energy and 1222 kgCO2eq annually. This research provides valuable insights into the optimal design and integration of renewable cooling for residential applications in extremely hot regions. هناك حاجة إلى أنظمة تبريد متجددة جديدة في جميع أنحاء العالم لتلبية الطلب المتزايد على التبريد. تقترح هذه الدراسة وتوضح تكاملًا جديدًا للتبريد بالامتصاص المدفوع بالطاقة الشمسية مع التخزين الحراري الكامن لتعظيم استخدام الطاقة المتجددة للتبريد في المناخات الحارة للغاية. تم إجراء تحليل بارامتري في TRNSYS لتحديد المعلمات الحرجة للتحجيم الأمثل المتعلق بحجم الحقل الشمسي وحجم الخزان وعزل الخزان ونقطة ضبط التسخين الإضافية وزاوية إمالة المجمع. علاوة على ذلك، تمت مقارنة التكامل مع نظام تبريد الامتصاص التقليدي الذي يعمل بالطاقة الشمسية باستخدام تخزين الحرارة المعقول (خزان الماء الساخن) ونظام تبريد ضغط البخار الذي يعمل بالكهرباء. تظهر النتائج أن حجم الحقل الشمسي 1.5 متر مربع/كيلو واط مكعب، وحجم خزان تخزين الحرارة الكامن 30 لتر/متر مربع، والعزل الكافي أقل من 0.8 واط/متر مربع، ودرجات حرارة نقطة الضبط المناسبة للغلاية المساعدة توفر الأداء الأمثل لتحقيق أقصى قدر من الجزء الشمسي. مقارنة بالتبريد بالامتصاص التقليدي القائم على الطاقة الشمسية، توضح الدراسة كيف زادت مادة تغيير الطور (PCM) من الجزء الشمسي بنسبة 4.2 ٪ (من 70.3 إلى 74.5 ٪) بسبب ارتفاع درجة الحرارة المستقرة وانخفاض خسائر الخزان (انخفضت بنسبة 44 ٪). بالإضافة إلى ذلك، على الرغم من ارتفاع تكلفة الاستثمار الأولي لنظام التبريد المقترح القائم على الطاقة الشمسية PCM مقارنة بنظام تبريد ضغط البخار، فإن النتائج تسلط الضوء على أن تكلفة دورة الحياة أقل بكثير في المناخات الحارة للغاية. بعد 25 عامًا، انخفضت تكلفة دورة الحياة بنسبة 34 ٪ مقارنة بضغط البخار وبنسبة 9 ٪ مقارنة بنظام التبريد التقليدي الذي يعمل بالطاقة الشمسية. بالمقارنة مع تقنية تبريد ضغط البخار، يمكن للنظام المقترح توفير 31.6 ٪ من الطاقة الأولية و 1222 كجم من مكافئ ثاني أكسيد الكربون سنويًا. يوفر هذا البحث رؤى قيمة حول التصميم الأمثل ودمج التبريد المتجدد للتطبيقات السكنية في المناطق شديدة الحرارة.

Transit-Oriented Development (TOD) is advocated for achieving sustainable transportation through development around transit stations. TOD’s global implementation revealed varied outcomes, with many cities failing to achieve the intended objectives. TOD implementation in the Jakarta Metropolitan area still in its infancy. Through a geospatial information system and a survey of 400 commuters who live inside the 1 km radius of planned TOD, this longitudinal study aimed to examine an eight-year lapse between 2013 and 2020 of changes in two aspects, specifically land-use and spatial distribution as well as commuters’ travel behavior and preferences in TOD implementation and travel changes due to the COVID-19 pandemic. Key findings are as follows: increased diversity in the residential function around planned TOD areas in the Jakarta capital and a decrease in the suburbs, reflecting the commuters’ improved readiness to reside in planned TOD areas. Furthermore, kinship relations were the commuters’ main reason when selecting house locations, with no capacity to change their workplaces. A significant increase in public facilities at the expense of green open space (GOS) indicates that TOD implementation was conducted by the government with the sole authority to manage GOS, lacking private sector involvement. The cost factor was the most dominant reason for the commuter’s use of public transportation, instead of new transport modes such as MRT and LRT. Moreover, the commuter’s travel behavior in all studied transit stations, whilst it showed evidence of changes in time and frequency, was not greatly influenced by the COVID-19 related restrictions.

To meet the challenges of increased thermal loads and performance demands on aero-engine turbine blades, more advanced cooling techniques are required. This study used a modification of the well-known Goldstein equation to predict film effectiveness for an individual film cooling hole and applied the Sellers’ superposition method to apply these films across effusion-cooled configurations. In doing so, it tackles a relatively unchallenged problem of film holes in close spanwise proximity. An experimental set-up utilised infrared cameras to assess the film effectiveness of nine geometries of varying spanwise and streamwise spacings. Higher porosity led to increased thermal protection, and the spanwise spacing had the most profound impact, with film effectiveness approaching 0.9. Additionally, greater uniformity in the spanwise direction was observed. The modified Goldstein-Sellers method showed good agreement with experimental results although lateral mixing was underestimated. This method represents a tool that could be easily implemented in the industry for rapid assessment of novel cooling geometries.