• Energy Research
• EU close
• NL close
• FI close

Dans les latitudes tempérées élevées, les ongulés donnent généralement naissance dans une fenêtre temporelle étroite lorsque les conditions sont optimales pour la survie de la progéniture au printemps ou au début de l'été, et utilisent une photopériode changeante pour les conceptions temporelles afin d'anticiper ces conditions. Cependant, dans les basses latitudes tropicales, la variation de la durée du jour est minime et la variation des précipitations rend le cycle saisonnier moins prévisible. Néanmoins, plusieurs espèces d'ongulés conservent des pics de naissance étroits dans de telles conditions, tandis que d'autres montrent que les naissances se propagent assez largement tout au long de l'année. Nous avons étudié comment la variation des précipitations d'une année à l'autre et d'une année à l'autre a influencé le moment de la reproduction de quatre espèces d'ongulés montrant ces modèles contrastés dans la région de Masai Mara au Kenya. Les quatre espèces présentaient des pics de naissance au cours de la période optimale putative au début de la saison humide. Pour le hartebeest et l'impala, le pic de naissance est diffus et la progéniture naît tout au long de l'année. En revanche, le topi et le phacochère ont montré une concentration saisonnière étroite de naissances, avec des conceptions supprimées une fois que les précipitations mensuelles sont tombées en dessous d'un seuil. Les fortes précipitations de la saison précédente et les fortes pluies précoces de l'année en cours ont amélioré la survie au stade juvénile de toutes les espèces, à l'exception de l'impala. Nos résultats révèlent comment la variation des précipitations affectant la croissance des graminées et donc la nutrition des herbivores peut régir la phénologie reproductive des ongulés dans les latitudes tropicales où la variation de la longueur du jour est minime. Le mécanisme sous-jacent semble être la suppression des conceptions une fois que les gains nutritionnels deviennent insuffisants. En réagissant de manière proximale à la variation des précipitations au cours de l'année, les ongulés de la savane tropicale sont moins susceptibles d'être affectés négativement par les conséquences du réchauffement climatique sur la phénologie de la végétation que les ongulés du Nord montrant un contrôle photopériodique plus rigide sur le moment de la reproduction. En latitudes templadas altas, los ungulados generalmente dan a luz dentro de una ventana de tiempo estrecha cuando las condiciones son óptimas para la supervivencia de la descendencia en primavera o principios del verano, y utilizan conceptos cambiantes de fotoperíodo a tiempo para anticipar estas condiciones. Sin embargo, en latitudes tropicales bajas, la variación de la duración del día es mínima, y la variación de las precipitaciones hace que el ciclo estacional sea menos predecible. Sin embargo, varias especies de ungulados conservan picos de nacimiento estrechos en tales condiciones, mientras que otras muestran nacimientos muy extendidos a lo largo del año. Investigamos cómo la variación interanual de las precipitaciones influyó en el tiempo reproductivo de cuatro especies de ungulados que muestran estos patrones contrastantes en la región de Masai Mara en Kenia. Las cuatro especies exhibieron picos de nacimiento durante el periodo óptimo putativo en la estación húmeda temprana. Para hartebeest e impala, el pico de nacimiento era difuso y las crías nacían durante todo el año. Por el contrario, topi y jabalí mostraron una estrecha concentración estacional de nacimientos, con concepciones suprimidas una vez que las precipitaciones mensuales cayeron por debajo de un nivel umbral. Las altas precipitaciones en la temporada anterior y las altas lluvias tempranas en el año en curso mejoraron la supervivencia en la etapa juvenil para todas las especies, excepto los impalas. Nuestros hallazgos revelan cómo la variación de la precipitación que afecta el crecimiento de la hierba y, por lo tanto, la nutrición de los herbívoros, puede gobernar la fenología reproductiva de los ungulados en latitudes tropicales donde la variación de la duración del día es mínima. El mecanismo subyacente parece ser la supresión de las concepciones una vez que las ganancias nutricionales se vuelven insuficientes. Al responder proximalmente a la variación de las precipitaciones dentro del año, es menos probable que los ungulados de la sabana tropical se vean afectados negativamente por las consecuencias del calentamiento global para la fenología de la vegetación que los ungulados del norte que muestran un control fotoperiódico más rígido sobre el tiempo reproductivo. In high temperate latitudes, ungulates generally give birth within a narrow time window when conditions are optimal for offspring survival in spring or early summer, and use changing photoperiod to time conceptions so as to anticipate these conditions. However, in low tropical latitudes day length variation is minimal, and rainfall variation makes the seasonal cycle less predictable. Nevertheless, several ungulate species retain narrow birth peaks under such conditions, while others show births spread quite widely through the year. We investigated how within-year and between-year variation in rainfall influenced the reproductive timing of four ungulate species showing these contrasting patterns in the Masai Mara region of Kenya. All four species exhibited birth peaks during the putative optimal period in the early wet season. For hartebeest and impala, the birth peak was diffuse and offspring were born throughout the year. In contrast, topi and warthog showed a narrow seasonal concentration of births, with conceptions suppressed once monthly rainfall fell below a threshold level. High rainfall in the previous season and high early rains in the current year enhanced survival into the juvenile stage for all the species except impala. Our findings reveal how rainfall variation affecting grass growth and hence herbivore nutrition can govern the reproductive phenology of ungulates in tropical latitudes where day length variation is minimal. The underlying mechanism seems to be the suppression of conceptions once nutritional gains become insufficient. Through responding proximally to within-year variation in rainfall, tropical savanna ungulates are less likely to be affected adversely by the consequences of global warming for vegetation phenology than northern ungulates showing more rigid photoperiodic control over reproductive timing. في خطوط العرض المعتدلة العالية، تلد ذوات الحوافر عمومًا في غضون فترة زمنية ضيقة عندما تكون الظروف مثالية لبقاء النسل في الربيع أو أوائل الصيف، وتستخدم تغيير الفترة الضوئية إلى مفاهيم زمنية لتوقع هذه الظروف. ومع ذلك، في خطوط العرض الاستوائية المنخفضة، يكون تباين طول اليوم ضئيلًا، ويجعل تباين هطول الأمطار الدورة الموسمية أقل قابلية للتنبؤ. ومع ذلك، فإن العديد من الأنواع ذوات الحوافر تحتفظ بقمم ولادة ضيقة في ظل هذه الظروف، في حين أن البعض الآخر يظهر أن الولادات تنتشر على نطاق واسع خلال العام. لقد حققنا في كيفية تأثير التباين في هطول الأمطار خلال العام وبين الأعوام على التوقيت التكاثري لأربعة أنواع من ذوات الحوافر تظهر هذه الأنماط المتناقضة في منطقة ماساي مارا في كينيا. أظهرت جميع الأنواع الأربعة قمم ولادة خلال الفترة المثلى المفترضة في موسم الأمطار المبكر. بالنسبة لحيوان النحل والامبالا، كانت ذروة الولادة منتشرة وولدت ذرية على مدار العام. على النقيض من ذلك، أظهر التوبي والخنزير الحربي تركيزًا موسميًا ضيقًا للولادات، مع قمع المفاهيم بمجرد انخفاض هطول الأمطار الشهري إلى ما دون مستوى العتبة. عزز ارتفاع هطول الأمطار في الموسم السابق وارتفاع الأمطار المبكرة في العام الحالي البقاء على قيد الحياة في مرحلة الشباب لجميع الأنواع باستثناء الإمبالا. تكشف النتائج التي توصلنا إليها كيف أن تباين هطول الأمطار الذي يؤثر على نمو العشب وبالتالي تغذية الحيوانات العاشبة يمكن أن يحكم الفينولوجيا الإنجابية لذوات الحوافر في خطوط العرض الاستوائية حيث يكون تباين طول اليوم ضئيلًا. يبدو أن الآلية الأساسية هي قمع المفاهيم بمجرد أن تصبح المكاسب الغذائية غير كافية. من خلال الاستجابة القريبة من التباين في هطول الأمطار خلال العام، فإن ذوات الحوافر في السافانا الاستوائية أقل عرضة للتأثر سلبًا بعواقب الاحترار العالمي على فينولوجيا الغطاء النباتي من ذوات الحوافر الشمالية التي تظهر تحكمًا دوريًا ضوئيًا أكثر صرامة في توقيت التكاثر.

We study the role of technology subsidies in climate policies, using a simple dynamic equilibrium model with learning-by-doing. The optimal subsidy rate of a carbon-free technology is high when the technology is first adopted, but falls significantly over the next decades. However, the efficiency costs of uniform instead of optimal subsidies, may be low if there are introduction or expansion constraints for a new technology. Finally, supporting existing energy technologies only, may lead to technology lock-in, and the impacts of lock-in increase with the learning potential of new technologies as well as the possibilities for early entry and thight carbon constraints.

Biofuels have been identified as a mid-term GHG emission abatement solution for decarbonising the transport sector. This study examines the techno-economic analysis of biofuel production via biomass fast pyrolysis and subsequent bio-oil upgrading via zeolite cracking. The aim of this study is to compare the techno-economic feasibility of two conceptual catalyst regeneration configurations for the zeolite cracking process: (i) a two-stage regenerator operating sequentially in partial and complete combustion modes (P-2RG) and (ii) a single stage regenerator operating in complete combustion mode coupled with a catalyst cooler (P-1RGC). The designs were implemented in Aspen Plus® based on a hypothetical 72 t/day pine wood fast pyrolysis and zeolite cracking plant and compared in terms of energy efficiency and profitability. The energy efficiencies of P-2RG and P-1RGC were estimated at 54% and 52%, respectively with corresponding minimum fuel selling prices (MFSPs) of £7.48/GGE and £7.20/GGE. Sensitivity analysis revealed that the MFSPs of both designs are mainly sensitive to variations in fuel yield, operating cost and income tax. Furthermore, uncertainty analysis indicated that the likely range of the MFSPs of P-1RGC (£5.81/GGE  £11.63/GGE) at 95% probability was more economically favourable compared with P-2RG, along with a penalty of 2% reduction in energy efficiency. The results provide evidence to support the economic viability of biofuel production via zeolite cracking of pyrolysis-derived bio-oil.

Steel is an indispensable material for the sustainable maintenance and progress of modern civilization. Its versatility in terms of mechanical and thermal characteristics, corrosion resistance, raw material availability, energy consumption and recyclability provides a clear advantage in a fast-changing technological landscape. In order to adapt to the changing needs, steel production methods have been evolving and improving over time. One such improvement opportunity in terms of energy efficient production is the ”heat pipe assisted annealing” concept. The cold rolling of steel is a process where the steel strip is cold-worked by means of rolls to achieve thickness reduction and better uniformity. This results in the strain hardening of steel. To reduce the hardness of steel and to render it more workable, it is thermally treated by heating it to a target soaking temperature and then cooling it down. This process is called annealing and it is an energy intensive process. Conventionally, heating is achieved with natural gas fired furnaces, whereas cooling is done using convective gas cooling. With this setting, the thermal energy extracted from the steel strip during the cooling stage is not used in any way. Moreover, none of the energy that is introduced during the heating stage is retained in the final product.An alternative technology for the annealing of steel was developed at Tata Steel IJmuiden R&D with the objective of recovering and using some of the heat removed during the cooling stage and thus, achieving more energy efficient annealing. With this technology called heat pipe assisted annealing, the cooling strip is thermally linked to the heating strip with multiple rotating heat pipes. In this way, each heat pipe transfers a certain amount of heat from the cooling strip to the heating strip. Only final heating and cooling of the steel strip is carried out in a conventional way. This concept is applicable to relatively low temperature (sub-critical) annealing where the cooling rate is not crucial. Therefore, packaging steel is a good candidate for the application of this technology.A rotating heat pipe is a highly efficient heat transfer device which is a wickless hollow cylindrical vessel rotating around its symmetric axis and containing a fixed amount of working fluid. The working fluid acts as a thermal energy carrier, transporting heat from one end of the heat pipe to the other. This basically occurs in four steps: (i) heat added to the evaporator part of the heat pipe causes the evaporation of the liquid, (ii) vapor travels to the condenser end of the heat pipe due to pressure difference, (iii) vapor condenses in the condenser section where heat is removed from the heat pipe, (iv) liquid returns to the evaporator with the help of the static pressure head and the centrifugal force induced by rotation. The heat pipe assisted annealing concept has been patented and subsequently further studied by Tata Steel Europe R&D. A water-filled rotating heat pipe test rig integrated with steel strips provided the bulk of the prior work. This test rig served as the proof-of-principle installation and it showed that heat can be transported from a hot strip to a cold one with a rotating heat pipe. In this context, several gaps have been identified to further acquire the knowledge on the system components, the concept performance and feasibility.This thesis focuses on four main aspects of the fundamentals and the feasibility of the heat pipe assisted annealing concept: (i) contact heat transfer between the steel strip and the rotating heat pipe, (ii) computationally efficient modelling of the interior dynamics of a rotating heat pipe, (iii) applicable working fluids for the high temperature range, (iv) behavior of the heat pipe assisted annealing system as a whole. These aspects are studied through a thermal engineering perspective. The heat pipe assisted annealing concept relies on the effective transfer of heat from the strip to the rotating heat pipe and vice versa. Therefore, it is important to understand the underlying physics governing this heat transfer and to be able to predict the heat transfer rate for possible configurations. In this context, in Chapter 2 of this thesis, the contact heat transfer between a steel strip and a rotating heat pipe is investigated both experimentally and numerically. The numerical model is based on first principles. It finds the thickness and the pressure of the gas layer between the strip and the heat pipe and subsequently considers different heat transfer mechanisms. The experimental work was carried out on the proof of- principle test rig. The model is validated with the experimental results. The contact heat transfer coefficient in the uniform region varied between 4,000 to 20,000 W/(m2.K). It showed an increase in the contact heat transfer with decreasing strip velocity and increasing radial stress. For the considered cases, conduction through the gas layer was the dominant heat transfer mechanism. Additionally, a simplified expression has been developed for the calculation of contact heat transfer through multiple regression analysis. The modelling of a rotating heat pipe is a crucial step for the detailed study of the heat pipe assisted annealing technology. Although modelling of rotating heat pipes has been the subject of many studies in the literature, these models are not computationally efficient enough to allow for the simultaneous modelling of multiple heat pipes linked to each other with strips. On this ground, in Chapter 3, a novel computationally efficient engineering model describing the transient behavior of the heat pipe is developed. In this model, the liquid and the vapor cells are allowed to change size radially in order to allow for the tracking of the liquid / vapor interface without the need for fine meshing or re-meshing. The model is also adapted to capillary-driven heat pipes. The model is validated with experimental and numerical studies from the literature. The deviation is computed to be around 2% with the numerical and analytical studies and around 6% with the experimental study.The heat pipe assisted annealing concept requires the operation of heat pipes within a temperature range of 25 °C to 700 °C. In order to operate within this range, different working fluids need to be used for different temperature ranges due to constraints of vapor pressure, life time, performance and safety. These working fluids are studied in Chapter 4. First, a selection of the working fluids is made based on a literature review. This selection yielded water, Dowtherm A, phenanthrene and cesium. Then, a life time test has been carried out with thermosyphons to test the stability of phenanthrene. At the end of a 3 months long test at 460 °C, thermal decomposition of phenanthrene was observed. However, these tests should be repeated with better initial vacuum and at multiple temperatures. Finally, Dowtherm A has been used in a rotating heat pipe setup to test its applicability and performance. It has been shown that Dowtherm A is suitable to be used in a rotating heat pipe at the designated temperature range in terms of performance, provided that annular flow is avoided. With the knowledge gathered from the previous chapters of this thesis, a model of the heat pipe assisted annealing line has been developed in Chapter 5. The aim of this model is to quantify the energy efficiency advantage brought by the concept for different number of heat pipes and to understand the behavior of the system as a whole. The simulations were run for a fixed plant layout with varying number of heat pipes and an average wrap angle of 104°. The energy recoveries for the simulations run for a strip of 0.25 mm and a line speed of 6.133 m/s were 76.5%, 73.4%, 69.4% and 63.9% for a total number of 90, 75, 60 and 45 heat pipes, respectively. From the simulation results it follows that cesium heat pipes are more efficient than organic heat pipes. Finally, the simulation results showed that the thermal cycle requirements can be satisfied with this new technology. Large Scale Energy Storage

Sustainability of agro-food supply chains has recently become the subject of greater interest from consumers, firms, governmental organizations and academia as the environment continues to deteriorate. One of the most critical factors influencing the sustainability of an agro-food supply chain is its network design. A particularly challenging aspect in this context is the broad range of influencing indicators associated with the Triple Bottom Line (TBL) of sustainability that need to be considered. However, many of these indicators could not be fully integrated or measured by single-step optimization problems. This paper presents a critical literature review of operational research methods for the design of sustainable supply chains. A novel two-stage hybrid solution methodology is proposed. In the first stage, a partner selection is performed using a hybrid multi criteria decision making based on Analytic Hierarchy Process (AHP) method and the Ordered Weighted Averaging (OWA) aggregation method. The result obtained in the first stage is used in the second stage to develop a multi-objective mathematical model to optimize the design of the supply chain network. This approach allows the simultaneous consideration of all three dimensions of sustainability including carbon footprint, water footprint, number of jobs created and the total cost of the supply chain design. The proposed approach generates a Pareto frontier to aid users in making decisions. Numerical experiments are completed utilizing data from an agro-food company to demonstrate the efficiency and effectiveness of the proposed solution methodology. The analyzes of the numerical results provide important organizational, practical and policy insights on (1) the impact of financial and environmental sustainability on supply chain network design (2) the tradeoff analysis between environmental emission, water footprint, societal implications and associated cost for making informed decision on supply chain investment.

The SBE19 Brussels - BAMB-CIRCPATH "Building as Material Banks - A Pathway for a Circular held in Brussels on 5 to 7 of February 2019, is an initiative of the Consortium of the H2020 BAMB Project together with the Sustainable Built Environment (SBE) series of conferences. Being within the SBE series, this event gathers the support of CIB International Council for Research and Innovation in Building and Construction, iiSBE International Initiative for a Sustainable Built Environment, the United Nations Environment Programme, and FIDIC International Federation of Consulting Engineers. The goal of this series of regional and international conferences is to disseminate innovative policies and developments in the field of sustainable urban environment to a broad international audience of specialists in policy, design, construction and operation of buildings and related infrastructure. info:eu-repo/semantics/publishedVersion