• Energy Research
• 13. Climate action close
• 14. Life underwater close
• University of North Sumatra close

Abstract Bottlenecks on the development of biodiesel production could be eliminated using direct transesterification (DT). This review presents a comprehensive overview for DT from oleaginous seed crops (edible and non-edible), microalgal and fungal/yeast biomass. Effects of key operational parameters, affecting the yield of biodiesel, such as feedstock, feedstock processing technologies, feedstock water content, catalyst choice, temperature, co-solvent and reaction time are summarised and critically assessed. 15% and 68% of published data showed high fatty acid (FA) yields and FA to fatty acid methyl ester (FAME) conversion efficiencies, respectively. Highest fatty acid yielding feedstock were Jatropha and a novel non-edible Mediterranean crop, Cynara cardunculus, the microalgae Chlorella and Nannochloropsis, and the fungi/yeast Trichosporon oleaginosus, Rhodosporidium toruloides, Lipomyces starkeyi, Mortierella isbellina, and Pichia guilliermondi. For wet microalgal biomass, a preference for acid-catalysed direct transesterification was determined, while base-catalysed DT was more suitable for dry biomass, except for turbo-thin film-assisted DT of microalgal biomass. The data highlight that DT operational parameters and technologies need optimisation for feedstock and water content and outcomes may be strongly strain-dependent for microalgal feedstock. To bring commercial biodiesel potential of some high-yielding feedstock to reality, comprehensive life cycle – and techno-economic analyses are required for intensified and non-intensified DT processing, taking feedstock production and possibilities of biorefinery concepts into account whilst also focussing on those processing platforms that can esterify fatty acids in wet biomass.

AbstractAimLarge trees (d.b.h. ≥ 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan‐tropical scales.LocationPan‐tropical.MethodsAboveground biomass (AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights (AICc‐wi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB/density of large trees and environmental and species trait variables correcting for spatial autocorrelation.ResultsDensity of large trees explained c. 70% of the variation in pan‐tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean) ± 105.0 (SD) Mg ha−1] versus Palaeotropical forests (Africa 418.3 ± 91.8 Mg ha−1; Asia 393.3 ± 109.3 Mg ha−1). Pan‐tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents.Main conclusionsDensity of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in‐depth analyses of the community dynamics of large trees.

Today, using systems based on renewable resources is a suitable alternative to fossil fuels. However, due to problems such as the lack of access in all the times needed to supply cargo and high-investment cost, it has not been well-received. Therefore, in this research, the modeling of the photovoltaic system with battery storage has been done to supply the required load, and various scenarios have been evaluated in terms of economic parameters and reliability indicators of the studied system for a better understanding of the comparison indicators. It has been evaluated from two modes, one connected to the network and one disconnected from the network. One of the important results is the supply of 56% of the load by the photovoltaic cell in the presence of the grid, which, in this scenario, the electrical load is supplied by the photovoltaic cell and the grid is 164.155 kWh/yr and 128.504 kWh/yr, respectively.

Récemment, une grande attention a été accordée à l'application des énergies renouvelables dans les questions environnementales. Pendant ce temps, l'industrie des piles à combustible, qui est considérée comme une industrie respectueuse de l'environnement, est l'une des composantes importantes de ce projet. Ce sont en fait des dispositifs pour la conversion directe de l'énergie chimique en énergie électrique par une réaction électrochimique sans avoir besoin de pièces mécaniques. Dans cette étude, on tente de modéliser l'un de leurs types importants, appelé pile à combustible à membrane échangeuse de protons, afin qu'il puisse être utilisé pour prédire le comportement de la pile à combustible et examiner divers paramètres affectant les performances de la pile. L'idée principale est d'estimer les paramètres optimaux pour les piles à combustible à membrane échangeuse de protons en minimisant la valeur d'erreur quadratique totale entre la tension de sortie empirique et la tension de sortie approchée. Pour donner de meilleurs résultats en termes de précision et de fiabilité, une nouvelle conception d'une métaheuristique appelée l'algorithme équilibré Water Strider est utilisée. Les résultats de la méthode suggérée sont finalement validés par comparaison avec plusieurs derniers optimiseurs appliqués sur un cas de test pratique. Après avoir exécuté tous les optimiseurs 30 fois indépendamment, la méthode proposée avec une erreur absolue minimale est égale à 3,4831e−4 montre les meilleurs résultats par rapport aux autres. Recientemente, se prestó mucha atención a la aplicación de energías renovables en temas ambientales. Mientras tanto, la industria de pilas de combustible, que se considera una industria respetuosa con el medio ambiente, es uno de los componentes importantes de este proyecto. De hecho, son dispositivos para la conversión directa de energía química en energía eléctrica mediante una reacción electroquímica sin necesidad de piezas mecánicas. En este estudio, se intenta modelar uno de sus tipos importantes, llamado celdas de combustible de membrana de intercambio de protones, para que pueda usarse en la predicción del comportamiento de la celda de combustible y examinar varios parámetros que afectan el rendimiento de la celda. La idea principal es la estimación óptima de los parámetros para las celdas de combustible de membrana de intercambio de protones minimizando el valor total de error al cuadrado entre el voltaje de salida empírico y el voltaje de salida aproximado. Para dar mejores resultados en términos de precisión y confiabilidad, se utiliza un nuevo diseño de una metaheurística llamada Algoritmo equilibrado Water Strider. Los resultados del método sugerido se validan finalmente mediante la comparación con varios de los últimos optimizadores aplicados en un caso de prueba práctico. Después de ejecutar todos los optimizadores 30 veces de forma independiente, el método propuesto con un error absoluto mínimo igual a3.4831e −4 muestra los mejores resultados hacia los demás. Recently, much attention was paid to the application of renewable energy in environmental issues. Meanwhile, the fuel cell industry, which is considered an environmentally friendly industry, is one of the important components of this project. They are in fact devices for the direct conversion of chemical energy into electrical energy by an electrochemical reaction without the need for any mechanical parts. In this study, it is attempted to model one of their important types, called proton exchange membrane fuel cells, so that it can be used in predicting the behavior of the fuel cell and examining various parameters affecting the performance of the cell. The main idea is to optimal parameters estimation for the proton exchange membrane fuel cells by minimizing the total Squared Error value between the empirical output voltage and the approximated output voltage. For giving better results in terms of accuracy and reliability, a new design of a metaheuristic called the balanced Water Strider Algorithm is utilized. The results of the suggested method are finally validated by comparison with several latest optimizers applied on a practical test case. After running all of the optimizers 30 times independently, the proposed method with minimum absolute error equals 3.4831e−4 shows the best results toward the others. في الآونة الأخيرة، تم إيلاء الكثير من الاهتمام لتطبيق الطاقة المتجددة في القضايا البيئية. وفي الوقت نفسه، تعد صناعة خلايا الوقود، التي تعتبر صناعة صديقة للبيئة، أحد المكونات المهمة لهذا المشروع. وهي في الواقع أجهزة للتحويل المباشر للطاقة الكيميائية إلى طاقة كهربائية عن طريق تفاعل كهروكيميائي دون الحاجة إلى أي أجزاء ميكانيكية. في هذه الدراسة، يتم محاولة نمذجة أحد أنواعها المهمة، يسمى خلايا وقود غشاء التبادل البروتوني، بحيث يمكن استخدامه في التنبؤ بسلوك خلية الوقود وفحص المعلمات المختلفة التي تؤثر على أداء الخلية. الفكرة الرئيسية هي تقدير المعلمات الأمثل لخلايا وقود غشاء التبادل البروتوني عن طريق تقليل إجمالي قيمة الخطأ التربيعي بين جهد الخرج التجريبي وجهد الخرج التقريبي. لإعطاء نتائج أفضل من حيث الدقة والموثوقية، يتم استخدام تصميم جديد لميتاهيوريستيك يسمى خوارزمية سترايدر المياه المتوازنة. يتم التحقق من صحة نتائج الطريقة المقترحة أخيرًا بالمقارنة مع العديد من أحدث المحسنات المطبقة على حالة اختبار عملية. بعد تشغيل جميع المحسنات 30 مرة بشكل مستقل، فإن الطريقة المقترحة مع الحد الأدنى من الخطأ المطلق تساوي 3.4831e -4 تظهر أفضل النتائج تجاه الآخرين.

The biodiesel industry is a downstream palm oil industry group that is projected to continue to grow in Indonesia. In addition to meeting national needs in order to fulfill the mandatory biodiesel acceleration program B20 in Year 2020 and B40 in Year 2050, the penetration of Indonesian palm oil biodiesel export market to the EU is more open with RED enforcement. Nevertheless, Indonesia's downstream palm oil industry including biodiesel industry is faced with various negative campaign issues as it has not achieved the value of GHG Emission saving default value of 35 percent to be called an environmentally friendly product. The purpose of this study is to identify the dominant global environmental aspects and impacts of the biodiesel production process from Indonesian palm oil and to provide improvement recommendations that encourage the reduction of greenhouse gas emissions in the transportation sector of national biodiesel products. The sustainability of palm oil biodiesel industry is evaluated using life cycle impact assessment method. The research is done by combining quantitative and qualitative approach. The field survey was conducted in oil palm plantation companies, crude palm oil producers, and biodiesel producers located in North Sumatra. Improvement recommendations for improving the sustainability of Indonesia's downstream palm oil industry, especially the biodiesel industry from crude palm oil raw materials, refers to best practices and expert discussions.

Thermal energy storage is an important element in order to conserve the energy and optimize the overall efficiency. Development of energy storage system for local purposes requires some information on the raw material which is abundantly available in the local market. This study aimed to investigate the characteristics of traditionally produced salt in Aceh in terms of its potential use as a raw material for thermal energy storage. The sample was collected from the Aceh Besar District and treated by heating at temperatures of 400˚C and 800˚C in a muffle furnace. This treatment is carried out to study the changes in properties and define the best procedure for salt preparation. All samples were characterized under a number of techniques including XRF, XRD, SEM/ EDS, TGA/ DSC analysis, density, thermal conductivity, and electrolytic conductivity. The XRF characterization showed that the local Aceh salt was graded as a category III salt. Furthermore, according to the TGA/ DSC characterization, the melting temperature is close to 800 degrees Celsius, and the enthalpy value is close to 492 KJ/ kg. It is ample evidence that the Aceh salt can be used as a thermal energy storage material. Furthermore, increasing the temperature of local salt's heat treatment contributes to increasing the enthalpy value, crystal size, density, thermal conductivity, and electrolyte conductivity.

A case study of the manufacture of an OTEC factory on a floating ship has been carried out using 100 MW Titanium material at a fairly expensive cost, so the OTEC system was researched using a copper-tin alloy. The behavior of the tin-copper heat exchanger between the Aspen Plus simulation and the Computational Fluid Dynamics (CFD) simulation on Shell And Tube evaporators of Bonnet Divided Flow fixed and Bonnet One-pass Shell fixed (BEM) types is investigated. The difference in temperature between water at sea level of 29 °C and water at a depth of 1000 meters at a temperature of 5 °C is assumed to produce electricity. A marine thermal energy conversion power plant is a continuous source of energy sourced from nature an evaporator heat exchanger with ammonia working fluid will produce power that can drive a turbine forwarded to a generator. The simulation results of CFD of a Bonnet Divided Flow fixed type Heat Exchanger on the hot water inlet line has a temperature of 29.9 °C, when exiting the evaporator shell the temperature decreases to 26.4 °C. At the inlet line, the working fluid of ammonia enters the evaporator at 7.9 °C and when it leaves the tube, the temperature rises to 26.3 °C. The best results of the simulation of Aspen Plus Heat Exchanger type BEM Inlet Ammonia temperature 8 °C and at CFD 7.99 °C. Meanwhile, at the ammonia outlet at 28 °C and in the CFD simulation, the ammonia outlet temperature was 28.21 °C. Aspen Plus Inlet heating water temperature is 30 °C, and in CFD simulation, the temperature is 29.99 °C. While the heating water outlet is 28 °C, and in the CFD simulation, the heating water outlet is 28.15 °C. The conclusion from the simulation results is that the BEM-type heat exchanger is very good and suitable for experimental prototyping.