Journal of Energy
ISSN / EISSN : 0146-0412 / 1555-5917
Published by: American Institute of Aeronautics and Astronautics (AIAA) (10.2514)
Total articles ≅ 715
Latest articles in this journal
Journal of Energy, Volume 2020, pp 1-10; https://doi.org/10.1155/2020/8816296
The present technology of transesterification of vegetable oils to produce biodiesel, which is suited to replace petrodiesel, has economic challenges, and therefore, alternative sources are being explored. Microalgae, a renewable, third-generation biofuel resource, have the potential to become a viable feedstock due to their high oil content and environmentally friendly nature. The present study investigates the effect of microwave irradiation on the simultaneous extraction and transesterification of algae lipids to produce fatty acid methyl ester (FAME), in a batch reaction system using sulphuric acid catalyst. In situ transesterification combines the two steps of lipid extraction and transesterification into a single step. The microwave synthesis unit comprised of a 3-neck round bottom flask inside a 1300-Watt microwave oven, fitted with a quick-fit condenser and having an external stirrer. Response surface methodology (RSM) was used to analyse the influence of process variables, dry algae to methanol ratio 1 : 4 − 1 : 14 g / ml , algae biomass to catalyst ratio 1 : 0.0032 − 1 : 0.0368 wt % , and reaction time 1 − 11 min , at 500 rpm stirring rate for in situ reaction. FAME was analysed using gas chromatography (GC). The total lipid content of Arthrospira Spirulina platensis microalgae biomass was found to be 10.7 % by weight. The algae biomass also contained proteins at 51.83 % , moisture content at 7.8 % , and ash content 14.30 % by weight. RSM gave the optimum process conditions as dry algae biomass feed to methanol wt / vol ratio of 1 : 9, catalyst concentration of 2 wt % , and reaction time of 7 minutes for a maximum FAME yield of 83.43 wt % . The major fatty acid composition of FAME was palmitic 43.83 % , linoleic 38.83 % , and linolenic 19.41 % . FAME properties obtained according to European Standards (EN 14214) and American Society for Testing and Materials (ASTM D 6751) standards were as follows: flash point 16 4 o C calorific value 32,911 kJ / kg , acid value 0.475 KOH / g , viscosity 4.45 m m 2 / s , and specific gravity 0.868 . The study showed that Arthrospira Spirulina platensis microalgae lipid FAME met the biodiesel standards (EN 14214 and ASTM D 6751) and has the potential to replace petrodiesel. Microwave irradiation increased the reaction rate resulting in a reduced reaction time of 7 minutes (as compared to 8 hours for conventional heating) and therefore was found to be a superior heating mode as compared to conventional heating.
Journal of Energy, Volume 2020, pp 1-8; https://doi.org/10.1155/2020/8861190
During the working period of decay heat removal system, the flow rate of liquid sodium in wire-wrapped fuel assembly is very low, generally Re < 1000 . In the present study, both experimental methods and numerical simulation methods are applied. First, water experiment of 37-pin wire-wrapped rod bundle was carried out. Then, the numerical simulation study was carried out, the experimental data and the numerical simulation results were compared and analyzed, and a suitable turbulence model was selected to simulate the liquid sodium medium. Finally, numerical simulations under different boundary conditions were performed. Results indicate that except for the low Reynolds number k - ε turbulence model, other turbulence models have little difference with the experimental results. The results of realizable k - ε turbulence model are the most close to the experimental results. Compared with the friction factor obtained by using water medium and liquid sodium medium, the calculation results of water medium and sodium medium under the same condition are basically consistent, with the deviation within 1%. The reason is that the velocity of water is higher than sodium medium at the same Reynolds number, and the transverse disturbance caused by helical wire is larger.
Journal of Energy, Volume 2020, pp 1-12; https://doi.org/10.1155/2020/8873058
Energy has become the driving force for national infrastructure development, including the socioeconomic development of every society. Ghana, like many other African countries, formulated developmental policies to attain middle-income status in the medium term. Socioeconomic growth comes with an upsurge in electricity consumption. Ghana seeks to use industrialization to achieve its middle-income target. To achieve this target, there is a need to develop a reliable, sustainable and affordable energy supply in a benign environment. The entry point for Ghana to become a middle-income economy is a cost-effective and reliable electricity supply. Ghana is endowed with fossil fuel, hydro and renewable resources to drive its industrial ambitions, but the indigenous gas fields feeding some thermal plants for electricity production are decreasing and could run out by early 2030 unless new fields are discovered and may also be affected by price volatility. The untapped hydro resources are also small and unreliable if the country seeks to become a middle-income country. Despite the abundant renewable resources, they are intermittent and do not present a baseload option. In safeguarding Ghana’s energy security, the country seeks to include nuclear energy into her energy mix. This research paper discusses the major drivers for nuclear energy inclusion.
Journal of Energy, Volume 2020, pp 1-4; https://doi.org/10.1155/2020/8815484
Energy is one of the most important needy resources that found in the form of renewable and nonrenewable sources. The world demand for energy grows rapidly, and therefore, it is a time to look alternative and renewable energy resources to replace the rapidly depleting supply of fossil fuels. This study is aimed at analyzing the effects of temperature (°C), retention time (days), and potential of animal waste on the biogas production and its %CH4 compositions as responses to the factors of the study. The materials used in this study were cow dung, sheep, and pig manures. Anaerobic batch digesters (plastic water bottle) with a total volume of 2000 ml were used as digester (bioreactor) in this experiment. The glucose drip (tube) was fitted to the lids of each digester. Average temperature of digester was increased starting from the 6th to 10th day in cow dung and sheep manure. In this experiment, optimum time for best biogas yield was recorded. Analysis of the gas component shows the significant volume of methane component recorded in cow dung (66.9%) followed by sheep manure (62.1%). Cow dung was one of the best in producing biogas, while the sheep manure was medium, and pig manures are fewer producers as compared to others.
Journal of Energy, Volume 2020, pp 1-11; https://doi.org/10.1155/2020/8844433
A numerical study for heat exchanger for spray-assisted low-temperature desalination system is presented for an existing low-temperature desalination unit at Arusha Technical College. This is aimed at recognizing the effect of mass flow and physical parameters like tube layout (diameter and length) on the overall heat transferred and the pressure drop in the shell-and-tube heat exchanger (STHX), as well as the impact of these parameters on the heat transfer coefficient and the overdesign of the STHX. Also, the study provides a suitable mathematical model for the replacement of the current condensation unit which tends to reduce energy consumption by reducing some of the electrical components in the system. A Math CAD model was developed using the Delaware method to obtain the mentioned parameters. The results show that at 0.8 kg/s flow rate a maximum heat transfer coefficient of 23212 W/m2K is achieved in a minimum diameter of 10 mm within a maximum tube length of 1000 mm heat exchanger and the pressure drop seems to be very low in a range of 0.328-0.957 Pa from all configurations. The configuration with 1000 mm tube length and 10 mm diameter performed well on the mass flow of 0.3 kg/s-0.8 kg/s by providing a suitable overall heat transfer coefficient of 2306-2539 W/m2K, while 12.8 is a maximum overdesign coefficient achieved on 0.8 kg/s mass flow. The study results show the possibility of using STHX instead of the current condensation unit in implementing a proposed system layout with the minimum effect of energy consumption.
Journal of Energy, Volume 2020, pp 1-9; https://doi.org/10.1155/2020/8813254
The inefficient indoor burning of fuelwood on traditional cookstoves generates pollutants, primarily carbon monoxide and many other human health-damaging emissions. It is from this risk that it is necessary to have an immediate shift to alternative cleaner fuel sources. Biogas, which is among the biofuels from biomass, is one of the resources that play a considerable part in a more diverse and sustainable global energy mix. For domestic purposes in rural areas of Tanzania, biogas provides a better option that can supplement the use of fossil fuels such as wood, charcoal, and kerosene, which is nonrenewable. However, the low efficiency experienced in the locally made biogas burners hinders the large-scale use of biogas among the population in the country. With the locally made burners, the users of biogas for the domestic application face problems including heat loss and high gas consumption which affects the whole cooking process. It is against this backdrop that the current study objectives incline on designing and improving the efficiency of the locally manufactured burners to achieve the uniform flow of fuel in the mixing chamber, which will result to the consistent heat distribution around the cooking pot. The optimization of the burner was done by using computational fluid dynamics (CFD) through varying the number of flame portholes and air holes as well as the size of the jet before fabrication. The increased efficiency of the burner has also contributed by the addition of the fuel distributor. The results showed that the optimum hole diameter of the jet was 2.5 mm and that of the manifold was 100 mm. The currently developed biogas burner was tested and compared with the other two locally made burners. The water boiling test (WBT) on these three burners showed that the developed burner has a thermal efficiency of 67.01% against 54.61% and 58.82% of the Centre for Agricultural Mechanization and Rural Technology (CARMATEC) and Simgas, respectively. Additionally, the fuel consumption of the developed burner was 736 g/L as compared to 920 g/L for CARMARTEC and 833 g/L for that of Simgas. The developed burner and its corresponding cookstove are both environmentally friendly and economical for household utilization in Tanzania and other developing countries.
Journal of Energy, Volume 2020, pp 1-11; https://doi.org/10.1155/2020/8892279
Energy shortage is the main problem while preparing food at the university in Ethiopia. Baking of injera consumes a lot of firewood due to the nature of baking mitad and layout of the system. The daily average firewood consumption is 8600 kg which is equivalent to 790.3 m3 of gas. In this study, an investigation of energy yield from food waste is examined by assessing the daily waste generation rate from the university student cafeteria and configuring the baking stove (mitad) that utilizes biogas energy. CFD is used to investigate the performance and heat distribution of baking mitad. In the study, the measured average daily biodegradable food waste and kitchen waste generation rate in the campus is around 863 kg/day. The conversion of this food waste using the anaerobic digestion system yields 43.2 m3 biogas per day. Utilizing the daily biogas generated for baking injera improves the overall food making process and reduces firewood consumption by 5.4%. This biogas energy yield is considered to be utilized for baking injera in the kitchen. The designed biogas mitad (stove) does not generate smoke due to the type of fuel used and configuration of baking mitad. Furthermore, the stove has an insulation mechanism considered to conserve the heat loss to the surrounding. Generally, the utilization of the biogas system and integration of the biogas injera baking stove will improve the overall food processing mechanism in the university.
Journal of Energy, Volume 2020, pp 1-6; https://doi.org/10.1155/2020/8823720
Ghana thought of nuclear energy early in the 1960s but has not been able to realize this dream of generating electricity from nuclear power. Ghana’s electricity generation dates back to the Gold Coast era where the main source of electricity supply (isolated diesel generators) was owned by industrial establishments, municipalities, and other institutions. The electricity sector has developed over the years and has diversified its power generation development to take advantage of available and sustainable sources of energy, mainly hydro, natural gas, liquefied petroleum products, and renewables. These sources sought to increase the electricity production capacity in the country, but unfortunately, it has not been able to catch up with the rate of economic growth, urbanization, industrialization, and rural electrification projects. This has led to Ghana’s persistent energy crisis, with inadequate and unpredictable power supply coupled with erratic and prolonged cuts of electricity to homes, industries, and businesses which is now colloquially referred to in the local parlance as “dumsor.” The Government of Ghana and key stakeholders have therefore decided to add nuclear energy to the energy mix of the country to complement the country’s two main energy sources being hydro and thermal electricity. The details of the developments in the electricity sector leading to the choice of nuclear energy as the best solution for Ghana have been outlined.
Journal of Energy, Volume 2020, pp 1-10; https://doi.org/10.1155/2020/9205283
Solar energy has become a viable alternative energy because it is a clean type of energy that converts solar radiation into heat energy for various applications such as heating water, power generation, cooking, and food drying. The solar dryer, integrated with the heat energy storage system, uses nitrate salt as a heat storage medium which was designed and tested by drying 1000 grams of red pepper at 19.6 to 62.4°C. The average ambient temperature ranged from 19.3 to 37.4°C, and the maximum temperature of the heat storage media ranged from 87.8 to 125°C. The solar drying process was compared to open sun drying system loaded with 1000 grams of red pepper. The findings showed that the solar dryer maintained color and flavor and lowered the original moisture content from 86% to 10% for 24 hours compared to 36 hours of drying in open air. In this study, nitrate salt is shown to be the perfect heat storage medium for drying food products; it preserved heat for about 4 hours when there is no active sunlight.
Journal of Energy, Volume 2020, pp 1-23; https://doi.org/10.1155/2020/2760140
This article starts by introducing the ongoing South Africa electricity crisis followed by thermoelectricity, in which eighteen miscellaneous applicable case studies are structurally analysed in detail. The aim is to establish best practices for the R&D of an efficient thermoelectric (TE) and fuel cell (FC) CCHP system. The examined literature reviews covered studies that focused on the thermoelectricity principle, highlighting TE devices’ basic constructions, TEGs and TECs as well as investigations on the applications of thermoelectricity with FCs, whereby thermoelectricity was applied to recover waste heat from FCs to boost the power generation capability by ~7–10%. Furthermore, nonstationary TEGs whose generated power can be increased by pulsing the DC-DC power converter showed that an output power efficiency of 8.4% is achievable and that thicker TEGs with good area coverage can efficiently harvest waste heat energy in dynamic applications. TEG and TEC exhibit duality and the higher the TEG temperature difference, the more the generated power—which can be stabilised using the MPPT technique with a 1.1% tracking error. A comparison study of TEG and solar energy demonstrated that TEG generates more power compared to solar cells of the same size, though more expensively. TEG output power and efficiency in a thermal environment can be maximised simultaneously if its heat flux is stable but not the case if its temperature difference is stable. The review concluded with a TEC LT-PEM-FC hybrid CCHP system capable of generating 2.79 kW of electricity, 3.04 kW of heat, and 26.8 W of cooling with a total efficiency of ~77% and fuel saving of 43.25%. The presented research is the contribution brought forward, as it heuristically highlights miscellaneous thermoelectricity studies/parameters of interests in a single manuscript, which further established that practical applications of thermoelectricity are possible and can be innovatively applied together with FC for efficient CCHP applications.