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To reduce and convert biodegradable waste into energy-rich biogas, anaerobic digestion technology is usually employed. Hence, this takes place inside the biogas digester. Studies have revealed that these digesters are designed and constructed using bricks, cement, and metal; often require a large footprint; and are bulky and expensive. The innovation of portable biogas digesters has come into the market to address these challenges. This present review provides an overview of the in-depth and comprehensive information on portable biogas digesters in the literature. Areas covered in the review include the modification of the biogas digester design, the need for a portable biogas digester, recent studies on the factors affecting the performance of portable biogas digesters, and specific assumptions taken into consideration for designing any portable biogas digester. Convincingly, portable biogas digesters appeal to small rural families because of their ease of operation, maintenance, and ability to save space. The material for the construction and comparison of the portable biogas digester with other designs and the economic feasibility of the system were also reviewed. Implications: The full-scale design, fabrication, and utilization of a portable biogas digester are viable but not widely employed compared to other designs. However, there is a lack of readily available information on the portable design of biogas digesters. This review presents various aspects relating to portable biogas digesters and the quality of biogas produced. Therefore, the review suits audiences in energy process design and engineers, energy researchers, academics, and economists. [ABSTRACT FROM AUTHOR]

South Africa has been experiencing an energy crisis since 2007 and continues to the present. This has resulted in load-shedding (action to interrupt electricity supply to avoid excessive load on the generating plant). One way to address this problem is to further explore the potential and contribution of bioenergy through research conducted and implementing energy reports. Therefore, the study aims to provide the state of bioenergy and its contribution to the country's economic sector and to enhance the replacement of fossil fuels with bioenergy resources and technology. A total blackout of 15,913 h has been experienced since 2014, according to the weekly system status report released by ESKOM. The power utility (Eskom) responsible for power generation and utility has attributed this problem to insufficient generation and capacity. Based on this, the country is embarking on solving this problem. Although the country is dominated by coal (fossil fuel), constituting 73.8% of the total energy supply, this poses a serious environmental risk and health hazard. Renewable energy is considered an alternative energy source, and its introduction and implementation look promising in reducing and solving the current energy crisis. With abundant renewable energy potential, representing 8.7% of the total energy supply, around 85% is bioenergy. This review's findings revealed that bioenergy contributed mainly towards heat, and fuels admit other energy sources, which is recommended. Therefore, its deployment on a large scale is promising and possible. This study will guide and further encourage the deployment of bioenergy projects in South Africa. [ABSTRACT FROM AUTHOR]

Governments and energy providers all over the world are moving towards the use of renewable energy sources. Solar photovoltaic (PV) energy is one of the providers' favourite options because it is comparatively cheaper, clean, available, abundant, and comparatively maintenance-free. Although the PV energy source has many benefits, its output power is dependent on continuously changing weather and environmental factors, so there is a need to forecast the PV output power. Many techniques have been employed to predict the PV output power. This work focuses on the short-term forecast horizon of PV output power. Multilayer perception (MLP), convolutional neural networks (CNN), and k-nearest neighbour (kNN) neural networks have been used singly or in a hybrid (with other algorithms) to forecast solar PV power or global solar irradiance with success. The performances of these three algorithms have been compared with other algorithms singly or in a hybrid (with other methods) but not with themselves. This study aims to compare the predictive performance of a number of neural network algorithms in solar PV energy yield forecasting under different weather conditions and showcase their robustness in making predictions in this regard. The performance of MLPNN, CNN, and kNN are compared using solar PV (hourly) data for Grahamstown, Eastern Cape, South Africa. The choice of location is part of the study parameters to provide insight into renewable energy power integration in specific areas in South Africa that may be prone to extreme weather conditions. Our data does not have lots of missing data and many data spikes. The kNN algorithm was found to have an RMSE value of 4.95%, an MAE value of 2.74% at its worst performance, an RMSE value of 1.49%, and an MAE value of 0.85% at its best performance. It outperformed the others by a good margin, and kNN could serve as a fast, easy, and accurate tool for forecasting solar PV output power. Considering the performance of the kNN algorithm across the different seasons, this study shows that kNN is a reliable and robust algorithm for forecasting solar PV output power. [ABSTRACT FROM AUTHOR]

A comparative analysis of aboveground and underground biogas digesters is described in relation to their performance and effect of temperature, pH, and hydraulic retention time. The digestion chamber of the two biogas systems under study was fabricated using high‐density polyethylene (HDPE) plastic, while the inlet and outlet chamber were constructed with bricks. The performance of small‐scale digesters, particularly of the fixed‐dome type, should be improved. Cow dung served as substrate in the performance test. Biogas production from the two systems was measured by a customized gas temperature pressure measurement sensor. Evidently, the insulation provided to the underground digester helped to achieve a more stable internal temperature for the digester. [ABSTRACT FROM AUTHOR]