Renewable energy technologies produce sustainable, clean energy from sources such as the sun, the wind, plants and water. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation and rural (off-grid) energy services. According to the Rwanda Energy Group, in 2018, the total installed capacity of Rwanda's power generating plants was recorded at 218MW. Renewable sources of energy accounted for about 113.14 MW (52.4%) of total energy consumption in Rwanda. Renewable energy technologies have the potential to strengthen the nation's energy security, improve environmental quality and contribute to a strong energy economy. The purpose of this paper is to review the current renewable energy technologies in Rwanda with an estimation of their potential; the challenges of new and existing renewable energy technologies are also presented. The most important renewable energy technologies (i.e., hydro, solar and biomass energy) are discussed and analysed.Moreover, each renewable energy technology's description is followed by its current potential share, its challenges, the advantages of increased adoption, future perspectives and disadvantages. The results show that 35.13% of Rwandan households are connected to the national grid and 11.33% accessing through off-grid systems. These show that access to electricity remains low, so in the rural areas, efforts are also required to provide electricity to those who are not close to the national grid.

Rwanda is adopting a new concept of using an alternative energy source as a cooking fuel, where more than the majority of the population live in a rural area and use wood for all heating needs. Biomass in the form of firewood and charcoal plays a significant part in Rwanda's economy. This accounted for 83 per cent of Rwanda's energy consumption in 2020. Biomass technology can be converted into fuel through some different processes, including solid fuel combustion, digestion, pyrolysis, fermentation and catalyzed reactions. With the government engaging in improving the health and protection of the environment, it becomes mandatory to look for alternative fuels not harmful or way to improve the methodology and the quality of stoves used in the country. In this study, the impacts of using biomass energy were assessed and mitigation measures were also proposed. The result shows that reducing reliance on unsustainable use of wood fuel and adds ongoing efforts in Rwanda to transition from the traditional use of biomass to Liquefied Petroleum Gas (LPG) or other improved cooking technology for fuel in a sustainable way. Along with this, the use of biomass for fuel is having harmful effects through health impacts and emissions. The article fills an important gap on the energy literature on Rwanda, as it gives detailed info on the cooking sector.

This work investigates the effect of low frequency vibratory processing for cleaning and washing various machine components parts from rusts and old paints deposits. The experimental investigation was carried out with special prepared samples that were weighted and exposed to paints and rust contaminants. These samples were treated in universal horizontal vibration machine UVHM 4 × 10 with different combination of instrumental processing medium, process fluid, machine amplitude and frequency of oscillations. They were periodically reweighted after processing and compared to etalon with control of quantity of dust that have been removed, sample cleanliness and also other functional parameters. Statistical analysis has been used to characterize ongoing process and full factorial analysis to establish experimental parameters dependency. The result is showing the complex dependence of samples cleanliness to each processing parameters like processing time, amplitude of oscillations, frequency of oscillations, process fluid parameters, instrumental medium, etc. Between this parameters although the most important successively the amplitude of oscillations, the frequency of oscillations the processing medium and the processing fluid depending to his considered composition, the optimal processing time can be reach only by complex combination of all this parameters every of them carry an amplify coefficient. Low frequency oscillations can be used to monitor and optimize washing and cleaning operations of paints and rusts contaminations. That guarantees process automation, its effectiveness for a large industrial application.

The combustion within the boiler burns fuel to create heat energy which then produces electrical power. The combustion of fuel is its reaction with oxygen available in the air. The amount of fuel that can be well burnt is limited by the quantity of oxygen. Once all the fuel is not burnt at all, some of it stays in the boiler and other quantity goes to the atmosphere. Most of the fuels used in the boiler are hydrocarbons which release hydrogen and carbon as residuals. It causes small efficiency and degradation of the air. It is needed to take the faction of air/fuel to the optimum value to reduce these problems. This paper provides different reviewed algorithms that control the combustion within the boiler and the role of environmental temperature. The author found that the separation of the oxygen from the air combined with the preheating both fuel and oxygen taking into account environmental temperature would provide better stoichiometric values, which improve the performance.

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