RP-Department of Energy Engineering

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Advances in wind energy resource exploitation in urban environment: A review
(Elsevier, 2014) Ishugah, T.F.; Li, Y.; Wang, R.Z.; Kiplagat, J.K.
Wind energy continues to stand out as a more established and mature technology to offset a large proportion of power. Efforts aimed at improving wind energy use to meet the energy demand in turbulent urban wind environment have been the main technical focus. In previous studies on wind resource and behavior in urban environment, different designs of horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) have been reviewed. This paper vividly captures the fact that wind resource has a great potential to be fully explored and developed in the urban environment. Varying ways of application and application techniques being applied for electrical generation, ventilation and pollution dispersion, onshore cooling and dehumidification of coastal urban cities, and economics and environmental benefits of applying wind energy in urban environments are summarized. Although many new ideas and solutions that factor technical, economical and environmental sustainability in urban areas are coming up every day, challenges in design are gradually being solved to take advantage of urban low and turbulent wind speed characteristics, installation space challenges, vibration and noise reduction, among others. Some of the unique solutions that have been and are being developed in the applications of wind energy technology in urban environments are also reported in this paper
Advances in wind energy resource exploitation in urban environment: A review
(Elsevier, 2014-09) Kiplagat, J.K.
Wind energy continues to stand out as a more established and mature technology to offset a large proportion of power. Efforts aimed at improving wind energy use to meet the energy demand in turbulent urban wind environment have been the main technical focus. In previous studies on wind resource and behavior in urban environment, different designs of horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) have been reviewed. This paper vividly captures the fact that wind resource has a great potential to be fully explored and developed in the urban environment. Varying ways of application and application techniques being applied for electrical generation, ventilation and pollution dispersion, onshore cooling and dehumidification of coastal urban cities, and economics and environmental benefits of applying wind energy in urban environments are summarized. Although many new ideas and solutions that factor technical, economical and environmental sustainability in urban areas are coming up every day, challenges in design are gradually being solved to take advantage of urban low and turbulent wind speed characteristics, installation space challenges, vibration and noise reduction, among others. Some of the unique solutions that have been and are being developed in the applications of wind energy technology in urban environments are also reported in this paper.
Briquette making in Kenya: Nairobi and peri-urban areas
(Elsevier, 2014) Kiplagat, J.K.; Ngusale, George K.; Luo, Yonghao
Briquettes made from biomass residues could contribute to ensuring the sustainable supply of biomass energy. The paper reviews the present briquette making process in Kenya especially in Nairobi and peri-urban areas. The paper introduces the energy situation in Kenya, then the briquette making process and finally presents the challenges and opportunities in briquette making. In the opportunities section, eighteen briquette producers participated in the question and answer exercise to quantitatively provide information on briquette making. Most producers use bare hands (handmade briquettes), others make use of novel-based machines such as ram-piston type, motorized screw press, shredder, wooden press and the mold-box piston type all made from locally available materials. The mixing ratios and the various ingredients used in briquette making are haphazard with no standard ratio and specific mixture for optimum briquette production. Despite these, most briquette producers are well along in the briquette business. At the same time, the end-use consumers are very positive in using the briquette fuel as an alternative fuel. Some of the end-use consumers are the schools, churches, hotels and some households. This study indicates that the opportunities for briquette making are immense and could help curb deforestation thereby reduce environmental degradation.
Characterization and Ranking of Various Mix Ratios of Cow, Pig and Sheep Manure
(Journal of Energy Research and Reviews, 2021-04) Matwek, Sheila Chepkirui; Nyaanga, Daudi M.; Osodo, B. O.
This work determined the characteristics of various mix ratios of the cow to pig to sheep manures and ranked them with help of principal component analysis (PCA). Ten mix ratios (by mass) namely 1:1:1, 3:1:1, 1:3:1,1:1:2, 2:1:1, 1:2:1, 1:1:2, 1:3:3, 3:3:1, 3:1:3 of cow, pig and sheep manures respectively were selected. Laboratory analysis was done to determine the total solid (TS) content, carbon to nitrogen ratio, pH, and volatile solid (VS) content using standard procedures. The results obtained (except that of pure feedstocks) were subjected to principal component analysis to determine the principal component scores for the mix ratios to enable ranking. The total solids content of pure cow, pig, and sheep manure were found to be 19.18%, 23.50%, and 30.35% respectively. Corresponding carbon to nitrogen ratios values were 23.68, 13.27 and 29.00, pH values were 6.50, 7.90 and 7.00 and volatile content were 88.37%, 84.57% and 80.00%. Upon mixing the three manures at various mix ratios total solid content varies from 22.28% to 26.75%. Total solids content, carbon to nitrogen ratio, pH and volatile solids content varies from 22.28% to 26.75%, 18.76 to 25.05, 7.13 to 7.56 and 85.94% to 82.59% respectively. Using the first principal component scores mix ratio 1:1:3 of cow dung, pig, and sheep manure was the top-ranked followed by 3:1:3 and the third one was 1:1:2 with scores of 2.540, 1.638, and 1.580 respectively. The 4th ranked mix ratio was 1:3:3, 5th ranked was1:1:1, 6th ranked was 2:1:1, the 7th one was 3:1:1, 8th one was 1:1:2, then 3:1:1 and lastly 1:3:1 with the scores of 0.191, -0.006, -0.147, -0.259, -1.440, -1.810 and -2.287 respectively. Higher positive scores were associated with a possibility of producing higher biogas yield possibly due to the right combination of the several parameters in the mixture while a lower score might indicate a lower gas yield due to an improper combination of parameters. It was then concluded that principal component analysis is a suitable method for selecting few mix ratios to use in anaerobic digestion among the many. It saves on time and resources due to the reduced number of experiments.
Characterization and Ranking of Various Mix Ratios of Cow, Pig and Sheep Manure
(Journal of Energy Research and Reviews, 2021-04) Matwek, Sheila Chepkirui; Nyaanga, Daudi M.; Osodo, B. O.
This work determined the characteristics of various mix ratios of the cow to pig to sheep manures and ranked them with help of principal component analysis (PCA). Ten mix ratios (by mass) namely 1:1:1, 3:1:1, 1:3:1,1:1:2, 2:1:1, 1:2:1, 1:1:2, 1:3:3, 3:3:1, 3:1:3 of cow, pig and sheep manures respectively were selected. Laboratory analysis was done to determine the total solid (TS) content, carbon to nitrogen ratio, pH, and volatile solid (VS) content using standard procedures. The results obtained (except that of pure feedstocks) were subjected to principal component analysis to determine the principal component scores for the mix ratios to enable ranking. The total solids content of pure cow, pig, and sheep manure were found to be 19.18%, 23.50%, and 30.35% respectively. Corresponding carbon to nitrogen ratios values were 23.68, 13.27 and 29.00, pH values were 6.50, 7.90 and 7.00 and volatile content were 88.37%, 84.57% and 80.00%. Upon mixing the three manures at various mix ratios total solid content varies from 22.28% to 26.75%. Total solids content, carbon to nitrogen ratio, pH and volatile solids content varies from 22.28% to 26.75%, 18.76 to 25.05, 7.13 to 7.56 and 85.94% to 82.59% respectively. Using the first principal component scores mix ratio 1:1:3 of cow dung, pig, and sheep manure was the top-ranked followed by 3:1:3 and the third one was 1:1:2 with scores of 2.540, 1.638, and 1.580 respectively. The 4th ranked mix ratio was 1:3:3, 5th ranked was1:1:1, 6th ranked was 2:1:1, the 7th one was 3:1:1, 8th one was 1:1:2, then 3:1:1 and lastly 1:3:1 with the scores of 0.191, -0.006, -0.147, -0.259, -1.440, -1.810 and -2.287 respectively. Higher positive scores were associated with a possibility of producing higher biogas yield possibly due to the right combination of the several parameters in the mixture while a lower score might indicate a lower gas yield due to an improper combination of parameters. It was then concluded that principal component analysis is a suitable method for selecting few mix ratios to use in anaerobic digestion among the many. It saves on time and resources due to the reduced number of experiments.
Characterization of food wastes from the hotel industry as a potential feedstock for energy production
(Elsevier, 2025) Muchele,Emily Machuma; Osodo,Booker; Omosa, Isaiah; Kombe,Emmanuel Yeri
Food waste contribute to 38% of total Municipal Solid Wastes (MSW) in Kenya and end up in landfills. Due to high competition in the available space, most cities, including Nairobi, do not have enough space for landfills. Therefore, there is a need for efficient ways to manage the generated waste. Developed countries have embraced Waste-to-Energy technologies, minimizing waste generation and converting generated waste into energy and other resources. Waste characterization is a key element in the energy generation process not only to identify important parameters but also to guide biomass source segmentation. In this study, food wastes were collected from 21 hotels within Nairobi City County, in different mixed ratios and subdivided into five samples for investigation and analysis. The average feedstock characteristics were observed to be moisture content (6.0%, p < .001, R2 = 90.70 %), total solid (93.7%, p < .001, R2 = 99.97 %), volatile solid (84.3%, p < .001, R2 = 99.80 %), ash content (4.2%, p = .005, R2 = 48.54 %), fixed carbon (5.4%, p < .001, R2 = 88.61%), nitrogen (3.6%, p = .04, R2 = 36.81 %), carbon to nitrogen ratio C/N (4.0), crude protein (22.4%, p = .004, R2 = 49.36 % ), crude lipids (12.1%, p < .001, R2 = 89.06 %), total organic carbon (44%, p < . 001, R2 = 94.70%), potassium (0.6%), sodium (1.2%), calcium (0.2%), and phosphorus (0.4%). The potassium, sodium, calcium and phosphorus p and R2 values all calculated together were p < .001 and R2 = 72.35%. The results showed a significant difference in the means of the samples with the majority of the parameters registering a strong positive correlation of above 50%. The analysis revealed that the feedstock under investigation contained well-balanced parameters for briquette, biogas, syngas and biochar production. Therefore, the findings of this research provide vital knowledge in integrating energy production from food wastes thereby improving the efficiency of food waste utilization
Characterization, Performance Evaluation and Optimization of Wheat Straw – Bagasse Blended Fuel Pellets
(CBIORE, 2024-02) Matasyoh, Isabel Musula; Osodo, Booker; Kombe, Emmanuel; Muguthu, Joseph
This study was carried out to assess the fuel pellets produced from wheat straw and sugarcane bagasse. The wheat straw and bagasse were blended into four ratios including; 10:90, 30:70, 70:30 and 90:10 (wheat straw: bagasse) and developed into fuel pellets. The fuel pellets were characterized to determine the moisture content, volatile matter, fixed carbon, ash content, calorific value, bulk density and mechanical durability. The ignition time, burning rate and specific fuel consumption of the wheat straw – bagasse blended fuel pellets were studied at varying blend ratios (10:90, 30:70, 70:30 and 90:10), moisture contents (9.1%, 10.6%, 12.6% and 14.7%) and raw material particle sizes (2 mm, 4 mm, 6 mm and 10 mm). Results indicated that the wheat straw: bagasse blend ratios containing more proportion of bagasse (30:70 and 10:90) recorded a shorter ignition time, higher burning rate and lower specific fuel consumption. Larger raw material particle sizes exhibited shorter ignition time, higher burning rate and specific fuel consumption. Moreso, the fuel pellets with low moisture contents also recorded shorter ignition time, higher burning rate and lower specific fuel consumption. It was concluded that fuel pellets with high quantity of bagasse, large particle sizes and low moisture content demonstrated favorable combustion characteristics. Response surface methodology was used in the optimization so as to determine the optimum combination of blending ratio, moisture content and raw material particle size that would result in the lowest ignition time, highest burning rate and lowest specific fuel consumption. Results indicated that an optimum combination of a wheat straw: bagasse blend ratio of 10:90, moisture content of 14.70% and a particle size of 10.00 mm resulted in the lowest ignition time, highest burning rate and lowest specific fuel consumption.
Climate Change Mitigation and Adaptation through Anaerobic Digestion of Urban Waste in Malawi: A Review
(ResearchGate, 2020-05) Chamdimba, Hope Baxter Nqcube; Mugagga, Reuben Gad; Ako, Elias Onyango
Improper waste management and disposal in major cities of Malawi transpires to be one of the major environmental setbacks as waste remains uncollected and usually disposed in open dump sites. Such waste emits greenhouse gases (GHGs) into the atmosphere that contribute to global warming and climate change in addition to pollution of water sources. The effects of climate change to Malawi have been far reaching to the extent of experiencing floods and droughts. This in retrospect has also had lasting impacts on Shire River where more than 95% of the country’s electricity is generated. Consequently, the rate of power generation is greatly hindered which has thus left only 11% of the population with access to electricity partly due to droughts. This paper therefore focusses on the capturing of methane from municipal solid waste as a solution to climate change and energy challenges through the utilization of methane, a combustible gas which is beneficial in regard to cooking, heating and electricity generation. This is amplified with particular review of the challenges, opportunities, policy framework in place and the pertinent role of anaerobic digestion as the game changer in climate change mitigation and adaptation in Malawi.
A combined doubleway chemisorption refrigeration cycle based on adsorption and resorption processes
(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.
An innovative combined double-way chemisorption refrigeration cycle based on adsorption and resorption processes is presented. Two different reactive salts were used as sorbents and ammonia was utilized as the refrigerant in the proposed cycle. The useful cold was obtained from the evaporation heat of the refrigerant during the adsorption process and from the reaction heat of the low-temperature salt during the resorption process. The proposed combined double-way cycle has a distinct advantage of higher coefficient of performance (COP) in comparison with conventional adsorption cycle or resorption cycle. Experimental verification indicated that the advanced combined double-way cycle is feasible for refrigeration application, and the ideal COP of the basic cycle was about 1.24. Theoretical results showed that the proposed combined double-way cycle could improve COP by 167% and 60% when compared with conventional adsorption cycle and resorption cycle, respectively.
A Comprehensive Review on Status of Solar PV Growth in Uganda
(Journal of Energy Research and Reviews, 2019) Mugagga, Reuben Gad; Chamdimba, Hope Baxter Nqcube
Uganda is faced with a challenge of huge energy deficit just like many other developing countries in Africa. Currently, only 26.7% of the total population has access to electricity. Energy being the life – blood of any growing economy, subsequent endeavors and strategies need to be put in place in order to expand the use of renewable energies for socio-economic development and environmental sustainability. Uganda being endowed with plenty of solar energy resource, its role in achieving national ambitions of Sustainable Energy for All (SE4All) cannot be underestimated. This paper therefore reviews the growth of Solar Photovoltaics (PV) in Uganda that was birthed in the 1980’s and continues to mature steadily today contributing 4.24%(50MW) to the national grid with several un documented off – grid systems. This progress has been realized under different market segments inclusive of the pico and macro solar home systems, Institutional PV, mini-grids, telecommunications and street lighting. Notwithstanding the prevalent challenges, there are numerous existing opportunities for solar PV development consisting of the financial, environmental, Institutional and the socio-economic factors. With more government and different stakeholder engagement however, this growth in the country could be accelerated further as the costs of the technology continue to plummet.
Determination of the Physiochemical Characteristics of Hotel Food Waste and Its Biogas Fuel Potential
(CIGR, 2025) Chamdimba,Hope B.; Omosa,Isaiah; Wandera, Simon M.
Hotels are the source of large quantities of food waste, which can potentially be used for the generation of biogas for different applications, including agriculture. Thus, the purpose of this study was to investigate the physiochemical characteristics and biogas potential of the food waste generated by hotels in Nairobi City County, Kenya. To achieve this, a composition and physiochemical analysis of the feedstock were undertaken, which involved collecting and analysing a food waste sample of 130 kg, which gives an accuracy the same as that of a 1000 kg sample, according to the literature. In addition, the theoretical biomethane potential of food waste was determined using the Buswell and Carbon Balance equations, and the theoretical results were validated using anaerobic digestion experiments. The analysis showed that the fractions of different FW groups were fruits and vegetables (46%), roots and tubers (17%), meat and fish (14%), grains and cereals (9%), others (8%), bakery (4%), and tea and coffee (2%). The hotel food waste total solids, volatile solids, pH, COD, carbohydrates, and protein contents were determined to be 9.6%, 8.81%, 4.65, 142.3 g L-1, 70%, and 13%, respectively. The C, H, O, N, and S compositions of the FW were 48.46%, 9.8%, 30.48%, and 2.2%, respectively. The test results showed that, based on these physiochemical characteristics, the hotel food waste had a theoretical methane yield of 643.07 mL gVS-1 and an experimental methane yield of 518.53 ± 9.69 mL gVS-1. The experimental yield was almost equal to an average biomethane potential of food waste (i.e., 525.65 CH4 ml gVS-1) based on the results of the other similar studies. Therefore, the hotel food waste can be used as an alternative feedstock for biogas generation if it is properly secured by, among other things, promoting onsite segregation of the hotel food waste.
Developments in solar drying using forced ventilation and solar regenerated desiccant materials
(Elsevier, 1996) Thoruwa, T. F. N.; Smith, J. E.; Grant, A. D.; Johnstone, C. M.
In many countries, grains are naturally sun dried in the field, resulting in large-scale spoilage. Purpose-built solar grain dryers are being introduced with some success, but to be effective, their performance must be carefully controlled to prevent cracking of grains, fungal growth and aflatoxin production during storage. This paper describes some of the performance aspects of an autonomous solar desiccant maize dryer developed for village use in Kenya. Since most commercial desiccants are expensive, a low cost solid desiccant was fabricated from bentonite clay and calcium chloride materials. This desiccant is capable of regeneration at 45°C, has high moisture sorption of 45% (dwb), significantly extends the drying process at night and reduces aflatoxin contamination of the grain. Laboratory and field testing took place to determine the drying performance and allow conclusions to be drawn. This showed the prototype dryer had the capability of drying 90kg of fresh maize from 38% (dwb) to 15% (dwb) within 24 hours
Effect of Furnace Temperature on the Distribution of Tar during Gasification of Miscanthus
(Journal of Energy Research and Reviews, 2018-12) Kombe, Emmanuel Yeri
Biomass has been extensively recognised as a clean and sustainable energy source with the highest probability to substitute fossil fuel in the energy market. Its utilisation for energy generation is of particular interest to the world at large because of its potential to reduce global carbon dioxide emission. Concerning these considerations, gasification technology comes to the forefront of biomass conversion to various forms of energy for some reasons. Primarily, gasification offers a high flexibility in utilising different kinds of biomass feedstock to produce a combustible gas, making it more active process than pyrolysis and direct combustion. However, the major challenge associated with thermal gasification of biomass is tars and particulates formation. These compounds compromise the state of syngas, potentially harming end use systems especially those delicate to the quality of gas. In this research, tar sampling and analysis was performed based on a modified standard tar protocol followed by gas chromatography-flame ionisation detector (GC-FID) so as to quantify tar concentration in syngas produced from gasification of Miscanthus. Experiments was carried out at various furnace temperature in the range 350-650℃, with temperature enhancement, the abundance of phenolic compounds increases.
Enforcement of Access to Effective Technical Support Services in the Kenyan Solar Energy System
(JENRR, 2019) Mugo, Jackbed Gakii; Muguthu, Joseph N.
Energy is the prime mover of development cutting across industrialisation, manufacturing and residential consumption. Recently, Kenya, being ranked high among the most developed countries in Africa, has mapped way for embracement of renewable energy technology with increasing debate on sustainable development and environmental issues associated with fossil fuels, as the prime energy sources. Generally, Kenya is making efforts to Scale - Up renewable energy programs via construction of stand-alone solutions as well as various types of mini - grids. However, a common problem cutting across all these consumers is quick failure of such projects with very little access to technical solutions or none at all. Substantial developments in solar energy in Kenya, as one of the renewable energy sources, has been mainly challenged by lack of effective capacity building and poor technical support. This cuts across both domestic systems as well as the most rising aspect of small and medium sized minigrids. This paper aims at investigating the leading role of access to viable technical support services in mitigating solar energy adoption challenges. The paper focuses on challenges faced by small and medium sized consumers in search for technical advice and support prior to purchase, during installation and after purchase and installation stages. The research conducted survey via questionnaries, analyzed data obtained, identified technical support factors in order of priority and gives adaptable recommendation for the state in ensuring that solar projects are sustainable and that customers find value for their money.
Geothermal Energy Development in East Africa: Barriers and Strategies
(Journal of Energy Research and Reviews, 2018-12) Kombe, Emmanuel Yeri; Muguthu, Joseph
The East African Rift is among the most crucial regions of the world endowed with a remarkable geothermal potential. Using current technologies, East African countries have a geothermal power potential of more than 15,000 MWe. Nevertheless, the zone is still at an early stage of geothermal development with few plants producing a few hundred MWe. Among East African countries that have carried out research on geothermal resources, Kenya is leading in utilising geothermal energy resources for electricity generation. Eritrea, Uganda, Tanzania and Djibouti are at exploration stage while Malawi and Rwanda have so far not gone past geothermal resource potential record work. This study sought to address the challenges and barriers to the adoption of geothermal energy as well as the strategies to implement geothermal energy plans in East Africa
The Impact of Air Mass on the Performance of a Monocrystalline Silicon Solar Module in Kakamega
(Physical Science International Journal, 2019-03) Musanga, Ligavo Margdaline; Maxwell, Mageto; Barasa, Wafula Henry; Kombe, Emmanuel Yeri
This paper investigates the outdoor performance of a 20 W monocrystalline silicon solar module in relation to air mass (AM) in Kakamega. Direct measurement of air mass and module output parameters from experimental setup was done in Kakamega at a location 0.28270 N and 34.7519 E. Experimental results showed a decrease in ISC and VOC with increasing AM. The maximum output power produced by the module reduced with an increase in AM. Maximum power was therefore seen to be produced at noon in this region. VOC increased from 19.47 to 20.04 then decreased to 19.49 V while ISC increased from 0.36 to 1.19 then decreased to 0.48A. It was observed that both the FF and  of a monocrystalline solar module increase with increase in air mass. The module performed better during the afternoon than morning and evening hours with the peak performance observed close to AM 1.
The Impact of Roof Material Profile and Pigmentation on the Performance of Photovoltaic Modules
(MDPI, 2023-11) Aigbedion, Nosakhare; Njoka, Francis; Munji, Mathew
This study combines simulations and experiments to study the heat interactions between various types of roofs and the photovoltaic (PV) modules installed on them. Specifically, the performance of PV modules on a clay roof was compared with their performance on two types of metal roofs, a Box-profile metal roof and an Orientile metal roof, which differ in shape and geometry. Additionally, this study examined the cooling potential of three common metal roof pigments, iron (iii) oxide (Fe2O3 ), titanium dioxide (TiO2 ) and basalt, on roof-installed PV modules. An unpigmented roof was also studied for comparison purposes. Model development and simulation were implemented in COMSOL Multiphysics, and the simulation results were validated and compared with field experiments. The maximum open-circuit voltages of the PV installations were found to be 21.096 V for the clay roof, 20.945 V for the Box-profile metal roof and 20.718 V for the Orientile metal roof. This study revealed that the unpigmented roof had higher solar cell temperatures compared to the pigmented models, with temperature gains ranging from 2.2 ◦C to 2.71 ◦C. Moreover, the unpigmented model displayed significantly higher surface radiosity than the pigmented models. The performance output of the modules also varied depending on the metal roof sheet shape and geometry, with the Box-profile metal roof yielding better results than the Orientile metal roof sheet. These results indicate that a specific roof pigmentation may have a small impact on a single PV module, but it can become significant in a large array of modules, especially if cooling through natural convection is hindered.
Investigation on Optimal Cutting Parameters in Turning AISI 8660 Steel Using Silicon (Sic) Whisker Reinforced Ceramic Tool
(ResearchGate, 2017-07) Wathigo1, J.M; Keraita2, J.N; Byiringiro3, J.B; Muguthu4, J.N
This research was to investigate the effects of process parameter that is cutting speed, feed rate, depth of cut and machining time on the response variables in turning AISI 8660 material using whisker reinforced ceramic cutting tool. Cutting tools are weak and there is continuous effort to improving their performance and wear characteristics so that different grades of materials with varied degree of hardness are machined at minimal cost and economies of production can be realized during machining. This study investigated the rate tool wear and the cutting forces involved during the machining process. High speed machine lathe (Type: MORESEKI) was used on which a three force component dynamometer was mounted on the tool post to measure the cutting forces involved during the machining process. A Toolmakers microscope (model no: 80091) was used to measure the tool flank wear (VB) and the maximum tool wear recorded was 0.27mm and occurred at approximately 3.0 minutes during the machining process. Design of Experiment based on Taguchi technique was developed to obtain the experimental data. Response Surface Methodology (RSM) was used to analyze the data by developing 3D surface plots, contour plots and Main effects plots for Signal to Noise Ratio. The residuals plots analysis for cutting force revealed a normal probability plot for the data used indicating a close fit to the best of line. The histogram indicated 80% and 10% as the highest and lowest frequency for the cutting force. The optimal cutting conditions for toolwear were obtained at v = 158.28 mm/min, f = 1.116mm/rev, d = 1.38mm, and t = 2min with the process having a high composite desirability at 0.8557. The high composite desirability means that the process variable satisfies the target goals which are minimizing cutting forces and toolwear and that SiC whisker reinforced cutting is the recommended tool when machining this material.
Lithium Chloride–Expanded Graphite Composite Sorbent for Solar Powered Ice Make
(2010) Kiplagat, J.K.; Wang, R.Z.; Oliveira, R.G.; Li, T.X.
Consolidated composite material made from expanded graphite (EG) powder impregnated with LiCl salt is proposed for use in solar powered adsorption ice makers. Laboratory experiments were done to test the adsorption and desorption performance of the sorbent under different temperature conditions suitable for solar energy utilization. More than 75% of the reaction between LiCl and ammonia was completed after 30 min of synthesis at evaporation temperatures of −10 and −5°C and adsorption temperature between 25 and 35°C. Under the same period, it was possible to obtain 80% conversion in the desorption phase, when the generation temperatures ranged between 75 and 80°C, and the condensation temperature varied from 25 to 35°C. The highest average specific cooling power during the synthesis phase was 117 W per kg of the block. The calculated theoretical coefficient of performance (COP) under different cycle conditions was nearly constant at 0.47. Moreover, the new composite sorbent showed higher Specific Cooling Capacity (SCC), compared to activated carbon (AC)/methanol pair. Experiments done with blocks with different proportion of EG, showed that the proportion of EG influence the cooling capacity per unit mass of salt and had almost no influence on the cooling capacity per unit mass of the block. Moreover, the reaction enthalpy (ΔH) and entropy (ΔS) were calculated from experimental data obtained experimentally, and confirmed previous reported
Modeling, Simulation and Performance Evaluation of a PVT System for the Kenyan Manufacturing Sector
(Cell Press, 2023) Ngunzi, Veronica; Njoka, Francis; Kinyua, Robert
Manufacturing is an end-use sector that uses the most delivered energy, accounting for around 50% of all transported fuel globally and 40% of carbon dioxide emissions worldwide. Solar photovoltaic-thermal (PVT) energy can substitute the transported energy to meet thermal and electrical energy requirements, mitigating high energy costs and climatic problems. This research aimed to develop, simulate, and evaluate the capabilities of a solar photovoltaic-thermal system for potential use in Kenya’s manufacturing sector. A multistage cluster sampling technique was used in the study to characterize the manufacturing industry. Additionally, a PVT system was simulated using MATLAB Simulink to ascertain the relationship of temperature and the PV electrical efficiency. The impact of incorporating a thermal collector into the PV system on electrical, thermal, and overall system efficiency, and also the system’s potential for use in thermal processes in manufacturing, were assessed. From the characterization results, the agroprocessing sector dominates with 35% representation, and the small-scale thermal energy category dominates at 80%. The simulation findings show that a small temperature increase leads to a small increment in short circuit current but a significant decline in open circuit voltage. As a consequence, the maximum power (Pmax) of the PV decreases, lowering its electrical efficiency. However, the integration of PV with thermal collector improved the electrical, thermal, and the entire system efficiencies by, 16.01%, 20%, and 36.13%, respectively. More than 75% of the electrical and thermal energy processes fall in the small energy category. Hence, the PVT system is suitable for small-scale low-to-medium heat thermal energy categories or as a substitute system for higher temperature processes to raise feed water temperatures and reduction of thermal energy cost. This study gives a new approach of the application of PVT system for thermal industrial applications.

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