RP-Department of Energy Engineering
Permanent URI for this collection
Browse
Browsing RP-Department of Energy Engineering by Author "Kiplagat, J.K."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item 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 paperItem 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.Item Briquette making in Kenya: Nairobi and peri-urban areas(Elsevier, 2014) Kiplagat, J.K.; Ngusale, George K.; Luo, YonghaoBriquettes 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.Item 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.Item 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 reportedItem Novel Composite Sorbent for Resorption Systems and for Chemisorption Air Conditioners Driven by Low Generation Emperature(Elsevier, 2009-12-31) Kiplagat, J.K.; Oliveira, R.G.; Wang, R.Z.; Wang, C.Y.The utilization of a composite sorbent (NaBr and expanded graphite) in chemisorption air conditioning systems driven by low-grade heat source, and in resorption systems with simultaneous heating and cooling effects was experimentally investigated using bench-scale prototypes. The mass of ammonia desorbed and adsorbed was measured, and used to calculate the specific cooling capacity. The sorbent produced 219 kJ kg−1 of cooling at 5 °C and 510 kJ kg−1 at 15 °C, when the heat source temperature was 65 °C and the heat sink temperature was 30 °C. The air conditioning system mean specific cooling power (SCP), and mean coefficient of performance (COP) were calculated based on the desorbed and adsorbed masses, and on the variation of temperature in the reactors. For the same heat source and heat sink temperatures mentioned above, the air conditioning system had a SCP of 129 ± 7 W kg−1 and a COP of 0.46 ± 0.01, when cooling occurred at 15 °C. Regarding the utilization of the composite sorbent in resorption machines, the prototype was tested for production of cooling/heating at −5/50 °C, and at 10/70 °C. In the former condition, the COP was only 0.02, but in the latter condition, there was a tenfold increase in the COP, and the combined coefficient of performance and amplification reached 1.11, which indicates the energy saving potential of resorption systems using the studied sorbent.Item Performance study of a consolidated manganese chloride-expanded graphite compound for sorption deep freezing processes(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.A consolidated composite sorbent made from manganese chloride and expanded graphite was produced for sorption deep-freezing processes and used for cold production at a temperature as low as −35 °C. Experimental results showed that the addition of a porous graphite matrix can prevent the agglomeration and the attenuation of sorption capacity of reactive salt. The composite sorbent could incorporate 0.537 kg of ammonia per kg of reactive salt and the average specific cooling power (SCP) obtained varied between 200 W kg−1 and 700 W kg−1 when the evaporation temperature ranged from −35 °C to 0 °C. The analysis of the data suggested that the heat transfer characteristic in the composite sorbent was strongly influenced by chemical reaction and the conversion rate was very sensitive to the constraint temperatures. The SCP and coefficient of performance (COP) of a simple sorption deep-freezing system were 350 W kg−1 and 0.34, respectively, at the generation temperature of 180 °C, the heat sink temperature of 25 °C and the evaporation temperature of −30 °C.Item Renewable energy in Kenya: Resource potential and status of exploitation(Elsevier, 2011) Kiplagat, J.K.; Wang, R. Z.; Li, T. X.This paper presents an assessment of renewable energy resource potential and the current status of exploitation in Kenya. As an importer of petroleum fuels, Kenya spends a substantial amount of foreign reserves to import oil. The oil import bill in 2008 consumed 55% of the country's foreign exchange earnings from exports. On the other hand, there is a high dependence on wood biomass energy, leading to an imbalance in its supply and demand. This has exerted considerable pressure on the remaining forest and vegetation stocks, thereby accelerating the processes of land degradation. Moreover, despite the abundance of potential and a strong growth in demand for electricity, the country faces constraints in satisfying electricity demand. At the national level, only 18% of the households have access to grid electricity. The access is much lower in rural areas where only 4% of the households have grid electricity. Kenya has a liberalized energy sector and has made significant progress in the recent past in formulation of renewable energy policies. What is more, Kenya's electricity power mix is among the most sustainable in the world, with 80% of electricity coming from renewable sources. However, a substantial proportion of renewable energy resources are unexploited. Of the potential renewable sources, Kenya has harnessed only about 30% of its hydropower sources, approximately 4% of the potential geothermal resources and much smaller proportions of proven wind and solar power potentials. Furthermore, a large potential exists for the development of biomass based energy such as biogas, biodiesel and power generation form baggasse. The strong growth in energy demand provides excellent opportunities for private investors to invest in renewable energy power generation.Item Thermodynamic study of a combined double-way solid–gas thermochemical sorption refrigeration cycle(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.A combined double-way thermochemical sorption refrigeration thermodynamic cycle was proposed and tested. Both adsorption refrigeration and resorption refrigeration processes were combined in order to improve the system performance. Two different consolidated composite materials were used as the reactive sorbents and ammonia was used as the refrigerant. Experimental results showed that a system operating with such proposed cycle can have two useful cold productions during one cycle at the expense of only one heat input at high temperature. The average specific cooling power (SCP) during the adsorption refrigeration phase was 301 W kg−1. Analysis of the experimental data showed that the driving equilibrium drop during the resorption process was much lower than that during the adsorption process, when the cold production temperature was similar. The proposed combined double-way sorption cycle has a larger cooling capacity per unit of heat input and the maximum theoretical coefficient of performance (COP) is 1.24 when MnCl2 and BaCl2 are used as the reactive sorbents.