Energy Solution

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Design and optimization of HPLWR high pressure Turbine gamma ray shield
(Elsevier, 2014-12-20) Kebwaro, Jeremiah Monari; Zhao, Yaolin; He, Chaohui
This work proposes the optimum gamma ray shield thickness around the HPLWR high pressure turbine for different occupancy periods in the turbine building. Monte Carlo method was employed in the design process and only radioactive nitrogen-16 was considered as the source of radiation. Five grades of concrete (ordinary, magnetite, heavy magnetite, steel magnetite and barite) were used as shielding materials. The isotope source term in the high pressure turbine was estimated by modeling the HPLWR three pass core in MCNP and tracking the inventory using a simple algorithm. The high pressure turbine was thereafter modeled in MCNP with a concrete shield arrayed in layers around it. The surface flux tally and ICRP74 dose conversion coefficients were employed to estimate the dose profile across the shield. For some shielding materials, exponential functions were fitted on the calculated data to extrapolate dose values beyond the model thickness. The optimum shield thickness was determined by comparing the calculated dose profiles with dose limit proposals in the IAEA standard (NS-G-1.13) on radiation protection considerations during nuclear power plant design. It was observed that with a 120cm thick heavy concrete shield, the turbine building would be safe for most occupancy periods. However for ordinary concrete the shield would require some extension to guarantee safety. For very long occupancy (more than 10 person hours per week), magnetite shield may also require slight extension. It can therefore be concluded that the shield thickness recommended for BWR turbines (which operate on a direct cycle like HPLWR) could be sufficient for HPLWR if high density concretes are used.
Design and Testing of a Demand Response Q-Learning Algorithm for a Smart Home Energy Management System
(Institute of Electrical and Electronics Engineers (IEEE), 2021-09-28) Angano, Walter; Musau, Peter; Wekesa, Cyrus Wabuge
Growth in energy demand stimulates a need to meet this demand which is achieved either through wired solutions like investment in new or expansion of existing generation, transmission and distribution systems or non-wired solutions like Demand Response (DR). This paper proposes a Q-learning algorithm, an off-policy Reinforcement Learning technique, to implement DR in a residential energy system adopting a static Time of Use (ToU) tariff structure, reduce its learning speed by introducing a knowledge base that updates fuzzy logic rules based on consumer satisfaction feedback and minimize dissatisfaction error. Testing was done in a physical system by deploying the algorithm in Matlab and through serial communication interfacing the physical environment with the Arduino Uno. Load curve generated from appliances and ToU data was used to test the algorithm. The designed algorithm minimized electricity cost by 11 % and improved the learning speed of its agent within 500 episodes.
Effects of 15^th January 2010 Annular Solar Eclipse on Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles over Low Latitude Regions of East Africa
(Hindawi Publishing Corporation, 2022-09-21) Athwart, Davis Odhiambo; Ndinya, Boniface; Baki, Paul
The influence of the 15th January 2010 annular solar eclipse on traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) is studied using data from six global navigation and satellite system (GNSS) receivers spread across the path of annularity over the low latitude region of East Africa. The GNSS receivers are stationed at Nairobi (RCMN), Malindi (MAL2), and Eldoret (MOIU) in Kenya; Mbarara (MBAR) in Uganda; Kigali (NURK) in Rwanda; and Mtwara (MTWA) in Tanzania. The study period ranges from 12th to 18th January 2010, three days before and after the 15th January 2010 annular solar eclipse. The year 2010 marked the beginning phase of solar cycle 24, evidently observed in low total electron content (TEC) values and the disturbed storm time index (Dst). The eclipse started at 7 : 06 LT and ended at 10 : 14 LT, with MOIU and RCMN experiencing eclipse magnitudes of 0.946 and 0.93, respectively. The maximum obscuration occurred between 8 : 21 LT and 8 : 34 LT across most of the stations. A detrending on vertical TEC (VTEC) derived from GNSS receivers across or close to the path of totality revealed a reduction of ∼2-3 TECU during the maximum phase of the eclipse. The level of reduction was highly close to the totality path and decreased smoothly away from the totality path. Using a background polynomial fitting technique on diurnal TEC, we analyzed TIDs along NURK-MBAR-MOIU and MOIU-RCMN-MAL2 GPS arrays. The results revealed a wavelike perturbation with a virtual horizontal velocity of 830m/s and ∼1 TECU amplitude propagating eastward along the MOIU-RCMN-MAL2 GPS array. The study reports a moderate scintillation activity of 0.5 ≤ ROTI ≤ 0.9 values, demonstrating the presence of few EPBs over the region. The results show a latitudinal variation in GPS-TEC scintillation activities and suggest a possible influence of the eclipse on the observed increase in average scintillation levels across East Africa.
Electrical and Structural Properties of Aluminium Doped tin Oxide Codoped with Sulphur for Solar Energy
(Elsevier, 2016-08) Muramba, Valentine Wabwire; Mageto, Maxwell
Thin films of Tin Oxide co-doped with 28 atomic percentages of Aluminium (i.e. 28 at% Al) and varied concentration of Sulphur were prepared on 1mm thick, 1cm by 1cm glass substrates at 470 0C by Spray Pyrolysis technique. Films were produced from 2.0M solution of hydrous Tin Chloride dissolved in Ethanol with 38% Hydrochloric acid concentration, 1.5M aqueous Aluminium chloride and 2.0M aqueous solution of Ammonium Sulphide. The effects of Sulphur concentration on structural and electrical properties of transparent Tin Oxide thin films were investigated in the atomic percentage of Sulphur content ranging from zero to fifty (i.e. 0at%S -50at%S) with a fixed 28at%Al content. Polycrystalline structures without any second phases were observed with preferential orientations along the (110), (101), (200) and (211) planes. The average grain size as determined from the (110) peaks lay in the range 19.2 nm-47.7nm. The minimum resistivity was found to be 1.15x10-3Ωcm for the Tin Oxide films doped with 32 at% Al content and 9.59x10-3Ωcm for Tin Oxide films co-doped with 28 at% Al and 20 at% S content. It was observed that Aluminium doping lowered the grain size significantly but doping to optimum level of 32 at% Al content increases electrical conductivity of tin oxide. When Sulphur was intentionally introduced in the crystal structure of 28 at% Al doped Tin Oxide, the electrical conductivity decreased appreciably and the grain size increased.
Exhaust Gases Energy Recovered from Internal Combustion Engine for Useful Applications
(IOSR Journal of Mechanical and Civil Engineering, 2017-06-01) Orido, George; Ngunjiri, Prof; Rugiri, Musa
Abstract : The importance of this study is primarily to address the energy problem. The main contribution of this study, in addition to conserving energy through recovery technique, is reduction in the impact of global warming due to exhaust gas emission to the environment. The objective of the research is to recover exhaust gases energy from internal combustion engines for utilization. The experimental set-up consisted of a single cylinder, four-stroke, multi-fuel engine connected to eddy current dynamometer for loading. Thermocouple temperature sensors and transmitters were used to measure exhaust gas to calorimeter inlet temperature and exhaust gas from calorimeter outlet temperature. Exhaust gas mass flow rate and temperature measurements were used to determine the recovered energy. Recovered heat energy was 1.257% of fuel energy when the engine was operated on diesel at 1000 rpm and a torque load of 18 Nm. 3.153% of fuel energy was recovered at 1500 rpm and a torque load of 6 Nm when biodiesel was used. At a speed of 1000 rpm 22.6% and 23.004% of the thermal energy through exhaust was recovered when the engine used diesel and biodiesel at torque loads of 6 Nm and 14 Nm respectively.
Improvement of Ceramic Insulation of Cook Stoves Using Carbonized Organic Waste
(Journal of Energy Research and Reviews, 2023-06-29) Kyuvi, Esther; Nyangaya, James; Aganda, Alex
Many households and small hotels in Kenya source their energy from biomass; mainly wood and charcoal. For the urban poor, their energy source is basically charcoal. With increasing population, rural urban migration, tough economic times, the use of charcoal must be as efficient as possible. In cognizance of this need, development of energy efficient biomass (charcoal) cook stoves is paramount. The main objective of the project was to optimize the insulating properties of ceramic insulation used in ceramic cook stoves using carbonized organic waste as the burnout additive. Carbonized organic waste herein referred to as char was collected and ground to fine dust. The char was used as a burnout medium in the clay to create pores, reduce density and increase porosity thereby improving insulation properties of the fired clay. Optimization was achieved by using different ratios of clay to char. Testing of biomass cook stove is provided for in ISO- 19867-0; the harmonized laboratory test protocol. The results showed that the apparent porosity of the sample increased from 34% with no char to 87% when the sample had 50% char. On the other hand, the bulk density reduced from 2.8 g/cm3 with no char to 1.2 g/m3 with 50% char. The prototype thermal efficiency was 33% and 25.8% for the control cook stove. The prototype and control cook stove cooking power were 0.97kW and 0.71kW respectively. The prototype PM2.5 emissions estimated to be 76 mg/MJd and CO emissions at 21 g/MJd which were lower than the Kenya standard KS 1814:2019 maximum emission of 137 mg/MJd and 25 g/MJd respectively This study has shown that when clay was mixed with char, there was a significant increase in desirable characteristics, which results in increased efficiency of biomass (charcoal) cook stoves and lower emissions.
Optimization of Hole Transport Layer Materials for a Lead-Free Perovskite Solar Cell Based on Formamidinium Tin Iodide
(Energy Technology, 2021-10-31) Rono, Nicholas; Merad, Abdelkrim E.; Kibet, Joshua K.; Martincigh, Bice S.; Nyamori, Vincent O.
Recently, lead-based perovskite solar cells have been mainly studied; however, these cells suffer from two main problems: the toxicity of lead and the instability of the devices, which limit their commercialization. Herein, a theoretical investigation of a lead-free perovskite solar cell based on formamidinium tin iodide (HC(NH2)2SnI3) with the general architecture: glass/FTO/WS2/HC(NH2)2SnI3/HTL/Au is reported. All calculations are performed with the SCAPS-1D solar cell simulator. Two inorganic (CuSCN and Cu2O) and two organic (P3HT and D-PBTTT-14) hole transport layer (HTL) materials are tested in this model. The effect of the external operating temperature and different metal work functions of the back contact of the cell on the overall performance of the devices is also studied. Simulations showed that, with the introduction of CuSCN, Cu2O, and P3HT as HTLs, the device can attain a remarkable efficiency of ≈21%. All the modeled devices showed remarkable performance of above 20% at higher temperatures of 380–420 K but degraded slightly when this range is exceeded. Relatively cheaper Pt, Ni, and Pd metals perform better, thus, can replace gold. These simulation results can provide avenues and directions for future advancement of the performance of lead-free perovskite solar cells.
Reduced graphene oxide-germanium quantum dot nanocomposite: electronic, optical and magnetic properties
(IOP Publishing, 2017-11-13) Amollo, Tabitha A.; Mola, Genene T.; Nyamori, Vincent O.
Graphene provides numerous possibilities for structural modification and functionalization of its carbon backbone. Localized magnetic moments can, as well, be induced in graphene by the formation of structural defects which include vacancies, edges, and adatoms. In this work, graphene was functionalized using germanium atoms, we report the effect of the Ge ad atoms on the structural, electrical, optical and magnetic properties of graphene. Reduced graphene oxide (rGO)-germanium quantum dot nanocomposites of high crystalline quality were synthesized by the microwave-assisted solvothermal reaction. Highly crystalline spherical shaped germanium quantum dots, of diameter ranging between 1.6–9.0 nm, are anchored on the basal planes of rGO. The nanocomposites exhibit high electrical conductivity with a sheet resistance of up to 16 Ω sq−1. The electrical conductivity is observed to increase with the increase in Ge content in the nanocomposites. High defect-induced magnetization is attained in the composites via germanium adatoms. The evolution of the magnetic moments in the nanocomposites and the coercivity showed marked dependence on the Ge quantum dots size and concentration. Quantum confinement effects is evidenced in the UV–vis absorbance spectra and photoluminescence emission spectra of the nanocomposites which show marked size-dependence. The composites manifest strong absorption in the UV region, strong luminescence in the near UV region, and a moderate luminescence in the visible region.
Structural, Electronic and Mechanical Properties of Re Doped FeMnP_0.67A_0.33 (A=Ga and Ge): A DFT Study
(International Journal of Physics, 2022-02-14) Chirchir, Gabriel Kipkemei; Mulwa, Winfred Mueni; Adetunji, Bamidele Ibrahim
The structural, electronic and mechanical properties of Re doped FeMnP0.67A0.33 (A= Ga and Ge) were examined by use of density functional theory (DFT) within the generalized gradient approximations as demonstrated in Quantum ESPRESSO code. The optimized structural parameters as well as derived lattice parameters are in consistent with other computational and achievable experimental results. The computed independent elastic constants confirm the mechanical stability of the investigated materials. The computed Poisson’s and Pugh’s ratios as well as Cauchy pressure, verify that FeMn0.67Re0.33P0.67Ga0.33 is the most ductile among the studied compounds. The calculated values of bulk modulus, shear modulus and Young’s modulus confirm high values of bond strength, hardness and stiffness of the investigated materials respectively. Therefore, the four compounds considered may be appropriate for industrial applications. The results report that FeMn0.67Re0.33P0.67Ga0.33 compound is more ductile and mechanically stable compared to other investigated compounds. This is the first qualitative computational prediction of the elastic properties of FeMnP0.67Ge0.33, FeMnP0.67Ga0.33, FeMn0.67Re0.33P0.67Ge0.33 and FeMn0.67Re0.33P0.67Ga0.33 compounds and this awaits experimental ratification. The calculated electronic density of states confirms that the Re_2p states are located in the conduction band (CB) in the unite cell while Re_3d dominate the CB in the supercell. Results from the doped compounds could not be compared with experimental or computational findings because to the best of our knowledge, this has not been done.

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