In recent years scarcity of resources and environmental aspects have stimulated research on renew... more In recent years scarcity of resources and environmental aspects have stimulated research on renewable and recyclable resources for particleboard production 1. This paper deals with single- layer particleboards based on corn cobs, rice husks and groundnut shells, abundantly available agricultural residues in Nigeria. Panels were produced at densities between 550 and 900 kg/m3 using a natural tannin-based adhesive. On the side of the process parameters, the moisture content after adhesive application and the press temperature were varied. While the mechanical properties of rice husk and groundnut shell derived particleboard fail to satisfy European standard requirements in terms of bending strength, those made of corn cob achieve the specifications, but at higher density compared to common wood-based particleboard and holding a swelling behaviour not conform for use in wet area. Meanwhile, the particle geometry and -size as well as the board structure leave room for improvement to catch up with wood-based materials. On the side of rice husk and groundnut shells, alternative areas of application as thermal insulation and decorative cladding material are thinkable.
Objectives: To evaluate the energy and exergy performances of a designed ORC system and to quanti... more Objectives: To evaluate the energy and exergy performances of a designed ORC system and to quantify loses within the system and measure its output.The study also assesses the economic performance of the ORC system to determine the feasibility of the business. Methods: Thermodynamic analysis assessing the energy performance and cost estimation using manufacturers’ prices to generate generic equations for estimating costs of the components of the designed ORC system. Findings: The results of the exergy evaluation of the ORC show a system thermal efficiency of 6.39%, net power output of 3.10kWe, exergy destruction of 9.07kW, and exergy efficiency of 54.6%. The economic estimation has a capital investment cost of £8,381.98, a specific investment cost of £2,754.36/kWe, annual savings of £1,233.34, and a payback period of 6.8years. Novelty: The use of exergetic method of analysis and the assessment of the potential economic benefits of installing the module in commercial trucks which form...
International Journal of Energy Research, Jun 17, 2021
Research into improving the performance of photovoltaic (PV) systems using thermoelectric generat... more Research into improving the performance of photovoltaic (PV) systems using thermoelectric generators (TEGs) has gained increased interest in recent times. Few studies have separately investigated the effects of multistaging, thermoelectric geometry, and type of PV cell on overall performance of PV‐thermoelectric (PV‐TE) systems. Thermoelectric leg geometries considered in these studies were either rectangular or trapezoidal legs. The research work related to examine the combined consequences of PV cell type, TEG leg geometry and multistaging on the overall performance of PV‐TEs has not been carried out till date. Therefore, a three‐dimensional model of this hybrid system considering two different types of PV cells and the rectangular and circular TEG leg geometries in single and multistage arrangements has been investigated using ANSYS 2020 R2 software. A parametric study considering the effects of concentrated solar irradiation, TEG cold junction convective film coefficient and load resistance on the overall performance of the hybrid system has been carried out. Results show that, for both types of PV cell, the circular leg geometry of TEG provides the highest PV‐TE performance. Also, the PV cell type significantly affects the optimum number of TEG stages in the PV‐TE system. Finally, multistaging increases the thermal stresses developed in the PV‐TE system, although the circular leg TEG provides the least thermal stresses as compared with the traditional rectangular leg TEG. Quantitatively, the PV‐TE system with single and two‐stage circular leg TEGs reduced the thermal stress levels of their rectangular leg counterparts by 3.31% and 0.78%, respectively. The findings of this study can be used as a reference for all types of PV cell in the PV‐TE systems.
Abstract The performance of thermoelectric devices improves either by changing the thermoelectric... more Abstract The performance of thermoelectric devices improves either by changing the thermoelectric material properties or the geometry of the thermoelectric leg. Many research papers show that the tapered leg geometry improves the performance of thermoelectric generators (TEGs). However, they assume isothermal conditions across the hot and cold junctions of both variable area and rectangular area leg-based TEGs. This is rather inaccurate and unrealistic, because when exposed to same heat flux, temperatures vary across the hot and cold junctions of these devices. Scarcely has anything been said pertaining the performance evaluation and optimisation of variable area leg TEGs using realistic isoflux conditions. Therefore, this study presents a thermo-mechanical analysis of variable area and rectangular area leg TEGs, using ANSYS 2020 R2 software, with realistic isoflux boundary conditions instead of previous unrealistic isothermal ones. The leg height, area, external load resistance and optical concentration ratio are optimised. Results indicate that short legs are crucial for maximum power while long legs improve the device efficiencies. Also, although tapered thermoelectric leg TEGs improve the electrical performance of conventional rectangular leg TEGs, they decrease the device mechanical performance and thermodynamic stability. Finally, the optimum ranges in which tapered leg TEG outperforms the conventional device are obtained.
Indian Journal of Environment Engineering (IJEE), May 30, 2022
In this work, hourly global radiation and extraterrestrial data for three locations in Ghana, nam... more In this work, hourly global radiation and extraterrestrial data for three locations in Ghana, namely Accra, Kumasi, and Navrongo, were used to estimate the daily clearness, monthly mean clearness index, and monthly-averaged hourly clearness index of the study areas. It was observed that the monthly average clearness index of Accra ranged from 0.4505 to 0.6975 and that of Kumasi and Navrongo varied from 0.4553 to 0.6908 and 0.4529 to 0.6949, respectively. There was no overcast sky in the year 2018 for all the three study areas in Ghana, and approximately two-thirds of the year’s day length experienced clear-sky conditions. Partly cloudy conditions were predominant in the wet season of the year.
Generating electricity from the sun using a combination of a compound parabolic concentrator (CPC... more Generating electricity from the sun using a combination of a compound parabolic concentrator (CPC) and a thermoelectric module (TEM) has been studied. The system was modeled, analyzed and tested. The model equations and the methodology used for the demonstration are presented and experimentally validated. The experimental setup comprised a manually fabricated CPC placed on a commercially available TEM. The results showed that the combination can generate and sustain enough power for a small appliance. It was also shown that there is enough dissipated heat from the system which could be harnessed for additional uses. The cost is still high, about $35/Wp, but if credit is given for the thermal energy the initial cost goes down.
Abstract In this paper, a model based on the first and second laws of thermodynamics is developed... more Abstract In this paper, a model based on the first and second laws of thermodynamics is developed in MATLAB R2020a Simulink software and is utilised in thermodynamically optimizing a bismuth telluride based solar thermoelectric generator (STEG) while estimating all system irreversibilities. This study aims at presenting a cheaper and simpler method of optimising the performance of traditional STEGs without using segmentation or cascading. This is achieved by studying the effects of operating thermal and electric parameters such as load-resistance ratio (LRR), optical concentration ratio (OCR), thermal concentration ratio (TCR), hot junction temperature ( T h ), cold junction temperature, current and voltage on STEG power output, energy and exergy efficiencies, respectively. The results obtained are validated with experimental and numerical data from previous studies. Results indicate that for an OCR of 30, a STEG exergy efficiency of about 6.5% is obtained from a conventional bismuth-telluride single-stage module. Also, a means of maximising STEG performance while reducing system irreversibilities to the barest minimum is presented. The results obtained herein will provide useful information in the maximisation of conventional and complex STEG systems employing segmentation or cascading.
In recent years scarcity of resources and environmental aspects have stimulated research on renew... more In recent years scarcity of resources and environmental aspects have stimulated research on renewable and recyclable resources for particleboard production 1. This paper deals with single- layer particleboards based on corn cobs, rice husks and groundnut shells, abundantly available agricultural residues in Nigeria. Panels were produced at densities between 550 and 900 kg/m3 using a natural tannin-based adhesive. On the side of the process parameters, the moisture content after adhesive application and the press temperature were varied. While the mechanical properties of rice husk and groundnut shell derived particleboard fail to satisfy European standard requirements in terms of bending strength, those made of corn cob achieve the specifications, but at higher density compared to common wood-based particleboard and holding a swelling behaviour not conform for use in wet area. Meanwhile, the particle geometry and -size as well as the board structure leave room for improvement to catch up with wood-based materials. On the side of rice husk and groundnut shells, alternative areas of application as thermal insulation and decorative cladding material are thinkable.
Objectives: To evaluate the energy and exergy performances of a designed ORC system and to quanti... more Objectives: To evaluate the energy and exergy performances of a designed ORC system and to quantify loses within the system and measure its output.The study also assesses the economic performance of the ORC system to determine the feasibility of the business. Methods: Thermodynamic analysis assessing the energy performance and cost estimation using manufacturers’ prices to generate generic equations for estimating costs of the components of the designed ORC system. Findings: The results of the exergy evaluation of the ORC show a system thermal efficiency of 6.39%, net power output of 3.10kWe, exergy destruction of 9.07kW, and exergy efficiency of 54.6%. The economic estimation has a capital investment cost of £8,381.98, a specific investment cost of £2,754.36/kWe, annual savings of £1,233.34, and a payback period of 6.8years. Novelty: The use of exergetic method of analysis and the assessment of the potential economic benefits of installing the module in commercial trucks which form...
International Journal of Energy Research, Jun 17, 2021
Research into improving the performance of photovoltaic (PV) systems using thermoelectric generat... more Research into improving the performance of photovoltaic (PV) systems using thermoelectric generators (TEGs) has gained increased interest in recent times. Few studies have separately investigated the effects of multistaging, thermoelectric geometry, and type of PV cell on overall performance of PV‐thermoelectric (PV‐TE) systems. Thermoelectric leg geometries considered in these studies were either rectangular or trapezoidal legs. The research work related to examine the combined consequences of PV cell type, TEG leg geometry and multistaging on the overall performance of PV‐TEs has not been carried out till date. Therefore, a three‐dimensional model of this hybrid system considering two different types of PV cells and the rectangular and circular TEG leg geometries in single and multistage arrangements has been investigated using ANSYS 2020 R2 software. A parametric study considering the effects of concentrated solar irradiation, TEG cold junction convective film coefficient and load resistance on the overall performance of the hybrid system has been carried out. Results show that, for both types of PV cell, the circular leg geometry of TEG provides the highest PV‐TE performance. Also, the PV cell type significantly affects the optimum number of TEG stages in the PV‐TE system. Finally, multistaging increases the thermal stresses developed in the PV‐TE system, although the circular leg TEG provides the least thermal stresses as compared with the traditional rectangular leg TEG. Quantitatively, the PV‐TE system with single and two‐stage circular leg TEGs reduced the thermal stress levels of their rectangular leg counterparts by 3.31% and 0.78%, respectively. The findings of this study can be used as a reference for all types of PV cell in the PV‐TE systems.
Abstract The performance of thermoelectric devices improves either by changing the thermoelectric... more Abstract The performance of thermoelectric devices improves either by changing the thermoelectric material properties or the geometry of the thermoelectric leg. Many research papers show that the tapered leg geometry improves the performance of thermoelectric generators (TEGs). However, they assume isothermal conditions across the hot and cold junctions of both variable area and rectangular area leg-based TEGs. This is rather inaccurate and unrealistic, because when exposed to same heat flux, temperatures vary across the hot and cold junctions of these devices. Scarcely has anything been said pertaining the performance evaluation and optimisation of variable area leg TEGs using realistic isoflux conditions. Therefore, this study presents a thermo-mechanical analysis of variable area and rectangular area leg TEGs, using ANSYS 2020 R2 software, with realistic isoflux boundary conditions instead of previous unrealistic isothermal ones. The leg height, area, external load resistance and optical concentration ratio are optimised. Results indicate that short legs are crucial for maximum power while long legs improve the device efficiencies. Also, although tapered thermoelectric leg TEGs improve the electrical performance of conventional rectangular leg TEGs, they decrease the device mechanical performance and thermodynamic stability. Finally, the optimum ranges in which tapered leg TEG outperforms the conventional device are obtained.
Indian Journal of Environment Engineering (IJEE), May 30, 2022
In this work, hourly global radiation and extraterrestrial data for three locations in Ghana, nam... more In this work, hourly global radiation and extraterrestrial data for three locations in Ghana, namely Accra, Kumasi, and Navrongo, were used to estimate the daily clearness, monthly mean clearness index, and monthly-averaged hourly clearness index of the study areas. It was observed that the monthly average clearness index of Accra ranged from 0.4505 to 0.6975 and that of Kumasi and Navrongo varied from 0.4553 to 0.6908 and 0.4529 to 0.6949, respectively. There was no overcast sky in the year 2018 for all the three study areas in Ghana, and approximately two-thirds of the year’s day length experienced clear-sky conditions. Partly cloudy conditions were predominant in the wet season of the year.
Generating electricity from the sun using a combination of a compound parabolic concentrator (CPC... more Generating electricity from the sun using a combination of a compound parabolic concentrator (CPC) and a thermoelectric module (TEM) has been studied. The system was modeled, analyzed and tested. The model equations and the methodology used for the demonstration are presented and experimentally validated. The experimental setup comprised a manually fabricated CPC placed on a commercially available TEM. The results showed that the combination can generate and sustain enough power for a small appliance. It was also shown that there is enough dissipated heat from the system which could be harnessed for additional uses. The cost is still high, about $35/Wp, but if credit is given for the thermal energy the initial cost goes down.
Abstract In this paper, a model based on the first and second laws of thermodynamics is developed... more Abstract In this paper, a model based on the first and second laws of thermodynamics is developed in MATLAB R2020a Simulink software and is utilised in thermodynamically optimizing a bismuth telluride based solar thermoelectric generator (STEG) while estimating all system irreversibilities. This study aims at presenting a cheaper and simpler method of optimising the performance of traditional STEGs without using segmentation or cascading. This is achieved by studying the effects of operating thermal and electric parameters such as load-resistance ratio (LRR), optical concentration ratio (OCR), thermal concentration ratio (TCR), hot junction temperature ( T h ), cold junction temperature, current and voltage on STEG power output, energy and exergy efficiencies, respectively. The results obtained are validated with experimental and numerical data from previous studies. Results indicate that for an OCR of 30, a STEG exergy efficiency of about 6.5% is obtained from a conventional bismuth-telluride single-stage module. Also, a means of maximising STEG performance while reducing system irreversibilities to the barest minimum is presented. The results obtained herein will provide useful information in the maximisation of conventional and complex STEG systems employing segmentation or cascading.
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Papers by Chigbo Mgbemene