Sagar Kafle | Tribhuvan University (original) (raw)

Papers by Sagar Kafle

When biomass is in pyrolysis stage, it produced tar primarily through depolymerization process in... more When biomass is in pyrolysis stage, it produced tar primarily through depolymerization process in the temperature range of 200oC-500oC. In this temperature range, the cellulose, hemicellulose, and lignin components of biomass break down into primary tar. Due to increased reaction temperature, secondary reactions occur in the gas phase, which convert oxygenated tar compounds to lighter hydrocarbons, aromatics, oxygenates and olefins subsequently forming higher hydrocarbons and larger Polycyclic Aromatic Hydrocarbon (PAH) in tertiary processes (Milne et al., 1998). Tar is an unavoidable by-product of thermal conversion (Basu, P., 2013), it is condensed at low temperature and makes problems. In boiler case, it gets foul on the heating plate and flue pipes and reduces the heat transfer rate, hence decreases the performance of the boiler. It can be destructed or reduced, but still now, there is not any method to completely get rid of tar (Kafle et al., 2014). European pellets allowed up-...

We investigated the energy usage, economics, and global warming potential (GWP) of spring rice pr... more We investigated the energy usage, economics, and global warming potential (GWP) of spring rice production via farm sizes in Nepal. Seventy farmers were selected via purposive sampling methods, and data were collected by interviewing the farmers on site. It was found that 22,987 mega joules of energy per hectare (MJ/ha) was invested in order to yield 77,355 MJ/ha worth of outputs (5262 kg/ha). The analysis shows that the highest share of energy input was contributed by machinery (33.50%) and least by chemicals (0.96%). It was further found that spring rice farming in Nepal is less energy productive (0.23 kg/MJ) and less energy efficient (3.37) than that of neighboring countries—such as India, China, and Pakistan. The total GWP is estimated about 720.56 kg CO2eq/ha. The average cost of production was found to equate to USD810.24/ha (or USD0.154/kg of production), and that profit only reached USD73.93/ha. This study found that energy use, cost of production, and yield per ha all genera...

International Journal of Green Energy

ABSTRACT The academic institute, a huge consumer of energy, is still depending upon the grid and/... more ABSTRACT The academic institute, a huge consumer of energy, is still depending upon the grid and/or conventional fuel despite having potential areas of a solar PV installation. No such study has been reported in Nepal which has techno-economically discussed the potential use of academic institute rooftops for solar PV installation. In this study, we have investigated the techno-economic and environmental assessment of a 1 megawatt (MW) rooftop solar PV using PVsyst for Purwanchal Campus, Nepal. It has been estimated the plant will produce about 1,660 MWh of usable AC electricity annually and out of which 95% can be supplied to the grid. The remaining can fulfill the demand of the campus at sunshine hours. For this, a capital investment of about USD 961,404 is needed for the plant with an annual operating cost of USD 8,008. This project gives a 190% return of investment within its life of 25 years with a Levelized cost of energy (LCOE) of 0.069 USD/kWh. The performance ratio and payback period of the project are calculated at about 0.765 and 8.4 years, respectively. The system will produce about 97% less emission than that of diesel generator, which is currently being used for power backup. It is concluded that a 1 MW grid-connected solar PV system is feasible for the studied campus.

Earth's Future, 2021

The COVID-19 pandemic has impacted social, economic, and environmental systems worldwide, slowing... more The COVID-19 pandemic has impacted social, economic, and environmental systems worldwide, slowing down and reversing the progress made in achieving the Sustainable Development Goals (SDGs). SDGs belong to the 2030 Agenda to transform our world by tackling humankind's challenges to ensure well-being, economic prosperity, and environmental protection. We explore the potential impacts of the pandemic on SDGs for Nepal. We followed a knowledge co-creation process with experts from various professional backgrounds, involving five steps: online survey, online workshop, assessment of expert's opinions, review and validation, and revision and synthesis. The pandemic has negatively impacted most SDGs in the short term. Particularly, the targets of SDG 1, 4, 5, 8, 9, 10, 11, and 13 have and will continue to have weakly to moderately restricting impacts. However, a few targets of SDG 2, 3, 6, and 11 could also have weakly promoting impacts. The negative impacts have resulted from imped...

IOP Conference Series: Earth and Environmental Science

Maize is the second largest crop grown in Nepal and is grown in all three geographic zones. The o... more Maize is the second largest crop grown in Nepal and is grown in all three geographic zones. The objective of this study is to analyse the energy input-output of maize production systems. The study is conducted in Sundarharaincha municipality of Morang district, Nepal, using direct questionnaires methods for the collection of primary data of varying landholding sizes farmers. The study revealed that total energy input and output for maize production system found about 10, 999.61 MJ/ha and 45, 501.52 MJ/ha, respectively, with the highest share by farmyard manure (FYM) about 50%. The energy use efficiency was found 4.14. Total CO2, N2O and CH4 emissions due to chemical inputs were found 163.24 kg/ha, 0.03 kg/ha and 0.33 kg/ha, respectively. The total Global warming potential was found 178.58 CO2 eq. per ha. The average cost of production were calculated USD 301.35/ha and profit USD 272.26/ha.

Renewable and Sustainable Energy Reviews

The primary objectives of this study were to understand the energy plans and policies of the Repu... more The primary objectives of this study were to understand the energy plans and policies of the Republic of Korea (ROK) and outline its development in the energy sector. Both qualitative and quantitative information were gathered and evaluated in the context of the defined objectives. The study has outlined that the primary motivational factor for achieving the current improved energy status of the ROK was to support the rapid industrial growth and socio-economic development of the country. The major steps taken were to manage the country's escalating energy demand and to minimize the greenhouse emissions in energy sector along its progressive economic development. The economic growth of the country had good correlation with the escalating fossil fuel consumption. This is however among the great concerns in the country in today's global agenda of sustainable energy managements. The country has been primarily relying on the imported energy sources, which averaged to 84% (including nuclear generation) of the total primary energy supply (TPES) during the period of 2000–2014. Oil has been the main source of energy supply in the country, followed by coal and natural gas. Penetration of renewable energy technologies was primarily motivated to meet the country's strategic goals, including the downscaling of GHG emission by 37% by 2030 compared to the business-as-usual (BAU) situation. Despite the different initiations in the energy management, renewable energy sources covered only 4.5% of the TPES in 2014. In addition, the country's urgent need now is also towards the management of the available natural resources to support the growing demand of bio-economy. At this particular interest, the country needs to identify the sustainable availability of resources to balance the multi-fold sectors. This demands comprehensive energy-system analysis along with identifying the avenues of the utilization of biomass resources.

Energy

The high yield and fouling of tar reduces thermal efficiency of the wood pellet boiler. In order ... more The high yield and fouling of tar reduces thermal efficiency of the wood pellet boiler. In order to achieve better performance of wood pellet boiler, the effect of tar fouled on thermal efficiency should be investigated. This study presents CFD (Computation Fluid Dynamics) simulation of thermal behavior of the boiler and analysis the thermal efficiency affected by tar fouling on the heating surface of the combustion chamber. A model has been developed to predict the thermal behavior of the combustion gas and heating water in the boiler using the conservation of mass, momentum and energy equations. To investigate the effect of tar fouling on thermal efficiency, the experiments were performed by combusting the 1st and the 3rd grade wood pellets, and compared with the simulations. By about 1 mm tar fouling in heating surface of the boiler the thermal efficiency dropped by 7.26%p and 9.19%p in the 1st and the 3rd grade wood pellets, respectively. Compared to experiment using the 1st grade wood pellet, simulation results were relatively deviated, the outlet water temperature increased by 0.53 K in non-tar condition and decreased by 0.02 K in tar-existence condition. This study can be used to improve the overall performance of the boiler.

Energy

Abstract Fouling of tar in wood pellet boiler reduces its thermal efficiency and demands periodic... more Abstract Fouling of tar in wood pellet boiler reduces its thermal efficiency and demands periodical maintenance to keep its original performance. The fouling of tar in wood pellet boiler was studied along with the physical and thermal characteristics of the pellets. Four different samples were prepared and accessed: a sample of control pellets without additives and three other samples each with 2% additives (dolomite and/or lime). Experiments for each sample were carried out in the pellet boiler for 20 h and fouling of tar is investigated. It is observed that the fouling of tar is drastically reduced in the pellets with additives 1% dolomite plus 1% lime: 76% by area-density (kg/m 2 ) and 82% by thickness (mm). At the same time, the particle density, mechanical durability, bulk density, and heating value are also found to be improved leading to an improved overall performance of the pellets and the boiler. The pellets with the additives are, therefore, found to be a better option to reduce tar in wood pellet boilers and are recommended.

Applied Thermal Engineering

International Journal of Green Energy, 2016

ABSTRACT In the current study, the potential of forest-based biomass supply for the pellet produc... more ABSTRACT In the current study, the potential of forest-based biomass supply for the pellet production in Nepal is investigated. This study showed that about 2.76 million tonnes (Mt) biomass in the form of pellets are potentially available from forest-based biomass. Considering a processing capacity of 6 tonnes (t)/hr of a pellet plant, the production cost of the pellets was calculated to be $43.53/t. Pellets are generally used as fuel to produce thermal energy in industries, which helps to save the economy and the environment of the country.

Nepal, a country rich in biomass, still does not have any commercial pellet production plants and... more Nepal, a country rich in biomass, still does not have any commercial pellet production plants and is wasting large amounts of agricultural crop residue. The current study showed that about 5.61 million tonnes (Mt) of biomass in the form of pellets are potentially available from agricultural crop residues. The brick and cement industries could use these agro-pellets. Co-firing of pellets in such industries could play an important role in reducing the import volume of coal and minimize the related environmental loadings.

When biomass is in pyrolysis stage, it produced tar primarily through depolymerization process in... more When biomass is in pyrolysis stage, it produced tar primarily through depolymerization process in the temperature range of 200oC-500oC. In this temperature range, the cellulose, hemicellulose, and lignin components of biomass break down into primary tar. Due to increased reaction temperature, secondary reactions occur in the gas phase, which convert oxygenated tar compounds to lighter hydrocarbons, aromatics, oxygenates and olefins subsequently forming higher hydrocarbons and larger Polycyclic Aromatic Hydrocarbon (PAH) in tertiary processes (Milne et al., 1998). Tar is an unavoidable by-product of thermal conversion (Basu, P., 2013), it is condensed at low temperature and makes problems. In boiler case, it gets foul on the heating plate and flue pipes and reduces the heat transfer rate, hence decreases the performance of the boiler. It can be destructed or reduced, but still now, there is not any method to completely get rid of tar (Kafle et al., 2014). European pellets allowed up-...

We investigated the energy usage, economics, and global warming potential (GWP) of spring rice pr... more We investigated the energy usage, economics, and global warming potential (GWP) of spring rice production via farm sizes in Nepal. Seventy farmers were selected via purposive sampling methods, and data were collected by interviewing the farmers on site. It was found that 22,987 mega joules of energy per hectare (MJ/ha) was invested in order to yield 77,355 MJ/ha worth of outputs (5262 kg/ha). The analysis shows that the highest share of energy input was contributed by machinery (33.50%) and least by chemicals (0.96%). It was further found that spring rice farming in Nepal is less energy productive (0.23 kg/MJ) and less energy efficient (3.37) than that of neighboring countries—such as India, China, and Pakistan. The total GWP is estimated about 720.56 kg CO2eq/ha. The average cost of production was found to equate to USD810.24/ha (or USD0.154/kg of production), and that profit only reached USD73.93/ha. This study found that energy use, cost of production, and yield per ha all genera...

International Journal of Green Energy

ABSTRACT The academic institute, a huge consumer of energy, is still depending upon the grid and/... more ABSTRACT The academic institute, a huge consumer of energy, is still depending upon the grid and/or conventional fuel despite having potential areas of a solar PV installation. No such study has been reported in Nepal which has techno-economically discussed the potential use of academic institute rooftops for solar PV installation. In this study, we have investigated the techno-economic and environmental assessment of a 1 megawatt (MW) rooftop solar PV using PVsyst for Purwanchal Campus, Nepal. It has been estimated the plant will produce about 1,660 MWh of usable AC electricity annually and out of which 95% can be supplied to the grid. The remaining can fulfill the demand of the campus at sunshine hours. For this, a capital investment of about USD 961,404 is needed for the plant with an annual operating cost of USD 8,008. This project gives a 190% return of investment within its life of 25 years with a Levelized cost of energy (LCOE) of 0.069 USD/kWh. The performance ratio and payback period of the project are calculated at about 0.765 and 8.4 years, respectively. The system will produce about 97% less emission than that of diesel generator, which is currently being used for power backup. It is concluded that a 1 MW grid-connected solar PV system is feasible for the studied campus.

Earth's Future, 2021

The COVID-19 pandemic has impacted social, economic, and environmental systems worldwide, slowing... more The COVID-19 pandemic has impacted social, economic, and environmental systems worldwide, slowing down and reversing the progress made in achieving the Sustainable Development Goals (SDGs). SDGs belong to the 2030 Agenda to transform our world by tackling humankind's challenges to ensure well-being, economic prosperity, and environmental protection. We explore the potential impacts of the pandemic on SDGs for Nepal. We followed a knowledge co-creation process with experts from various professional backgrounds, involving five steps: online survey, online workshop, assessment of expert's opinions, review and validation, and revision and synthesis. The pandemic has negatively impacted most SDGs in the short term. Particularly, the targets of SDG 1, 4, 5, 8, 9, 10, 11, and 13 have and will continue to have weakly to moderately restricting impacts. However, a few targets of SDG 2, 3, 6, and 11 could also have weakly promoting impacts. The negative impacts have resulted from imped...

IOP Conference Series: Earth and Environmental Science

Maize is the second largest crop grown in Nepal and is grown in all three geographic zones. The o... more Maize is the second largest crop grown in Nepal and is grown in all three geographic zones. The objective of this study is to analyse the energy input-output of maize production systems. The study is conducted in Sundarharaincha municipality of Morang district, Nepal, using direct questionnaires methods for the collection of primary data of varying landholding sizes farmers. The study revealed that total energy input and output for maize production system found about 10, 999.61 MJ/ha and 45, 501.52 MJ/ha, respectively, with the highest share by farmyard manure (FYM) about 50%. The energy use efficiency was found 4.14. Total CO2, N2O and CH4 emissions due to chemical inputs were found 163.24 kg/ha, 0.03 kg/ha and 0.33 kg/ha, respectively. The total Global warming potential was found 178.58 CO2 eq. per ha. The average cost of production were calculated USD 301.35/ha and profit USD 272.26/ha.

Renewable and Sustainable Energy Reviews

The primary objectives of this study were to understand the energy plans and policies of the Repu... more The primary objectives of this study were to understand the energy plans and policies of the Republic of Korea (ROK) and outline its development in the energy sector. Both qualitative and quantitative information were gathered and evaluated in the context of the defined objectives. The study has outlined that the primary motivational factor for achieving the current improved energy status of the ROK was to support the rapid industrial growth and socio-economic development of the country. The major steps taken were to manage the country's escalating energy demand and to minimize the greenhouse emissions in energy sector along its progressive economic development. The economic growth of the country had good correlation with the escalating fossil fuel consumption. This is however among the great concerns in the country in today's global agenda of sustainable energy managements. The country has been primarily relying on the imported energy sources, which averaged to 84% (including nuclear generation) of the total primary energy supply (TPES) during the period of 2000–2014. Oil has been the main source of energy supply in the country, followed by coal and natural gas. Penetration of renewable energy technologies was primarily motivated to meet the country's strategic goals, including the downscaling of GHG emission by 37% by 2030 compared to the business-as-usual (BAU) situation. Despite the different initiations in the energy management, renewable energy sources covered only 4.5% of the TPES in 2014. In addition, the country's urgent need now is also towards the management of the available natural resources to support the growing demand of bio-economy. At this particular interest, the country needs to identify the sustainable availability of resources to balance the multi-fold sectors. This demands comprehensive energy-system analysis along with identifying the avenues of the utilization of biomass resources.

Energy

The high yield and fouling of tar reduces thermal efficiency of the wood pellet boiler. In order ... more The high yield and fouling of tar reduces thermal efficiency of the wood pellet boiler. In order to achieve better performance of wood pellet boiler, the effect of tar fouled on thermal efficiency should be investigated. This study presents CFD (Computation Fluid Dynamics) simulation of thermal behavior of the boiler and analysis the thermal efficiency affected by tar fouling on the heating surface of the combustion chamber. A model has been developed to predict the thermal behavior of the combustion gas and heating water in the boiler using the conservation of mass, momentum and energy equations. To investigate the effect of tar fouling on thermal efficiency, the experiments were performed by combusting the 1st and the 3rd grade wood pellets, and compared with the simulations. By about 1 mm tar fouling in heating surface of the boiler the thermal efficiency dropped by 7.26%p and 9.19%p in the 1st and the 3rd grade wood pellets, respectively. Compared to experiment using the 1st grade wood pellet, simulation results were relatively deviated, the outlet water temperature increased by 0.53 K in non-tar condition and decreased by 0.02 K in tar-existence condition. This study can be used to improve the overall performance of the boiler.

Energy

Abstract Fouling of tar in wood pellet boiler reduces its thermal efficiency and demands periodic... more Abstract Fouling of tar in wood pellet boiler reduces its thermal efficiency and demands periodical maintenance to keep its original performance. The fouling of tar in wood pellet boiler was studied along with the physical and thermal characteristics of the pellets. Four different samples were prepared and accessed: a sample of control pellets without additives and three other samples each with 2% additives (dolomite and/or lime). Experiments for each sample were carried out in the pellet boiler for 20 h and fouling of tar is investigated. It is observed that the fouling of tar is drastically reduced in the pellets with additives 1% dolomite plus 1% lime: 76% by area-density (kg/m 2 ) and 82% by thickness (mm). At the same time, the particle density, mechanical durability, bulk density, and heating value are also found to be improved leading to an improved overall performance of the pellets and the boiler. The pellets with the additives are, therefore, found to be a better option to reduce tar in wood pellet boilers and are recommended.

Applied Thermal Engineering

International Journal of Green Energy, 2016

ABSTRACT In the current study, the potential of forest-based biomass supply for the pellet produc... more ABSTRACT In the current study, the potential of forest-based biomass supply for the pellet production in Nepal is investigated. This study showed that about 2.76 million tonnes (Mt) biomass in the form of pellets are potentially available from forest-based biomass. Considering a processing capacity of 6 tonnes (t)/hr of a pellet plant, the production cost of the pellets was calculated to be $43.53/t. Pellets are generally used as fuel to produce thermal energy in industries, which helps to save the economy and the environment of the country.

Nepal, a country rich in biomass, still does not have any commercial pellet production plants and... more Nepal, a country rich in biomass, still does not have any commercial pellet production plants and is wasting large amounts of agricultural crop residue. The current study showed that about 5.61 million tonnes (Mt) of biomass in the form of pellets are potentially available from agricultural crop residues. The brick and cement industries could use these agro-pellets. Co-firing of pellets in such industries could play an important role in reducing the import volume of coal and minimize the related environmental loadings.