Sunil Lohani | Kathmandu University (original) (raw)

Papers by Sunil Lohani

Clean Energy, 2021

A radical transformation of the global energy system is underway. Solar photovoltaics and wind no... more A radical transformation of the global energy system is underway. Solar photovoltaics and wind now comprise three-quarters of the global net new electricity-generation-capacity additions because they are cheap. The deep renewable electrification of energy services including transport, heating and industry will allow solar and wind to largely eliminate fossil fuels over the next few decades. This paper demonstrates that Nepal will be able to achieve energy self-sufficiency during the twenty-first century. Nepal has good solar and moderate hydroelectric potential but has negligible wind- and fossil-energy resources. The solar potential is about 100 times larger than that required to support a 100% solar-energy system in which all Nepalese citizens enjoy a similar per-person energy consumption to developed countries, without the use of fossil fuels and without the environmental degradation resulting from damming Nepal’s Himalayan rivers. Nepal has vast low-cost off-river pumped hydro-e...

Renewable Energy, 2019

The project intends to design, fabricate and test a highrate anaerobic reactor that can treat the... more The project intends to design, fabricate and test a highrate anaerobic reactor that can treat the domestic wastewater and produce biogas as a byproduct. The biogas is a combustible mixture of methane, carbon monoxide, hydrogen gases etc. and can be used in the table burner. The target of the biogas reactor is to treat the wastewater generate from domestic wastewater at Kathmandu University. The major outcome of this project is to be a working design of the biogas digester which can be fabricated and can be coupled with domestic septic for the domestic wastewater treatment. The septic tank uses as a primary treatment of the wastewater whereas UASB is taken as a secondary treatment. We design pilot scale UASB wastewater treatment system and test know the proper operation of the reactor. The septic tank-UASB combine system has TSS and CODt removal efficiency of 83% and 88% respectively. This system is one of the appropriate systems for onsite wastewater treatment in the developing country.

Renewable Energy, 2010

The energy and exergy flow for a space heating systems of a typical residential building of natur... more The energy and exergy flow for a space heating systems of a typical residential building of natural ventilation system with different heat generation plants have been modeled and compared. The aim of this comparison is to demonstrate which system leads to an efficient conversion and supply of energy/ exergy within a building system. The analysis of a fossil plant heating system has been done with a typical building simulation software IDA-ICE. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for other cases of building heating systems where power generation plants are considered as ground and air source heat pumps at different operating conditions. Since there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis revealed that the ground source heat pump heating system is better than air source heat pump or conventional heating system. The realistic and efficient system in this study ''ground source heat pump with condenser inlet temperature 30 C and varying evaporator inlet temperature'' has roughly 25% less demand of absolute primary energy and exergy whereas about 50% high overall primary coefficient of performance and overall primary exergy efficiency than base case (conventional system). The consequence of low absolute energy and exergy demands and high efficiencies lead to a sustainable building heating system.

Energy, 2010

In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air s... more In this paper, we deal with the energy and exergy analysis of a fossil plant and ground and air source heat pump building heating system at two different dead-state temperatures. A zone model of a building with natural ventilation is considered and heat is being supplied by condensing boiler. The same zone model is applied for heat pump building heating system. Since energy and exergy demand are key parameters to see which system is efficient at what reference temperature, we did a study on the influence of energy and exergy efficiencies. In this regard, a commercial software package IDA-ICE program is used for calculation of fossil plant heating system, however, there is no inbuilt simulation model for heat pumps in IDA-ICE, different COP (coefficient of performance) curves of the earlier studies of heat pumps are taken into account for the evaluation of the heat pump input and output energy. The outcome of the energy and exergy flow analysis at two different dead-state temperatures revealed that the ground source heat pumps with ambient reference have better performance against all ground reference systems as well as fossil plant (conventional system) and air source heat pumps with ambient reference.

Sustainability

A shift from a linear economy to a circular economy of resource consumption is vital for divertin... more A shift from a linear economy to a circular economy of resource consumption is vital for diverting the value from lost resources to resource-efficient products towards developing a sustainable system. Household digesters provide one opportunity to create a biogas-based circular economy. Because household digesters are typically fed a wide and variable range of substrates, it is important to determine the ideal mixing ratios for them. In this study, an anaerobic digester startup process was analyzed and an assessment of anaerobic co-digestion of food waste with different livestock manures was carried out at ambient temperatures. Food waste (FW), cow manure (CM), poultry litter (PL) and goat manure (GM) were co-digested at mixing ratios (FW:PL:CM) of 2:1:1, 2:2:1, 1:1:2, 1:1:1 (wt/wt) and FW:PL:GM at mixing ratios of 2:1:1 and 1:1:2, at an organic loading rate of 1 g volatile solid (VS)/L/day, and 8% total solids. A maximum methane yield was obtained from co-digestion of FW:PL:GM at a...

Wastewater management in Kathmandu is a challenge to the government of Nepal. The current trend o... more Wastewater management in Kathmandu is a challenge to the government of Nepal. The current trend of wastewater disposal is to drain the effluents directly into the water recipients like Bagmati and other rivers and streams without any treatment, which cause serious environmental and public health problems besides destroying the aesthetic beauty of the city. This paper deals with the evaluation of wastewater management practices, challenges and possible solutions in Nepal based on published materials. The data shows that wastewater generation in Kathmandu valley has increased from 81x106 l/day in year 2000 to about 145x106 l/day in year 2014, which is 79 percent increase in 15 years. Wastewater must be treated before discharge in order to comply with wastewater legislations and guidelines. This can be achieved through decentralized treatment. There is a need of careful planning, adequate and suitable treatment and regular monitoring to achieve unpolluted wastewater discharge into rece...

Anaerobic digestion of food waste alone is not very stable due to its acidic nature and high biod... more Anaerobic digestion of food waste alone is not very stable due to its acidic nature and high biodegradability. Co-digestion of food waste with alkaline substrate such as chicken manure and goat manure could enhance process stability and biogas yield. In this study comparison of mono digestion of food waste with 8% total solid content at an ambient temperature and co-digestion of food waste, goat and chicken manure at ratio 5:2:3 and 2:1:1 with 8% total solid content at an ambient temperature in hilly region of Nepal were carried out. Biogas yield was highest with mixing ratio of 5:2:3 with the values of 109 ml/gVS followed by mixing ratio of 2:1:1 with the values of 80 ml/gVS. Mono digestion of food waste was not stable and broke down after two weeks of operation. Findings from this study suggests that co-digestion could be a suitable method for addressing the problem related to stability in a single substrate digestion in an ambient temperature condition. Moreover, mixing ratio of ...

This paper reviews the status of biomass as a source of household energy and indoor air pollution... more This paper reviews the status of biomass as a source of household energy and indoor air pollution in Nepal. The current statistics show that about 89% of total energy is consumed in residential sector is largely for cooking and heating purpose. The major sources of residential energy are fuel wood (86.5%), animal dung (6.5%) and agricultural residue (3.7%), which clearly indicates a huge demand for biomass as household energy in the country. Several studies have shown that particulate matter (PM ) concentration on 10 cooking place was about 8000 µg/m against the national standard of 120 µg/m in 24 hours average time. 33 Similarly, the total suspended particle (TSP) was about 8,800 µg/m against national standard of 230 µg/m , 33 21 ppm of carbon monoxide (CO) against national standard of 9 ppm in 8 hour average was found where biomass was used as fuel. Moreover, these studies have also shown that mortality and morbidity rates among children and women are extremely high due to acute r...

H2S is produced in the anaerobic digestion process by the degradation of organic compounds (i.e.,... more H2S is produced in the anaerobic digestion process by the degradation of organic compounds (i.e., proteins) and reduction of the inorganic species (SO42−) present in the feedstock. H2S is required to be removed from the biogas due to concerns about health, safety, and corrosion during transmission, storage, and use. Higher concentrations of H2S in biogas limit its applications in various technologies like turbines, internal combustion engines, fuel cells, and grid injection. This chapter reviews the range of different technological options, that is, physicochemical processes such as water scrubbing, membrane separation, adsorption onto activated charcoal, metal oxides, and absorption in organic solvents. Likewise, various in situ and ex situ biological biogas desulfurization methods such as the use of biological air filtration, direct and indirect microaeration techniques, and combined two-step chemical-biological processes are discussed. The prospects and limitations of the existin...

The energy flow analysis in the building heating system alone can not provide sufficient thermody... more The energy flow analysis in the building heating system alone can not provide sufficient thermodynamic insight of the different process involved mainly because it is unable to divulge quality content of the energy that limits application of energy conservation principle and therefore exergy analysis came in to picture, which provides more insight of each process involved and open up possibility of finding new source of renewable energies for sustainable buildings and likely optimization area in the system. The energy and exergy flow for a space heating systems of a typical residential building of natural ventilation system with different heat generation plants have been developed and compared. The aim of this comparison is to demonstrate which system leads to an efficient conversion and supply of energy/exergy within a building system.

Energy Sources, Part A: Recovery, Utilization, and Environmental Effects

Energy, Environment, and Sustainability

Sustainable Energy Technologies and Assessments

Clean Energy

Clean-cooking energy is key to meeting climate-mitigation goals and a range of development object... more Clean-cooking energy is key to meeting climate-mitigation goals and a range of development objectives, especially for improving the well-being of women and children. Inefficient burning of solid biomass for cooking releases household air pollution that is hazardous to health, while putting pressure on forest resources. This paper provides an overview of the household-cooking-energy transition in Nepal to date. Despite numerous efforts by the government and other actors to speed this transition, energy data spanning the years 2000–18 reveal that ~69% of households nationwide still rely on solid fuels for cooking today. The proportion of solid-fuel users is especially high in rural regions, reaching >80%. Moreover, if the current rate of progress is not accelerated, the use of solid fuels will remain high even in 2030, preventing the achievement of Sustainable Development Goal (SDG) 7. Cooking-fuel choices are heavily constrained by accessibility, demographic and socio-economic fac...