• Energy Research
• NP close

Investigating the impact of climate variables on net primary productivity is crucial to evaluate the ecosystem health and the status of forest type response to climate change. The objective of this paper is (1) to estimate spatio-temporal patterns of net primary productivity (NPP) during 2001 to 2010 in a tropical deciduous forest based on the input variable dataset (i.e.meteorological and biophysical) derived from the remote sensing and other sources and (2) to investigate the effects of climate variables on NPP during 2001 to 2010. The study was carried out in Katerniaghat Wildlife Sanctuary that forms a part of a tropical forest and is situated in Uttar Pradesh, India, along the Indo-Nepal border. Mean annual NPP was observed to be highest during 2007 with a value of 878 g C m-2 year-1 and 781.25 g C m-2 year-1 for sal and teak respectively. A decline in mean NPP during 2002-2003, 2005 and 2008-2010 could be attributed to drought, increased temperature and vapour pressure deficit (VPD). The time lag correlation analysis revealed precipitation as the major variables affecting NPP, whereas combination of temperature and VPD showed dominant effect on NPP as revealed by generalized linear modelling. The carbon gain in NPP in sal forest was observed to be marginal higher than that of teak plantation throughout the study period. The decrease in NPP was observed during 2010, pertaining to increased VPD. Contribution of different climatic variables through some link process was revealed in statistical analysis and clearly indicated the co-dominance of all the variables in explaining NPP.

Investigating the impact of climate variables on net primary productivity is crucial to evaluate the ecosystem health and the status of forest type response to climate change. The objective of this paper is (1) to estimate spatio-temporal patterns of net primary productivity (NPP) during 2001 to 2010 in a tropical deciduous forest based on the input variable dataset (i.e.meteorological and biophysical) derived from the remote sensing and other sources and (2) to investigate the effects of climate variables on NPP during 2001 to 2010. The study was carried out in Katerniaghat Wildlife Sanctuary that forms a part of a tropical forest and is situated in Uttar Pradesh, India, along the Indo-Nepal border. Mean annual NPP was observed to be highest during 2007 with a value of 878 g C m-2 year-1 and 781.25 g C m-2 year-1 for sal and teak respectively. A decline in mean NPP during 2002-2003, 2005 and 2008-2010 could be attributed to drought, increased temperature and vapour pressure deficit (VPD). The time lag correlation analysis revealed precipitation as the major variables affecting NPP, whereas combination of temperature and VPD showed dominant effect on NPP as revealed by generalized linear modelling. The carbon gain in NPP in sal forest was observed to be marginal higher than that of teak plantation throughout the study period. The decrease in NPP was observed during 2010, pertaining to increased VPD. Contribution of different climatic variables through some link process was revealed in statistical analysis and clearly indicated the co-dominance of all the variables in explaining NPP.

Abstract Nepal is very rich in hydropower. Unfortunately, due to the mountainous topography it is difficult to build a comprehensive electrical grid. Only 30% of the population (primarily in urban areas) currently has access to electricity from the national grid and about 5% from non-grid (micro-hydropower and solar). In addition the power is seasonal, resulting in poor “load factor”. On a seasonal basis, the power generated by large hydropower stations during the summer surpasses the peak demand of the country. The peak load varies from 400 MW to 560 MW from 17:00 to 21:00 hours. The maximum demand recorded on December 8, 2004 was 557.53 MW at 18:16 hour. Thus, the widespread hydroelectric potential is not effectively utilized. One of the methods to utilize the available power is production of hydrogen by electrolysis using hydropower, a clean source of renewable energy. Nepal is very rich in perennial rivers and has a potential of 83,000 MW of which 43,000 MW of it is considered economically viable. Only about 550 MW (∼1%) of this potential has been harnessed till now. This paper highlights possibilities of generation of hydrogen from the existing hydropower plants during off-peak load and utilization of this hydrogen energy to replace the existing fossil fuels used in transportation, cooking and lighting and to meet the growing peak electricity demand by generating electricity using fuel cell in future. Different scenarios of utilization of hydropower during off-peak load have been forecasted and possible replacement of conventional fuels by hydrogen has been discussed.

Abstract Nepal is very rich in hydropower. Unfortunately, due to the mountainous topography it is difficult to build a comprehensive electrical grid. Only 30% of the population (primarily in urban areas) currently has access to electricity from the national grid and about 5% from non-grid (micro-hydropower and solar). In addition the power is seasonal, resulting in poor “load factor”. On a seasonal basis, the power generated by large hydropower stations during the summer surpasses the peak demand of the country. The peak load varies from 400 MW to 560 MW from 17:00 to 21:00 hours. The maximum demand recorded on December 8, 2004 was 557.53 MW at 18:16 hour. Thus, the widespread hydroelectric potential is not effectively utilized. One of the methods to utilize the available power is production of hydrogen by electrolysis using hydropower, a clean source of renewable energy. Nepal is very rich in perennial rivers and has a potential of 83,000 MW of which 43,000 MW of it is considered economically viable. Only about 550 MW (∼1%) of this potential has been harnessed till now. This paper highlights possibilities of generation of hydrogen from the existing hydropower plants during off-peak load and utilization of this hydrogen energy to replace the existing fossil fuels used in transportation, cooking and lighting and to meet the growing peak electricity demand by generating electricity using fuel cell in future. Different scenarios of utilization of hydropower during off-peak load have been forecasted and possible replacement of conventional fuels by hydrogen has been discussed.

Piezoelectric energy harvesting from traffic load has gained extensive attention for potentiality as a renewable energy source. In existing in situ experiments, generally only one vehicle is employed, while the wheel-path of the vehicle and embedded positions of piezoelectric energy harvester (PEH) units are both fixed. However, in an actual traffic condition, vehicles travel randomly along width of pavements, which means the wheel-path varies over time and among vehicles. In this study, an electromechanical model is established for the PEH units under actual traffic conditions with wheel-path distribution, and is validated with finite element analysis and experiments. Then the electrical performance of PEH units embedded at various locations along pavements’ lateral direction is investigated under various traffic speeds. It is found that the optimal lateral embedded locations of the PEH units should be adjusted according to the prescribed traffic speed of the roads. Specifically, PEH units should be embedded at the tire-road contact areas for road with low traffic speeds (<15 m/s), while they should be embedded at the center of the pavement with high traffic speeds (>25 m/s). These mathematical results may serve as guidelines for selecting optimal lateral embedded locations for PEH units embedded in pavements.

Piezoelectric energy harvesting from traffic load has gained extensive attention for potentiality as a renewable energy source. In existing in situ experiments, generally only one vehicle is employed, while the wheel-path of the vehicle and embedded positions of piezoelectric energy harvester (PEH) units are both fixed. However, in an actual traffic condition, vehicles travel randomly along width of pavements, which means the wheel-path varies over time and among vehicles. In this study, an electromechanical model is established for the PEH units under actual traffic conditions with wheel-path distribution, and is validated with finite element analysis and experiments. Then the electrical performance of PEH units embedded at various locations along pavements’ lateral direction is investigated under various traffic speeds. It is found that the optimal lateral embedded locations of the PEH units should be adjusted according to the prescribed traffic speed of the roads. Specifically, PEH units should be embedded at the tire-road contact areas for road with low traffic speeds (<15 m/s), while they should be embedded at the center of the pavement with high traffic speeds (>25 m/s). These mathematical results may serve as guidelines for selecting optimal lateral embedded locations for PEH units embedded in pavements.

Assessment of future water resources under climate change is required in the Himalayas, where hydrological cycle is poorly studied and little understood. This study focuses on the upper Dudh Koshi river of Nepal (151km(2), 4200-8848ma.s.l.) at the toe of Mt. Everest, nesting the debris covered Khumbu, and Khangri Nup glaciers (62km(2)). New data gathered during three years of field campaigns (2012-2014) were used to set up a glacio-hydrological model describing stream flows, snow and ice melt, ice cover thickness and glaciers' flow dynamics. The model was validated, and used to assess changes of the hydrological cycle until 2100. Climate projections are used from three Global Climate Models used in the recent IPCC AR5 under RCP2.6, RCP4.5 and RCP8.5. Flow statistics are estimated for two reference decades 2045-2054, and 2090-2099, and compared against control run CR, 2012-2014. During CR we found a contribution of ice melt to stream flows of 55% yearly, with snow melt contributing for 19%. Future flows are predicted to increase in monsoon season, but to decrease yearly (-4% vs CR on average) at 2045-2054. At the end of century large reduction would occur in all seasons, i.e. -26% vs CR on average at 2090-2099. At half century yearly contribution of ice melt would be on average 45%, and snow melt 28%. At the end of century ice melt would be 31%, and snow contribution 39%. Glaciers in the area are projected to thin largely up to 6500ma.s.l. until 2100, reducing their volume by -50% or more, and their ice covered area by -30% or more. According to our results, in the future water resources in the upper Dudh Koshi would decrease, and depend largely upon snow melt and rainfall, so that adaptation measures to modified water availability will be required.

Assessment of future water resources under climate change is required in the Himalayas, where hydrological cycle is poorly studied and little understood. This study focuses on the upper Dudh Koshi river of Nepal (151km(2), 4200-8848ma.s.l.) at the toe of Mt. Everest, nesting the debris covered Khumbu, and Khangri Nup glaciers (62km(2)). New data gathered during three years of field campaigns (2012-2014) were used to set up a glacio-hydrological model describing stream flows, snow and ice melt, ice cover thickness and glaciers' flow dynamics. The model was validated, and used to assess changes of the hydrological cycle until 2100. Climate projections are used from three Global Climate Models used in the recent IPCC AR5 under RCP2.6, RCP4.5 and RCP8.5. Flow statistics are estimated for two reference decades 2045-2054, and 2090-2099, and compared against control run CR, 2012-2014. During CR we found a contribution of ice melt to stream flows of 55% yearly, with snow melt contributing for 19%. Future flows are predicted to increase in monsoon season, but to decrease yearly (-4% vs CR on average) at 2045-2054. At the end of century large reduction would occur in all seasons, i.e. -26% vs CR on average at 2090-2099. At half century yearly contribution of ice melt would be on average 45%, and snow melt 28%. At the end of century ice melt would be 31%, and snow contribution 39%. Glaciers in the area are projected to thin largely up to 6500ma.s.l. until 2100, reducing their volume by -50% or more, and their ice covered area by -30% or more. According to our results, in the future water resources in the upper Dudh Koshi would decrease, and depend largely upon snow melt and rainfall, so that adaptation measures to modified water availability will be required.