Binod K. Bhattarai

Dependence of perovskite solar cells performance on temperature and solar irradiation

Perovskites have proved to be a promising candidate for solar cells. In this paper we present the simulations work related to the new topics; influence of temperature and multi-Sun (solar concentrator) on performance of perovskite based solar cells. The study shows the dependence of all PV parameters on the operating temperature and solar irradiance. Performance of the perovskite based PV devices is higher at 277 K, the temperature lower than room temperature, and at around 5 Suns.

Aerosol climatology in Kathmandu using Sun Photometry

Direct and global solar radiation measurements carried out in Kathmandu valley (N, E 1350 masl) have been analyzed in this study. Observations were made using a microprocessor controlled portable aerosol meter Microtops II working in ultraviolet (340, 380 nm) and visible range (440, 500, 675 nm) under cloudless conditions. Aerosol optical depth at 380 nm was found to be 0.33, 0.48, 0.21 and 0.45 in summer, autumn, spring and winter season respectively. Monitoring of global solar radiation was done with a ground based ultraviolet radiometer (GUV). From the aerosol optical depth from Sun Photometer, Angstrom turbidity parameters were estimated by means of the least square fitting technique. The aerosol optical depth is also utilized to make a model fit for UV index and compare the GUV data. A decrease in humidity by about 70% is found to increase the UV index by about 22%. The atmospheric turbidity parameter (β) is found high in the morning and show decreasing trends from morning to late afternoon on average. The wavelength exponent (α) becomes smaller during noon indicating existence of higher proportion of tiny particles in lower atmosphere in day time. Finally an inversion of spectral optical depth measurements technique allowed estimating aerosol size distribution changing between unimodal to bimodal functions yearly.

The Scenario of Carbonaceous Aerosols and Total Solar Radiation in Two Cities in Nepal

Measurement of elemental carbon (EC) and black carbon (BC) aerosols was carried out using AE-31, 7 channel aethalometer at Kathmandu and Biratnagar; two mega cities of Nepal, for five months, January to May 2011 to study its temporal and spatial variation. Total solar radiation was also monitored using Kipp and Zonen CMP 6 pyranometer. Monthly concentration variation for EC and BC was distinct in both study sites. At Biratnagar, monthly EC concentration varies from 3.3 -20.7 µg /m 3 while in Kathmandu it varies between 6.0-13.7 µg /m 3 . Similarly, BC monthly concentration ranges from 3.3 -20.1 µg /m 3 and 7.0-14.9 µg /m 3 respectively. It was found that both EC and BC were highest during January in both the sites and it decreases gradually. Monthly average solar radiation shows a maximum value in May and minimum in January. A distinct anti-correlation between monthly average carbonaceous aerosols and total solar radiation was observed. Moreover, there was a pronounced diurnal variation of both carbonaceous aerosols EC and BC in the sites with two high peaks one in the morning at about 9:00 and another at late evening 20:00 local time with minimum concentration in the afternoon. The nature of peaks were different at two sites. Biratnagar shows a larger evening peak while Kathmandu shows in the morning inferring heavy domestic and industrial fuel consuming activities in evening and morning respectively. In addition to this, daily and monthly concentration of EC was more than BC at Biratnagar reflecting slightly more biomass fuel consumption than fossil fuel for domestic, industrial and other urban activities. In contrast to this, Kathmandu shows more domination of fossil fuel than biofuel because of reverse order concentration of carbonaceous aerosols. Total solar radiation also shows apparent diurnal variation in both sites with the highest value at around noon time.