There has been an enormous infusion of new ideas in the field of solar cells over the last 15 years; discourse on energy transfer has gotten much richer, and nanostructures and nanomaterials have revolutionized the possibilities for new technological developments. However, solar energy cannot become ubiquitous in the world's power markets unless it can become economically competitive with legacy generation methods such as fossil fuels. The new edition of Dr. Stephen Fonash's definitive text points the way toward greater efficiency and cheaper production by adding coverage of cutting-edge topics in plasmonics, multi-exiton generation processes, nanostructures and nanomaterials such as quantum dots. This book's new structure improves readability by shifting many detailed equations to appendices, and balances the first edition's semiconductor coverage with an emphasis on thin-films. Further, it now demonstrates physical principles with simulations in the well-known AMPS computer code developed by the author. This classic text is now updated with new advances in nanomaterials and thin films that point the way to cheaper, more efficient solar energy production and, many of the detailed equations from the first edition have been shifted to appendices in order to improve readability. It carries important theoretical points are now accompanied by concrete demonstrations via included simulations created with the well-known AMPS computer code.

太阳电池器件物理 = Solar cell device physics

Traditionally, III–V multi-junction cells have been used in concentrator photovoltaic (CPV) applications, which deliver extremely high efficiencies but have failed to compete with ‘flat-plate’ silicon technologies owing to cost. Here, we assess the feasibility of using metal halide perovskites for CPVs, and we evaluate their device performance and stability under concentrated light. Under simulated sunlight, we achieve a peak efficiency of 23.6% under 14 Suns (that is, 14 times the standard solar irradiance), as compared to 21.1% under 1 Sun, and measure 1.26 V open-circuit voltage under 53 Suns, for a material with a bandgap of 1.63 eV. Importantly, our encapsulated devices maintain over 90% of their original efficiency after 150 h aging under 10 Suns at maximum power point. Our work reveals the potential of perovskite CPVs, and may lead to new PV deployment strategies combining perovskites with low-concentration factor and lower-accuracy solar tracking systems. Metal halide perovskites offer the potential for high-efficiency, low-fabrication-cost solar cells. This study now explores their prospects if deployed in concentrator photovoltaics and finds they perform well up to a concentration of 53 Suns and retain good stability under 10 Suns for over 150 h.

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High irradiance performance of metal halide perovskites for concentrator photovoltaics

Performance analysis of MAPbI3 based perovskite solar cells employing diverse charge selective contacts: Simulation study

Nepal has been suffering from a serious energy crisis for decades. It has severely affected its economic, social and political developments. Owing to the continuously evolving energy situation in Nepal, and the recent progress in renewable energy technologies, this study aims to provide an up to date perspective on the current energy crisis in Nepal. In particular, the current energy production and consumption profiles are reviewed, and the main factors contributing to a widening gap between the energy supply and demand are identified. These factors concern delayed and overpriced hydropower projects, outdated and insufficient energy infrastructure, transmission and distribution losses, energy theft, deficient energy management, lack of energy conservation, low efficiency of equipment, unsustainable energy pricing strategies and unsatisfying energy market regulations. Other essential factors worsening the energy crisis can be attributed to specific geographical and geopolitical problems, the strong dependence on energy imports, and inadequate exploitation of the vast amounts of renewable energy resources. The status of existing and planned large hydropower projects is summarized. The recent policies and investment initiatives of the Nepalese government to support green and sustainable energy are discussed. Furthermore, a long-term outlook on the energy situation in Nepal is outlined using the energy modeling software LEAP in order to show how to exploit the tremendous renewable energy resources in Nepal. Our findings suggest that renewable resources are crucial not only for mitigating the present energy crisis, but also to ultimately provide energy independence for Nepal by establishing reliable and secure sources of energy.

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Mitigating the current energy crisis in Nepal with renewable energy sources

Tin Halide Perovskites: Progress and Challenges

This paper presents a comparative study on organometal halide perovskite based solar cells using two different transparent conducting oxides such as TiO2 and ZnO as electron transporting materials. Simulation is an interesting tool for studying the behavior of every component of a solar cell device as well as for analyzing the performance of the full device. Solar cell capacitance simulator (SCAPS)-1D has been the tool used for numerical simulation of such devices. Influences of thickness of absorber and ETMs, interface trap density of states and dopant concentration of ETMs on the performance of photovoltaic solar cells are studied. Comparable efficiencies of 22.35% and 22.49% for PV devices made of spiro-MeOTAD/MAPbI3/TiO2 and spiro-MeOTAD/MAPbI3/ZnO, respectively, with 400/400/90 nm thicknesses under 1 Sun illumination are observed. The performance of both devices indicates the replacement of the TiO2 by a ZnO layer. It could be a good option to reduce the cost and increase the mobility of ETM for this type of solar cells. Generally, increase in thickness of MAPbI3 perovskite up to around 700 nm results into increase in the power conversion efficiency (PCE) of the solar cells. On the other hand, TiO2 and ZnO layers thicker than 90 nm results into decrease in the efficiency of the devices. Furthermore, the increase in interface trap density is found to reduce the efficiency of the devices. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Comparative study on MAPbI3 based solar cells using different electron transporting materials

Rational and accurate solar energy databases, essential for designing, sizing and performing the solar energy systems in any part of the world, are not easily accessible in different localities of Nepal. In this study, daily global solar radiation, sunshine hours and meteorological data for Biratnagar, Kathmandu, Pokhara and Jumla have been used to derive the regression constants. The linear regression technique has been used to develop a model for Biratnagar, Kathmandu, Pokhara and Jumla. The model has calculated the global solar radiation for these locations. The values of global solar radiation estimated by the model are found to be in close agreement with measured values of respective sites. The estimated values were compared with Angstrom-Prescott model and examined using the root mean square error (RMSE), mean bias error (MBE), mean percentage error (MPE), coefficient of regression (R), coefficient of determinant (R 2 ) and correlation coefficient (CC) statistical techniques. Thus, the resultant correlations and linear regression relations may be then used for the locations of similar meteorological/geographical characteristics and also can be used to estimate the missing data of solar radiation for the respective site.

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Estimation of Global Solar Radiation for Four Selected Sites in Nepal Using Sunshine Hours, Temperature and Relative Humidity

Solar radiation is the best option and cost effective energy resources of this world from 21st century onwards. In this study monthly, seasonal and annual variation of global solar insolation at Biratnagar, Lukla, Kathmandu, Pokhara, of the year 2007 to 2012, Jumla of the year 2011 to 2012 and Simikot 2011/2012 were carried out. The study has shown the variation of global solar insolation with month, season, year, atmospheric condition, and altitude of the site concerned. The maximum value of monthly, seasonal, and yearly global solar insolation was reported at Jumla whereas the minimum monthly, seasonal, and yearly global solar insolation were observed at Kathmandu. From the observation the abundant solar irradiation in Nepal shows encouraging atmosphere for solar farming venture in near future relating to energy management for Nepal. DOI: http://dx.doi.org/10.3126/jie.v9i1.10675 Journal of the Institute of Engineering, Vol. 9, No. 1, pp. 95–106

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Solar Energy Potential in Nepal and Global Context

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.

Dependence of perovskite solar cells performance on temperature and solar irradiation

Routinely surface solar radiation and aerosol optical depth (AOD) were measured at Kathmandu Valley during all possible days of the year from December 2011 to March 2013 to investigate the effects of aerosols on the surface solar radiation in clear sky. The analysis shows that the solar radiation changes with maximum (15.64 MJ/m2) in pre monsoon season to minimum (7.08 MJ/m2) in winter season whereas the relative humidity changes with minimum in pre monsoon to maximum in winter and monsoon seasons. The temperature in the valley varies from 31.4 °C in pre monsoon to 2.7 °C in winter with correlation coefficient, R = 0.72 between solar radiation and temperature. The relative humidity was found to increase AOD and Angstrom’s coefficient β. Calculated from AOD, the values of β found to vary from 0.16 ± 0.03 to 0.35 ± 0.15 with high values in summer and low values in winter. The higher values of β (>0.1) show that Kathmandu Valley is one of the most polluted cities. This study shows that Angstrom’s exponent α and Angstrom’s coefficient β vary with an anti correlation, R = −0.59. This variation is affected by humidity, temperature, wind speed, and transboundary transport of aerosols as well as by rainout and washout. It is found that solar radiation and β vary in opposite way which is consistent with the fact that higher the values of β, greater is the aerosols that produces more extinction of energy in solar radiation reaching the earth’s surface.

Shekhar Gurung

Papers

Comparative study on MAPbI3 based solar cells using different electron transporting materials

Estimation of Global Solar Radiation for Four Selected Sites in Nepal Using Sunshine Hours, Temperature and Relative Humidity

Solar Energy Potential in Nepal and Global Context

Dependence of perovskite solar cells performance on temperature and solar irradiation

Effects of aerosols on the solar radiation in mid-hill of Nepal: a case study in the Kathmandu Valley