Monthly Mean Solar Radiation Research Articles

Variation on Atmospheric Transmittance Solar Radiation at Kathmandu Valley

The daily solar irradiance was measured using CMP6 first class pyranometer at the horizontal surface of Kathmandu Valley (Lat.:-27.7° N, Long.:-85.5° E, Alt. 1350 m above sea level.) from January to December, 2012 (one year). Monthly mean of atmospheric transmittance is calculated based on different meteorological parameters. The effect of different meteorological parameters as well as physical parameters on the atmospheric transmittance of solar radiation was analyzed. The maximum and the minimum monthly mean solar radiation are found to be 21.32 ± 4.14 MJ/m2/day and 10.93 ± 2.03 MJ/m2/day in May and January, respectively. The value of yearly mean solar radiation measures is 16.68 ± 4.60 MJ/m2/day. Similarly, the annual average of atmospheric transmittance value of 0.51 ± 0.12 was obtained that was due to cloudy and more precipitation day during the months of measurements taken. The yearly mean of atmospheric transmittance 0.983, 0.987, 0.698 and 0.889 are found due to Rayleigh scattering followed by ozone, water vapor, gas mixture and aerosols respectively, the maximum atmospheric transmittance due to water vapor and while minimum due to gas mixture. This research work will be beneficial for the further identification of other affecting factors of different parameters for the interaction with radiation at different places of the country.

Global Solar Radiation Characteristics at Calabar and Port Harcourt Cities in Nigeria

This study analyzed the inter-annual variability in solar radiation at Port Harcourt and Calabar, aiming at improving knowledge of solar resources. For the investigation, monthly mean global solar radiation data for fifteen years (2000 – 2014) was collected from Nigerian Meteorological Agency (NIMET), and the monthly mean extraterrestrial solar radiation was determined using globally recognized standard relation. The clearness index parameter was employed for characterizing the spatial variability of solar radiation for Calabar and Port Harcourt. The statistics of the monthly mean solar radiation deviations of Port Harcourt and Calabar was tested using the Kolmogorov–Smirnov method. The test results showed that they are normally distributed random variables. Furthermore, the analysis of sequential properties showed that the coefficients of the auto-correlation with lag 1 are significant for both stations. The auto-correlation coefficients with lag 1, though usually not significant, are negative for both stations. The auto regression lag 1 (AR-1) is the recommended procedure (model equation) for generating monthly solar radiation synthetic time series, with auto-correlation coefficients varying from 0.30 to 0.47 for both stations in the South-South of Nigeria. Citation: Amadi, S. (2020). Global Solar Radiation Characteristics at Calabar and Port Harcourt Cities in Nigeria. Trends in Renewable Energy, 6, 101-120. DOI: 10.17737/tre.2020.6.2.00114

A Hybrid Method for Generation of Typical Meteorological Years for Different Climates of China

Since a representative dataset of the climatological features of a location is important for calculations relating to many fields, such as solar energy system, agriculture, meteorology and architecture, there is a need to investigate the methodology for generating a typical meteorological year (TMY). In this paper, a hybrid method with mixed treatment of selected results from the Danish method, the Festa-Ratto method, and the modified typical meteorological year method is proposed to determine typical meteorological years for 35 locations in six different climatic zones of China (Tropical Zone, Subtropical Zone, Warm Temperate Zone, Mid Temperate Zone, Cold Temperate Zone and Tibetan Plateau Zone). Measured weather data (air dry-bulb temperature, air relative humidity, wind speed, pressure, sunshine duration and global solar radiation), which cover the period of 1994–2015, are obtained and applied in the process of forming TMY. The TMY data and typical solar radiation data are investigated and analyzed in this study. It is found that the results of the hybrid method have better performance in terms of the long-term average measured data during the year than the other investigated methods. Moreover, the Gaussian process regression (GPR) model is recommended to forecast the monthly mean solar radiation using the last 22 years (1994–2015) of measured data.

Energy–exergy analysis and optimization of the solar-boosted Kalina cycle system 11 (KCS-11)

Energy–exergy analysis and parameter design optimization of the KCS-11 solar system with an auxiliary superheater are studied in low-grade thermal energy conversion (LTEC). Firstly, from a thermodynamics point of view, the corresponding calculation model is built to solve the system state points as well as the exergy input/output/loss for each system component. And then, according to the characteristics of the KCS-11 solar system, the verification items are given to verify the correctness of the calculation model. Afterward the model is proved to be correct by sampling check a set of calculation data. On that basis, the corresponding parameter design optimization and system performance analysis are carried out from the viewpoint of the maximization of the exergy output in KCS-11 solar system at a certain scale. Results show that the mass flow rates of working fluid and solar collector subcycle and also ammonia mass fraction are important system operation parameters that should be optimized to deduce the irreversible behavior of the solar system for producing more useful energy. Meanwhile, the heat-transfer rate distribution ratio of the superheater should be large enough to ensure that the expanding vapor in the turbine is superheated. Finally, an optimization calculation case is designed for illustration by using the monthly mean solar radiation statistics in Kumejima Island of Japan. In this case, the maximum generated power is 491kW showing 35.6% exergy efficiency and 6.48% energy efficiency of the system for the month of August. The size of the system in terms of power generated of each major equipment is listed as follows: solar evaporator (370kW), superheater (106kW), condenser (298kW), turbine (491kW), separator (43kW), absorber (37kW), pump (8kW), regenerator (38kW), and diffuser (17kW). And the main system exergy losses are associated with internal consumptions of exergy in turbine (92kW) and condenser (97kW) due to irreversibilities. In this way, the maximum annual power generation of the KCS-11 solar system is about 553,520kWh.

Simulation and Comparison on Photoelectric Conversion Efficiency for Auto Tracking Solar System and Fixed Solar System

Assuming the clearness and cloudless weather in Beijing area, the received solar radiation power is simulated according to three different auto-tracking solar systems and fixed solar system by Matlab. The tracking intervals of three different auto-tracking solar systems are separately 60mins, 30mins and 10mins. The daily mean solar radiation, the monthly mean solar radiation and the yearly mean solar radiation are simulated for three auto-tracking solar systems and fixed solar system. The simulation results can be used as the auto-tracking solar system design reference for engineers, and helpful for solar system optimizing.

Modelling of solar energy potential in Nigeria using an artificial neural network model

In this study, an artificial neural network (ANN) based model for prediction of solar energy potential in Nigeria (lat. 4–14°N, log. 2–15°E) was developed. Standard multilayered, feed-forward, back-propagation neural networks with different architecture were designed using neural toolbox for MATLAB. Geographical and meteorological data of 195 cities in Nigeria for period of 10 years (1983–1993) from the NASA geo-satellite database were used for the training and testing the network. Meteorological and geographical data (latitude, longitude, altitude, month, mean sunshine duration, mean temperature, and relative humidity) were used as inputs to the network, while the solar radiation intensity was used as the output of the network. The results show that the correlation coefficients between the ANN predictions and actual mean monthly global solar radiation intensities for training and testing datasets were higher than 90%, thus suggesting a high reliability of the model for evaluation of solar radiation in locations where solar radiation data are not available. The predicted solar radiation values from the model were given in form of monthly maps. The monthly mean solar radiation potential in northern and southern regions ranged from 7.01–5.62 to 5.43–3.54 kW h/m 2 day, respectively. A graphical user interface (GUI) was developed for the application of the model. The model can be used easily for estimation of solar radiation for preliminary design of solar applications.

Change of Dissolved Gaseous Mercury Concentrations in a Southern Reservoir Lake (Tennessee) Following Seasonal Variation of Solar Radiation

A 12-month field study was conducted consecutively from June 2003 to May 2004 to quantify temporal variations of dissolved gaseous mercury (DGM) concentrations in Cane Creek Lake, a southern reservoir lake (Cookeville, TN). Diurnal changes of DGM concentrations in two periods (morning increase vs afternoon decrease with an around-noon peak) were observed, and the changes closely followed daily solar radiation variation trends. The diurnal patterns prevailed in the late spring and summer, but became vague in the late fall and winter. The monthly mean DGM concentrations peaked at 40.8 pg L(-1) in July and reached the lowest at 14.2 pg L(-1) in December and 21.9 pg L(-1) in January; this DGM concentration change closely followed the monthly mean solar radiation variation trend. The increase of the lake DGM concentration from January to July and its decrease from July to December mirror the typical daily rhythm of DGM concentration variations in the two periods. This finding supports the following hypothesis: The natural phenomenon of daily oscillation of freshwater DGM concentrations that follows diurnal solar radiation variation would manifest on a seasonal scale. High DGM concentrations were found in the spring and summer and low in the fall and winter (seasonal mean: 34.2, 37.5, 20.0, 24.4 pg L(-1), respectively). This seems to suggest an annual occurrence of two periods of the seasonal DGM level fluctuation (spring and summer high vs fall and winter low DGM levels). Linear relationships of the monthly mean DGM concentrations were found with the monthly mean global solar radiation (R2 = 0.82, P < 0.05) and UVA radiation (R2 = 0.84, P < 0.05). Linear relationships of the seasonal mean DGM concentrations were also found with the seasonal mean global solar radiation (R2 = 0.85, P = 0.08) and UVA radiation (R2 = 0.93, P < 0.05).

Role of aerosols on the Mediterranean solar radiation

The shortwave radiation constitutes a major driving force for the oceanic thermohaline circulation and must be accurately parameterized. An extensive comparison between the monthly mean solar radiation measured at numerous meteorological stations along the Mediterranean coast and the estimated solar radiation from a widely used bulk formula leads to two important conclusions: first, there is systematic overestimation of the shortwave radiation from the bulk formula at the station sites of about 25 W m−2 (averaged over a 30 year period), and second, there is significant interannual variability in the observed solar radiation that cannot be explained either by the variability in the available data for the cloudiness or by the absorption due to water vapor content in the atmospheric column. As the overestimation occurs during summer cloud‐free months, we assume that cloud attenuation is adequately parameterized and the discrepancy between the observations and the estimates comes from the formula for clear‐sky insolation. A correction to the clear‐sky insolation formula is attempted on the basis of recent satellite data on aerosol optical thickness index. Results from our analysis indicate that aerosols may provide an explanation for both the observed weaker shortwave radiation and its interannual variations. This implies that a different parameterization scheme must be sought for the aerosol attenuation in the shortwave radiation formula.

Wind and solar energy at Dhahran, Saudi Arabia

Hourly wind-speed data recorded at automatic solar radiation and meteorological monitoring station, Dhahran (26° 32' N, 50° 13' E), Saudi Arabia, has been analyzed to determine monthly wind power. The wind power is then compared with the monthly mean solar radiation energies for the period 1987–1990. The monthly average wind speeds for Dhahran range from 4.46 to 6.89 m/s while the solar radiation varies from 3.46 to 7.43 kWhr/m 3/day. The annual maximum attainable wind power potential per unit area of the wind stream is 543 kWhr/m 2/year and the annual solar potential per unit area of the earth surface is 2.03 MWhr/m 2/year.

Wind and solar energy in Pakistan

Hourly wind-speed data at four meteorological observatories (Quetta, Karachi, Peshawar, and Lahore) in Pakistan have been analysed to determine monthly and annual wind power and these are then compared with the monthly mean solar radiation energies for the period 1980–1984. The monthly average wind speeds for the four stations range from 2.5 to 4.4, 2.75 to 6.7, 0.6 to 1.7, and 0.7 to 1.6 m/sec while the solar radiation varies from 3.6 to 7.65, 3.39 to 6.31, 2.4 to 6.35, and 2.8 to 6.27 kWh/m 2, respectively.