Monthly Average Daily Values Research Articles

Estimation and Correlation of Surface Water Vapour Density in Benin, Nigeria

The present study investigated the monthly average daily mean temperature, relative humidity, surface pressure, cloud cover, and sunshine hours associated with monthly variations in surface water vapour density (SWVD) for the period extending from 1979 to 2016 for Benin (Latitude 6.320N, Longitude 5.100E). The daily variation of SWVD for the dry season (November to March) and rainy season (April to October) for the year 2014 was examined. Statistical indices of coefficient of determination (R2), mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), Nash-Sutcliffe equation (NSE), and index of agreement (IA) were used to compare and evaluate the generated two variable SWVD-based models. The findings revealed that the level of SWVD varied throughout the investigation period on each day of the month. The SWVD is higher during the wet season than it is during the dry season, based to the monthly average daily values. The average SWVD was found to be at its highest point in the month of August during the rainy season and its lowest point in the month of December during the dry season (21.1448 gm-3). The greatest amount of SWVD was observed on 23rd May, 2014 with 27.5731gm-3 and the lowest on 26th December, 2014 with 9.6567 gm-3. Pressure and precipitable water vapour are related to each other using a multivariate correlation regression model that was constructed with R2 = 100%, MBE = -0.0204 gm-3, RMSE = 0.0206 gm-3, MPE = 0.1105 %, NSE = 99.9897% and IA = 99.9974% was better appropriate for SWVD estimation with the best fitting and therefore can be used for estimating SWVD in Benin.

Türkiye’de İki İlde Optimum Eğim Açılarında Eğimli Yüzeyde Aylık, Mevsimsel, Yıllık Toplam Güneş Işınımının Tahmini

In solar energy systems that use solar panels, it's important to know the best tilt angle to optimize solar energy production. Monthly, seasonal, and annual optimum tilt angles were determined in this study using meteorological insolation data from many years in the provinces of Tekirdag and Konya, which are located in different regions of Turkey. At optimum tilt angles, monthly, seasonal, and annual total radiation on the tilted surface were 1516.7 kWh m-2 year-1, 1504.1 kWh m-2 year-1 and 1448.1 kWh m-2 year-1 in Tekirdag, respectively. In Konya, these values were 1851.4 kWh m-2 year-1, 1833.51 kWh m-2 year-1 and kWh m-2 year-1, respectively. In the seasonal and annual optimum tilt angles, there was an approximately 1% and 5% loss in the total radiation values on the tilted surface, respectively, according to the monthly optimum tilt angle. In addition, the coefficients of the relationship between the monthly mean daily radiation on the tilted surface and the tilt angles were determined for each month using the cubic regression model in both provinces. The Cubic regression model coefficients are computed for each month in the provinces of Tekirdag and Konya. All months in both provinces had R2 (Coefficient of determination) values of 0.999 for the Cubic model. To determine whether there is a difference between the total amounts of radiation reaching the tilted surface for each month at the best tilt angles obtained by the two methods, the t-test was used. The monthly average daily radiation values on the tilted surface obtained by the two methods at the best tilt angles in both provinces have not been found to differ statistically (p>0.05; t=0.001).

Estimation of Surface Water Vapour Density and its Variation with other Meteorological Parameters over Akure, Nigeria

In this paper, the monthly variation of Surface Water Vapour Density (SWVD) with meteorological parameters of monthly average daily mean temperature, relative humidity, surface pressure, cloud cover and sunshine hours during the period of thirty-eight (38) years (1979 - 2016) for Akure (Latitude 7.280N, Longitude 5.300E, 375m above sea level) were investigated. The daily variation of surface water vapour density for the two distinct seasons considering two typical months in each during the period of year 2014 was examined. The results showed fluctuation in the amount of surface water vapour density in each day of the month for the period under investigation. The monthly average daily values indicated that the surface water vapour densities are greater during the rainy season than in the dry season. It was observed that the maximum average value of surface water vapour density of 20.1019 gm-3 occurred in the month of September during the rainy season and minimum value of 15.5110 gm-3 in the month of January during the dry season. The highest value of surface water vapour density was observed on the 4th of June, 2014 with 26.3320 gm-3 and the lowest on the 31st day of December, 2014 with 6.0276 gm-3. The comparison assessment of the developed two variable SWVD based models was carried out using statistical indices of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA). The developed multivariate correlation regression model that relates pressure and precipitable water vapour with R2 = 100%, MBE = -0.0177, RMSE = 0.0179, MPE = 0.1034, NSE = 99.9956% and IA = 99.9989% was found more suitable for surface water vapour density estimation with good fitting and therefore can be used for estimating surface water vapour density in Akure.

EMPIRICAL MODELS FOR CORRELATION OF CLEARNESS INDEX WITH CLOUD INDEX AT ZARIA, KADUNA STATE

In this study, the monthly average daily values of global solar radiation and relative sunshine hours on a horizontal surface over a period of five years (2011-2015) using multi-linear polynomial form of the AngstromPrescott model have been developed to estimate global solar radiation for Zaria (northern part of Nigeria) which lies on latitude 11°04'N and longitude 7o 42' E. Five different mathematical correlations models (first order, second order, exponential, powered, and logarithmic) was considered and it was found that first order, second order polynomials, exponential and powered gives a good model for estimating total solar radiation in Zaria. The agreement between the measured values (that obtained from the Nigerian Meteorological Agency) and the computed values is remarkable and the models are recommended for Zaria

Estimation of Surface Water Vapour Density and Its Variation with Other Meteorological Parameters Over Owerri, South Eastern, Nigeria

In this paper, the monthly variation of Surface Water Vapour Density (SWVD) with meteorological parameters of monthly average daily mean temperature, relative humidity, surface pressure, cloud cover and sunshine hours during the period of sixteen years (2000 – 2015) for Owerri (Latitude 5.48°N, Longitude 7.00°E, and 91m above sea level) were investigated. The daily variation of surface water vapour density for the two distinct seasons considering two typical months in each during the period of year 2015 was examined. The results showed fluctuation in the amount of surface water vapour density in each day of the month for the period under investigation. The monthly average daily values indicated that the surface water vapour densities are greater during the raining season than in the dry season. It was observed that the maximum average value of surface water vapour density of 21.002gm-3 occurred in the month of June during the raining season and minimum value of 14.653gm-3 in the month of January during the dry season. The highest value of surface water vapour density was observed on 9th May, 2015 and the lowest on 14th January, 2015. The comparison assessment of the developed SWVD based models was carried out using statistical indices of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA). The developed multivariate correlation regression model that relates temperature and relative humidity with R2=99.9% MBE=0.1259 RMSE=0.1462 MPE=-0.6739 NSE=99.8402% and IA=99.9611% was found more suitable for surface water vapour density estimation with good fitting and therefore can be used for estimating surface water vapour density in the location under investigation and region with similar climatic information. The results of the descriptive statistical analysis revealed that the surface water vapour density, mean temperature, relative humidity, cloud cover and sunshine hours data spread out more to the left of their mean value (negatively skewed), while the surface pressure data spread out more to the right of their mean value (positively skewed). The surface water vapour density data have positive kurtosis which indicates a relatively peaked distribution and possibility of a leptokurtic distribution while the mean temperature, relative humidity, surface pressure, cloud cover and sunshine hours data have negative kurtosis which indicates a relatively flat distribution and possibility of platykurtic distribution.

English

Empirical models to estimate global solar radiation require the development of a set of equations that relate it to other meteorological parameters and from the monthly average daily value of clearness index and relative sunshine spanning of a period of 5 years, the Angstrom- Prescott model was developed for the estimation of global solar radiation of Ijebu-Ode (Lat. 6.81⁰N. Long. 3.92⁰E), a tropical region of Southern part of Nigeria. Regression analysis was done based on the season of the year and the results obtained were compared. The predictive efficacy in terms of mean bias error (MBE) and root mean square error (RMSE) of the model are also tested. The developed correlation model is expressed as with the correlation coefficient of 89.13%. The result obtained therefore seems to point to the fact that the Angstrom – Prescott model is locally dependable and rainy season model was found to be more satisfactory for the study area with MBE of 0.052 and RMSE of 6.240X107 Key words: Clearness index, global solar radiation, model, rainy season

Global, diffuse and direct solar radiation at the surface in the city of Rio de Janeiro: Observational characterization and empirical modeling

The city of Rio de Janeiro and others 18 cities compose the Metropolitan Area of Rio de Janeiro. The main objective of this work is to characterize observationally the diurnal and seasonal evolution of the solar radiation components in the city of Rio de Janeiro. The measurements of global and diffuse solar radiation and standard meteorological variables at the surface have been carried out regularly at the Geoscience Institute of Federal University of Rio de Janeiro since October of 2011. The microclimatic conditions show that the period 2011–2014 was warmer during most of the year and drier in summer and spring in comparison with climate normal. All solar radiation components present a well defined diurnal cycle with maximum at noon. The estimates of global and direct solar radiation indicate a great potential available for solar energy at the surface, particularly in summer. The behavior of the clearness index and diffuse solar radiation fraction is similar in summer and winter. The Angstrom formula represents properly the estimate of the monthly average daily value of global solar radiation. The sigmoid logistic function is statistically more significant in comparison with others correlation models to represent the diffuse fraction as a function clearness index.

Analysis of erythemal UVB and UVA irradiance at Beer Sheva, Israel from 1994 through 2012

The erythemal UVB and UVA irradiance monitored at Beer Sheva, Israel from June 1994 through March 2012 has been analyzed. A statistical analysis was applied to the daily values for each month and average, median, standard deviation, coefficient of variation (%), maximum and minimum values are reported. The maximum and minimum monthly average daily values for both erythemal UVB and UVA occur in June and December, respectively. They are 1.658 Wm−2(ER) and 0.346 Wm−2(ER) for the case of erythemal UVB and the corresponding values for UVA are 300.78 Wm−2 and 135.52 Wm−2. A similar statistical analysis was performed on the monthly average daily values throughout the time interval of this study. In addition, the monthly average daily values were analyzed to determine if there existed any trends for the individual months. A linear regression analysis was applied to the monthly average daily erythemal UVB and UVA irradiance as a function of year. No statistically significant trends were observed, based upon the corresponding p-values; a possible exception being the UVA irradiance during February, which may have a slight negative trend. Typical erythemal UVB and UVA irradiance meteorological years were developed for Beer Sheva and its environs.

Radiation balance at the surface in the city of São Paulo, Brazil: diurnal and seasonal variations

The main goal of this work is to describe the diurnal and seasonal variations of the radiation balance components at the surface in the city of Sao Paulo based on observations carried out during 2004. Monthly average hourly values indicate that the amplitudes of the diurnal cycles of net radiation (Q*), downwelling and upwelling shortwave radiation (SWDW, SWUP), and longwave radiations (LWDW, LWUP) in February were, respectively, 37%, 14%, 19%, 11%, and 5% larger than they were in August. The monthly average daily values indicate a variation of 60% for Q*, with a minimum in June and a maximum in December; 45% for SWDW, with a minimum in May and a maximum in September; 50% for SWUP, with a minimum in June and a maximum in September; 13% for LWDW, with a minimum in July and a maximum in January; and 9% for LWUP, with a minimum in July and a maximum in February. It was verified that the atmospheric broadband transmissivity varied from 0.36 to 0.57; the effective albedo of the surface varied from 0.08 to 0.10; and the atmospheric effective emissivity varied from 0.79 to 0.92. The surface effective emissivity remained approximately constant and equal to 0.96. The albedo and surface effective emissivity for Sao Paulo agreed with those reported for urban areas in Europe and North America cities. This indicates that material and geometric effects on albedo and surface emissivity in Sao Paulo are similar to ones observed in typical middle latitudes cities. On the other hand, it was found that Sao Paulo city induces an urban heat island with daytime maximum intensity varying from 2.6°C in July (16:00 LT) to 5.5°C in September (15:00 LT). The analysis of the radiometric properties carried out here indicate that this daytime maximum is a primary response to the seasonal variation of daily values of net solar radiation at the surface.

Analysis of solar radiation measurements at Ghardaïa area, south Algeria

Abstract This study aims to explore the solar radiation field in southern Algerian peninsula, hourly measurements of global and diffuse radiant fluxes collected at Ghardaia site (32.360 N, 3.810 W, 450 m above MSL), from 1 January 2005 to 31 December 2008, are employed. These data were used to further addressing radiant fluxes distribution on hourly, daily, monthly and seasonal basis that in turn are of particular important from the point of view of proper design of building energy systems as well as accurate evaluation of thermal environment within buildings. Results obtained suggest that the annual value of clearness and diffuses indexes are respectively 0.68 and 0.37, and the monthly average daily values of global solar radiant flux exhibits seasonal variability with higher values in summer (7762 Wh/m2) and lower ones during winter (3915 Wh/m2). Regarding diffuse radiant flux, measurements shows that the monthly average daily value is about (1173 Wh/m2) in winter, while it is around (2829 Wh/m2) in summer.

Dynamics of photosynthetic photon flux density (PPFD) and estimates in coastal northern California

Plants require solar radiation for photosynthesis and their growth is directly related to the amount received, assuming that other environmental parameters are not limiting. Therefore, precise estimation of photosynthetically active radiation (PAR) is necessary to enhance overall accuracies of plant growth models. This study aimed to explore the PAR radiant flux in the San Francisco Bay Area of northern California. During the growing season (March through August) for 2 years 2007–2008, the on-site magnitudes of photosynthetic photon flux densities (PPFD) were investigated and then processed at both the hourly and daily time scales. Combined with global solar radiation (R S) and simulated extraterrestrial solar radiation, five PAR-related values were developed, i.e., flux density-based PAR (PPFD), energy-based PAR (PARE), from-flux-to-energy conversion efficiency (fFEC), and the fraction of PAR energy in the global solar radiation (fE), and a new developed indicator—lost PARE percentages (LPR)—when solar radiation penetrates from the extraterrestrial system to the ground. These PAR-related values indicated significant diurnal variation, high values occurring at midday, with the low values occurring in the morning and afternoon hours. During the entire experimental season, the overall mean hourly value of fFEC was found to be 2.17 μmol J−1, while the respective fE value was 0.49. The monthly averages of hourly fFEC and fE at the solar noon time ranged from 2.15 in March to 2.39 μmol J−1 in August and from 0.47 in March to 0.52 in July, respectively. However, the monthly average daily values were relatively constant, and they exhibited a weak seasonal variation, ranging from 2.02 mol MJ−1 and 0.45 (March) to 2.19 mol MJ−1 and 0.48 (June). The mean daily values of fFEC and fE at the solar noon were 2.16 mol MJ−1 and 0.47 across the entire growing season, respectively. Both PPFD and the ever first reported LPR showed strong diurnal patterns. However, they had opposite trends. PPFD was high around noon, resulting in low values of LPR during the same time period. Both were found to be highly correlated with global solar radiation R S, solar elevation angle h, and the clearness index K t. Using the best subset selection of variables, two parametric models were developed for estimating PPFD and LPR, which can easily be applied in radiometric sites, by recording only global solar radiation measurements. These two models were found to be involved with the most commonly measured global solar radiation (R S) and two large-scale geometric parameters, i.e., extraterrestrial solar radiation and solar elevation. The models were therefore insensitive to local weather conditions such as temperature. In particular, with two test data sets collected in USA and Greece, it was verified that the models could be extended across different geographical areas, where they performed well. Therefore, these two hourly based models can be used to provide precise PAR-related values, such as those required for developing precise vegetation growth models.

SIZING OF AUTONOMOUS WIND/SOLAR HYBRID ENERGY CONVERSION SYSTEMS FOR URLA, TURKEY

In this paper, an optimum sizing procedure of autonomous hybrid (wind+solar) energy system is presented which can be used to satisfy the requirements of given load distribution. The main purpose of this study is to find out an appropriate wind-photovoltaic hybrid energy system to satisfy electricity consumption of GSM (Global System for Mobile communication) base station at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. To do this, monthly average daily solar radiation and wind speed data are collected. The monthly average wind speeds are measured at 10m height during 3 years period on Izmir Institute of Technology Campus Area. The monthly average wind speed values are obtained between 5.7 and 7.7m/s, on the other hand, the monthly average daily value of solar radiations on horizontal surfaces are ranged from 1.4 to 6.9kWh/m 2 at Izmir Institute of Technology Campus Area. The hybrid system considered in the present analysis consists of one 5kW nominal power wind energy conversion systems (WECS), 21.82m 2 of photovoltaic (PV) panels (18 mono crystal PV panels each having 75W power output) together with a battery storage system.

Barometric pressure, dry bulb temperature and vapor pressure at the lowest terrestrial site on earth, Dead Sea basin, Neve Zohar, Israel

The Dead Sea basin is located at the lowest terrestrial site on the earth and, thereby, has the tallest atmospheric air column above its surface. Consequently, the Dead Sea basin is expected, a priori, to have the highest terrestrial barometric pressure and, thereby, the highest molecular oxygen density on the earth. The barometric pressure and dry bulb temperature have been monitored continuously at Neve Zohar, located on the western shore of the Dead Sea, since January 1995. The monthly average daily barometric pressure values exceed normal atmospheric pressure by a maximum of 4.83 hPa (4.77%) and a minimum of 33.1 hPa (3.26%) for December and July, respectively. This increase in barometric pressure can serve as a simple way to improve arterial oxygenation in hypoxemic patients. As a result, a number of research projects have been initiated on the treatment of patients suffering from pulmonary and cardiac diseases at the Dead Sea basin. The hourly barometric pressure data with regard to both its diurnal and monthly variation and the correlation between barometric pressure and dry bulb temperature will be analyzed.

Optimal sizing of battery storage for stand-alone hybrid (photo-voltaic + diesel) power systems

An important element of hybrid photo‐ voltaic(PV) + diesel sytem is battery storage. Size of battery storage plays a role in optimum operation of the hybrid system. Emphasis needs to be placed on this issue. In this perspective, hourly solar radiation data, for the period 1986–93 recorded at Dhahran, Saudi Arabia, have been analyzed to investigate the optimum size of battery storage capacity for hybrid (PV + diesel) power systems. Various sizing configurations have been simulated. The monthly average daily values of solar global radiation range from 3.61 to 7.96 kWh/m2. As a case study, hybrid systems considered in the present analysis consist of 225 m2 PV array area (panels/modules) supplemented with battery storage unit and diesel backup generators (to meet the load requirements of a typical residential building with annual electrical energy demand of 35,200 kWh). The monthly average energy generated from the aforementioned hybrid system for different scenarios has been presented. More importantly, the study explores the influence of variation of battery storage capacity on hybrid power generation. The results exhibit a trade-off between size of the storage capacity and diesel power to be generated to cope with annual load distribution. Concurrently, the energy to be generated from the diesel generator and the number of operational hours of the diesel system to meet the load demand have been also addressed. The study shows that for optimum operation of diesel system, storage capacity equivalent to 12–18 h of maximum monthly average hourly demand need to be used. It has been found that in the absence of battery bank, ∼58% of the load needs to be provided by the diesel system. However, use of 12 h of battery storage (autonomy) reduces diesel energy generation by ∼49% and the number of hours of operation of the diesel system get reduced by about ∼82%. The findings of this study can be employed as a tool for sizing of battery storage for PV/diesel systems for other regions having climates similar to the location considered in the study.

Statistical analysis and inter-comparison of the solar UVB, UVA and global radiation for Beer Sheva and Neve Zohar (Dead Sea), Israel

A statistical analysis and inter-comparison of the solar UVB, UVA and global radiation for Beer Sheva and Neve Zohar (Dead Sea) are presented utilizing data measured from January 1995 through December 2002. Beer Sheva is located approximately 65 km to the west of and ∼700 m above Neve Zohar. The monthly average hourly and daily values for all radiation types at both sites are reported. The standard errors of the monthly average daily values have been calculated in order to ascertain whether the average daily radiation intensities are representative, i.e. if the magnitude of the standard error is less than the inherent measurement uncertainty of the instruments, and, thereby, justify an inter-comparison between the two sites. The relative magnitude of the global, UVB and UVA radiation intensity at the two sites is attributed to the enhanced scattering of the incident solar radiation at the Dead Sea location due to the longer optical path length it must traverse to arrive at the Dead Sea, the lowest terrestrial point on earth. The degree of attenuation of solar radiation due to the scattering phenomena is inversely proportional to the wavelength raised to some power and, consequently, it is greatest for UVB and negligible for global radiation.

Promoting applications of hybrid (wind+photovoltaic+diesel+battery) power systems in hot regions

Depleting oil and gas reserves, combined with growing concerns of atmospheric pollution/degradation, have made the search for energy from renewable sources of energy, such as solar and wind, inevitable. Literature indicates that commercial/residential buildings in Saudi Arabia consume an estimated 10–40% of the total electric energy generated. In the present study, hourly mean wind-speed and solar radiation data for the period 1986–1997 recorded at the solar radiation and meteorological monitoring station, Dhahran (26°32′ N, 50°13′ E), Saudi Arabia, have been analyzed to investigate the potential of utilizing hybrid (wind+solar) energy conversion systems to meet the load requirements of a typical commercial building (with annual electrical energy demand of 620 000 kWh). The monthly average wind speeds for Dhahran range from 4.1 to 6.4 m/s. The monthly average daily values of solar radiation for Dhahran range from 3.6 kWh/m 2 to 7.96 kWh/m 2. The hybrid systems considered in the present analysis consist of different combinations of commercial 10 kW wind energy conversion systems (WECS), photovoltaic (PV) panels supplemented with battery storage unit and diesel back-up. The study shows that with 30 10-kW WECS together with 150 m 2 PV, and 3 days of battery storage, the diesel back-up system has to provide 17% of the load demand. However, in the absence of battery storage, about 38% of the load needs to be provided by the diesel system.

Opportunities for utilization of stand-alone hybrid (photovoltaic + diesel + battery) power systems in hot climates

There is a growing awareness that combustion fuels are a limited resource and burning of these fuels is the principal cause of air pollution, and possibly environmental warming. This recognition is elevating interest and activity toward the development and application of alternative/renewable sources of energy, such as solar energy to displace some of the use of fossil fuels. In this context, Saudi Arabia being enriched with fairly high degree of solar radiation, is a suitable candidate for deployment of solar photo-voltaic (PV) panels for power generation in crisis. Literature shows that residential buildings in Saudi Arabia consume about 47% of the total electric energy generated/consumed. In the present study, hourly mean solar radiation data for the period 1986–1993 recorded at the solar radiation and meteorological monitoring station, Dhahran (26° 32’ N, 50°13’ E), Saudi Arabia, have been analyzed to examine/investigate the potential of utilizing hybrid (PV + diesel) power systems to meet the load requirements of a typical residential building (with annual electrical energy demand of 35 200 kWh). The monthly average daily values of solar global irradiation for Dhahran range from 3.61 kwh/m 2 to 7.96 kwh/m 2. The hybrid systems considered in the present analysis consist of different combinations of PV panels/modules (different array sizes) supplemented with battery storage unit and diesel back-up. The study shows that with 225 m 2 PV together with 12 h of battery storage, the diesel back-up system has to provide 9% of the load demand. However, in absence of battery bank, about 58% of the load needs to be provided by the diesel system.

Methodology for generating daily clearness index index values K t starting from the monthly average daily value [formula omitted]. Determining the daily sequence using stochastic models

The facility to generate weather data from limited inputs and independently of specific locations would allow simulations of energetic systems to be run at locations for which detailed weather records do not exist. This article presents a methodology to calculate synthetic daily solar radiation values and describes how sequences of daily global radiation can be generated using as input the monthly average radiation. A stochastic model, ARIMA(1,1,1) is presented, as well.

Performance evaluation of hybrid (wind/solar/diesel) power systems

Depleting oil and gas reserves, combined with the growing concerns of global warming, have made it inevitable to seek alternative/renewable energy sources. The integration of renewables such as solar and wind energy is becoming increasingly attractive and is being used widely, for substitution of oil-produced energy, and eventually to minimize atmospheric degradation. The literature shows that commercial/residential buildings in Saudi Arabia consume an estimated 10–40% of the total electric energy generated. In the present investigation, hourly wind-speed and solar radiation measurements made at the solar radiation and meteorological monitoring station, Dhahran (26°32′ N, 50°13′ E), Saudi Arabia, have been analyzed to investigate the feasibility of using hybrid (wind+solar+diesel) energy conversion systems at Dhahran to meet the energy needs of twenty 2-bedroom houses. The monthly average wind speeds for Dhahran range from 4.1 to 6.4 m/s. The monthly average daily values of solar radiation for Dhahran range from 3.6 kWh/m 2 to 7.96 kWh/m 2. The performance of hybrid systems consisting of different rated power wind farms, photovoltaic (PV) areas, and storage capacities together with a diesel back-up are presented. The monthly average daily energy generated from the above hybrid system configuration has been presented. The deficit energy generated from the back-up diesel generator and the number of operational hours of the diesel system to meet a specific annual electrical energy demand of 702,358 kWh have also been presented.

Analysis and correlation of ultraviolet solar radiation from routine meteorological measurements over Egypt

For three years (1990-92) measurements of the monthly average daily global, G, and ultraviolet, UV, solar radiation incident on a horizontal surface at Cairo (30°15'N, 31°17'E) and Aswan (23°58'N, 32°47'E) are presented. processed and analysed. It was found that the computed monthly average daily values for the obtained solar radiation components, G and UV, were (18.1 MJ/m2, 0.55 MJ/m2, for Cairo and (22.1 MJ/m2, 0.71 MJ/m2, for Aswan. The effect of atmospheric dust on the measured solar radiation components is also investigated and discussed. The ratio of the ultraviolet to global radiation (UV/G) are calculated and compared with other sites in the Arabian Peninsula. A regression analysis has been done to find a correlation between G and UV at the selected sites during the three year period and the recommended correlation equations have also been stated.
 
 Since the meteorological measurements of UV solar radiation are not available over Egypt. except at Cairo (Lower Egypt) and Aswan (Upper Egypt) stations, our correlation equations can be used to calculate this component from the available global solar radiation measurements at any site in the two zones of Upper and Lower Egypt.