Solar & Wind Technology最新文献

The aim of this study is: (a) to propose a new simple model for estimating the monthly mean daily diffuse radiation D, MJ m⁻² day⁻¹, using as input only the clearness index K_t and minimum air mass and (b) to develop a map of diffuse solar radiation incident on a horizontal surface in Italy. The correlation herein suggested is D = 5.6 K_t^−0.55 (sin h_n)^1.58 where h_n is the noon altitude of the sun on the 15th of the month, in degrees, and K_t = G/H₀; G and H₀ are the monthly mean daily global and extraterrestrial solar radiation respectively. This equation is applied to Adrano, Palermo, Macerata and Genova stations, provided with measured data of global and diffuse radiation, and the relative computed values of D are compared both with the experimental data and with ones computed by the following correlation suggested by Coppolino in a previous work: D = 7 (s/S)^−0.25(sin h_n)^1.55 where s/S is the monthly mean daily value of the relative sunshine duration. The values of D computed by the above equations, respectively, result as nearly equal to each other for each month and each location. The validity of both considered correlations to fit the measured data of D for each tested station is shown by the standard per cent error of estimate φ (%). For both considered equations these errors are < 10 for Adrano, Palermo and Macerata and little higher than 10 for Genova. Therefore, both above correlations are independent of the latitude, the altitude above sea level and geographical situation (inland or coastal site) of the location; consequently, both of them can be considered valid and useful to predict (with a high respect both the above correlations are applied, with good reliability, to 30 more locations displaced at various latitudes, altitudes above sea level and geographical situations in Italy.

The validity of various models for predicting the solar radiation on inclined surfaces was investigated by employing 2-year measured hourly irradiation data on horizontal and vertical surfaces for Nicosia, Cyprus. Models using isotropic and anisotropic distribution of sky radiance are evaluated. The results indicate that the annual root mean square error for all the tested algorithms varies from 3.6 to 7%.

The performance of a flat-plate collector, set up in a driving loop, has been studied when some parameters such as the solar irradiance, the saturation temperature or the absorber characteristics vary. A steady-state model of the collector has been studied. The equations are developed for a fluid in which first sensible heat transfer occurs, then boiling. The experimental and theoretical results are compared and it is concluded that the total heat loss conductance cannot be assumed as constant. The collector efficiencies have been calculated for different conditions.

The present work consists of an original and quick method allowing the determination of the optimal angle slope and the optimal orientation of solar collectors at any position in the Algerian National Territory, for different periods of possible utilization (15 days, 1–12 months) combined in a year (289 combinations for each position).

This paper deals with technology transfer and conditions for successful diffusion of renewable energy technologies in developing countries. Issues such as perception of needs and resources are fully discussed, whether on mega-scale or micro-scale; that is to say, whether for a specific project or a whole country. A distinction is made between technology and the technological device, the latter being a component which is injected into a social system creating new links into the pre-existing structure; therefore, even if perfect in itself, it may not fit into the system in which it has to operate. The need for a complete analysis of the effects of the injection (or transplant) of the technological device into the productive system (a farm, a village, etc.), is emphasized and some methodological guidelines are suggested in order to reduce the possibility of rejection.