Solar & Wind Technology最新文献

Hourly global solar radiation data measured on a horizontal surface in Amman, Jordan, available for the period 1983–1987, have been studied and analysed. Average values of daily, monthly and yearly global radiation, as well as maximum and minimum radiation values, were determined. The average monthly mean daily global radiation ranged from 8.001 to 2.653 kWh m⁻² per day. Over the 1983–1987 period, the annual daily mean of global radiation was 5.302 kWh m⁻² per day. The maximum monthly mean daily global radiation varied between 8.295 and 3.611 kWh m⁻² per day whereas that of the minimum monthly mean daily radiation varied between 7.590 and 1.680 kWh m⁻² per day. The calculated monthly mean daily global solar radiation data were employed to develop linear correlations between the sunshine hours and each of the average, maximum and minimum global radiation for Amman, using regression technique. The accuracy of the derived correlations was tested using measured radiation data for Amman. The results show that the developed correlations are adequate to predict monthly mean daily global radiation within a maximum error ranging between 6.6 and 9.6%. The average error incurred in predicting global radiation does not exceed 0.3%.

The present solar collector mathematical models and thermal testing methods, based on the latter, are reviewed. The exact solution of a two-node flat-plate solar collector model is obtained, and three-node model is introduced. The flat-plate solar collector thermal testing procedure is suggested, in which the necessity of collector temperature stabilization is avoided.

In the present paper a study of the starting torque and power coefficient of the Darrieus and Savonius machines have been realized. The results obtained were used to design a Darrieus-Savonius combined machine which is also fully analysed. Finally, a new design of the Darrieus-Savonius combined rotor is proposed and analysed.

Incoming solar radiation, insolation, is an important factor in many processes occuring at the earth surface. These include natural processes such as energy and moisture flux, photosynthesis, evapotranspiration, as well as quantities of interest in solar energy applications, such as energy available for focusing and non-focusing solar collectors and photovoltaic cells. In Brazil, solar radiation has been measured from 1978 through a network of pyranometers distributed all over the country. In the area limited by 15° and 34°S latitude and 40° and 67°W longitude, insolation estimates have been made using the geostationary satellite (GOES) from May 1982 to June 1984. It was thus possible to compare the simultaneous daily values of global solar radiation corresponding to the Southern part of Brazil during 1982 and 1983. The purpose of this paper is to analyse the accuracy of the estimates, presenting the results of the comparison. They show that standard error of the satellite-derived daily insolation values when compared against pyranometers is in the range of 15–30% of the mean values. Therefore, operational estimation of surface insolation in this region using GOES data appears normally feasible.

The effect of wind suppressors on the performance of a 4 m² solar pond, operating under the environment of the Arabian Gulf area characterized by windy, hot and humid conditions, is investigated experimentally. In addition to using screen nets on the pond's perimeter, two arrangements of wind suppressors of PVC floating pipes are considered. Climatological data relevant to the operation of solar ponds in this area namely wind speeds and evaporation rates are presented. Results of both salinity and temperature over a one year period are presented to evaluate the effect of wind suppressors and thermal insulation on the performance of the pond. The gradient zone was disturbed by invoking localized convective zones of different thicknesses to examine the effect of wind suppressors on the healing of those zones. Results show that wind suppressors of the floating piping type, can considerably slow down the movement of the upper convective-gradient zone interface and prohibit any formation of localized convective zones. Thermal insulation is a prerequisite for operating small solar ponds even in hot climates.