Solar & Wind Technology最新文献

This research paper is aimed at investigating means for space heating using processes suitable for implementation in areas where the conventional energy resources are scarce. Bearing in mind the low cost of capital investment and utilization possibilities, mainly space heating, we have designed and fabricated a simple solar collector-storage system. The objectives of this research paper are: (1) exploring the possibility of using different materials for the insulated base, the transparent coverings, the collecting plate, box structure, potential candidates for sensible heat storage, etc., (2) to design a suitable medium capacity solar collector-storage unit and (3) to discuss the constructional features of the system under investigation.

Several development projects are described. The most successful are the very small micro hydro generators, the photovoltaic battery lantern and the waterwheel.

The model introduced by Gopinathan to estimate the global radiation on a horizontal surface was evaluated. The model has been modified in order to allow a better estimation of the global radiation in Bahrain. The annual monthly mean of the global radiation was found to be $\text{19.49±5.11}\text{MJ m}{}^{\mathrm{-2}}\text{d}{}^{\mathrm{-1}}$. However, the calculated annual monthly mean of the diffused and direct radiation using other theoretical models were found equal to $\text{5.52±1.13}\text{and}\text{13.95±4.23}\text{MJ m}{}^{\mathrm{-2}}\text{d}{}^{\mathrm{-1}}$ respectively.

An ideal tracker which follows the sun both north-south and east-west is designed and constructed. It is suitable for mounting a linear concentrator, focusing parabolic concentrator or photovoltaic array of aperture area 2 m². The apparatus is built with two axes equational mount and controlled by a microprocessor system. The tracking is carried out by utilizing the astronomical coordinates of the sun. As such the present system gives improved tracking capability over the conventional sensor controlled tracker systems. The performance of the tracking system was studied with photovoltaic array mounted on it and tracking error of less than one degree was achieved. This tracking error can be reduced further by proper software.

A discrete time control algorithm for a solar heating model based on the characteristics path of the fluid element leaving the system is developed. The algorithm is verified on a solar system adopting the hyperbolic partial differntial equations in describing the model. The simulation tests have shown significant improvement of the control performance at the desired outlet load temperature with particular emphasis on the model parameters variations.

Performance evaluation studies of Syltherm-800 (a proprietary heat transfer fluid) and Partherm-290 (a proprietary heat storage salt) are reported based on the data collected for a 1-year operation of solar powered freeze desalination pilot plant (200 m³ capacity), located in Yanbu, Saudi Arabia. In spite of some operational problems, the thermal stability of these heat transfer media has been observed to be good, which ensures their prolonged use in solar power-generation technology.

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%.

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.