Solar & Wind Technology最新文献

In this presentation, the performance of a 10.5 kW stand-alone photovoltaics system (SAPVS) installation that has been in operation for over 2 years is discussed. Using standard parameters for similar systems, the technical features of the plant have been assessed. With a simplified but reasonably accurate approach, the average monthly insolation at the site has next been correlated with available meteorological data at the location. The computed results agree very well with the insolation values used by the designers. The study shows that only about 6% of the available solar energy is fed to storage batteries, and the final energy utilization amounts to about 3.9% of the incident insolation. Since its installation, the PV arrays have been used to charge batteries that are used to provide night-time lighting, and are disconnected as soon as the batteries are fully charged. The findings of the study suggest that instead of disconnecting the arrays after the batteries are fully charged, the energy could have been used for water pumping, grinding and other basic industrial purposes.

Optical designs and performance characteristics of a linear Fresnel reflector solar concentrator (LFRSC) with a flat vertical absorber have been presented. Two different approaches have been utilized for designing a LFRSC. One of the approaches allows a variation in the width of the constituent mirror elements, while the second approach uses mirror elements of equal width. A detailed performance analysis including the effect of variation in the height of the absorber from the concentrator plane, aperture diameter of the concentrator, width of the absorber and the width of the mirror elements on the concentration on the surface of the absorber has been made for each design. The distribution of local concentration ratio (L.C.R.) on the surface of the absorber, for each design, has been investigated using the ray trace technique. Results are plotted graphically and discussed.

In the present paper, a study is made to present the global radiation data available for 24 locations spreading all over Jordan. To achieve this objective, correlations between clearness index and fraction of bright sunshine hours, derived for 10 Jordanian stations, are utilized as measured data of global radiation and bright sunshine hours are only available for those locations. The derived linear regression correlations are used to estimate global radiation for the other 14 stations where only records of bright sunshine hours are available. The results for all stations are presented in the form of monthly global radiation table and annual solar radiation map.

The methodological development for the preliminary evaluation of the eolian potential of place of interest is shown in this paper. As an example of its application, results for Mérida City in the Yucatan Peninsula are shown, as well as the parameter values of Weibull's distribution for a given period of analysis.

In a previous paper Coppolino has proposed a very simple model for predicting the monthly mean daily global solar radiation G(MJm⁻² day⁻¹) at any Italian location using as input only the sunshine duration s (hours) and the noon altitude of the sun on the 15th of the month h_n (degrees). The correlation suggested is G = 7.8s^0.5(sin h_n)^1.15. Herein the validity of this model is verified by extending its application to dat from 24 stations displaced at various latitudes, altitudes above sea level and geographical situations in the European, African, Asian and North American areas. Furthermore the validity of this model to fit the data of the tested stations is compared with that of the well-known linear Ångström equation. The test results show that: (a) The correlation proposed by Coppolino fits well enough the measured data of the monthly mean daily global radiation for all tested stations, independent of their latitude, altitude above sea level, meteorological conditions and geographical situation (inland or coastal site). In fact the related standard per cent error of estimate Φ(%) is less than 10% for all tested locationswith the exception of Goose Bay, Canada, for which it is a little higher than 10%. (b) Although the values of the regression constants of the Ångström equation vary from location to location and for some locations from north to month, the values of Φ(%) referring to the two compared correlations are nearly equal to each other for each station considered. Consequently it must be deduced that the very simple model suggested by Coppolino is suitable and useful to predict the monthly mean daily global solar radiation with good reliability, even in the locations of the European, African, Asian and North American areas lacking actinometric instruments but provided with sunshine duration data.

An experimental investigation of a shell-and-tube heat exchanger concept for use in a latent thermal energy storage system for solar heating applications has been carried out. The thermal analysis provides the influence of the water inlet temperature and mass flow rate on the storage charging/discharging times and temperature gradients for heat flow into or out of two different storage substances: paraffin wax and asphalt. Results indicate the capability of the heat exchanger concept to operate within small temperature potentials (< 16 K) for realistic heat input rates.

In order to meet the growing energy demand, natural energy sources like water, sun and wind should be used as much as possible because of their advantages of being clean, inexpensive and renewable. This paper presents an entirely new system of wind turbine, which allows a radical increase of wind potential in the north-eastern wind called the “bora”. The “bora” occurs in Senj for 4.117 hours annually at an average speed of 8.35 m/s. It always comes from the ENE quadrant, which is essential for this system. If electric power is to be generated on a large scale the free air stream in which conventional wind turbines operate should be replaced by a programmed, concentrated stream in nozzle, similarly to what has already been done with hydropower by means of dams. As to the wind power plant Senj, nozzles would be erected in a semiconductive dam to direct the accelerated air mass to the turbine rotor and then by means of a deflector behind the rotor to ensure a reduction in velocity in order to obtain the maximum performance. A greater number of wind turbines in the nozzle, arranged as sections one next to the other, form an array (row) or a wind dam. If several arrays are then placed one after another it is possible to obtain a large wind power plant. Because of the variations in the behaviour of the “bora” and its multiplication in the nozzle, it is necessary to provide double control, both on the stator and the rotor, so as to ensure favourable operating characteristics.

Grain boundaries play a dominant role in understanding the properties of polycrystalline silicon and make it difficult to analyse the results. By illuminating the samples with light of approximately solar intensity, the potential barriers at the grain boundaries can be removed and thus approach single crystal behaviour. When the barriers are removed, the mobility between 200 and 400 K is found to vary as $\text{T}{}^{\mathrm{-2}}$, which is the dependence observed in single crystals for the same order of magnitude of doping. The free carrier concentration of 5 × 10¹⁵ cm⁻³ is not affected by illumination. The room temperature mobility in 1 mm grain size material after barrier elimination by light is 900 cm² V⁻¹ s⁻¹. The theory of Hall mobility in polycrystalline silicon which explains these observations has been examined.

A low-energy house has been built utilizing passive solar, wind power and heat recovery for all space heat. The remote island population, 79, has been surveyed in detail for all energy use. Space heating requirement per person is twice the U.K. average because of the northerly latitude, 5°C average annual temperature, traditional housing, and high wind speeds average 8.2 m/s. The 10 kW wind turbine generator heats a 2000 1 storage tank for a controlled wet heating system to radiators. Full details and costs are given of this EEC DG17 supported project.