Solar & Wind Technology最新文献

Several species of short rotation coppice trees can be considered for production of fuelwood for both the domestic and industrial markets. The preferred species in most districts of New Zealand is eucalyptus. Planted at 5000 trees/hectare, the first harvest after three years yields around 60 t/ha air dried. Subsequent harvests are likely to be at two-yearly intervals subject to further evaluation. The cost analyses of establishment, production and processing including transport, storage, and distribution costs, are discussed. A market assessment of domestic firewood is summarized along with a technique to compare the costs of competitive fuels.

In an earlier work [Ideriah (1985), Solar Energy34, 271], a previous theoretical model [Ideriah (1981), Solar Energy26, 447] for calculating the direct and diffuse solar radiation was examined in detail for the harmattan haze season (November-January) of 1975–1980 at Ibadan, when the atmosphere is often heavily overcast with dust. This led to an improved method of calculating the transmission coefficients of insolation. This study extends the previous work to compute the daily global insolation received at Ibadan during the dust-free seasons (February-October) of the years 1975–1980. The calculated values of the daily global insolation generally fall within 10%, while the calculated 6-year monthly average values are largely within 6% of the experimental data provided by the International Institute of Tropical Agriculture (I.I.T.A.), Ibadan.

In this work a statistical analysis of wind energy available in different parts of Nigeria is carried out, using Weibull distribution and 15 years of wind data. Twelve sites are selected in the four distinctive regions identified; 1.0–2.0, 2.1–3.0, 3.1–4.1 and >4.1 m/s. The results show the Weibull distribution, power and speed duration curves, the values of shape and scale parameters of the Weibull distribution, the speed frequency distribution and their cumulative duration in hours. The wind energy potential is evaluated for the use of rural communities in these regions. The cost benefit analysis shows the economic feasibility of using wind energy conversion systems for electric power generation and supply in the country.

Direct current motors are employed in photovoltaic water pumping systems; therefore, the understanding of the system operation and the matching of the system components (arrays and dc motor type) are important factors of the system design. The present study deals with the performance analysis of dc motors (series and shunt motors) powered by a solar cell array (without bypass and with bypass diode) under different shadowing conditions. The result shows that the shunt motor gives good matching to the solar cell array under shadow conditions and it has better shadow tolerance.

Many authors have presented plots of $\text{r}{}_{\mathrm{<mtext>d</mtext>}}\text{=}\text{I}{}_{\mathrm{<mtext>d</mtext>}}\text{/}\text{H}{}_{\mathrm{<mtext>d</mtext>}}\text{vs}\text{S}{}_0$, where $\text{I}{}_{\mathrm{<mtext>d</mtext>}}$ is the monthly average hourly diffuse radiation and $\text{H}{}_{\mathrm{<mtext>d</mtext>}}$ the monthly average daily global radiation, both on a horizontal surface, $\text{S}{}_{\mathrm{)}}$ being the monthly average daily number of possible sunshine hours. These plots are established using all the measured values of the hourly diffuse radiation, independently of the state of the sky. In the present work the dependence of the $\text{r}{}_{\mathrm{<mtext>d</mtext>}}$ vs $\text{S}{}_0$ plots on the values of σ = S/S₀ is studied for Uccle, S being the daily number of sunshine hours and S₀ the astronomical day length. Values of $\text{I}{}_{\mathrm{<mtext>d</mtext>}}$ are used for days with σ = 0; 0 < σ ⩽ 0.1; …; 0.8 < σ ⩽ 0.9; σ > 0.9. For σ > 0.5 and the hours centred at 0.5, 1.5, 2.5, 3.5, 4.5, 5.5 and 6.5 h from the solar noon a dependence of the $\text{r}{}_{\mathrm{<mtext>d</mtext>}}$ vs $\text{S}{}_0$ plots on σ is obtained.

Two box-type solar ovens were performance tested under various measured solar intensity conditions. One oven was the Kerr-Cole Eco-cooker assembled from a prefabricated cardboard kit. The second model was made of plywood and involved more elaborate construction. We adopt a simple parameter-free index to aid in the comparison of oven performance. Unlike other oven test procedures this index emphasizes the dynamic cooking capability of the ovens. We find that despite a substantially reduced thermal capacity the cardboard oven exhibited a maximum temperature and sufficient thermal stability for cooking similar quantities of food to that of the plywood model. The prospects for large scale introduction of the ovens in Nicaragua is evaluated in terms of local needs and interest.

The Energy Studies Unit (University of the South Pacific, Suva, Fiji) has been monitoring a number of photovoltaic installations in remote island locations in the South Pacific region. Household lighting schemes are reviewed in Tuvalu and Tonga. Medical refrigeration is reviewed in the Solomons, Tuvalu and Papua New Guinea. Serious problems were found with all the systems.