Journal of Energy Engineering

As a result of the worldwide energy crisis, research and development activities in the field of wind energy have been gaining momentum for the last few years in many countries. Although this technology has been greatly improved during that time, the available technical know-how is not yet adequate to develop reliable wind energy converting systems for Indian conditions at low wind speeds. In spite of a few indigenous efforts, the developments of wind energy converting systems working at low wind speeds of 2–5 m/s, which is available for a considerable period of the year in the major part of the country, remain unfulfilled. This issue continues to be a matter of great concern for the Indian researchers. This paper introduces a new concept of amplifying the wind speed before it comes in contact with the rotor blades of a Savonius turbine by using a convergent nozzle. This novel work emphasizes the improvement of the efficiency of Savonius rotors, which normally extract less than 25% of the power in the wind and have been commercially unsuccessful. A research program involving wind tunnel tests of five different nozzle models has been conducted. Some necessary modifications in the design of the turbine have been suggested and verified practically with the help of working models. Analysis of different nozzle dimensions has also been outlined. The variation of the output speed with different values of input wind speed and different lengths placed at different distances from the wind tunnel are presented in the paper.

The wind turbine technology has a unique technical identity and unique demands in terms of the methods used for design. Remarkable advances in wind power design have been achieved due to modern technological developments. Since 1980, advances in aerodynamics, structural dynamics, and “micrometeorology” have contributed to a five percent annual increase in the energy yield of the turbines. Current research techniques are producing stronger, lighter, and more efficient blades for the turbines. The annual energy output per turbine has increased enormously and the weight of turbine and the noise they emit have been halved over the last few years. The deployment of modern wind turbines has resulted in experience in the production and use of wind turbines, which has led to improved turbines and reduced cost of wind-generated electricity. The paper reviews the research and development of technology of wind turbines and its impact on the cost of wind energy systems. Also the important gaps between the theoretical research and practical implementation have been analyzed and the problems associated with this have been discussed. The need and areas for further research and development effort have also been outlined.

The velocity head and momentum exchange at the T-junction between the surge tank with a riser and the tail water tunnel of hydroelectric powerplants have been introduced by using the Gardel’s head-loss formula. The effects of the velocity head and momentum exchange on the critical sectional area of the downstream tank have been analyzed. With Thoma’s assumption, the critical stable sectional area of the downstream throttled surge tank is derived theoretically. The study shows that the velocity head has an unfavorable effect on water level stability in the downstream surge tank while the effect of the momentum exchange is positive. These two effects counteract. Thus, the critical sectional area of a downstream throttled surge tank is close to that of a corresponding simple surge tank. However, if the size and shape of a riser are optimized, the area of the downstream surge tank may be further reduced. It is also demonstrated that a downstream throttled surge tank can reduce electricity loss and easily meet the requirements of stability in large flow oscillations when compared to a simple downstream tank.