Effects of Rotor-Blade Deformation onto Performance of Domestic Wind Turbines

Paper is focused on the influence that blade deformations by torsion and bending due to drag, lift, and gravitational effects has on the performance of small wind turbines. A blade model of stiff finite elements connected by rotating junctions is used. Mechanical deformations are simulated by controlled gravity and torsional forces, and their effects are measured through the response of the wind turbine. Tests have been run before and after the deformation process under different wind conditions in a wind tunnel. No centrifugal stiffening and gyroscopic moments are considered due to the low angular speed. Wind speed was controlled to determine the effect of the deformation on the performance of the wind turbine as a function of the wind power. The results have shown that in all cases, the effects of the deformation are negative, and the decrease in power has been calculated depending on wind conditions.

Analysis of The Performance of A PV/PCM System in Variable Solar Radiation Conditions

This paper studies the performance of a PV/PCM system operating at variable solar radiation conditions. The system has been tested for six different solar radiation levels, from 250 W/m2 to 950 W/m2 determining the steady-state temperature for every case. An algorithm has been developed to predict the steady-state temperature. This prediction has produced values within 97% accuracy of experimental data. A reduction of temperature up to 18.9ºC has been achieved. An algorithm has been developed to correlate reduction in temperature with solar radiation levels. This algorithm can be combined with the classical expression for the PV panel efficiency resulting in a good method for determining the increase of the efficiency. Additionally, the system has been tested for continuous solar radiation evolution, analyzing the system response under the transient state. The procedure has been conducted for the former six solar radiation levels considering the solar radiation evolves linearly from one value to another during a time interval. The simulation has been tested against outdoor solar radiation with an accuracy higher than 98%. The predicted value of the PCM Temperature at the end of the day as shown matches the melting point of the PCM used in the experiment (55ºC), which has been verified experimentally. Besides, the transient state analysis has given the temperature evolution of the PCM at every interval, resulting in a very good match with experimental tests. The analysis of the transient state that the system reaches the melting point at 1/3 of the solar day length, maintaining the phase change state for the rest of the day. This is in good agreement with the experimental observation.

Modeling Cogeneration System in Shallow Geothermal Installations

This paper presents a theoretical modeling of a cogeneration system using multiple heat exchangers and thermoelectric generator. The modeled system, designed for shallow geothermal energy, is a closed piping unit containing water as heat transfer fluid that circulates through a closed loop releasing thermal energy at the surface for heating and sanitary hot water. In addition, a Peltier cells array is attached to the piping system to generate electricity, thus the system is self-sufficient in terms of electric energy. This system helps in alleviating resource scarcity, achieves reduction in pollutant emissions, saves energy and creates sustainable environment for housing developments.