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No description available.

No description available.

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The purpose of the work was to investigate the thermal stratification in solar storage containers. Three domestic thermally stratified hot water storage containers were designed with the main object of improving and stabilizing thermal stratification of the stored water as a means of improving the overall efficiency of solar water heating systems. Testing of the three storage containers was carried out under similar conditions and the results showedthat TYPEI storage container behaves as a three-segment stratified system, TYPEII storage container behaves as a two-segment stratified system with a thermocline occupying approximately half of the height of the storage container, and TYPEIII storage container behaves as a two-segment stratified system with a thermocline occupying two thirds of the height of the storage container. It was found that TYPEI storage container, with a LID equal to 3/1, gave the best results in terms of heat collected, and also had the maximum stratification which is the main goal of this study. The effect of each of three flow rates (0.01 kg/Sm2 , 0.015 kg/sm2 , 0.02 kg/sm2 ) on stratification was studied and it was found that the flow rate of 0.01 kg/Sm2 of collector area gave the better result. A low-cost simulator for studying the performance of solar energy storage containers was designed. The design was based on a relatively inexpensive micro-computer linking into a mains power regulator with an 8-bit digital control system. Meteorological data was used to compute radiation income on any inclined plane and the output to the power regulator is controlled by the computed instantaneJus rate of energy gain from the collector system undergoing simulation. A comparison has been made between some of the experimental and theoretical results for mE I storage container. The theoretical prediction was based on two mathematical IOOdels of Duffie and 2 44 Beckman , and Close • A computer system model has been developed to assist in the design of a solar water heating system.

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No description available.

The technology of direct AC/AC power conversion (Matrix Converters) is gaining increasing interest in the scientific community, particularly for aerospace applications. The aim of this research project is to investigate the use of direct AC/AC three phase four-leg Matrix Converter as ground power unit to supply aircraft with power during stopover or maintenance in airports. The converter fourth leg is used to provide a path for the zero sequence components when feeding unbalanced or non-linear loads. A high bandwidth controller is required to regulate the output voltage of Matrix Converter with a 400Hz output frequency. However, the controller bandwidth is limited due to the reduced ratio between the converter switching frequency and the fundamental frequency. In this case undesirable, periodic errors and distortion will exist in the output voltage above all in the presence of a non-linear or unbalanced load. Digital repetitive control system is proposed to regulate the output voltage of a four-leg Matrix Converter in an ABC reference frame. The proposed control structure introduces a high gain at the fundamental and its integer multiple frequencies. Using the proposed repetitive controller will reduce the tracking error between the output and the reference voltage, as well as increasing the stability of the converter under balanced and unbalanced load conditions. Simulation studies using SABER and MATLAB software packages show that the proposed controller is able to regulate the output voltage during balanced and unbalanced load conditions and during the presence of non-linear load. In order to validate the effectiveness of the proposed controller, an experimental prototype of a 7.5KW has been implemented in PEMC laboratory using DSP/FPGA platform to control the converter prototype. The steady state and the dynamic performance of the proposed control strategy are investigated in details, and extensive experimental tests have showed that the proposed controller was able to offer high tracking accuracy, fast transient response and able to regulate the output voltage during balanced, unbalanced and non-linear loading.