Innovative solar energy conversion technique for sustainable building

Abstract

In this project the workings of a new method of solar energy conversion, 'piezoelectric energy harvesting' was researched and understood. Once the basic fundamentals of this method were understood the focus and main aim of the project was chosen. The output circuitry for the piezoelectric energy harvester was researched, designed and analysed to fulfil the scope of this project. The output of this harvester which includes the use of piezoelectric transducers was an AC voltage waveform therefore circuitry was required to be designed to convert this AC voltage waveform into a usable regulated DC signal. It was researched that this could be done through the use of a full wave bridge rectifier, a 'non-inverting' buck-boost converter, and a feedback control loop which would incorporate PWM to give a constant output voltage. The full bridge rectifier is the vital piece of circuitry which converts the AC waveform to DC, whereas the buck boost converter would "boost" and "buck" the DC wave by performing a DC-DC conversion, essentially "steppingup" and "stepping-down" the output of the rectifier stage, where appropriate. The rectifier and DC-DC converter open loop stages were designed to be as efficient as possible. Finally, a feedback control loop which incorporates PWM was designed to make the system closed loop with the aim of stabilising the output voltage of the DCDC buck-boost converter ensuring a constant usable voltage was output from the designed circuitry, if not included in the circuitry the output of the buck-boost converter would not be a constant stable output voltage. PWM alters the duty cycle of the circuitry, altering how long each of the transistors/switches within the buckboost circuit was switched "on", therefore altering the output voltage. Most efficient methods were chosen in the attempt to maximise the efficiency of the circuitry, ensuring the parameters selected were for optimum efficiency. Each individual designed part of the circuitry was simulated obtaining expected results. The rectifier circuit and buck-boost converter were also simulated together achieving an ever increasing non -stable output voltage from the converter as expected. Attempts were made to simulate the full design (rectifier, buck-boost converter and feedback control loop) but various problems were come across during simulation, therefore the circuit was altered and the expected results were achieved.