Date of Award

12-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Wagner, John

Committee Member

Gooding , Charles

Committee Member

Schweisinger , Todd

Committee Member

Wang , Yue

Abstract

Non-renewable energy sources such as coal, crude oil, and natural gas are being consumed at a brisk pace which is promoting a worldwide energy crisis. The burning of fossil fuels produces greenhouse gases such as carbon dioxide and nitrous oxides as well as soot which contribute to atmospheric pollution. Although fossil fuels will continue to be available for many decades, the amount of petroleum remaining in the earth and its associated cost remains an open issue. The utilization of green energy such as solar and wind offer renewable and pollution free sources. A worldwide shift is slowly underway towards the inclusion of renewable energy sources to generate electrical and mechanical power. To meet this emerging societal demand, research into alternative energy sources such as solar, wind, and thermodynamic power generation is underway at Clemson University.
This research encompasses two renewable energy strategies: a solar-based electrical microgrid, and an atmospheric thermodynamic driven mechanical clock. The concept of an electrical microgrid at Clemson University has been investigated as it promotes a renewable energy source to help realize a 'net zero' campus. For this case study, solar energy is harvested from the photovoltaic panels atop the Fluor Daniel Engineering Innovation Building which are capable of producing 15 kW of DC power at the full solar insolation rating. The electrical power produced varies throughout the day depending on the available solar irradiation and seasons. Next, compressed air energy storage has been evaluated using the generated electric power to operate an electric motor driven piston compressor. The compressed air is then stored under pressure and supplied to a natural gas driven Capstone C30 microturbine with attached electric power generator. In this approach, the compressed air facilitates the turbine's rotor-blade operated compression stage resulting in direct energy savings. The compressed air energy storage mitigates the intermittency of solar power and provides a continuous energy input to the microturbine over selected time periods.
In this thesis, a series of mathematical models have been developed for the solar panels, an air compressor, the pneumatic storage tank, and the microturbine as they represent the key microgrid system components. An illustrative numerical analysis was then performed to evaluate the feasibility and energy efficiency improvements. The experimental and simulation results indicated that 127.75 watts of peak power were delivered at 17.5 volts and 7.3 amps from each solar panel. The average DC power generation over a 24-hour time period from 115 panels was 75 kW which is equivalent to 30 kW of AC power from the inverter which could run a 5.2 kW reciprocating compressor for approximately 5 hours storing 1,108 kg of air at a 1.2 MPa pressure. The operation of the Capstone C30 microturbine was then simulated using a 0.31 kg/s mass flow rate with 100 air/fuel ratio. A case study indicated that the microturbine, when operated without compressed air storage, consumed 11.16 kg of gaseous propane for 30 kW∙hr of energy generation. In contrast, the microturbine operated in conjunction with solar supplied air storage could generate 50.84 kW∙hr of electrical energy for similar amount of fuel consumption. The study indicated an 8.1% of efficiency improvement in energy generated for the system which utilized compressed air energy storage over the traditional approach.
An atmospheric driven mechanical Atmos clock manufactured by Jaeger LeCoultre has been investigated due to its capability to harvest energy based on climatic temperature and/or pressure changes to power the clock's mechanisms. The clock's bellows is the power unit which winds the on-board mainspring. The unwinding of this mainspring provides torque to run the gear train, the escapement, and the torsional pendulum. A detailed analysis of the Atmos 540 clock dynamics has been performed using a library of derived mathematical models which describe the bellows' power generation, potential energy of the mainspring, gear train, escapement, and torsional pendulum. Experimental data has been collected using multiple sensors synchronized within the LabVIEW environment from National Instruments.
For this thesis, the mathematical models have been simulated using Matlab/Simulink and validated with the gathered experimental results. The linear motion of the bellows was nearly 6 mm which winds the mainspring over a temperature range of 290-292K. The maximum potential energy of the mainspring was 57e-03J, or 0.67e-06 watts over a 24-hour time period. The minute hand rotation was observed to be 6 degrees/min. The captured crutch motion indicated a `hold' position for a significant portion of the time (22 sec) and `impulse' motion for a small portion of the time (8 sec) every 30 seconds in opposite directions. The findings indicated miniscule torque requirement to run the clock. In terms of green energy, the bellows motion is thermo-mechanical energy harvesting.

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