For the past century and a half, the United States has enjoyed sustained growth in both per capita and total energy use. However, most of this expansion has been due to the consumption of fossil fuels, which have extremely slow replacement rates, and thus, under current consumption patterns are used unsustainably. In order for our society to stabilize or grow energy usage rates, a transition to renewable sources of energy must occur. The present work examines what role solar hydrogen could play in a future energy system through several different lenses. First, results of an experimental study of the increase of electrolysis (producing hydrogen through splitting water with electricity) efficiency through the application of ultrasound will be discussed. Second, increasing photovoltaic efficiency through ground source cooling will be presented with both technological and economic arguments. Lastly, results will be presented from a simulation performed to determine the economically optimum mix of solar, wind, and storage to produce all of the electricity for the PJM Interconnect (which includes many eastern mid-Atlantic states including Delaware). The conclusion of the current work is that, even with technological gains and lower costs, solar hydrogen's role in our future energy system is unclear.
One way solar hydrogen could be part of a future energy system is the production of hydrogen. This work examines the production of hydrogen by splitting water with electricity. This electrochemical water splitting reaction is more commonly referred to as electrolysis. Recently, it has been shown that ultrasound irradiation of electrochemical reactions can provide an increase in their reaction rate. In the present work, ultrasonic irradiation was added to the electrolysis reaction and it decreased the overpotential of the reaction, thus increasing the efficiency. However, because of the vast amount of power used by the ultrasound this may not be practical. Nevertheless, ultrasonic irradiation of electrolysis may prove to be a valuable analytical tool.
Just as the applied ultrasound power must be balanced with the power gained by lowered overpotential in electrolysis, the power used by a ground sourced photovoltaic cooling system must be balanced by the power gain in a solar module by employing the cooling. This cooling system was analyzed through a digital simulation. It will be shown that the overall efficiency of the system can increase by more than 9%. Also, the conclusion of an economic analysis is that the system costs will be paid back within the life of the installed system.
In a future solar hydrogen energy system, both electrolysis and photovoltaics could play a role. In the last phase of the work a simulation of a large scale energy system is performed to determine what role solar hydrogen could play. This simulation takes in costs for three generation technologies: offshore wind, inland wind, and photovoltaics. It also takes in costs for three storage technologies: hydrogen, vehicle to grid, and lithium-ion centralized storage. It then runs an hourly simulation for four years to decide what mix of generation and storage would both cover electricity load for the PJM Interconnect and minimize cost. The results of this simulation shows that vehicle to grid is chosen over hydrogen and lithium-ion. However, the results also show that the most economical mix includes over five gigawatts of photovoltaics even though it is more expensive than inland and offshore wind.
Given the above results and the fact that costs of technologies are hard to predict, the future of solar hydrogen in our energy system is unclear. More specifically, hydrogen's future is unclear, however, it may be useful as a strategic reserve of energy storage because of its low leakage rate from metal canisters.
|Advisor:||Goossen, Keith W.|
|Commitee:||Kempton, Willett, Kiamilev, Fouad, Opila, Robert L.|
|School:||University of Delaware|
|Department:||Department of Electrical and Computer Engineering|
|School Location:||United States -- Delaware|
|Source:||DAI-B 73/07(E), Dissertation Abstracts International|
|Subjects:||Alternative Energy, Chemical engineering, Public policy|
|Keywords:||Electrolysis, Ground source cooling, Solar hydrogen, Splitting water, Ultrasound irradiation, Wind power|
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