Browsing by Subject "Solar power"
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Item Analysis of classical root-finding methods applied to digital maximum power point tracking for photovoltaic energy generation(2011-08) Chun, Seunghyun; Kwasinski, Alexis; Grady, William; Driga, Mircea; Hallock, Gary; Byoun, JaesooThis dissertation examines the application of various classical root finding methods to digital maximum power point tracking (DMPPT). An overview of root finding methods such as the Newton Raphson Method (NRM), Secant Method (SM), Bisection Method (BSM), Regula Falsi Method (RFM) and a proposed Modified Regula Falsi Method (MRFM) applied to photovoltaic (PV) applications is presented. These methods are compared among themselves. Some of their features are also compared with other commonly used maximum power point (MPP) tracking methods. Issues found when implementing these root finding methods based on continuous variables in a digital domain are explored. Some of these discussed issues include numerical stability, digital implementation of differential operators, and quantization error. Convergence speed is also explored. The analysis is used to provide practical insights into the design of a DMPPT based on classical root finding algorithms. A new DMPPT based on a MRFM is proposed and used as the basis for the discussion. It is shown that this proposed method is faster than the other discussed methods that ensure convergence to the MPP. The discussion is approached from a practical perspective and also includes theoretical analysis to support the observations. Extensive simulation and experimental results with hardware prototypes verify the analysis.Item The application of systems engineering to a Space-based Solar Power Technology Demonstration Mission(2012-05) Chemouni Bach, Julien; Fowler, Wallace T.; Guerra, Lisa A.This thesis presents an end-to-end example of systems engineering through the development of a Space-based Solar Power Satellite (SSPS) technology demonstration mission. As part of a higher education effort by NASA to promote systems engineering in the undergraduate classroom, the purpose of this thesis is to provide an educational resource for faculty and students. NASA systems engineering processes are tailored and applied to the development of a conceptual mission in order to demonstrate the role of systems engineering in the definition of an aerospace mission. The motivation for choosing the SSPS concept is two fold. First, as a renewable energy concept, space-based solar power is a relevant topic in today's world. Second, previous SSPS studies have been largely focused on developing full-scale concepts and lack a formalized systems engineering approach. The development of an SSPS technology demonstration mission allows for an emphasis on determining mission, and overall concept, feasibility in terms of technical needs and risks. These are assessed through a formalized systems engineering approach that is defined as an early concept or feasibility study, typical of Pre-Phase A activities. An architecture is developed from a mission scope, involving the following trade studies: power beam type, power beam frequency, transmitter type, solar array, and satellite orbit. Then, a system hierarchy, interfaces, and requirements are constructed, and cost and risk analysis are performed. The results indicate that the SSPS concept is still technologically immature and further concept studies and analyses are required before it can be implemented even at the technology demonstration level. This effort should be largely focused on raising the technological maturity of some key systems, including structure, deployment mechanisms, power management and distribution, and thermal systems. These results, and the process of reaching them, thus demonstrate the importance and value of systems engineering in determining mission feasibility early on in the project lifecycle.Item Coupling photovoltaics and grid-scale energy storage : performance and sitability(2015-05) Stoll, Brady Leigh; Deinert, Mark; Baldick, Ross; Edgar, Thomas; Howell, John; Shi, Li; Webber, MichaelThe Fifth Assessment of the International Panel on Climate Change has called for a four fold increase in the use of low-carbon sources of electricity to help stabilize climate change by mid century. Many people look to solar power systems to help reduce carbon intensity, but cost and variability have been significant obstacles to their widespread deployment. However, the cost of photovoltaics has dropped significantly in recent years, and grid-scale energy storage technologies are available to allow for production of dispatchable electricity from photovoltaics. In particular, compressed-air energy storage is both low-cost and can be built in a wide variety of geologies as well as above ground. I show that coupling large-scale photovoltaic arrays and grid-scale storage allows for dispatchable electricity production at costs that are comparable to other low carbon electricity sources. I examine four load curves: base-load generation, on-peak generation, and averaged load curves for the Electric Reliability Council of Texas (ERCOT) and PJM Independent System Operators. I found that on-peak and ERCOT loads typically required the lowest amount of storage, up to 2000 MWh [subscript e] less than that for base-load generation. However, in some regions, and for some storage amounts, baseload output actually provided the lowest cost of electricity. I also show that such coupled systems could provide base-load electricity for ≤ 0.08/kWh [subscript e] on more than 40% of global land surface, with a capacity factor equivalent to that of the US nuclear fleet. Importantly, this is below the projected cost of electricity from new nuclear power systems. While cost is a major factor, also of importance is where systems of photovoltaics and grid-scale storage would provide the most benefit. Locations expected to provide energy at the lowest cost do not necessarily correspond to load and population centers, where the electricity is most needed. I use multi-criteria decision analysis techniques to perform a global study of the optimal locations for siting these coupled systems to maximize their social benefit. I found that the most ideal locations are generally located in Africa, Iraq, and southeast Asia, as these locations have both high irradiance levels as well as expanding populations and low grid connectivity.Item Going solar in paradise : solar water heaters on the island of Hawaii(2006-05) Murray, Julie Marie; Oden, MichaelEnergy efficient technologies and renewable energy technologies are becoming less of a novelty in the American energy mix. These technologies offer the promise of a decreased dependence on foreign oil, considerable savings of energy bills, and protections for the environment. Despite the many potential benefits, these technologies face many barriers to adoption. The lack of renewable energy technologies and energy efficient technologies is particularly damaging in the State of Hawaii, where 90% of energy needs are met with imported fossil fuels. This report focuses on the current energy policies in Hawaii and the barriers to the incorporation of renewable energy technologies and energy efficient technologies, specifically solar water heaters.Item How dynamic cloud cover affects solar power plant output(2012-05) Stoll, Brady Leigh; Deinert, MarkPredicting the amount of solar radiation that reaches the earth’s surface is critical to understanding the performance of solar power systems, and cloud cover has a particularly strong impact on both the amount and direction of this radiation. Due to its variable nature, solar power is typically thought of as able to provide electricity only as a supplement to traditional power sources. However, by incorporating energy storage into solar facility design, it is possible to mitigate the variations in power production due to changes in sunlight. A key question then is how much energy storage would be required to account for daily solar irradiance variations and allow a solar power facility to produce electricity at least 80% of the year, comparable to traditional coal and natural gas plants. I have developed a simple algorithm for computing the intensity and angular distribution of light transmitted through, and reflected from, clouds. This result allows for accurate determination of variations in irradiance values across the globe. I have also created a model for the energy produced from a 100MW(e) solar power facility coupled to a large-scale thermal energy storage system. I used daily solar irradiance values to determine the array size needed at every location on the planet, and compared the power output at every location when both 1200MWh(e) and 1800MWh(e) of storage were incorporated into the plant design. I then computed the fraction of the year that power was produced at the rated capacity and the amount of time before the facility energy requirements are recouped. My analysis shows that more than 69% of the global land mass has sufficient solar resources provide continuous electricity output more than 80% of the time, and 27% of the land mass can do this more than 90% of time. In these locations the energy payback time ranges from 1.75 to 10 years.