Doctor of Philosophy

dissertationRenewable energy systems are becoming popular choices for power generation. Well-established technologies (e.g. solar and wind energy) have been widely implemented. However, other emerging technologies (e.g. ocean energy) have not been properly commercialized due to the expensive capital investment. Potential economic benefit is one of the main aspects considered when assessing renewable energy resources. The economic benefit is often calculated over large regions, even though renewable energy technologies are locationally-dependent. Site-specific implementations of renewable energy systems can yield additional benefits, such as lower capital costs and higher energy conversion. Another issue associated with renewable energy systems is that they are also subject to uncertainties caused by technical limitations. For instance, the intermittent nature of some renewable energy resources can lead to interruptions in power generation. As a result, the integration of renewable energy systems can be challenging, and therefore requires optimized planning. To better understand the potential of renewable energy systems, this research focuses on the following objectives: Aim I: Evaluate the feasibility of emerging renewable energy systems for power generation by utilizing local resources: Pressure retarded osmosis (PRO) is an emerging renewable energy technology and is categorized as a part of ocean energy. A PRO energy system generates electricity by converting osmotic energy into electrical energy. The dissertation presents an evaluation of a 25 MW osmotic power plant at the Great Salt Lake in terms of technical integration and economic value. The hypersaline characteristic of the Great Salt Lake offers a unique opportunity for higher energy conversion, even though the levelized cost of electricity (LCOE) of PRO with current technology ($0.2025/kWh) is still higher than other renewable energy technologies. The results from this study identify challenging issues and lay the groundwork for PRO system integration research at potential locations for osmotic energy power generation. Aim II: Assess technical limitations of renewable energy technologies and estimate their thermo-economics via global sensitivity analyses: The results from Aim I suggest that uncertainty plays a prominent role in evaluating the performance and economics of PRO. Aim II of the dissertation studies uncertainties in power generation of renewable energy technologies, both developed and emerging. This study focuses on technical integration and cost-effective use of renewable energy systems within the U.S. energy sector. This assessment identifies technical issues such as dispatchability, variability, scalability, energy storage, geographic limitations, and investment costs. Furthermore, a global sensitivity analysis based on a Monte Carlo approach is used to investigate traditional and renewable energy resources under uncertainty and variability. The results from the global sensitivity analysis show that statistical distributions of uncertain variables affect the LCOE estimation of energy technologies. Opportunities for cost reductions from power generation of renewable energy technologies and guidelines for future research and development are subsequently provided. Aim III: Optimize renewable energy systems in a district energy system (DES) by incorporating their associated uncertainties: The technical limitations of renewable energy resources identified in Aim II are applied to integrated energy systems with distributed generation. Residential solar PV systems in Utah are studied under three different energy policies for selling excess solar PV generation: net metering, wholesale, and no payback. Furthermore, a stochastic operating cost optimization, which considers the uncertainties of renewable energy resources, is performed on a DES scale. Statistical analyses are utilized to handle the intermittency and unpredictability of power generation from renewable energy resources. The results from the optimization study suggest that operating cost savings (3.5% operating cost reduction compared to traditional systems) can be achieved with renewable energy systems integrated into DES. The research findings from this dissertation contribute to the understanding of practical implementations of renewable energy systems. This research provides new frameworks for (1) evaluating the scalability of emerging renewable energy technologies, (2) identifying economic and technological issues or energy technologies, and (3) providing solutions for optimal integration. Guidance for applications of emerging and developed renewable energy technologies is provided to offer pathways for a reliable and sustainable energy future