Power Systems Optimization to Analyze Renewable Energy Policy and Resource Diversity

This thesis is organized into two chapters, which will be submitted separately for publication. The abstracts for each chapter are given below. Chapter 1: Many state-level Renewable Portfolio Standards (RPS) include preferences for solar generation, with goals of increasing the diversity of new renewable generation, driving down solar costs, and encouraging the development of local solar industries. Depending on their policy design, these preferences can impact the RPS program costs and emissions reduction. This study introduces a method to evaluate the impact of these policies on costs and emissions, coupling an economic dispatch model with optimized renewable site selection. Three policy designs of an increased RPS in Michigan are investigated: 1) 20% Solar Carve-Out, 2) 5% Distributed Generation Solar Carve-Out, and 3) 3x Solar Multiplier. The 20% Solar Carve-Out scenario was found to increase RPS costs 28%, while the 5% Distributed Generation Solar Carve-Out increased costs by 34%. Both of these solar preferences had minimal impact on total emissions. The 3x Solar Multiplier decreases total RPS program costs by 39%, but adds less than half of the total renewable generation of the other cases, significantly increasing emissions of CO2, NOx , and SO2 relative to an RPS without the solar credit multiplier. Sensitivity analysis of the installed cost of solar and the natural gas price finds small changes in the results of the Carve-Out cases, with a larger impact on the 3x Solar Multiplier. Setting the correct level for a solar multiplier to achieve one’s goals may prove difficult in light of changing costs associated with multiple technologies. The effective use of a credit multiplier can undermine objectives to increase renewable generation and decrease emissions, but do allow market forces to determine the level of solar development relative to other qualified renewable options. The Solar Carve-Out scenarios have a smaller impact on other non-solar related objectives, but may compel the development of high-cost solar, increasing the cost of implementing an RPS. Chapter 2: The variability of wind power introduces new challenges for the operation of the power system, including increased system ramping requirements. One method to reduce wind variability is to diversify the wind power resource by interconnecting diverse wind resources across a larger geography. This study uses a modified version of mean-variance portfolio optimization (MVP) to assess the potential for diverse wind to reduce the impacts of wind variability. To understand the value of the reduced variability to the power system, different portfolios of wind power are assessed using a unit commitment and economic dispatch model. Using MVP, diverse wind portfolios are shown to significantly reduce wind power variability, at the cost of increased installed wind capacity to meet the same level of wind generation of less diverse wind portfolios. However, the value of the reduced variability is complicated by complexities of the power system, including transmission constraints and the time of day of ramping need.Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/109710/1/Novacheck_Thesis_December_2014.pd

Increasing thermal plant flexibility in a high renewables power system

Thermal generation is a vital component of mature and reliable electricity markets. As the share of renewable electricity in such markets grows, so too do the challenges associated with its variability. Proposed solutions to these challenges typically focus on alternatives to primary generation, such as energy storage, demand side management, or increased interconnection. Less attention is given to the demands placed on conventional thermal generation or its potential for increased flexibility. However, for the foreseeable future, conventional plants will have to operate alongside new renewables and have an essential role in accommodating increasing supply-side variability. This paper explores the role that conventional generation has to play in managing variability through the sub-system case study of Northern Ireland, identifying the significance of specific plant characteristics for reliable system operation. Particular attention is given to the challenges of wind ramping and the need to avoid excessive wind curtailment. Potential for conflict is identified with the role for conventional plant in addressing these two challenges. Market specific strategies for using the existing fleet of generation to reduce the impact of renewable resource variability are proposed, and wider lessons from the approach taken are identified

The Role of Energy Storage With Renewable Electricity Generation

Renewable energy sources, such as wind and solar, have vast potential to reduce dependence on fossil fuels and greenhouse gas emissions in the electric sector. Climate change concerns, state initiatives including renewable portfolio standards, and consumer efforts are resulting in increased deployments of both technologies. Both solar photovoltaics (PV) and wind energy have variable and uncertain (sometimes referred to as “intermittent”) output, which are unlike the dispatchable sources used for the majority of electricity generation in the United States. The variability of these sources has led to concerns regarding the reliability of an electric grid that derives a large fraction of its energy from these sources as well as the cost of reliably integrating large amounts of variable generation into the electric grid. Because the wind doesn’t always blow and the sun doesn’t always shine at any given location, there has been an increased call for the deployment of energy storage as an essential component of future energy systems that use large amounts of variable renewable resources. However, this often-characterized “need” for energy storage to enable renewable integration is actually an economic question. The answer requires comparing the options to maintain the required system reliability, which include a number of technologies and changes in operational practices. The amount of storage or any other “enabling” technology used will depend on the costs and benefits of each technology relative to the other available options. To determine the potential role of storage in the grid of the future, it is important to examine the technical and economic impacts of variable renewable energy sources. It is also important to examine the economics of a variety of potentially competing technologies including demand response, transmission, flexible generation, and improved operational practices. In addition, while there are clear benefits of using energy storage to enable greater penetration of wind and solar, it is important to consider the potential role of energy storage in relation to the needs of the electric power system as a whole. In this report, we explore the role of energy storage in the electricity grid, focusing on the effects of large-scale deployment of variable renewable sources (primarily wind and solar energy). We begin by discussing the existing grid and the current role that energy storage has in meeting the constantly varying demand for electricity, as well as the need for operating reserves to achieve reliable service. The impact of variable renewables on the grid is then discussed, including how these energy sources will require a variety of enabling techniques and technologies to reach their full potential. Finally, we evaluate the potential role of several forms of enabling technologies, including energy storage

Renewable Electricity Futures Study. Volume 4: Bulk Electric Power Systems: Operations and Transmission Planning

The Renewable Electricity Futures (RE Futures) Study investigated the challenges and impacts of achieving very high renewable electricity generation levels in the contiguous United States by 2050. The analysis focused on the sufficiency of the geographically diverse U.S. renewable resources to meet electricity demand over future decades, the hourly operational characteristics of the U.S. grid with high levels of variable wind and solar generation, and the potential implications of deploying high levels of renewables in the future. RE Futures focused on technical aspects of high penetration of renewable electricity; it did not focus on how to achieve such a future through policy or other measures. Given the inherent uncertainties involved with analyzing alternative long-term energy futures as well as the multiple pathways that might be taken to achieve higher levels of renewable electricity supply, RE Futures explored a range of scenarios to investigate and compare the impacts of renewable electricity penetration levels (30%-90%), future technology performance improvements, potential constraints to renewable electricity development, and future electricity demand growth assumptions. RE Futures was led by the National Renewable Energy Laboratory (NREL) and the Massachusetts Institute of Technology (MIT)