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With the rapid development of new natural gas resources in the United States has come a number of proposals for new natural gas transmission infrastructure. We use a unique and fine-grained data set on natural gas spot pricing and gas transmission operations to model how a local pipeline expansion connecting a Marcellus Shale producing area to the main Transco pipeline system would affect flow patterns and zonal gas pricing across the Transco. Our modeling approach is based on arbitrage cost models for constrained energy networks, accounting for the effects of zonal gas transmission rates as mandated by the U.S. Federal Energy Regulatory Commission. Application of our model to a data set of daily gas market outcomes and operating conditions on the Transco between 2012 and mid 2014 suggests that the modeled pipeline expansion would increase overall economic welfare in the spot market for Transco deliveries by $1.7 billion and have positive net social benefits of about $0.4 billion. However, more than 80% of this estimated welfare gain occurs in one season (winter 2014) featuring high gas demand due to colder weather. Thus, the spot market efficiency gains associated with pipeline projects in the Marcellus region may be limited by the frequency of extreme cold weather conditions. To examine the sensitivity of our estimates of welfare gains to different weather conditions, we calculate the expected benefits of the pipeline expansion in terms of historical temperatures from 1992 to 2011, and find that Atlantic Sunrise would have increased welfare by approximately $1.8 billion over a two and half year period, on average. [ABSTRACT FROM AUTHOR]

The integration of renewable power supplies into existing electrical grids, or other major technology transitions in electric power, is a complex sociotechnical process. While the technical challenges are well-understood, the process of adapting electricity policy and market rules to these new technologies is understudied. Planning and market rules are a critical determinant of the technical success of renewable energy integration efforts and the financial viability of renewable energy investments. Organizational adaptation can be particularly complex in electric power, where transmission grids cross multiple political boundaries and decisions are made not by central authorities or governments, but in cooperative regional frameworks that must accommodate many divergent interests. We add to a recently emerging literature on the governance of regional organizations that plan and operate electric power grids by developing and illustrating a novel approach to the study of political power in multistakeholder electricity organizations. We use semistructured interviews with participants in a specific regional electric grid authority, the PJM Regional Transmission Operator in the Mid-Atlantic United States, to elicit perceptions of where tensions arise in stakeholder-driven processes for changing PJM's rules and perceptions of those groups of stakeholders that possess political power. We treat these perceptions as hypotheses that can be evaluated empirically using five years of data from PJM on how stakeholders voted on a wide variety of regional electricity policy issues. Representing voting behavior as a network, we use a community detection method to identify strong coalitions of stakeholders in PJM that provide support for some stakeholder perceptions of political power and refute other perceptions. The degree distribution of the voting network exhibits a fat tail relative to those in other canonical graph models. We show, using relatively simple network metrics including degree, betweenness, and the mixing parameter, that the reason for this fat tail in the degree distribution is the existence of "swing" voters in RTO stakeholder networks. These voters are identifiable in the tail of the degree distribution of the voting network and are influential in pushing highly contentious rule change proposals towards passage or failure. The method we develop is generalizable to other contexts and provides a new framework for the study of regional electricity policy formation. [ABSTRACT FROM AUTHOR]

In the United States, Regional Transmission Organizations (RTOs) operate the power grid serving nearly 70% of electricity customers and are critical organizations for ensuring reliable system operations and facilitating the integration of new technologies and market participants. RTOs are designed to be stakeholder-driven organizations, with rules and policies crafted through a highly participatory process. While the decisions that RTOs make have implications for industry, society and the environment, their decision processes have not been modeled in any systematic way. In this paper, we develop a modeling framework for the stakeholder process of PJM, an RTO serving thirteen states plus the District of Columbia, adapting some of the seminal literature from political science and political economy on the theory of voting systems. This modeling framework can generate predictions of stakeholder process outcomes, identify strong coalitions among stakeholders and identify shifts in political power in the formulation of RTO market rules. We illustrate this analysis framework using a detailed data set from stakeholder deliberations of capacity market reform in PJM. Our model predicts that the current structure of the stakeholder process in PJM makes the passage of capacity market reforms through the stakeholder process virtually impossible because it creates strong coalitions that would favor or oppose changes to capacity market rules. In the capacity market case, we also identify a small subset of voters that act as swing voters and confirm that political power is shifted to these voters by deviations from otherwise strong coalitions and abstentions from the voting process altogether. Our framework represents the first attempt to model the decision-making behavior of RTOs in any systematic way, and points towards emerging research needs in evaluating the governance structure of RTOs. [ABSTRACT FROM AUTHOR]

Combined heat and power (CHP) generates electricity and heat from the same fuel source and can provide these services at higher equivalent conversion efficiency relative to grid-purchased electricity and stand-alone steam production. Previous work has focused on the economic factors and optimal operation strategy that influence the decision to install a single CHP unit. The approach discussed in this paper is to assess the economic potential for CHP in an electricity-market equilibrium framework, accounting for the impact that CHP adoption at scale will have on electricity prices—incremental installations of CHP reduce the demand for grid-provided electricity in some locations, thus reducing wholesale prices in that location. A statistical model of electricity supply and pricing is utilized to estimate locational electricity supply curves that reflect the impact of transmission congestion on locational price formation and location-specific elasticities of supply. The zonal electricity pricing model is coupled with the model of CHP adoption and utilization in commercial buildings for two locations in the PJM power grid. Under a range of operational assumptions and fuel prices, returns to incremental CHP deployment decrease rapidly in both locations for the first 100 MW of building-integrated CHP deployed, although CHP becomes an uneconomical decision only at much higher deployment levels. Although the elasticity of supply is an important determinant of economic potential for CHP, the authors find that in most cases, operating CHP units to follow building thermal demand (versus electrical demand, which would offset peak electricity-demand periods) yields higher returns over a broader range of CHP deployment levels. [ABSTRACT FROM AUTHOR]

Electrical generation units (EGUs) are important sources of nitrogen oxides (NOx) that contribute to ozone air pollution. A dynamic management system can anticipate high ozone and dispatch EGU generation on a daily basis to attempt to avoid violations, temporarily scaling back or shutting down EGUs that most influence the high ozone while compensating for that generation elsewhere. Here we investigate the contributions of NOxfrom individual EGUs to high daily ozone, with the goal of informing the design of a dynamic management system. In particular, we illustrate the use of three sensitivity techniques in air quality models—brute force, decoupled direct method (DDM), and higher-order DDM—to quantify the sensitivity of high ozone to NOxemissions from 80 individual EGUs. We model two episodes with high ozone in the region around Pittsburgh, PA, on August 4 and 13, 2005, showing that the contribution of 80 EGUs to 8-hr daily maximum ozone ranges from 1 to >5 ppb at particular locations. At these locations and on the two high ozone days, shutting down power plants roughly 1.5 days before the 8-hr ozone violation causes greater ozone reductions than 1 full day before; however, the benefits of shutting down roughly 2 days before the high ozone are modest compared with 1.5 days. Using DDM, we find that six EGUs are responsible for >65% of the total EGU ozone contribution at locations of interest; in some locations, a single EGU is responsible for most of the contribution. Considering ozone sensitivities for all 80 EGUs, DDM performs well compared with a brute-force simulation with a small normalized mean bias (–0.20), while this bias is reduced when using the higher-order DDM (–0.10). Implications: Dynamic management of electrical generation has the potential to meet daily ozone air quality standards at low cost. We show that dynamic management can be effective at reducing ozone, as EGU contributions are important and as the number of EGUs that contribute to high ozone in a given location is small (<6). For two high ozone days and seven geographic regions, EGUs would best be shut down or their production scaled back roughly 1.5 days before the forecasted exceedance. Including online sensitivity techniques in an air quality forecasting model can provide timely and useful information on which EGUs would be most beneficial to shut down or scale back temporarily. [ABSTRACT FROM PUBLISHER]

In this paper, we examine the effect of increased wind penetration on system marginal prices (SMPs) in South Korea's electricity market. Korea's renewable portfolio standard (RPS) went into effect in 2012, with a goal of increasing the share of renewable generation to 10% of the total load by 2022. We examine the output of wind installations across the Korean peninsula and simulate an increase in wind penetration consistent with Korea's RPS targets. Under a variety of assumptions on demand elasticity, we find that higher shares of wind generation in total supply reduce both the average SMP and its variation. In particular, we find that wind energy output on the Korean peninsula is more correlated with peak electricity demand than has been reported for other regions. The per-unit value of wind energy to owners of wind assets is thus higher for South Korea than would be the case for European or North American locations with a similar mix of fuels other than wind. [ABSTRACT FROM AUTHOR]

Identifying coherent sub-graphs in networks is important in many applications. In power systems, large systems are divided into areas and zones to aid in planning and control applications. But not every partitioning is equally good for all applications; different applications have different goals, or attributes, against which solutions should be evaluated. This paper presents a hybrid method that combines a conventional graph partitioning algorithm with an evolutionary algorithm to partition a power network to optimize a multi-attribute objective function based on electrical distances, cluster sizes, the number of clusters, and cluster connectedness. Results for the IEEE RTS-96 show that clusters produced by this method can be used to identify buses with dynamically coherent voltage angles, without the need for dynamic simulation. Application of the method to the IEEE 118-bus and a 2383-bus case indicates that when a network is well partitioned into zones, intra-zone transactions have less impact on power flows outside of the zone; i.e., good partitioning reduces loop flows. This property is particularly useful for power system applications where ensuring deliverability is important, such as transmission planning or determination of synchronous reserve zones. [ABSTRACT FROM PUBLISHER]

Coal-mining activities in the Appalachian Basin have left behind an environmental legacy of acid mine drainage (AMD), which collectively discharges more than 1.2 billion liters of low-pH contaminated water per day into freshwater streams. Meanwhile, concerns over the use of freshwater for hydraulic fracturing applications in the Appalachian Basin are rising, where an average daily withdrawal of freshwater for hydraulic fracturing may approach 60 million liters per day. The use of AMD as a substitute for freshwater has the joint advantages of mitigating existing environmental damage to surface waters and relieving some pressures on freshwater withdrawals, but the practice faces technical, economic, and regulatory hurdles. To reduce sulfate levels, coal-mine drainage that is currently treated to meet Clean Water Act standards may need additional treatment for hydraulic fracturing applications. Reducing sulfate levels without the use of additional freshwater may involve costs of several dollars per barrel versus less than one dollar per barrel for freshwater purchased directly. The cost of treatment to remove sulfates would need to decline by perhaps a factor of 4 in order to be cost-competitive with the purchase of fresh water. So-called abandoned (untreated) mine drainage poses a larger environmental challenge, but treatment and transportation costs may be orders of magnitude larger. Issues regarding handling liability and storage costs for abandoned-mine waters in particular represent significant regulatory barriers. We find that treatment, transportation, and storage costs are the most important factors affecting water-utilization decisions in shale-gas development. While Pennsylvania has proposed policy reforms to address environmental liability issues associated with AMD use, implementation itself will likely raise costs for its use in hydraulic fracturing as compared to the use of freshwater. AMD use may become cost-competitive with the development and use of low-cost AMD treatment technologies in centralized locations designed for long-term use, along with efficient water transfer and storage facilities.Environmental Practice 14:301–307 (2012) [ABSTRACT FROM AUTHOR]

The topological (graph) structure of complex networks often provides valuable information about the performance and vulnerability of the network. However, there are multiple ways to represent a given network as a graph. Electric power transmission and distribution networks have a topological structure that is straightforward to represent and analyze as a graph. However, simple graph models neglect the comprehensive connections between components that result from Ohm's and Kirchhoff's laws. This paper describes the structure of the three North American electric power interconnections, from the perspective of both topological and electrical connectivity. We compare the simple topology of these networks with that of random, preferential-attachment, and small-world networks of equivalent sizes and find that power grids differ substantially from these abstract models in degree distribution, clustering, diameter and assortativity, and thus conclude that these topological forms may be misleading as models of power systems. To study the electrical connectivity of power systems, we propose a new method for representing electrical structure using electrical distances rather than geographic connections. Comparisons of these two representations of the North American power networks reveal notable differences between the electrical and topological structures of electric power networks. [ABSTRACT FROM PUBLISHER]

Energy efficiency can be a powerful way to lower energy bills, as well as the external (social) costs associated with energy consumption. Previous experience and research, however, has demonstrated that consumers are often unwilling to make investments in energy efficiency, even when such investments have relatively short payback periods. Because energy efficiency can contribute to correcting negative externalities associated with energy use, subsidies and other programs have been proposed as a way to increase efficiency investments. Thus, under the right circumstances, such subsidies can improve economic efficiency. In this paper, we analyze the economics of energy-efficient space conditioning using data from an actual household in rural Pennsylvania to evaluate ground-source heat pumps (GHP). GHP technology has been advocated as a potentially appealing energy efficiency measure for rural communities. We find that with current subsidies GHP is economically viable for a wide range of electricity prices. We also find, however, that current subsidies are actually greater than those that can be economically justified. Using the efficient level of subsidies reduces, but does not eliminate, the economic case for GHP technology. We also evaluate the economics of efficiency subsidies using an ambitious program in Pennsylvania as a case study. The program, known as the Alternative Energy Investment Act (AEIA), provides subsidies for GHP among other technologies. We find that the substantial federal subsidies for GHP undercut the economic efficiency arguments for the AEIA with respect to GHP. [ABSTRACT FROM AUTHOR]

The flow regime of rivers is a complex but important measure of environmental quality and one that can be significantly impacted by conventional hydropower generation. While traditional hydropower scheduling creates a periodicity in downstream flows corresponding to seasonal and daily electricity demand patterns, deregulated electricity markets may provide financial incentives to further alter flows, as utilities respond to hourly market dynamics. This study investigates the potential for deregulated markets to impact both a hydropower utility's revenue stream and downstream flow regimes. Six operating scenarios are explored: (1-2) full-market participation (including real-time energy), with and without flow reregulation; (3) day-ahead market only; and (4-6) run-of-river operations (ROR), with and without flood control and flow reregulation. Results suggest that, relative to a day-ahead-only scenario, the scale of any differences in flow regime resulting from full-market participation is relatively small compared to the additional revenue-generating potential of such a strategy. Implementing a run-of-river policy frequently yields "more natural" flow regimes than the day-ahead only scenario; but, in some cases these improvements are modest, and in others the ROR scenarios exacerbate deviation from unregulated flows. Regardless, the effects of implementing an ROR strategy come at a substantial cost in terms of foregone hydropower revenue. [ABSTRACT FROM AUTHOR]

Hydropower can provide inexpensive, flexible fill-in power to compensate for intermittent renewable generation. Policies for hydropower dams maintain multiple services beyond electric generation, including environmental protection, flood control and recreation. We model the decision of a hydroelectric generator to shift some of its power production capacity away from the day-ahead energy market into a 'wind-following' service to smooth the intermittent production of wind turbines. Offering such a service imposes both private and social opportunity costs. Since fluctuations in wind energy output are not perfectly correlated with day-ahead energy prices, a wind-following service will necessarily affect generator revenues. Seasonal wind patterns produce conflicts with the goal of managing rivers for 'ecosystem services'-the maintenance or enhancement of downstream ecosystems. We illustrate our decision model using the Kerr Dam in PJM's territory in North Carolina. We simulate the operation of Kerr Dam over a three-year period that features hydrologic variability from normal water years to extreme drought conditions. We use an optimization framework to estimate reservation prices for Kerr Dam offering wind-following services in the PJM market. Wind-following may be profitable for Kerr Dam at low capacity levels during some time periods if ecosystems services are neglected and if side payments, or reserves-type payments, are provided. Wind-following with ecosystem services yields revenue losses that typically cannot be recovered with reserves market payments. Water release patterns are inconsistent with ecosystem-services goals when Kerr Dam dedicates significant capacity to wind-following, particularly in drought years. [ABSTRACT FROM AUTHOR]

In order to identify the extent to which results from topological graph models are useful for modeling vulnerability in electricity infrastructure, we measure the susceptibility of power networks to random failures and directed attacks using three measures of vulnerability: characteristic path lengths, connectivity loss, and blackout sizes. The first two are purely topological metrics. The blackout size calculation results from a model of cascading failure in power networks. Testing the response of 40 areas within the Eastern U.S. power grid and a standard IEEE test case to a variety of attack/failure vectors indicates that directed attacks result in larger failures using all three vulnerability measures, but the attack-vectors that appear to cause the most damage depend on the measure chosen. While the topological metrics and the power grid model show some similar trends, the vulnerability metrics for individual simulations show only a mild correlation. We conclude that evaluating vulnerability in power networks using purely topological metrics can be misleading. [ABSTRACT FROM AUTHOR]

Restructuring efforts in the U.S. electric power sector have tried to encourage transmission investment by independent (non-utility) transmission companies, and have promoted various levels of market-based transmission investment. Underlying this shift to "merchant" transmission investment is an assumption that new transmission infrastructure can be classified as providing a congestion-relief benefit or a reliability benefit. In this paper, we demonstrate that this assumption is largely incorrect for meshed interconnections such as electric power networks. We focus on a particular network topology known as the Wheatstone network to show how congestion and reliability can represent tradeoffs. Lines that cause congestion may be justified on reliability grounds. We decompose the congestion and reliability effects of a given network alteration, and demonstrate their dependence through simulations on a 118- bus test network. The true relationship between congestion and reliability depends critically on identifying the relevant range of demand for evaluating any network externalities. [ABSTRACT FROM AUTHOR]

This special issue of Environmental Engineering Science highlights the role of environmental engineering and science (EES) in interdisciplinary efforts to understand and protect food security, water resources, and sustainable energy. It includes articles that present model frameworks, theoretical constructs, as well as practical applications. Case studies provide a global perspective, as well as drawing attention to considerations of racial and ethnic inequalities, human health, and multiscale governance. As the EES community evaluates research efforts for 21st century challenges, food, energy, and water nexus research can provide interdisciplinary ideas for improving natural resource provisioning across the water, food, and energy spectrum. [ABSTRACT FROM AUTHOR]