US Hydropower Research Articles

Diversity in reservoir surface morphology and climate limits ability to compare and upscale estimates of greenhouse gas emissions

Greenhouse gas (GHG) emissions from reservoirs are influenced by many factors, including the reservoir's morphology, watershed, and local climate. Failure to account for diversity in waterbody characteristics contributes to uncertainties in estimates of total waterbody GHG emissions and limits the ability to extrapolate patterns from one set of reservoirs to another. Hydropower reservoirs are of particular interest given recent studies that show variable – and sometimes very high – measurements and estimates of emissions. This study uses characteristics describing reservoir surface morphology and location within the watershed to identify US hydropower reservoir archetypes that represent the diversity of reservoir features relevant to GHG emissions. The majority of reservoirs are characterized by smaller watersheds, smaller surface areas, and lower elevations. Downscaled climate projections of temperature and precipitation mapped onto the archetypes show large variability in hydroclimate stresses (i.e., changes in precipitation and air temperature) within and across different reservoir types. Average air temperatures are projected to increase for all reservoirs by the end of the century, relative to historical conditions, while projected precipitation is much more variable across all archetypes. Variability in projected climate suggests that despite similar morphology-related traits, reservoirs may experience different shifts in climate, potentially resulting in a divergence in carbon processing and GHG emissions from historical conditions. Low representation in published GHG emission measurements among several reservoir archetypes (roughly 14 % of the population of hydropower reservoirs), highlights a potential limit to the generalization of current measurements and models. This multi-dimensional analysis of waterbodies and their local hydroclimate provides valuable context for the growing body of GHG accounting literature and ongoing empirical and modeling studies.

Harnessing the power of environmental flows: Sustaining river ecosystem integrity while increasing energy potential at hydropower dams

Hydropower comprises the largest portion of the world's renewable energy portfolio yet induces significant environmental effects in river and floodplain ecosystems. Many countries are seeking to increase hydropower capacity primarily through the construction of new dams; however, this overlooks the potential energy that can be gained from optimizing existing hydropower infrastructure. Environmental regulatory protocols globally, and especially in the US, require hydropower facilities to provide environmental flows to downstream riverine ecosystems. Most of these facilities, however, fail to capture additional hydropower energy from these releases, such as passing them through smaller turbines. Herein, we conducted a US-wide analysis of the potential additional hydropower capacity and generation that could be available if environmental flows were harnessed for energy. We used two approaches based on availability of information: one reliant on available stream flow data to identify specific optimal turbine sizes, and another using a design-envelope approach, to accommodate situations where flow data was unavailable. Using available historical flow data and plant characteristics from over 200 existing hydropower facilities, the addition of minimum flow turbines could provide up to 730 MW of capacity and generate nearly 1.8 TWh of energy annually. Across the remaining hydropower fleet, the envelope approach suggests there may be anywhere from 12 TWh to 66 TWh of additional energy, supplied from a capacity increase of 2.5 GW–13.5 GW annually. Ultimately, this suggests that uncaptured environmental flows provide anywhere from 4% to 18% potential increase in US hydropower capacity and 4%–24% increase in generation.

Evaluation of Nominal Energy Storage at Existing Hydropower Reservoirs in the US

AbstractLong‐term planning and operation of hydropower reservoirs require an understanding of both water and energy storage. As energy storage needs of the evolving grid increase, we must account for the water and energy storage potential of these reservoirs. Given the limitations of current data on existing hydropower, we compile statistics related to storage volume and hydraulic head from publicly available data sets and examine differences in descriptions of US hydropower storage. Assembled characteristics are used to calculate nominal energy storage capacity, a simple measure of potential to generate power from a given volume of water, not factoring in detailed constraints. Inventory‐based estimates of energy storage are calculated at 2,075 dams, which helps put the potential for US hydropower to support energy storage in context with similar evaluations in other regions and with other energy storage technologies. The national energy storage capacity ranges between 34.5 and 45.1 TWh depending on the information used, with 52% of energy storage located at the 10 largest reservoirs in the US. Energy storage capacities are also calculated at 236 dams with historical volume and elevation data. Finally, reservoir inflows provide context for the storage volumes and sensitivities to hydrologic variability. Larger reservoirs with greater storage volume to inflow ratios are concentrated in the Western US, but the majority of hydropower reservoirs store less than the annual inflow. We address several infrastructure and water resource informatics challenges and highlight remaining issues, including representing seasonal or shorter variability in water volumes and representing connected hydropower facilities.

Solar-power replacement as a solution for hydropower foregone in US dam removals

There is a growing dam removal movement in the United States, driven in part by environmental, safety and cost considerations. These include electricity-producing hydro-dams, many of which are ageing and will require substantial maintenance or removal over the coming decades. However, hydropower has been and remains an important source of energy for the development of the United States, presently generating about 6% of the nation’s electricity while providing essential grid services. As a potential solution to the conflict between these imperatives, industrial-scale photovoltaics (PVs) could be used for replacement of the energy foregone from hydro-dam removals either by installing the PV infrastructure in the area formerly inundated by the dam reservoir or through offsite replacement. Presently, the total PV generation in the conterminous United States is 35,919 GWh yr−1, or approximately 13% of hydropower generation. On the basis of actual hydropower generation in the conterminous United States in 2016 (that is, 274,868 GWh yr−1), we estimated that 529,885 ha of PVs would be needed to replace the generation of all 2,603 hydro-dams—an area approximately equal to the land size of Delaware. PVs could replace the total annual energy produced from these dams while requiring only 13% of their existing reservoir area. If all the hydro-dams in the United States were removed and only 50% of the emergent land was used for PVs, 945,062 GWh yr−1 power could be generated, which is 3.44 times the current hydropower generation. These analyses are theoretical and do not consider costs, which would be highly site specific. Replacement by PVs without energy storage could not replicate the dispatchability and grid services provisions of existing hydropower facilities; however, improving battery storage capabilities may ameliorate this shortcoming. We suggest that PVs could replace much of the annual electricity output of hydro-dams in the United States while using substantially less land area and providing considerable environmental and ecological benefits. While renewable energy has often included hydropower, dams present their own environmental harms. This Analysis not only projects how much land would be needed for solar power to replace US hydropower, but also provides a model for further analyses in other countries.

Deploying effectively dispatchable PV on reservoirs: Comparing floating PV to other renewable technologies

In this article, we present a detailed simulation of floating photovoltaic's (PV) energy yield and associated evaporation reduction potential for the largest 128 US hydropower reservoirs. A recent article by Cavusoglu et al., published in the journal Nature Communications, outlined a hypothetical evaporation engine that could harness the energy of lake water evaporation while simultaneously conserving the water resource. Its authors suggest that evaporation engines deployed across all US lakes and reservoirs could, collectively, yield up to 70% of the total U.S. electricity production. We show that floating PV technology could: (1) deliver considerably more electrical energy than evaporation engines, amounting to 100% of the US production with only a fraction of the lakes; (2) deliver this energy on a firm, effectively dispatchable basis; and (3) conserve as much water as the evaporation engines.

Classification of US Hydropower Dams by their Modes of Operation

A key challenge to understanding ecohydrologic responses to dam regulation is the absence of a universally transferable classification framework for how dams operate. In the present paper, we develop a classification system to organize the modes of operation (MOPs) for US hydropower dams and powerplants. To determine the full diversity of MOPs, we mined federal documents, open-access data repositories, and internet sources. We then used CART classification trees to predict MOPs based on physical characteristics, regulation, and project generation. Finally, we evaluated how much variation MOPs explained in sub-daily discharge patterns for stream gages downstream of hydropower dams. After reviewing information for 721 dams and 597 power plants, we developed a two-tier hierarchical classification based on (i) the storage and control of flows to powerplants, and (ii) the presence of a diversion around the natural stream bed. This resulted in nine tier-1 MOPs representing a continuum of operations from strictly peaking, to reregulating, to run-of-river, and two tier-2 MOPs, representing diversion and integral dam-powerhouse configurations. Although MOPs differed in physical characteristics and energy production, classification trees had low accuracies (≤62%), which suggested that accurate evaluations of MOPs may require individual attention. MOPs and dam storage explained 20% of the variation in downstream subdaily flow characteristics and showed consistent alterations in subdaily flow patterns from reference streams. This standardized classification scheme is important for future research including estimating reservoir operations for large-scale hydrologic models and evaluating project economics, environmental impacts, and mitigation. Copyright © 2016 John Wiley & Sons, Ltd.

A fish-eye view of riverine hydropower systems: the current understanding of the biological response to turbine passage

One-way connectivity maintained by fish passing through hydropower turbines in fragmented rivers can be important to population dynamics, but can also introduce a new and significant source of mortality. Sources of mortality during turbine passage can come from several sources including blade strike, shear forces, cavitation, or pressure decreases and parsing the contributions of these individual forces is important for advancing and deploying turbines that minimize these impacts to fishes. We used a national hydropower database and conducted a systematic review of the literature to accomplish three goals: (1) report on the spatial distribution of turbine types and generation capacities in the USA, (2) determine fish mortality rates among turbine types and fish species and (3) examine relationships between physical forces similar to those encountered during fish turbine passage and fish injury and mortality. We found that while Francis turbines generate 56 % of all US hydropower and have the highest associated fish mortality of any turbine type, these turbines are proportionally understudied compared to less-common and less injury-associated Kaplan turbines, particularly in the Pacific Northwest. While juvenile salmonid species in actual or simulated Kaplan turbine conditions were the most commonly studied, the highest mortality rates were reported from percid fishes passing through Francis turbines. Future studies should focus on understanding which species are most at-risk to turbine passage injury and mortality and, subsequently, increasing the diversity of taxonomy and turbine types in evaluations of turbine injury and mortality.

Could Europe have more mini hydro sites? A suitability analysis based on continentally harmonized geographical and hydrological data

Abstract The paper introduces a transparent methodology to assess new suitable locations for mini and small hydro power plants in Europe. The expansion of hydro electricity production is a policy focus not only in Europe, but in the US (Hydropower Regulatory Efficiency Act of 2013) and in the developing world as well. The analysis of the technical potential points out the exact geographical locations and their corresponding capacities instead of only a theoretical potential; therefore it can serve as a reference for the policy debate over the sustainable management of water resources. This debate is reflected already in two major European policies: the Water Framework Directive (WFD) (2000/60/EC) and the RES Directive (2009/28/EC) on the promotion of the use of energy from renewable sources. As both policies have major influence on the priorities of water use, it is important to identify water management practices capable of accommodating sustainable energy purposes while maintaining water quality objectives at the same time. As the WFD poses limitation on the further expansion of large scale hydro options in the European water bodies, the present study focuses on local mini and small hydropower options and their suitability mapping. The presented, geographically explicit method is based on geospatial analysis and the results can contribute to the prioritization of potential hydro power sites in order to improve water quality and its use for energy simultaneously.

Hydropower license renewal and environmental protection policies: a comparison between Switzerland and the USA

Traditional hydropower creates a number of adverse environmental effects, nowadays largely recognized but still in conflict with rights granted in previous era of development. The Upper Rhone River basin is heavily developed for hydropower generation. As this region undergoes a period of new concession grants, environmental legislation should eventually be implemented to its full extent. This turning point also allows changes in dams’ ownership and institutional setting, and these aspects attract much of the political attention. The article compares the US hydropower regulatory framework and the country’s experience in dam relicensing to highlight shortcomings in the Swiss regulatory framework and possible outcomes of the concession reversion process in Canton Valais.

US hydropower dams: Environmental solution or problem?

Environmental concerns about hydropower generation have garnered significant US media attention in recent months. The hydropower industry, however, describes hydropower as a clean, renewable energy source that is more environmentally friendly than most-power generation methods. Hydropower advocates further emphasize that in our digital society, high electricity demands necessitate using a variety of generation methods to ensure grid stability. The debate has escalated recently as a result of a few key events. Cathy Swirbul takes a closer look.

Balancing Hydropower and Environmental Values: The Resource Management Implications of the US Electric Consumers Protection Act and the AWARE™ Software

This paper reviews the AWARE™ software distributed by the Electric Power Research Institute (EPRI). The program is designed to facilitate the Federal Energy Regulatory Commission (FERC) license renewal process for US hydropower installations. The discussion reviews the regulatory, legal, and social contexts that give rise to the creation and distribution of AWARE™. The principal legal impetus for AWARE™ is the Electric Consumer Protection Act (ECPA) of 1986 that directs FERC to give equal consideration to power and non-power resources during relicensing. The software is reviewed in this paper from several perspectives including those of natural resource economics, systems modeling, and the social context within which FERC licensing decisions are made. We examine both the software and its underlying methodology and find significant problems with each. Because of its flaws, AWARE™ does little to further ECPA's equal consideration requirement. We find that the conservation and restoration impact of ECPA for US fisheries could be seriously hampered by the widespread use of AWARE™.

Balancing Hydropower and Environmental Values: The Resource Management Implications of the US Electric Consumers Protection Act and the AWARE™ Software

This paper reviews the AWARE™ software distributed by the Electric Power Research Institute (EPRI). The program is designed to facilitate the Federal Energy Regulatory Commission (FERC) license renewal process for US hydropower installations. The discussion reviews the regulatory, legal, and social contexts that give rise to the creation and distribution of AWARE™. The principal legal impetus for AWARE™ is the Electric Consumer Protection Act (ECPA) of 1986 that directs FERC to give equal consideration to power and non-power resources during relicensing. The software is reviewed in this paper from several perspectives including those of natural resource economics, systems modeling, and the social context within which FERC licensing decisions are made. We examine both the software and its underlying methodology and find significant problems with each. Because of its flaws, AWARE™ does little to further ECPA's equal consideration requirement. We find that the conservation and restoration impact of ECPA for US fisheries could be seriously hampered by the widespread use of AWARE™.