Submitted by Rupak Thapaliya on Wed, 2011-04-06 13:22
Hydraulic potential stored in water reservoirs can be converted to useful power through the work of turbomachinery. However, nations around the world have large numbers of existing dams with hydropower potential left unused. These dams were mostly built during the latter half of the 20th century. At that time, thermal electric energy supply, generated with abundant cheap fossil fuels made small scale hydropower generation less attractive. Another reason for such low utilization of these clean renewable energy resources is the significant capital cost of equipment and hydropower plant construction. This made small hydropower development economically noncompetitive. With the rapid depletion of fossil fuel and the increased environmental and global warming concerns, it becomes highly desirable to harness clean renewable energy sources.To retrofit a conventional hydroturbine onto an existing dam brings out several major issues. They include structural integrity and safety of the dam, and the cost of construction and complex engineering tasks involved in properly integrating a powerhouse into the existing structure. These issues have seriously impeded the progress in developing these hydroelectric potentials. In addition, available data indicates that existing hydroturbine technology has some undesirable ecological impacts by causing injury and mortality to passing fish and deterioration of downstream environmental condition resulting from undesirable levels of dissolved gas.In this paper the authors will first briefly summarize current hydropower development needs and challenges, and then describe a new approach to effectively meeting these challenges by using an innovative hydroturbine system. The new hydroturbine system consists of four key design innovations: 1) an updraft flow arrangement, 2) a vertical pressure-balanced turbine flow control valve in place of the conventional wicket gates, 3) a divergent runner flow chamber serving the function of the draft tube, and 4) exit flow at the free surface in the tailwater terrace.
Since its inception in the 1930s, pumped storage hydro has provided significant benefits to our energy supply system including storage, load balancing, frequency control and reserve generation. Pumped storage is now being applied to firm the variability of renewable power sources, such as wind and solar generation. Pumped storage absorbs load at times of high output and low demand, while providing additional peak capacity. With the advent of state by state Renewable Portfolio Standards driving the planning and commissioning of a tremendous amount of variable renewable energy projects across the country, America’s electrical energy infrastructure needs storage capacity more than ever. Pumped storage hydro is proving to be an enabling technology for these growing variable renewable power sources’ penetration into the United States energy supply system.While the 31 GW of new pumped storage project proposals now before the Federal Energy Regulatory Commission demonstrates the hydropower industry’s commitment to building new pumped storage capacity to support variable renewable sources, developers still face significant obstacles, including an uncertain investment climate and long development timelines. Expanding the current investment and production tax credits, the possible creation of an energy storage credit, coupled with policies that recognize pumped storage as a part of the transmission system for purposes of qualifying for the transmission rate incentives currently afforded to transmission system upgrades and expansions, would encourage investment in pumped storage. This growth would displace the need for additional fossil-fuel based peaking generation, and provide the load management capacity necessary to meet our national renewable energy goals
With the recent and continuing increases in energy consumption, combined with strong environmental concerns, there has been a resurgence in the development of low-impact hydroelectric projects throughout North America and internationally. Within North America, the proposed developments have generally been limited to smaller run-of-river developments or the addition of low-head powerplants to existing in-river structures. Of particular interest have been the hydropower additions adjacent to existing lock and dam structures within the Ohio and Upper Mississippi River Basins. The existing lock and dam facilities are maintained and operated by the U.S. Army Corps of Engineers and were developed to provide safe and efficient navigation along the rivers for commercial transport of goods. With the addition of a hydropower project, the developer is required to demonstrate that there will be no adverse impacts on navigation and flood levels within the vicinity of the project.This paper will consolidate and discuss the results of nine physical model studies that have been conducted for hydropower additions adjacent to existing lock and dam projects. The primary objective for each of the studies was to evaluate and resolve any impacts on navigation that the proposed development might impose. Secondary objectives have included verifying that the project would not adversely impact flood levels, scour and erosion or environmental habitats in the vicinity of the project. In addition, the project designers have utilized the models to refine the alignment and geometry of the powerhouse approach channel to minimize head losses while providing uniform flow distribution entering the powerhouse intake. In each case, the physical modeling was instrumental in optimizing a project layout that minimized the impacts on river navigation while providing approach and tailrace flow conditions compatible with efficient power generation. The experience gained and the “lessons learned” on the various projects are summarized and discussed, and design recommendations are developed that can be applied to future projects
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