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There is an enormous untapped potential for hydropower generation in rivers with large head and high flow variation, currently not feasible for conventional hydropower dams. Conventional dams make use of the potential energy, but waste kinetic energy from spillage during periods of high flows. This article studies the possibility of harnessing energy from potential and kinetic energy from hydropower dams with large head and flow variation, analyses its potential, and shows possible technologies. Focus is given to a Moveable Hydro-Electric Power Plant (HEPP) system in which the turbine module can be adjusted according to the flow and water level in the river. During floods the exceeding flows can pass above and below the Moveable HEPP results in a sub-pressure environment after the turbine module, thereby reducing the dam’s downstream head, increasing the pressure difference between the turbine inlet and outlet and the flow through the turbine, which increases the electricity generation of the dam. Dams with head increaser arrangement have been implemented in several dams in the 1930–1950s and now are regaining attention in Middle Europe. The main intention for its implementation is harnessing hydropower generation at run-of-river plants, with low-head, with a 20%–30% cost reduction, lower flooded area at the dam site, the resulting evaporation and the impact on the aquatic fauna. A case study was performed with the proposal of the Aripuanã Moveable HEPP in the Madeira River with a 26 ms height dam and a generation capacity of 1400 MW. The increase in generation with the head increaser effect is as high as 21%. The estimated potential for this technology in the Amazon region is 20 GW. Other potential locations are discussed in the article. Dams with head increaser effect have been successfully implemented and have the potential to become a major alternative for base load renewable energy in the future. [ABSTRACT FROM AUTHOR]

In order to maintain greater control over the country's water resources and reduce the vulnerability of the Brazilian electricity sector, this paper presents a review of the Seasonal-Pumped-Storage (SPS) potential in Brazil, its benefits and the different ways in which SPS can be integrated with hydroelectric dams in cascade downstream. In addition to increasing the Brazilian energy storage potential, SPS has the potential to: regulate river flows allowing the control of hydropower generation; reduce the spillage and increase power generation in the hydroelectric dams in cascade; turn the construction of new dams more viable where there is no suitable geology for the construction of conventional storage reservoirs; control floods when the geology does not permit the construction of storage reservoirs; decrease the evaporation of accumulation reservoirs; store the electricity generated from intermittent renewable sources; store energy for peak generation; reduce transmission bottlenecks; decrease the cost of electricity transmission from hydroelectric plants in the Amazon; decentralize the energy storage capacity in Brazil to increase energy security and to reduce the risk of electricity rationing. [ABSTRACT FROM AUTHOR]

The new frontier for hydropower electricity generation in Brazil, the Amazon region, cannot be used for energy storage as the construction of storage reservoirs would have deep environmental and social impacts, thus run-of-the-river dams have been built instead. If Brazil still wants to generate 80% of its electricity from hydropower, there is the need to increase the country's energy storage capacity so that the excess generation coming from the dams in the Amazon region during the wet period can be used during the dry period. This article presents four ways to increase the storage capacity of a watershed. The most innovative alternative involves a large-scale pumped-storage site combined with a series of hydropower dams in cascade, which could store energy by pumping water to a new reservoir during the wet period and generate energy by releasing the stored water during the dry period. Even though pumped storage schemes have an average efficiency of around 75%, it has been calculated that the combination of a pumped storage site and a series of hydroelectric dams in cascade can increase the overall storage efficiency up to 90% and double the storage capacity of a watershed. This scheme was called EPS (Enhanced-Pumped-Storage). [ABSTRACT FROM AUTHOR]