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Brazil has an energy system with a hydrothermal characteristic that interconnects consumers and generators covering 98% of the demand for energy supplies. Most of the plants are concentrated in the southeast region, where the largest consumers and the largest population concentration are located. The expansion of this system, considering the hydroelectric contributions, will occur exploring the potentials located in the Amazon region. This analysis paper shows that the variations imposed by climate changes on some climatological variables create significant uncertainties about the power generation forecasts of the hydroelectric power plants to be installed in the Amazon, thus compromising the financial economic feasibility of these enterprises and also possibly compromising the expansion plans of the Brazilian energy system. The methodological approach uses information from various climate change scenarios and compares those with historical hydrological patterns and generation information. By exploring the characteristics of a large-scale hydrothermal system with high dependence on water resources, this paper provides valuable insights on how energy policy would address hydroelectric vulnerabilities and climate change. This analysis is focused on the Brazilian case but reveals important issues related to systems with hydro thermal characteristics. [ABSTRACT FROM AUTHOR]

Because of the maturity of its technology, small scale hydropower generation is one of the main energy sources to be considered to provide electricity to areas far from the national grid. Very often, because of the economic limitations of the communities that can be supplied with electricity, these projects are unappealing from the entrepreneur's point of view; however, they can have such a great positive impact on the life of these communities, with little impact on the environment, that they may well justify subsidies for their construction. This paper describes a mathematical model that combines multicriteria analysis and a knapsack problem formulation for optimizing the distribution of limited financial resources among several options available of hydropower projects with a stochastic behavior in their initial cost. The test data were obtained mainly from 14 prefeasibility studies of sites in rural Nicaragua with potential for small hydropower. Five scenarios are presented, assessing the impact of multicriteria and different subsidy conditions or economic efficiency requirements. The results indicate that the presented method is suitable to be used for an efficient distribution of limited monetary resources for funding small hydropower projects, and, therefore, can be a useful tool in decision making process. The proposed method can be adapted for application to projects based on other forms of renewable energy, and can also be adapted for prioritization of projects based on different energy resources. [ABSTRACT FROM AUTHOR]

Hydropower with water accumulation is an interesting option to consider in hybrid systems, because it helps dealing with the intermittence characteristics of renewable energy resources. The software HOMER (version Legacy) is extensively used in research works related to these systems, but it does not include a specific option for modelling hydro with reservoir. This paper describes a method for modelling a hydropower plant with reservoir with HOMER by adapting an existing procedure used for modelling pumped storage. An example with two scenarios in southern Brazil is presented for illustrating and validating the method explained in this paper. The results validate the method by showing a direct correspondence between an equivalent battery and the reservoir. The refill of the reservoir, its power output as a function of the flow rate and installed hydropower capacity are effectively simulated, indicating an adequate representation of a hydropower plant with reservoir is possible with HOMER. [ABSTRACT FROM AUTHOR]