This paper presents an optimization framework based on dynamic programming mathematic tool suitable to be implemented in programmable logic controllers to improve the automated control of parallel pumping loops aiming at energy conservation. The paper also contributes with simple methods to derive system curve and pumping head-flow speed-dependent characteristic from ordinary field measurements.

Climate change and environmental degradation has resulted in a reduction in water inflow at hydropower plants, as well as a decrease in reservoir levels. Existing hydropower plants suffer from water head reduction, mainly with decrease in efficiency of energy conversion in hydro turbines. This paper showcases the benefits of operations with variable speed in existing hydropower plants, when working at a lower water head than the rated one. Theoretical analyses and tests were performed in a special constructed laboratorial setup aiming at evaluating the amount of efficiency recovery with variable speed operation. Connection alternatives for a constant frequency grid and applications of the learned concepts in an existent hydropower plant are presented. The investigations were applied to the Furnas hydropower plant. The results point out that economic feasibility of the application can be achieved.

The Brazilian Labeling Program is a forceful instrument for the conservation of energy. In addition to allowing consumers to evaluate the best products from an energy point of view, it sets targets to make the products increasingly more efficient. In this context, buildings that can currently obtain the energy efficiency label are also included, demonstrating to customers the concern for sustainability. However, there are still many products and systems that can be labeled but for which legislation has not yet been enacted, including water supply systems. Owing to the different characteristics of the systems and the different possibilities for efficiency improvement, it is necessary to develop indicators that actually represent the reality of each system and make it possible to compare them. Thus, this study proposes the use of certain indicators for classification of the systems. A classification by sector benchmarking is also proposed in Brazil, and an example is presented for the classification of Brazilian systems based on four indicators obtained by the National Sanitation Information System.

a b s t r a c tIsolated generation in micro hydroeletric power plant (MHPP) through the induction generator (IG) has been the subject of extensive research due to the fact that this type of electrical machine is easy to operate, requires simplified maintenance, and has also a lower cost when compared to the synchronous machine, mainly in the range from 0.5 to 50 kW. In this work a single voltage control loop of an squirrel cage induction generator in an isolated operation system was implemented in a 30 kW MHPP. The proposed system uses a ballast load (BL) controlled via a digital circuit board. The generated voltage and frequency are maintained around their nominal rated values for typical applications in rural areas. For this purpose a control system has been implemented via phase antieparallel thyristors. Tests were made with varying loads to obtain the voltage waveforms in the main load (ML) and BL. The control allowed by the electronic board was also tested for performance under sudden connection and disconnection of loads. The proposed system proved to be robust and effective in controlling the voltage and frequency of the isolated system.

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