Abstract
Micro-hydro systems can be used as a promising new source of renewable energy generation, requiring a low investment cost of hydraulic, mechanical, and electrical equipment. The improvement of the water management associated with the use of pumps working as turbines (PATs) is a real advantage when the availability of these machines is considered for a wide range of flow rates and heads. Parallel turbomachines can be used to optimize the flow management of the system. In the present study, experimental tests were performed in two equal PATs working in parallel and in single mode. These results were used to calibrate and validate the numerical simulations. The analysis of pressure variation and head losses was evaluated during steady state conditions using different numerical models (1D and 3D). From the 1D model, the installation curve of the system was able to be defined and used to calculate the operating point of the two PATs running in parallel. As for the computational fluid dynamics (CFD) model, intensive analysis was carried out to predict the PATs′ behavior under different flow conditions and to evaluate the different head losses detected within the impellers. The results show system performance differences between two units running in parallel against a single unit, providing a greater operational flow range. The performance in parallel design conditions show a peak efficiency with less shock losses within the impeller. Furthermore, by combining multiple PATs in parallel arrangement, a site’s efficiency increases, covering a wide range of applications from the minimum to the maximum flow rate. The simulated flow rates were in good agreement with the measured data, presenting an average error of 10%.
Highlights
Hydropower is a renewable energy source, is non-polluting, with low operational costs, and is environmentally friendly compared to other sources of energy [1,2]
When a pumps working as turbines (PATs) operates at optimum flow conditions, pressure and flow direction act on the impeller resulting in shock and friction losses [14,19], which can be classified as internal losses due to fluid friction in the stationary and rotating blade passage
The results show, for two of the tested scenarios with the corresponding characteristic curves (CC) of the PATs, reliable values with correlation factors above 0.98 between 1D and experimental tests
Summary
Hydropower is a renewable energy source, is non-polluting, with low operational costs, and is environmentally friendly compared to other sources of energy [1,2]. The efficiency response provides an essential cost advantage; by keeping the operating efficiency as high as possible across variations in the system’s flow demand, the energy and maintenance costs of the PAT can be significantly reduced. If two or more PATs are operating in parallel, they can be switched on/off according to the available flow [12] In this situation, the flow rate and pressure requirements for an optimal energy production can be managed using multiple PATs in reverse mode [13]. The main focus of this research is to know the variation of the best efficiency when PATs are installed in parallel and their influence in the improvement of the flow water management in real case studies, and to evaluate the head losses distribution during reverse mode
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