DYNAMIC BEHAVIOR OF WATER WELLS COUPLED TO PV PUMPING SYSTEMS

摘要

Several programs of water supply with PV systems are being developed in the Northeast of Brazil to meet water requirements of rural communities. Evaluation of a water supply system requires an overall analysis of its behavior. In this process, some factors have to be considered, among them, the well performance and drawdown characteristics. The response of the water well is usually characterized by a single relationship between water table and water flow, representing its quasi-equilibrium behavior. However, for days with large and rapid variations of irradiance this relationship does not correspond to the well equilibrium curve. In order to simulate the well behavior under far from equilibrium conditions we have developed a model that takes into account the variation of well water level, pressure at the entrance of the well and static pressure of the aquifer, all of them related to the water flow. The model also considers the energy conservation equation of the system through the relationship between water flow and collected irradiance, allowing the simultaneous calculation of water level and water flow. Results of simulations show that, for days with large variations in solar irradiance, the static and dynamic analysis exhibit large differences in the instantaneous water head. The standard deviation (fraction of the average value) of the instantaneous variation obtained for water head, flow rate and hydraulic power for a day with large variations of solar irradiance are 11%, 14% and 6%, respectively. Values much larger than those obtained for a day with small irradiance variations (4%, 6% and 3%).