Large systems have been considered for pumping water for irrigation and villages. These can be classified into wind-assist and remote, stand-alone systems. Wind-assist water pumping is where the wind turbine and another power source work in parallel to provide power on demand. Wind assist is essentially a fuel-saving mode of operation, since it does not require any changes in irrigation application. Wind assist can be further divided into indirect and direct connection. The advantages of the indirect connect are that the wind turbine does not need to be located at the well, and electricity can be returned to the grid when the wind turbine is producing more power than is needed by the load. A direct mechanical connection to the gear head has also been tested where the conventional power source is electric or diesel [40, 41]. The disadvantages of the mechanical connection are that the wind turbine has to be near the well, and the wind turbine can only be used when water is needed.
The wind-electric water pumping system is a major change from the farm windmill in two aspects: efficiency and volume of water. The annual efficiency is double that of the farm windmill, and because wind turbines are available in larger sizes (1-10 kW and 50 kW permanent magnet alternators), wind-electric systems can pump enough water for irrigation and villages. The wind-electric system consists of a wind turbine generator connected directly to a standard three-phase induction motor driving a centrifugal or submersible turbine pump. There is a good match between the wind turbine output and the centrifugal pump, because both have power proportional to rpm cubed. Another advantage of the wind-electric system is that the wind turbine can be located some distance from the well or pump.
An example is the two wind-electric systems (10 kW) that were installed in Naima, Morocco, in 1989 for supplying water for villages and animals . The spring water is some distance from the villages. The first wind turbine pumps water from the collection tank to a large storage tank on top of the hill (Figure 10.7). There is gravity flow to two other storage tanks, and a second wind turbine to pump water to another village. The wind-electric systems replaced diesel pumping systems, which were inoperable. In 1997, an additional two 1.5 kW wind-electric water pumping systems were installed.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.