pumping system generally costs more initially than a gas, diesel, or propane-powered generator but requires far less maintenance and labor. Comparing installation costs (including labor), fuel costs and maintenance costs over 10 years, it is observed that solar is an alternate choice. These systems have the added advantage of storing water for use when the sun is not shining, eliminating the need for batteries, enhancing simplicity and reducing overall system costs. Solar water pumps are designed to use the direct current (DC) provided by a PV array, although some newer versions use a variable frequency AC motor and a three-phase AC pump controller that enables them to be powered directly by the solar modules. Because PV is expensive and its power production can be variable, solar pumps need to be as efficient as possible i.e. they need to maximize the gallons of water pumped per watt of electricity used. The key to PV’s choice is the low labor and maintenance costs relative to the other options. The long-term economics make PV pumps comparable to most other remote watering options in the rural areas. The lifetime of solar water pump is usually 20 years, which ultimately is lower than the life span period cost compared to the conventional pumps. Bangladesh is a potential place for implementing solar water pumping due to lack of electricity supply in the rural areas needing irrigation. By using photovoltaic pumps, load on the grid system can be reduced and the subsidy on the diesel can be lowered .The advantages of solar water pumping system over the conventional pumping are tabulated in the Table 3.1. Table 3.1: Comparison between Solar water pump and Conventional Water Pump Attributes Grid Electricity Needed? Maintenance Fuel Upfront Cost 20 years total cost
Solar Water Pump Conventional water Pump No Yes Low Maintenance and Need maintenance and unattended operation. replacement Simple and reliable No fuel cost or Spill Fuel often expensive and supply intermittent Upfront cost higher but Moderate capital cost last longer Lower Higher
3.3 Types of Solar Water Pumps Solar Water pumping System can be divided into two basic types. 1. According to the storage system. 2. According to the types of the motor used. Again, there are two types of solar-powered water pumping systems according to the storage system. 1. Battery-coupled 2. Direct-coupled. 3.3.1 Battery- coupled Solar Water Pump Battery-coupled water pumping systems consist of photovoltaic (PV) panels, charge control regulator, batteries, pump controller, pressure switch and tank and DC water pump (Figure 3.1 [7]). The electric current produced by PV panels during daylight hours charges the batteries, and the batteries in turn supply power to the pump anytime water is needed. The use