Seite - 50 - in Clean Water Using Solar and Wind - Outside the Power Grid

50 Clean Water Using Solar and Wind: Outside the Power Grid down. The energy to extract groundwater has helped the people to cope with the prolonged drought conditions. The population in the Sahel region of West Africa without access to safe drinking water dropped by 16% during a ten-year period leading up to 2009. In Kenya only 6% of the agricultural land is irrigated and the main reason for this is lack of energy for pumping. There are some 2.9 million farmers in Kenya. An ongoing project, supported by the Renewable Energy and Energy Efficiency Partnership (REEEP), seeks to implement solar-powered irrigation (IRENA, 2015b). A typical system can pump up to 20 m3 per day and operate at depths up to 15 m. The capital cost for the system is around 400 USD. Taking into account the savings on fossil fuels the payback time is estimated at two years. The programme aims for 30,000 pumping systems by 2018. There are positive social consequences: for example, women and children are relieved from manual pumping and carrying water. As in India, there is an apparent risk of groundwater overdrawing due to the negligible operational cost of PV pumps. As noted by Varadi et  al. (2018), Chapter 5.2, there are more than 30 solar water pump manufacturers in the world. The pumps can be purchased on the Internet, but systems are available locally in most countries in Africa and developing Asia. 4.3 PUMPING CHARACTERISTICS The most common pump type is the centrifugal pump, in which the pump principle is to convert mechanical energy from the motor to kinetic energy (i.e., energy related to the fluid speed or flow rate) in the pumped medium, the water. This will create a pressure difference in the media between the pump inlet and outlet. Here we will skip many details of pump characteristics; more details can be found in Olsson (2015), Chapter 16. The system characteristics or the load characteristics describe the pressure that the pump must produce to drive the flow. The pressure consists of both static and dynamic pressures. The static pressure (also called the static head) appears at zero flow rate and depends on how much the water must be lifted by the pump. In other words, a deep well requires a large static pressure to lift the water compared to a shallow well. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user