Page - 121 - in Clean Water Using Solar and Wind - Outside the Power Grid

Handling variable production 121 Institutions such as schools, health centres or community centres have a different load profile, since most of their activities take place during typical working hours, usually in the daytime. Since the highest power demand occurs during sunshine hours, a significant share of the PV-generated electricity can be used immediately when generated. The peak load and daily energy demand can vary significantly, depending on the specific user of the system. It may, for example, include running refrigerators for cooling medicines at a health centre or charging batteries and mobile phones for villagers at a community centre. A number of load profiles from various customers of a mini- grid in Tanzania are presented by Hartvigson and Ahlgren (2018). The authors had first estimated load profiles based on interviews, but later measurements of the load profiles showed quite different behaviour. The lesson learnt is that simplified load profiles may lead to inappropriate sizing of the power production. Predicted and measured load profiles for a household and for three small workshops with machine operation loads during the day are presented. The authors also emphasise the need for more data on load profiles in rural areas. The renewable electric energy will not primarily be used for heating since the regions considered are relatively warm countries. However, in rural areas in Asia there is a need for heating for substantial periods of the year The load profiles of water pumping and water cleaning can adapt to available electric power. Pumping water can be used as a balancing activity. When there is insufficient power supply pumping can be switched off and when power capacity exceeds the need pumping can be used to store energy in elevated water tanks. Water supply treatment via desalination and disinfection can also run intermittently. This of course requires water storage capacity for untreated as well as for treated water. Knowing the load profile is essential to find out the need for energy storage. Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user