Many off-grid PV systems power a single application. Examples include:
Water pumping: water supplies for people, livestock and irrigation.
Medical and vaccine cold chain refrigeration: highly efficient and low-energy DC fridges are used. Some have batteries, but others use PV-direct-drive compressors and to store cold overnight as ice, a cooled water tank or ice-lining chemicals. The World Health Organisation’s (WHO) list of fridges certified for vaccine cold chain use can be found at: https://apps.who.int/immunization_standards/vaccine_quality/pqs_catalogue/categorypage.aspx?id_cat=17
Refrigeration for the storage of veterinary medicines: highly efficient and low-energy DC fridges are used. These need to be approved by local authorities.
Cold storage rooms: large systems to produce crushed ice for fish processing; cold storage for vegetables and other perishable goods; and cooled milk at milk collection centres or on farms.
Electric fencing: very little power is required, so one small PV module is very often sufficient.
Portable systems: examples include portable lamps, small systems for charging mobile phones and laptops.
In principle, an off-grid PV system can be used to power any low-power application.