(introduction...)

2.1 Electricity provides services such as lighting, power for agriculture and industry, water pumping, refrigeration, telecommunications, and entertainment. The most familiar delivery mechanism for electricity is the conventional power grid which consists of generation facilities, long-distance transmission lines, and local distribution equipment. Other energy sources such as PV systems, batteries, diesel engines, kerosene or gas lighting, candles, wood, agricultural residues, or animal power have a role to play in rural energy service provision.

2.2 Photovoltaic systems are already used in a broad array of rural energy applications. They provide households and small businesses with services such as lighting, refrigeration, and entertainment; they are used to pump water for agricultural purposes; to deliver public services, including health care, water purification, and street lighting and to power remote telecommunications facilities (Shepperd and Richard 1993). PV systems are modular. They can thus serve loads ranging in size from milliwatt (for instance, a pocket calculator) to megawatt (for bulk power supply). Over the past decade, considerable experience has been gained in designing and implementing solar home system programs in remote areas. The current costs of PV systems make them an economical option in situations where conventional power is too expensive for the small amount of power required, where the supply must be absolutely reliable (as for vaccine refrigerators in rural health clinics) or in areas too remote or geographically isolated for grid connectors.