Off-Grid Electricity Systems

There are two main approaches to conduct rural electrification areas in a competitive and effective way: mini-grids and stand-alone systems (ARE, 2015). Both types of systems operate independently of the national electricity grid and are thus known as ‘off-grid systems’.

Mini-grids

A mini-grid, also sometimes referred to as a micro-grid or isolated grid, is an off-grid system that involves small-scale electricity generation (10 kW to 10MW) and which serves a limited number of consumers via a distribution grid that can operate in isolation from national electricity transmission networks (Mini-Grid Policy Toolkit, 2014).

Mini-grids can supply electricity to concentrated settlements, including domestic, business and institutional customers, with power at or above grid quality level.

Clean energy mini-grids (CEMGs) utilise one or several renewable energies (solar, hydro, wind, biomass) to produce electricity. Back-up power can be supplied by electricity stored in for example batteries or otherwise by diesel. Storage provides or absorbs power to balance supply and demand and to counteract the moment to moment fluctuations in customer loads and unpredictable fluctuations in generation. More information can be found at SEforALL HIO CEMG.

Stand-alone systems

The second and equally competitive option is to use stand-alone systems. Stand-alone systems are small electricity systems, which are not connected to a central electricity distribution system and provide electricity to individual appliances, homes or small productive uses such as a small business. They thus serve the needs of individual customers, while utilising locally available renewable resources.

Thanks to significant drops in prices for the used components, stand-alone off-grid systems powered by biomass, small wind, small hydro, s and solar power are becoming more and more common.

To extend the time of use energy storage systems have become more popular. Storage is typically implemented as a battery bank. Power drawn directly from the battery is often extra low voltage (DC) and this is used especially for lighting as well as for DC appliances. An inverter is used to generate AC low voltage which powers standard appliances. (ARE, 2013)

Stand-alone systems can be differentiated into pico, home and productive systems.

Advantages over national grid extension

Both mini-grids and stand-alone systems are in the vast majority of cases the more cost-competitive than extension of the national grid network. As rural areas in developing and emerging countries are often located far away from the national grid in difficult terrain or on islands, extending the national grid to rural areas is normally extremely costly and technically difficult, whereas off-grid systems are flexible, easy to use and adaptable to local needs and conditions.  With appropriate training they can also be operated by local technicians, which in turn leads to local employment.

Mountainous and forest areas as well as small islands for instance, with difficult access for machinery, require more time and resources to install transmission lines, whereas off-grid systems are easier and less costly to implement and can use local renewable energy sources to provide electricity.