A mini grid, also sometimes referred to as a “micro grid or isolated grid”, can be defined as a set of electricity generators and possibly energy storage systems interconnected to a distribution network that supplies electricity to a localized group of customers.”They involve small-scale electricity generation (10 kW to 10MW) which serves a limited number of consumers via a distribution grid that can operate in isolation from national electricity transmission networks.
This power delivery architecture can be contrasted to a single customer system such as in the case of a solar home system (SHS). Where there are no distribution network interconnecting customers it can be connected to a centralized grid system, where electrical energy is transmitted over large distances from large central generators where local generators are generally not capable of meeting local demand.[2]
Mini-grids have a unique feature as they can operate autonomously without being connected to a centralized grid. However, the mini-grid may be designed to interconnect with the central grid which means it operates under normal conditions as part of the central grid with disconnection occurring only if power quality needs to be maintained. For instance in the case of a central grid failure. Alternatively, a mini-grid may be designed to operate autonomously in a remote location with the option to connect to a central grid when grid extension occurs. A mini-grid can be supplied by all sorts of energy resources and power plants, however most of the time a mini-grid will use low AC voltage (220-380V) with a centralized production and a storage system and will have an installed capacity of between and 5 and 300kW even though bigger systems exist.
Sizing
There is no one single definition about the size of the mini-grids. Some organizations define mini-grids in terms of the generation capacity i.e. between 10 kW to 10 MW. Others define it in terms of customers reached i.e. mini-grids reaching 20-100 customers are called micro mini-grids and mini-grids reaching over 500 customers are called full mini-grids. A general consensus is that mini-grids should supply more than a few kW of electricity to multiple consumers such as community, hospitals or schools.