Mini-grid
A mini-grid is an aggregation of loads and one or more energy sources operating as a single system providing electric power and possibly heat isolated from a main power grid. A modern mini-grid may include renewable and fossil fuel-based generation, energy storage, and load control. A mini grid can be fully isolated from the main grid (wide area synchronous grid) or interconnected to it. If it is interconnected to the main grid, it must also be able to isolate (“island”) from the main grid and continue to serve its customers while operating in an island or autonomous mode. Mini-grids are used as a cost-effective solution for electrifying rural communities where a grid connection is challenging in terms of transmission and cost for the end user population density, with mini grids often used to electrify rural communities of a hundred or more households that are 10 km or more from the main grid. Mini grids and microgrids are similar, and the terms are sometimes used as synonyms. Both microgrids and mini grids include generation and distribution, and generally include electricity storage in the form of electrochemical batteries. Both can “island” in the event of a blackout or other disturbance or – common in mini grids – in the case that they were never connected to the main grid in the first place. In practice, the term “mini grid” is used more in a context common in low- and middle-income countries providing electricity to communities that were previously unelectrified, or sometimes used to provide reliable electricity in areas in which the national grid is present but where electricity is sporadic; across Sub-Saharan Africa, more than half of households connected to the main grid reported receiving electricity less than half of the time. The African Mini Grid Developers Association (AMDA) reports that uptimes of mini grids of its members for which data was available averaged 99% across countries. In contrast, the term “microgrid” is used more in higher income countries to refer to systems that provide very high levels of reliability (for example, “five nines” or 99.999%) for critical loads like data centers, hospitals, corporate campuses or military bases generally in service areas that already have high levels of reliability (e.g. “three nines” or 99.9% reliability) by global standards. Background History The electric grids of many developed, high-income countries once started out as mini-grids. These isolated electrical systems were then connected and integrated into a larger grid. This first generation of mini grids was pivotal to the early development and industrialization of most modern economies, including Brazil, China, Denmark, Italy, the Netherlands, Spain, Sweden, the United Kingdom, and the United States. Mini grid systems introduced in the late nineteenth and early twentieth centuries can be described as the first generation of mini grids. Starting in the 1980s and ramping up through the 1990s and early 2000s, a second generation of mini grids numbering in the tens of thousands was deployed in many low-income countries. These systems are typically small and isolated, powered by