Talk:Mini-grid/Sandbox

A mini grid is a distribution grid that receives electricity from one or more small generators (often renewable) and supplies electricity to a localized target group of consumers, typically including households, businesses and public institutions. Generation in a mini grid is typically located near the loads that it serves.  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 often a cost-effective solution for electrifying rural communities of a hundred or more households that are 10 km or more from the main grid. Remote households that are far from each other are generally best served by stand-alone solutions such as solar home systems, while areas that are close to the main grid are generally best served by a line extension 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

Mini grids are not a recent phenomenon. Nearly all centralized electricity grid systems began as isolated mini grids that were connected to each other over time. 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 diesel or hydropower, and built by local communities or entrepreneurs primarily to provide rural households with access to electricity, especially in areas not yet served by the main grid. Many of these systems were overtaken by the national grids. Some that still exist are now prime candidates for hybridization with solar photovoltaic (PV) systems to reduce the fuel cost.

Contemporary mini grids

Electricity consumption per country in million kWh, from CIA Factbook, accessed April 2006

Over the past few years, a third generation of solar mini grids has emerged. These mini grids, mostly solar PV hybrids, are owned and operated by private companies that leverage transformative technologies and innovative strategies to build portfolios of mini grids instead of one-off projects. The typical third-generation mini grid is grid-interconnection ready, uses batteries for storage, employs remote management systems, and prepay smart meters. Most solar mini grids are hybridized with a diesel generator that provides backup power in the event of extended cloudy periods. The diesel generator typically generates less than 10% of the energy consumed by mini grid customers on an annual basis. This third-generation mini grid also incorporates energy-efficient appliances for productive uses of electricity into its business model. These mini grids operate in more favorable business environments, taking advantage of cost reductions in the latest mini grid component technologies and regulations developed specifically for private-sector investment.

Mini grid technologies

Generation

With the rapid decline in the cost of solar photovoltaics, there is a strong and accelerating trend towards the use of solar electricity in mini grids. According to a 2022 study by the World Bank’s ESMAP, approximately 51 percent of installed mini grids are solar or solar hybrid (generally solar + diesel), followed by those powered only by hydro (35%), fossil fuel (10%), and other generation technologies such as wind (5%). The trend is accelerating: more than 10 times as many solar mini grids were built per year from 2016 to 2020 than fossil fuel mini grids. Almost 99 percent of all planned mini grids are solar or solar hybrid. Solar hybrid mini grids include one or more other sources of electricity generation, typically a diesel generator or sometimes a generator powered by biomass fuel to a provide a dispatchable source of electricity in the event of extended cloudily periods. Where suitable sites allow, small scale hydroelectricity (micro- or mini-hydropower) provide cost-effective 24-hour a day electricity generation. In areas where windspeeds are consistently high and/or sunlight is very restricted seasonally, wind is used to power mini grids, often in a hybrid configuration with solar or diesel or both.

Storage

Electricity in third generation mini grids is stored in electrochemical batteries. Prior to 2018, most mini grids were installed with lead acid batteries, however the rapid cost decline and superior lifetimes and performance of lithium-ion batteries has led to most new mini grids using lithium-ion batteries.

Hybrid power system combining wind, solar PV, and conventional diesel generation with energy storage.

Power conversion and management

In most mini grids, inverters convert the direct current (DC) electricity stored in batteries and produced by solar panels into alternating current (AC) power that powers appliances used in households and businesses.

In some particularly small communities with low loads, DC mesh mini grids are used. Mesh grids—or “skinny grids”—distribute DC electricity for lighting, electronics, and small appliances like fans and even efficient refrigerators or electric rickshaws. They take the form of clusters of solar home systems made up of solar panels affixed to customers’ premises and connected in a mesh network. Specialized controllers allow surpluses to be shared and households can upgrade to AC appliances by purchasing an inverter.

Energy management systems (EMS) optimize the balance between dispatching the diesel generator and drawing on energy storage, taking into account expected load and near future opportunities for solar charging. Many mini grids, even in remote areas, have cell-phone carrier based remote monitoring capabilities that monitor power production and consumption, battery state-of-charge, and voltage levels and upload information to the internet several times per hour. Remote monitoring can help operators to identify and address small problems early before they cascade and become larger problems.

Distribution

Electricity in mini grids is distributed over poles and wires. If there is the prospect that the main grid may someday arrive, the mini grid distribution network is built to utility standards so that the distribution network can be easily integrated into the national grid.  If the mini grid is certain to remain disconnected from the main grid (for example, if it is located on an island distant from shore) distribution networks are sometimes built to standards that are lower than the national grid, but still ensure safety and efficiency.

Electricity is sold to customers using either pre-pay or postpay meters. Pre-pay meters are more common and work like pre-paid phone plans, automatically disconnecting customes when the amount of purchased electricity is consumed. Because electricity consumed during sunny hours is less costly to produce than electricity that must be stored in batteries or generated from a diesel generator, mini grids metering systems sometimes provide lower tariffs for daytime consumption, or the ability to curtail lower-priority customers in the event of energy shortages.

The use of a pre-made ready-board with a few light switches and outlets can eliminate the costs of internal household wiring. If a feeder is longer than roughly 1 km in distance, then it is generally necessary to use transformers to step up the electricity to medium voltage (35 kV or below) to reduce ohmic losses.

Role in achieving SDG7 and market outlook by 2030

The UN’s Sustainable Development Goal #7 is ensuring access to affordable, reliable, sustainable and modern energy for all by 2030. Mini grids currently provide electricity to about 48 million people worldwide. Mini grids that are currently being planned are expected to bring electricity to an additional 35 million people, mostly in Sub-Saharan Africa. To reach universal electricity access by 2030, 490 million people will be served at least cost by 217,000 mini grids requiring an investment of $127 billion. With increasing economies of scale and decreasing costs of major components such as solar panels and batteries, the cost of electricity from mini grids is expected to decrease from an unsubsidized levelized cost of electricity from best-in-class hybrid solar mini grids today of $0.38 per kWh to about $0.20 per kWh by 2030.

10 building blocks for scaling up mini grids

It is generally accepted that scaling up mini grids will require significant work in multiple areas. The World Bank has identified ten: 1) reducing costs and optimizing design & innova­tion for solar mini grids; (2) planning national strategies and developer portfolios with geospatial analysis and digital platforms; (3) transforming productive livelihoods and improving business viability; (4) engaging communities as valued customers; (5) delivering services through local and international companies and utilities; (6) financing solar mini grid portfolios and end user appliances; (7) attracting exceptional talent and scaling skills development; (8) supporting institutions, delivery models, and champions that create opportunities; (9) enacting regulations and policies that empower mini grid companies and customers; and (10) cutting red tape for a dynamic business environment.