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.
In renewable energy mini-grids, storage plays a crucial role by balancing the intermittency of sources like solar and wind, ensuring a consistent and reliable supply of electricity, especially during periods when generation is low or demand is high. 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. In a World Bank ESMAP survey of 211 mini grids under commissioned in 2020 and 2021, 69% used Li-ion batteries and 31% used lead-acid batteries.[4]
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.
A mini-grid distribution system carries the energy produced by the generation source to the end users. It consists of poles and low voltage (<1000 V) distribution wires as well as protection equipment necessary to enable safe and effective energy distribution. If a feeder in the distribution system 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. Depending on the load requirements, a distribution system can be in AC single or three phase power or DC. [22]
If there is the prospect that the main grid may someday arrive, the mini grid distribution network is often 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 switchboard (sometimes referred to as a ready-board) with a few light switches and outlets can eliminate the costs of internal household wiring.
There are many potential benefits of mini-grids ranging from technical and environmental to social and financial advantages. Mini-grids can be used in rural areas and are often more efficient and cost-effective than other types of power systems. They can also strengthen the community while having less impact on the environment.[23]
Mini-grids are much more environmentally friendly than other types of grids. Since they reduce the need for diesel generators, greenhouse gas emissions are greatly reduced. This also improves air and noise pollution in the areas mini-grids are used.[23] The World Bank estimates that a rollout at scale of 217,000 mini grids to serve half a billion people by 2030 would avoid 1.2 billion tonnes of CO2 emissions.[4] The UNFCCC estimates that every megawatt-hour of electricity delivered to customers of mini-grids saves between 0.8 and 2.72 tons of carbon dioxide equivalent from being released into the atmosphere.[25]
Furthermore, the electricity mini-grids provide allows for more opportunities for social gatherings and events, which strengthen the community. Improved electricity also creates the opportunity to construct more buildings and expand the community.[23] Additionally, mini-grids have been shown to reduce the time spent on household chores such as collecting water and cooking fuel, which disproportionately benefits women and girls by freeing up time for education and other productive activities. This shift contributes to greater gender equality and empowers women with more opportunities for economic participation and decision-making in their communities.[1]
Although mini-grids have many benefits, there are also some drawbacks. There are some risks associated with their technology and organization as well as risks to the community they are implemented in.
Because of their complex nature, there are a few organizational risks associated with using mini-grids. In order to be effective, mini-grids must have effective business models to support their operations. There needs to be a steady flow of revenue to keep the business up and running and in order to keep providing customers with electricity.[23] Due to the remote and underdeveloped locations where mini-grids are typically implemented, it is difficult to transport supplies and skilled personnel to the areas they are needed. It is especially difficult when installing the system and when repairs are needed.[23]
Implementing a mini-grid into a community takes meticulous planning and cooperation between the people living in the area as well as the technicians installing the devices. There also needs to be communication among the community with regards to allotted energy quotas. Each user is typically assigned an energy quota to be used over a certain amount of time.[23] If some users over-consume the electricity, this leaves a deficit for the other users and could disrupt the entire system. The community must work in cooperation in order for the mini-grid to work successfully.[23]
Mini-grids provide communities with a reliable source of energy as well as many benefits to their economy. It is often too expensive for government electrical companies to attempt to bring electricity to undeveloped areas, and there is less potential for profit in these areas with poor economies.[26] Since mini-grids can operate separately from the larger national grids, private companies can implement them and provide rural communities with electricity more quickly than state-owned companies.[26]
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