Mini Grids

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Definition and Overview

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.
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.

Technologies

Mini-grids can be powered with different technologies such as solar, hydro, biomass or wind and are also coupled with energy storage systems such as batteries. The most common types of mini-grid technologies are:

• Solar mini-grids: Solar mini-grids are gaining popularity due to the falling cost of PV modules worldwide. Since they can generate electricity only in the day time, battery storage is required to meet the peak demand at night.
• Wind mini-grids: When the wind blows through the turbine, the wind’s kinetic energy is converted into electrical energy. These mini-grids are site specific and depend on the wind speed
• Hydro mini-grids (MHP): MHP has the lowest levelized cost of generation and is at par with grid electricity. Unlike large hydropower, they do not require a dam/reservoir for water storage. They are mostly run-of-river and therefore have very little environmental impacts. The water flows from a higher elevation to the turbines at a lower elevation via a penstock. The turbines then rotate to generate electricity. The electricity generation depends on the water flow and also require a certain elevation. This makes MHP restrictive to a particular geography.
• Hybrid mini-grids: Mini-grids with renewables sources when coupled with non-renewable sources such as diesel systems or with other renewable sources are called hybrid mini-grids. These mini-grids are flexible as they can generate power on demand. Examples of hybrid systems are solar-diesel mini-grids and solar biomass mini-grids.

Impacts

Implementation of mini-grids have proved to have a positive social impact by fostering and improving the local governance structure through the involvement of the community in the decision making process linked with the energy system. Furthermore, mini-grids are often the only economically viable option of electrifying rural communities. There are hundreds of diesel-based isolated grids worldwide which lend themselves to be retrofitted with renewable energy technologies. Sharing limited resources and power among users in a mini-grid requires rules and a tariff structure that ensures sustainability in the operation. In general, mini-grids involve intense preparation to ensure the systems operation and maintenance will be sustainable.

Opportunities

There are a lot of opportunities that have been observed with mini-grid systems:

• They can be used to increase the reliability of electricity supply. Due to their small scale in nature and enhanced local level ownership of physical infrastructure or management, power theft which is a commonly associated with centralized on grid systems can be reduced.
  
• Reliability of supply is generally greater from hybrid mini-grid systems as compared to a single technology. This not only lowers the net costs over the lifetime of a project, but also ensures availability of power when one system is not working.
• There is environmental improvement from the use of mini-grids. This is in terms of efficiency and reduction in carbon emissions. Hybrid mini-grid systems, for example, often incorporate a 75-99% renewable supply.
  
• Economic assessments indicate that of the renewable technologies available, biogas, geothermal, wind and micro-hydro systems costing US¢6-15/kWh are the potential least-cost generation options for mini-grids in developing countries, this however assumes that sufficient renewable energy resources are available. Biogas digesters and biomass gasifiers are particularly promising from this economic perspective; this is because of their high capacity factor and availability in size range matched to mini-grid load. Geothermal on the other hand also appears economically viable for countries that have geothermal resources although it is limited to larger grid connected systems.
  
• For countries where the grid system is not well developed and there is a vibrant private sector, mini-grids provide opportunities and they are adaptable due to the fact that they can be connected to the grid as they expand.
  
• Conversely as the cost of fossil fuel increases, mini-grid systems are becoming more economically attractive as the cost of renewable energy resources decrease. However subsidies are still required for the different schemes but they are a smaller percentage of the investment than on-grid subsidies

Challenges

Despite the opportunities with mini-grids, their penetration remains low in most developing countries. Progressive development in mini-grids has been greatest in China where there is an estimated 60,000 schemes, and in Nepal, India, Vietnam and Sri Lanka which have 100-1000 mini-grids each. Majority of the schemes however use diesel or hydro power generation and are run and maintained by the government.

Common challenges for the implementation of mini-grids include:

• Lack of maintenance or the use of poor quality or untested technology. This could be as a lack of sufficient funding to sustain the project over its lifetime or the shortage of local skills for maintenance of the mini-grid.
  
• Insufficient primary energy resource, in bio gasification projects for example, there are challenges in finding sustainable sources of biomass and operating effective supply chains for biomass feed stocks. Similar challenges can affect diesel powered mini-grids in remote locations where infrastructure is not adequate, thus most of these schemes remain in their pilot stages (e.g. in Zambia).
  
• Poor assessment that is mostly compounded by lack of data on the local physical parameters that affect the power output and economics including:
  
  • Population density within the location of the mini-grid - This will have an influence on the load factor as well as the overall economics of the mini-grid.
    
  • Type of terrain - This will have an impact on the various resources required for the mini-grid i.e. the cost of infrastructure, fuel cost (for diesel systems) as well as the operation and financing of the system.
  • Seasonal resource fluctuations - This includes solar isolation, wind speed fluctuations and river flows.
  • Future policies - These policies are important in determining the future investment capacity in renewable energies, as an example, they should include suitable sites and an ambitious rapid rural electrification programmes.

• Development of schemes without attention to developing supplementary programes dealing with issues such as market access, small medium enerterprise (SME) development and working with local financing institutions, has contributed to a lack of demand and inability to sustain the schemes.

Operator Models

The mini-grids models can be distinguished into four types: utility model, private model, community model and public-private model.

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Financing Mini Grids

Building a sustainable financial structure can be challenging despite the vast and growing understanding of financial barriers in project development and an increase in financing tools. While mini-grids may stand out as being economically more attractive than grid connections especially in remote areas, they are usually accompanied by high upfront costs which are usually predominant in certain renewable generation technologies as compared to the conventional option such as diesel run generators. Financial schemes are designed in a way that they need to be able to pay for themselves in order to be sustainable and that is achieved by setting realistic tariffs for the consumers despite potential equality implications.

Funding of mini-grids in many countries has been mostly through grants and subsidies, this is in order to cover the upfront capital cost and sometimes the ongoing cost. Although this is a good method, it can prevent the development of sustainable electricity market if not carefully designed. For example, the ProSolar project of GIZ in Kenya provides incentives for investment through a results-based financing (RBF) intervention, funded by DFID and implemented through Energising Development (EnDev). It aims to provide incentives to project developers to create a market for mini-grid electricity generation and trigger private sector investment. Another approach that can be used is through the use of microfinance schemes, however there is a limitation to these mainly due to lack of coordination between the energy and the microfinance sector as well as high perceived investment risk within the financial institutions.

Investment barriers can also be experienced from complicated or out of date energy regulations such as those related to the process of tariff setting. For example, KFW has been using a negative concession system to identify providers (i.e. lowest price for a preset number of connections) in countries such as Senegal and Mali and to increase efficiencies in delivery. In practice, however, this has led to very long and complex procedures with high transaction costs that are unattractive to investors.
While mini-grids schemes help in increasing access to electricity in rural area at a significant scale in some countries where the poorer members of the community may remain without energy access, the evidence between the impacts of mini-grid systems and poverty reduction is limited. On the other hand rural electrification programmes indicate that they have often failed to improve access for poor people. This is due to their incapability of paying fees and tariff structures which can result to them paying more. For example, if minimum monthly payments are required, people may face higher costs through payments for reconnection or find it hard to make payments due to fluctuating income throughout the year. In schemes which target poorer people, elite capture in management systems can result in inequities in supply. These opportunities and challenges are likely to vary between the different business model approaches.

Further Information

• MIni-grid portal on energypedia
  
• Clean Energy Mini-grid Policy Development Guide
• Basic Energy Services - Overview
• Grid Portal on energypedia
• Facing the Operational Challenges of Mini-grids
• The Potential of Mini Grids and Critical Factors
• Mini-grid Policy Toolkit
• Mini-Grid load assessment and system sizing handbook
• ProSolar handbooks: Site selection, Mini Grid Licensing, Mini-Grid Sizing.
• ProSolar 2016 factsheets: ProSolar project, Mini-Grids Result Based Financing (RBF) project.