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What are microgrids?

Last updated on 19 November 2018

As their name suggests, microgrids are small-scale versions of standard grids. They supply locally produced energy directly to a group of users.

Microgrids are a type of subsystem which are only connected to the general grid at a single point. This connection acts as a switch that makes it possible to disconnect a microgrid from the public grid (should there be a power failure, for example) and operate it temporarily in island mode.

How do microgrids work?

In order to work, microgrids must include three essential components:

  1. locally produced energy to ensure they can operate independently in the event they are disconnected (photovoltaic panels, wind turbines, cogeneration, heat pumps, biomass plants, hydroelectric turbines, etc.) and an additional back-up supply of energy (power generators). In theory indeed, microgrids can go completely off the grid, but so far this rarely occurs in practice;
  2. a storage system: batteries, a supply of water for pumped-storage hydroelectricity and, in the future, supercapacitors and a chemical-based latent-heat storage system;
  3. a smart management system to ensure the continuous balance between electricity generation and demand.

Smart management of microgrids

In the same way as smart grids, microgrids do not simply transmit energy – they transmit information as well.

Using this information, these grids can manage themselves via automated computer applications which take into account:

  • peaks in demand and production;
  • tariffs that vary according to the time of day and the weather conditions;
  • the production capacity of wind turbines, solar panels and hydroelectric power plants.

Depending on the circumstances, these computer applications can therefore decide to disconnect a microgrid from the main grid, begin charging an electric car or, conversely, feed the energy in the batteries back into the grid.

This computer-based management aims to maintain the equilibrium of the microgrids and use the energy as efficiently and cost-effectively as possible.

In what cases can microgrids be useful?

We find it so normal, but not everyone in the world is connected to a mains power supply network. Then again, in other areas, the network's reliability is often lacking, and that's when a microgrid can come in useful. Here are a few examples:

Remote 'Off-grid' microgrids

Due to economic issues or their unfavourable geographic location, it is impossible to connect some regions to a public power supply. The microgrids installed are then never connected to the macrogrid and constantly work in island mode.

Military microgrids

A reliable network is crucial for the physical and cyber security of military operations. The military therefore creates microgrids so the troops are not dependant on the public power supply.

Industrial microgrids

For some production processes, interruptions to the power supply or a very long start-up time can result directly in high losses of revenue. Microgrids are also a remedy for such essential industrial processes.

The energy production unit should, however, consist of an emergency group that runs on fossil fuel to ensure 100% reliability. Not exactly environmentally-friendly then.

And in cities?

Public electricity networks in Western urban areas are extremely dense and also closely monitored. Because macrogrids are highly reliable, microgrids are virtually unnecessary.

However, efforts are being made to introduce renewable energy into urban environments, too. This is possible through collective self-consumption, for example, where consumers and producers come together as part of a local project (association, cooperative, co-ownership, etc.).

The principle is simple. Let's say you want to generate sustainable energy, but you're renting an apartment, living in a protected building or your roof isn't suitable for solar panels. You can still form a cooperative with other individuals and generate electricity on the roof of a neighbouring school, office or warehouse, for example.

In Brussels, the distribution network operator Sibelga and Leefmilieu Brussel are examining the possibilities for collective self-consumption in the capital city.

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