Why does the electricity grid have to stay in balance?

The amount of electricity fed into the electricity grid must always be equal to the amount of electricity consumed, otherwise there's a black-out.

With the increase in renewable production, which can vary greatly depending on the weather, this has become much more complex.

Conventional power plants have to compensate for these constant fluctuations, especially since it is not possible to store electricity in large quantities over a long period of time.

How is this balance measured?

The equilibrium point for the European network, which operates on alternating current, is at a frequency of 50 Hertz. In the USA, the reference frequency is 60 Hertz.

Grid operators ensure that this frequency remains stable 24 hours a day, 7 days a week. The tolerance threshold is plus or minus 0.050 Hertz.

What happens if there is an imbalance?

Too much electricity, low demand

If too much electricity is fed into the grid in relation to the quantity consumed, the electrical frequency increases.  Since power plants are designed to operate within a certain frequency range, there is a risk that they will disconnect from the grid after a period of time. .

High power demand, low energy availability

If we feed in too little to meet demand, the frequency drops. From 49 Hz, the automatic load shedding plan is activated in order to avoid power cuts. This is because, if the frequency falls too much, the power plants switch off one after another, until there is a complete collapse of the grid, i.e. a power blackout.

Who is involved in managing the balance on the grid?

• Elia is the Belgian high-voltage transmission system operator (TSO). The TSO ensures a minute-by-minute balance between production and electricity consumption 24 hours a day, 7 days a week. It is responsible for providing a reliable network for long-distance transportation and electricity imports/exports.
   
• Access responsible parties (ARPs) are appointed for each point on the high-voltage grid where electricity is drawn off or fed in. They may be electricity producers, large consumers, suppliers or traders. They are also appointed by energy suppliers for some or all of their customers connected to the distribution grid. These ARPs are responsible for balancing the feeds and withdrawals of electricity by users in their portfolios every quarter of an hour.
   
• Producers of electricity feed electricity into the grid. It should be noted that more and more private consumers are also producing electricity using solar panels.
   
• Consumers affect the balance by consuming different quantities of electricity at certain times. We therefore play an active part in the balance on the grid, often without knowing it.

How can we act to maintain the balance?

1. Decreasing or increasing electricity production

We can temporarily regulate (upwards or downwards) certain power stations or start up reserve power plants. Gas reactors (CCGT - combined cycle gas turbine), which are highly reactive, play an important role here.

2. Reducing electricity use

Agreements are made with certain professional customers (consumers and prosumers). Where there is a risk of imbalance on the grid, these industrial customers agree to regulate their consumption and/or their production for a certain time. In return, they receive financial compensation.

In the longer term, grid operators could also influence consumer behaviour by modifying prices to smooth consumption. Already today, private consumers are encouraged to use electricity more cheaply (dual hourly tariff) when industrial customers are consuming less. Another example: the quarter-hourly rate system discourages industrial consumers from having excessive consumption peaks.

The development of smart meters could allow us to go further in implementing tariffs adapted to real-time conditions.

3. Importing or exporting electricity

As the Belgian grid is interconnected to a large European network, neighbouring grid operators can also be called upon to import or export electricity.

4. Load shedding

Load shedding consists of temporarily depriving some electricity consumers of supply to avoid widespread power cuts. This solution is only used as a last resort.

5. Storing electricity

This solution is not yet possible on a large scale on the grid. But in the future giant storage batteries in containers could act as buffers – several projects of this kind are under way. A large array of small domestic batteries connected to the smart grid could also play an important role. Electric vehicle batteries could have a similar effect.

Storage projects aim at smoothing the load on a 24-hour cycle – for example by charging batteries during the day when the solar panels are at maximum production – and returning the electricity during the evening peak.
With current technologies it is not possible to store electricity in summer to return it in winter.