07.09.2017 | How fluctuations in production and consumption are managed

Magic with control energy

What happens when power demand suddenly or unexpectedly peaks? Or when large, energy-intensive companies have to abruptly stop their production. That's where control energy comes in. It serves to balance out these types of unforeseeable fluctuations in production and consumption. Control energy? Find out more here.

Because it is (still) not possible to store electricity in large quantities, production and consumption must be in a constant equilibrium. This is the prerequisite for a stable power grid and ensures continuous power supply - at a frequency of 50 hertz (Hz) in Switzerland and Europe. However, this frequency fluctuates: If electricity consumption is higher than production, the frequency is below 50 Hz; if consumption is lower, it is higher than 50 Hz.

In Switzerland, the national grid company Swissgrid monitors the balancing of variances in the electricity system and ensures a stable grid. See when Swissgrid has to intervene here. Find out the current frequency here.

Two different markets

Fluctuations in electricity demand can be foreseen to a certain degree, for example somewhat higher consumption during cold weather (heating) and very hot weather (air-conditioning), or less demand on weekends when production is much lower and offices are closed. These fluctuations are taken into account in power generation and in trading on the power exchanges.

However, when unexpected fluctuations occur, control energy is required. Control reserves are traded on a separate market in different control zones. As a rule, there are three types of control reserves that the grid company can fall back on when needed. Primary control energy is used to balance out minimal fluctuations in the power grid in a matter of seconds. Suppliers, usually large hydropower plants, make it available automatically and is must be possible to retrieve it within 30 seconds. Procurement for Switzerland's primary control reserves (+/- 68 MW) takes place by means of a weekly tender between Austria, Germany, Holland and Switzerland. This cooperation is called "FCR Cooperation".

Balancing energy to stabilize power grids
Secondary and tertiary control

Secondary control comes into play in the case of a power plant outage or when an industrial company suddenly procures a great deal of power. Secondary reserves (+/- 400 MW) must be made available by the transmission grid operators within 5 minutes to relieve the primary reserve during longer grid fluctuations. Balancing such fluctuations usually takes place on the national level. Tertiary control, also known as minute reserve, must be available within 15 minutes.

Axpo is active

Logically, control energy is more expensive than the normal base load energy traded on the exchange. Technical requirements to make primary and secondary control energy available are quite high. The costs are invoiced to end customers under the tariffs for grid utilisation and ancillary services.

Axpo also participates in the control energy market (ancillary services market) in Switzerland and Europe with its power plants. For example, Axpo holds interests in three gas-fired combined-cycle power plants in Italy. The Calenia and Rizziconi plant were refurbished in recent years with investments of some CHF 32 million. Initial experience indicates that thanks to the flexible use of gas-fired combined-cycle power plants, good revenues can be generated on the control energy market. The new Limmern PSP could also be a new trump card for Axpo in terms of the control energy market in Switzerland and Europe.

More information on control energy and additional good explanations on energy issues can be found here in RP-Energielexikon.

Rizziconi gas-fired combined-cycle power plant: Used for production of balancing energy

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