Immediately after New Year’s Eve 2017, between 3 a.m. and 7 a.m. of January 1, 2018, Germany’s power output from renewables was equal to the country’s electricity use. What does this mean exactly and what can we learn from it?
At midnight on December 31, 2017, five main energy sources contributed to Germany’s electricityForm of energy resulting from the movement of charged particles (electrons) through a conductor... output: wind firms, particularly those located along the Baltic Sea, biomassIn the energy sector, biomass is defined as all organic matter of plant or animal origin... power plants, hydropower plants, coal- and gas-fired thermal powerIn physics, power is the amount of energy supplied by a system per unit time. In simpler terms, power can be viewed as energy output... plants, and nuclear power plants. Since it was nighttime, no electricity was generated from solar farms. The overall mix was typical of that used to ensure the security of a grid. Electricity generation data can be followed in real-time on the SMARD interactive website, which was launched in summer 2017 by German energy operators.
- After 3 a.m., the already strong wind picked up even more.
- From 6 a.m. to 7 a.m., wind turbines generated 35 gigawatt-hours (GWh) of electricity. Six additional gigawatt-hours were supplied by biomass and hydro, representing a total contribution of 41 GWh from renewable energies.
- Within the same time period, thermal power plants running on fossil fuels (primarily coalCoal is ranked by its degree of transformation or maturity, increasing in carbon content from... ) contributed 8 GWh and nuclear power plants generated 4.7 GWh. When combined with other conventional sources, such as incinerators, total electricity output reached 58 GWh.
- At the same time, electricity use fell to a very low level due to the slowdown that generally overcomes a country in the hours following New Year’s Eve celebrations. Power consumption amounted to 41 GWh for total production of 58 GWh, 41 GWh of which was sourced from renewables1.
European countries exchange electricity among themselves, with some regularly exporting more than 10% of their national output.
Based on this data, some media outlets proclaimed that Germany had run solely on renewables for a full hour. However, this is not entirely true, as output included some electricity sourced from fossil fuels and nuclear power. Would it have been possible to “turn off” the country’s seemingly superfluous coal-fired and nuclear plants? No, because while the output of hydro and biomass is predictable, that of wind depends on how strong the breeze is blowing. It should be noted that, at noon, the wind died down considerably, which means that it would have been too risky to rely solely on this source of energy. This situation summarizes the issue of the intermittency of wind and solar power in a nutshell.
So what did Germany end up doing with its 17 GWh of surplus power? It exported it to neighboring countries, with 6.4 GWh going to France, 5 GWh to Austria and 2 GWh to Denmark.
France received the incoming electricity without any issues, as shown by the graph – also in real-time – published by the French electricity transmission system operator (RTE)2.
Throughout the night and even the entire morning, France imported significant amounts of electricity from Germany (between 3,300 GW and 7,700 GW), but also exported it to Italy, Spain, Switzerland and the United Kingdom. In the afternoon, France then imported electricity from Spain while this time exporting it to Germany.
In effect for several years now, electricity exchanges between European countries are beneficial in many ways. For one, they provide a form of mutual assistance in the event that a country experiences a drop in output. In addition, interconnections help put the most competitively priced resources available at a given moment onto wholesale markets.
Exchanges also make it possible to more effectively regulate the integration of inherently intermittent wind and solar power into the grid. If there is no breeze blowing on the Baltic Sea, it may be turning wind turbines in southern Spain, meaning that combining electricity output onto a single grid can be beneficial to all. However, it is worth remembering that, although rare, there are periods of very low renewably sourced electricity generation across the entire European continent, due to little sunshine and almost no wind. If a cold spell occurs at the same time, it is difficult to meet peak demand.
(1) See the graphic on the website of the German Federal Network Agency (in German only)