A flexible energy system balances seasonal changes

The production and consumption of energy vary depending on the time of year. People use more energy in the winter as homes are heated to keep away the cold – especially in the Nordic countries, where the winters can be very cold. In warmer countries it is the opposite: peak electricity demand can occur during a hot summer day due to wide-spread use of air-conditioning. Intermittent power sources such as wind and solar need to be balanced since they do not always produce electricity when it is needed.

Solar and wind power parks

Energy consumption changes according to season, day of the week and even the time of day, as people turn on their various devices and kitchen appliances at the same time in the morning. The energy system needs to be able to respond to these changes and provide sufficient energy at all times. This means that production volumes must be adapted or energy storage solutions used to keep the balance. There is more solar power produced during the summer and more wind power in the winter. What they have in common is that the production varies significantly and can only be predicted as long as weather forecasts are reliable.

Hydropower is the key enabler for more wind and solar in the Nordics

The Nordic countries stand out from the rest of the world with a large share of flexible hydropower thanks to their geography with high mountains, rivers and lakes. Hydro reservoirs make it possible to store huge amounts of energy for later use. In the spring and summer, the snow melts and reservoirs fill up. During the winter or on a day when there is no wind or sunshine, the energy stored in the reservoir can be used to meet the demand. The annual consumption of electricity in the Nordics is close to 400 TWh, and more than half of that is covered by hydropower (220 TWh). The hydro reservoir act like huge batteries and can store 125 TWh of energy.

Gas power is the main source of flexible power in Central Europe

In Central Europe, natural gas is currently the most prominent energy form used to balance supply and demand. Similar to hydro, gas storages are filled up in the summer and emptied during the winter. The gas is not only used for power generation but also in the industrial sector and for producing heat. The share of renewables steadily continues to increase in Central Europe, but fossil-fired power plants still step in when wind and solar generation is low.

New interconnectors between countries contribute to the integration of European power markets. This makes it possible to transfer electricity across long distances. The Nordic countries are connected to Germany, Poland, Estonia, Russia, Netherlands, Lithuania and soon the UK. Depending on need and availability, electricity is either exported or imported. For example, on a windy day in Germany, power is exported to Sweden and Norway, but when the wind stops the flow switches direction as water stored in Nordic reservoirs is used to meet the demand.

Looking ahead

Utilities use models to predict the future demand for both electricity and heat. In the short perspective, weather is the largest uncertainty. In the longer run, electricity demand is expected to increase significantly due to the electrification of the transport sector and several industrial sectors as well as population growth. At the same time, the share of renewables and thereby less predictable energy in the system will continue to grow. While hydropower will remain the backbone for balancing the Nordic energy system, the challenge is much greater in Central Europe. In the Nordics, hydropower will enable continued significant increase of intermittent renewables to meet new demand.

As decarbonisation progresses, Central Europe will have to replace natural gas and coal with renewables. Production of hydrogen through electrolysis will likely be part of the solution. Excess production from wind and solar will then be used to produce hydrogen. Hydrogen could be used in many ways, for example as a replacement for natural gas. It can also be converted back to electricity even though losses occur at every step of the process. As processes are developed further and technology costs fall, we may see hydrogen taking a key position in the energy mix.

Developing the grid so that, for example, windier regions can support those where wind power is less productive would also be a step towards better energy security. New IT solutions, such as smart charging of EVs, will make the demand side of electricity more flexible without any impact for the end user. Energy storages solutions such as batteries are likely to remain expensive. But it all comes down to having sufficient plannable power generation as the basis of the system, so that the whole does not become too unpredictable. Households, factories and businesses must be able to trust that there is enough energy at all times of the year, in any weather.

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