(In)dependent of weather and wind conditions
With an increasing need for green electricity, Denmark is having to expand the electricity grid with 2,700 km of cables by 2030 and an additional 3,000–4,000 km of cables by 2050. At the same time, Denmark will have to build a large number of wind farms and solar cell plants to keep up with the increasing need for clean energy.
Transitioning to a system that draws all its energy from renewable energy sources presents several technological production, storage, and distribution challenges that must be solved. Among these, the new technologies must be integrable on a large scale, something which is not possible at the moment.
Electricity production from renewable energy sources cannot be controlled in the same way as a coal-fired power plant or gas turbines. Fluctuations in wind and weather conditions set an upper limit for how much electricity a wind turbine or a solar cell system can produce.
Renewable energy sources also generate varying amounts of energy during a day and depending on the season. One of the challenges in achieving 100 per cent renewable energy in the electricity grid is therefore also that the cables are not fully utilized.
When production from solar cells and wind turbines is at its maximum, the cables must be able to transmit the electricity, and it must be possible to store the excess power. When darkness falls or winds are calm, on the other hand, not enough energy is generated to utilize the cables’ maximum capacity.
It must be possible to step up production
Because we cannot control the weather, we need to develop technologies and energy systems that can ensure a stable power grid and a reliable electricity supply to consumers around the clock, all year round.
An important part of the solution is a hybrid power plant that combines several renewable energy sources and ways of storing energy. This will help to make it possible to control electricity production independently of the wind and weather, and step it up and down so that the electricity supply remains stable and the capacity of the cables can be better utilized.
When wind, solar, and storage are managed together in hybrid power plants, much more wind and solar can be connected without the risk of overloading the grid. This is possible because there is rarely maximum production from wind and solar at the same time, and because the controls at the hybrid power plant ensure that excess production is either stored or limited so that the electricity grid is not overloaded.
In this way, hybrid power plants can reduce the need for supplementary electricity production from fossil energy sources such as gas and oil, reduce the amount of energy generated from renewable sources that is wasted, and limit the need to expand the electricity grid.
Interplay between technologies is crucial
Initially, the hybrid power plant consists of two solar cell plants, two wind turbines, a high-capacity storage battery and an advanced interface to the electricity grid.
The hybrid power plant harvests the energy and stores any surplus energy in a battery, which can be used when production from renewable energy sources is low. It is expected that other technologies such as electrolysis and Power-to-X can also be included in future phases of the new, advanced test facilities.
The system is connected to the electricity grid. The electricity produced is dispatched into the electricity grid, contributing to the overall Danish electricity supply. Although Risø Hybrid Power Plant is a small plant focused on research, it will be able to produce almost 1 GWh per year, corresponding to the annual consumption of almost 200 households.
In comparison, future commercial full-scale hybrid power plants will be able to supply hundreds of thousands of homes. Researchers from both universities and companies can test production, storage, and control across energy sources.
"The new facility will play an important role in developing and testing new technologies before their scale-up for use in commercial hybrid power plants. This makes the new test facility a useful tool to ensure 100 per cent green energy, says DTU scientist and head of the DTU-TotalEnergies Excellence Centre for Clean Energy (DTEC) collaboration, Dr. Gregor Giebel.
"It will provide greater insight into the interplay between renewable energy sources in the electricity system so we can utilise and store renewable energy more efficiently in future while ensuring a stable electricity supply to consumers. For example, developing technical-economic methods to design and control hybrid power plants optimally,” Gregor Giebel says.
