Depending on the natural assets and the configuration of the power system, hydropower plants can provide considerable amounts of flexibility.
As the share of distributed renewable energy sources rises (especially solar and wind), planning supply- and demand-side flexibility is becoming increasingly important. Depending on natural assets and the configuration of the power system, hydropower plants can provide considerable amounts of flexibility.
In future, flexibility requirements will increase further still. Microgeneration and demand will need backing from new technology solutions. The focus will move to digital platforms for smart grids in combination with additional energy storage units.
Reservoirs offer a high degree of flexibility.
By flexibility we refer to the ability of the power system to respond to load changes by adjusting its sources. Loads can either increase or decrease.
Thanks to the flexibility of hydropower generation, grid integration of distributed renewable energy sources is easier in power systems with a high share of hydro in their generation mix.
In hydropower generation, the main sources of flexibility include variation of water levels in reservoirs. The ability to shut down or start a generation unit at short notice makes hydropower plants an important link in the flexibility chain.
An additional mechanism to provide flexibility is the ability of a hydropower plant to spill water, although this is a largely undesired measure as the energy is lost to the environment.
Operational and environmental constraints on flexibility in hydropower generation
When estimating the potential of hydro generation to provide flexibility, one needs to consider operational and environmental constraints and the water cycle. As a source, hydro power is entirely dependent on environmental factors, especially rain, or in wintertime on snow.
To be able to integrate hydropower sources in flexible energy systems, power industry professionals need a wealth of expertise and experience, and a great deal of historical data. One of the criteria that hydropower generation operators have to satisfy is ecological flows, i.e. the minimum amount of water required for the aquatic ecosystem in rivers to continue to thrive.
Types of hydropower and flexibility
Hydroelectricity is electrical energy that has been generated using natural forces, i.e. water’s kinetic energy. Hydro energy is converted into electricity by means of turbines and generators. Hydropower is one of renewable energy sources. Renewables are considered environmentally-friendly energy because no greenhouse gases are emitted in the atmosphere as they are transformed into electricity.
Types of hydropower:
- Storage hydropower plants store water in reservoirs, i.e. natural or artificial lakes. Such lakes usually have a considerable impact on the environment. On the other hand, by providing energy storage to the system, they are very important in offering flexibility on the supply side.
The largest dam in the world – the Three Gorges Dam – spans the Yangtze River in China. With a dam wall rising 181 metres high, the power station has 34 generators with a total capacity of 22.5 GW.
- Run-of-river/storage hydropower is a combination of run-of-river and storage hydropower plants. Such plants are usually constructed as a cascade of several facilities.
- Pumped-storage hydropower plants pump water uphill into reservoirs when prices of electricity, which is needed to pump the water, are low, to be released for generation when demand is high and electricity prices rise.
With their reservoirs, pumped-storage hydropower plants make large energy storage units, and will play an important role in the decentralised smart grids of the future. The largest pumped-storage hydropower plant in the world is Bath County. Also described as “the largest battery in the world”, the plant has a reservoir that can hold 43 million cubic metres of water, and six generators with a total capacity of 3003 MW.