Pumped storage power plant - principle of operation
Pumped storage power plants (PSPP) allow you to store clean energy that is produced from renewable energy sources (RES). Therefore, it is an ideal solution for power grids dependent on energy generated by photovoltaic and wind farms. This technology stores excess energy during periods of low demand and releases it when demand is high.
How do pumped storage power plants work?
Pumped storage power plants involves using the force of gravity to generate electricity using water that has previously been pumped from a lower source to an upper reservoir. This means that water is pumped to a higher source during periods of high renewable energy production and lower demand, when electricity prices are low. However, during periods of high demand - higher electricity prices - water is released from a higher reservoir, drives the generator turbine in the power plant and delivers green electricity to the energy network.
Pumped storage power plants can be called hydroelectric batteries for storing solar and wind energy. The ability to store energy in this type of systems depends on the size of its two tanks (upper and lower), and the amount of energy produced is directly related to the size of the turbine. For example, a facility with two reservoirs roughly the size of two Olympic swimming pools and a 500-meter elevation difference between their levels could provide a capacity of 3 megawatts (MW) and store up to 3.5 megawatt hours (MWh) of electricity.
Types of PSPP
It should be noted that there are two main types of pumped storage power plants. They are divided according to the type of circulation:
- Open-loop power plants, that is with an upper or lower reservoir that is permanently connected to a naturally flowing water source, such as a river.
- Power plants with a closed circuit that occurs "off the river" and produces energy from water pumped into an upper reservoir without a natural inflow.
Advantages and disadvantages of pumped storage power plants
There are many advantages associated with the use of pumped storage power plants compared to the use of conventional energy sources based on fossil fuels. It is worth highlighting some of them:
- Low operating costs and long service life. Once built, pumped storage power plants are characterized by a long service life and minimal maintenance requirements. It is assumed that they can work for up to 80 to 100 years, with minimal service work.
- Renewable and environmentally sustainable. Pumped storage can be described as "green batteries". They are the only real way to store energy on such a large scale with such a low impact on the environment. This is due to the fact that they work thanks to the water cycle, which is powered by renewable energy sources. It is therefore a completely renewable source of energy production.
- Minimal impact on the environment. Hydropower is a clean energy source. There are no additional direct waste products from the pumped storage power plant after construction is completed. However, greenhouse gas emission in this type of facilities is negligible compared to coal and gas power plants, which have a negative impact on the atmosphere.
- Possibility to plan electricity production. In PSPP you can control the flow and generation of electricity. Turbines can be programmed to pump water into an upper reservoir - using excess cheap energy - and then generate electricity when needed, wasting the water's potential energy. This allows electricity to be produced for short-term needs when it is expensive.
- Additional use of large water reservoirs. Most hydropower installations have large upper water reservoirs. This means they can be used for e.g. recreational and tourist purposes. This allows for effective use of land owned by the state, increasing the economic development of areas adjacent to pumped storage power plants.
- Water supply and flood protection. Reservoirs with dams allow the regulation of water transfer. On the one hand, they can constitute a water reserve in the event of drought, and on the other hand, control its flow in the event of a flood threat.
Nevertheless, an important issue related to pumped storage power plants is the lack of appropriate land for the construction of two reservoirs and a pumping station with a significant difference in height. This aspect primarily generates a number of problems presented below:
- High cost compared to other technologies. The biggest problem with pumped storage power plants are the extremely high initial costs associated with their startup.
- Energy losses. The main disadvantage for the overall efficiency of the PSPP is the fact that during its operating cycle, water must be pumped from the lower to the upper tank. For this purpose, the power plant itself consumes electricity.
- Impact on water environment. For example, a fish population may be at risk due to obstacles to their migration. Additionally, combining previously separate reservoirs may introduce new animals to previously inaccessible habitats, which threatens endemic species.
- Impact on water quality. Hydropower reservoirs and dams or underground water reservoirs can deteriorate water quality and flow. Both of these issues, in turn, become the main causes of deoxidation of water reservoirs below the pumped storage power plant.
- Dependence on climate. Pumped storage power plants are certainly sustainable energy sources, but they depend on the climate, e.g. the occurrence of droughts. In addition, the production capacity of a pumped storage plant may decline due to evaporation and water leakage in hot and dry climates.
Pumped storage power plants in Poland
It should be noted that pumped storage power plants have been operating in Poland for years. They currently have 1.9 GW of power. These include installations:
- Żarnowiec - with a capacity of 780 MW and providing 380 MWh of energy. Completed in 1983.
- Porąbka-Żar - with 552 MW of power, providing 2,015 MWh of energy. Commissioned in 1979.
- Niedzica - having 92 MW of power and able to provide 12,500 MWh of energy. Launched in 1997.
- Żydowo - where the installed capacity is 165 MW and can produce 687 MWh of energy. Completed in 1971.
- Dychów - with 90 MW of power, providing 224 MWh of energy. Commissioned in 1936.
It is also worth mentioning the pumped tank power plant in Solina with a capacity of 198 MW and the ability to produce 39,744 MWh. It is not a classic pumped storage power plant, but there are plans to rebuild it and increase its capacity to 520 MW.
Power plant network
Expansion of the network of pumped storage power plants in Poland
Renewable energy (RES) somehow enforces the need to store energy. For this reason, investments planned in Poland are related to the construction of new PSPPs with a total capacity of 2.5 GW. It is worth mentioning here such projects as:
- Tolkmicko power plant, which capacity is to be 1,040 MW. This is an investment of PKN Orlen and is scheduled to be launched in 2029.
- Młoty power plant. This is to be the second new investment in our country, after the Tolkmicko power plant, in terms of installed capacity. Młoty Power Plant is a project of the Polish Energy Group (PGE) with a capacity of 750 MW, which is to be completed in 2030.
- Rożnów II power plant is the third largest new investment in terms of capacity, after the Młoty power plant, run by Tauron, scheduled to be launched in 2030. The Rożnów II power plant will have a capacity of 700 MW.
As you can see, these are large projects with high capacities that can constitute safe energy storage for the rapidly developing renewable energy market in our country.
Is it worth investing in pumped storage power plants?
To sum up, it is advisable to consider whether it is justified to build new PSPPs. Of course, they have some advantages and disadvantages, which were mentioned in more detail above. PSPPs will have their staunch supporters, and probably, due to the high construction costs and ecological aspects, there will also be opponents of this type of power plants. Nevertheless, hydropower and pumped storage are the safest way of storing energy in the world. It represents over 94% of installed global energy storage capacity, significantly outpacing all battery storage. Therefore, if you have no other alternatives, it is worth using this technology.