Through the green transition, our energy needs are being increasingly met with wind and solar power. However, due to the intermittent nature of renewable energy, our energy systems need to be balanced using back-up power from quick-start power plants or energy storage. While many think of batteries as the number one way of storing energy, large-scale batteries are just one option of many. Here are a few other energy storage methods and example projects from around the world.
Large-scale hydro-storage not far from Tervakoski Film’s factory
In hydro-storage, water is pumped from a reservoir to a higher elevation with excess electric power (e.g., from surplus wind energy on a windy day) to be later released through turbines to produce electricity. In this way, the energy used to pump the water is saved for a later day when the demand for it is greater and electricity prices are higher.
A large-scale example of hydro-storage can be found only 30 kilometres from Tervakoski Film’s factory in Svit. The Čierny Váh plant is Slovakia’s largest pumped storage plant and hydroelectric power plant, and it has been in operation since 1982. The plant’s upper water reservoir is located
1 160 metres above sea level, and thanks to a drop of 427 metres and seven turbo-sets, the Čierny Váh has an installed capacity of 735 MW and an annual generation of 200 GWh. The Čierny Váh plant can be up and running in only seven minutes, making it an important piece in the Slovakian and European energy puzzle with its ability to stabilize the grid and prevent blackouts.
Harnessing sun-heated seawater in Helsinki
In thermal storage, excess energy is used to heat or cool a material, so that the energy can be deployed later when needed. A simple form of thermal energy is sensible thermal energy storage, where, for instance, a water tank is heated up for later use. Other types of thermal power include latent heat storage, where the state of a material is changed (e.g., solid to liquid, liquid to gas), and thermochemical heat storage, where chemical reactions are used to store and release energy.
In Helsinki, a seasonal thermal storage facility is being built in the new seaside neighbourhood of Kruunuvuorenranta, which by 2030 will house 13 500 residents. Once finished in 2024, the facility will heat one third of the buildings in the neighbourhood by storing sun-heated seawater in two old underground oil caverns. Warm water will fill up the caverns in the summertime and be used as the energy source for the facility’s heat pumps in the winter. Thanks to the thermal storage facility, the carbon footprint of the residential neighbourhood will be close to zero.
Splitting water into oxygen and hydrogen with solar power in China
Power-to-gas is a chemical energy storage method where electricity is converted into gaseous fuels, such as hydrogen or methane. Green hydrogen is, for instance, created when excess solar or wind electricity is used to split water into oxygen and hydrogen in a process called electrolysis. The created hydrogen can be used as such in transportation and energy generation. The benefit of burning hydrogen as opposed to natural gas is that it does not release carbon dioxide.
In summer 2023, the world’s largest green hydrogen facility began operations in China. The Kuqa project in Xinjiang is built in connection to a 300-MW solar park. The produced solar energy is converted into hydrogen with 52 5-MW electrolysers. These have an annual output of 20 000 tons of green hydrogen, which will be used at a neighbouring oil refinery. The energy storage facility is expected to reduce carbon dioxide emissions by as much as 485 000 tons a year, which equals the annual emissions of over 100 000 passenger cars.
A supercapacitor made of concrete
Capacitors store energy in the electrostatic field between their conductive plates and can be used in some of the applications where batteries are used. Capacitors store less energy than batteries of the same size, but charge and release small amounts of energy more quickly. Researchers are working on developing so-called supercapacitors, which could be used to store and release energy from intermittent renewable energy sources using more conductive materials.
Researchers from the Massachusetts Institute of Technology (MIT) have recently created an energy-storing supercapacitor from cement, carbon black and water. The mixture creates a fractal-like structure with an extremely large surface area, which, when used in a superconductor, has remarkable storage power. According to the researchers, a 45 m2 block of the concrete can store about 10 kWh of energy, which is the average daily electricity usage of a household. If the foundation of a house would be built as a supercapacitor from this concrete, the foundation could store a day’s worth of electricity.