Given the geographical conditions of the Czech Republic, the future of Czech energy lies in a combination of nuclear power and renewable sources. However, the energy mix will also need to be complemented by flexibility provided by combined-cycle gas turbine (CCGT) plants and battery systems. Alongside the massive expansion of photovoltaics, wind energy has long been underestimated in the Czech Republic, according to Ing. Luděk Dušek, Technical Department Manager at ČEZ.
“Photovoltaics and wind energy complement each other very well in terms of generation hours. However, the Czech Republic is unfortunately significantly behind in wind energy compared to photovoltaics. On the other hand, at ČEZ we already have projects for wind power plants prepared. These represent 1,300 megawatts,” said Mr Dušek, adding that ČEZ currently has a total of 65 wind farm projects ready, which are intended to help stabilise production during periods without sunlight. However, preparations are also slowed by local opposition, as residents do not want wind turbines near their properties.
ČEZ plans to replace electricity and heat from gradually decommissioned coal-fired heating plants—being phased out—with primarily gas-fired sources by 2030. These represent an ideal combination of electricity and heat generation and are therefore economically optimal.
“We estimate that after coal is phased out, we will need to add 3.5 to 5.5 gigawatts of capacity in the Czech Republic. Approximately 1.4 GW will be covered by ČEZ through the transformation of heating plants to gas,” said Mr Dušek. Another 1 gigawatt may be provided by operators of other heating plants, with the remainder accounted for by purely power-generation sources.
ČEZ will build two combined-cycle gas plants in Mělník. The first is expected to be operational as early as 2029. With both units, the Mělník site should reach a total electrical output of over 800 megawatts, along with approximately 430 megawatts of heat output. Another CCGT plant is being prepared in Trmice, with a planned capacity of 150 megawatts of electricity and 100 megawatts of heat supply.
The duck curve and innovations in energy storage
With the expansion of photovoltaic power plants, whose production does not align with daily consumption patterns, the typical daily curve of PV generation and grid load resembles the shape of a duck (the so-called duck curve).
To use renewable energy generated during the day efficiently, it must be shifted to periods of higher demand. From this perspective, the implementation of energy storage technologies is essential for greater utilisation of renewable sources, with battery-based technologies currently playing the primary role.
At present, China accounts for nearly 85% of the world’s battery cell production capacity. ČEZ is also investing in energy storage systems and has already launched tenders for large battery storage facilities in Prunéřov (with a planned capacity of 70 MW / 140 MWh) and in Dětmarovice (200 MW / 400 MWh).
However, battery systems are not the only option for energy storage. A wide range of alternatives exists at various stages of development and commercial readiness. Aside from fully developed technologies such as pumped-storage hydropower, promising solutions—particularly those that have seen significant recent progress—include storage based on potential energy using a crane-like principle. When electricity is cheap, a crane lifts massive concrete blocks. When demand is high, the blocks are lowered. Gravity drives a generator, producing electricity and feeding it back into the grid.
“This system is characterised by very high efficiency. It targets storage capacities on the order of several hours and can deliver energy within seconds of receiving a request. In terms of technical parameters, it competes with battery systems. Another advantage is its long lifespan,” explained Dr Jan Opatřil, an expert in thermal sources at ČEZ.
Another interesting technology is storage using liquefied air. Its lifespan is similar to that of the crane-based system, at around 35 to 40 years. Unlike the crane system, however, this method experiences losses in standby mode. The principle is as follows: charging occurs by compressing air, which is then cooled and liquefied. The liquefied air is stored, though some losses occur despite insulation. Discharging works by evaporating the air, which then expands through a turbine. The system achieves an efficiency of 50–60 per cent.
“What is remarkable is that this system is not dependent on natural conditions, unlike pumped-storage plants. It can be built anywhere and does not use any toxic substances—the working medium is simply air,” emphasised Dr Opatřil.
Another technology is based on a similar principle to liquefied air but uses CO₂ as the working fluid in a closed cycle, meaning it requires only a one-time charge. This type of storage is being developed by an Italian company founded as recently as 2019, which launched its first pilot project with a capacity in the megawatt range in 2022. Its first commercial unit was commissioned approximately six months ago. The system’s efficiency ranges between 70 and 80 per cent, with storage capacity of around 10 hours and a lifespan of about 30 years.
“We can imagine it as something like an inflatable double-layer sports hall filled with CO₂ at nearly atmospheric pressure. During charging, CO₂ is extracted, compressed, liquefied, and stored in tanks. Discharging works in reverse, with expansion through a turbine, and the CO₂ in gaseous form returns to the ‘sports hall’,” explained Dr Opatřil.
Physics Thursday with ČEZ thus demonstrated that the future of energy lies in complementing nuclear power with renewable sources. The ability not only to generate energy but also to store it efficiently and use it at the right time will be key to a successful transition towards climate neutrality.
