The combination of extreme heatwaves and drought presented a massive stress test for the power systems of Southeast Europe. Low water resource availability, operational restrictions on nuclear power plants, and high electricity demand for cooling increased pressure on the transmission grid. According to analysts, the system coped with the crisis better than expected, but it simultaneously exposed shortcomings in flexibility, cross-border cooperation, and grid resilience.
This summer tested the ability of Southeast Europe’s power sector to handle a combination of multiple adverse factors. Heatwaves with temperatures hovering around 40°C occurred simultaneously during a drought period, which restricted hydropower generation and the availability of certain nuclear units. According to Greek electricity market analyst Konstantinos Pappas, it was a comprehensive system-wide stress test.
Although he noted that the system adapted to the situation better than originally expected, the crisis revealed deficiencies in regional flexibility. Pappas stated that flexibility essentially became an internationally traded commodity during this summer. The importance of cross-border cooperation grew significantly at moments when some countries had an electricity surplus while others faced a deficit.
The Role of Batteries and Renewables
Bulgaria played a significant role. According to Pappas, the country has battery energy storage systems with a total power output of approximately 6 GW and a capacity of 16 GWh, which were increasingly utilized as a regional flexibility hub. Batteries stored cheap electricity from photovoltaic power plants during periods of high generation and subsequently released it during evening peaks. They primarily helped stabilize the situation in Romania.
Regional stabilization was also aided by high surpluses from renewable energy sources in Greece. Electricity exports from Greek solar and wind farms helped balance differences between generation and consumption in neighboring countries.
Conversely, the situation was complicated by high gas prices, which increased the cost of generation from gas-fired power plants. At the same time, electricity consumption grew due to cooling needs, and the evening drop in solar generation created sharp changes in system load.
Heatwaves Reduce Transmission Capacity of Power Lines
The stress was not limited to electricity generation. Goran Levacic from the Croatian transmission system operator HOPS pointed out that high air temperatures reduce the transmission capacity of power lines, increase conductor temperatures, and cause conductor sag. Simultaneously, transmission losses rise and equipment aging accelerates.
"Heatwaves reduce the transmission capacity of overhead lines because higher air temperatures increase conductor temperatures and sag, increase losses, and accelerate equipment aging," Levacic stated.
Transmission system operators responded by evaluating several measures, including requirements for battery flexibility and demand-side response, dynamic line rating (DLR), improved weather monitoring, and replacing conductors on critical lines with high-temperature low-sag (HTLS) conductors.
Grid planning is also increasingly incorporating extreme weather scenarios. For example, operators must assess whether the system can handle the outage of a major transmission line during extreme heat and plan infrastructure reinforcements or power flow redirections accordingly.
This year's situation in Southeast Europe shows once again that with the growing share of renewables, power system flexibility will be an increasingly critical topic.
Jiří Dvořák
Partner, Advisory
Key Will Be Better Utilization of Existing Resources
According to Pappas, the short-term solution will not be solely the construction of new power plants and cross-border lines, as major generation and infrastructure projects are unlikely to be completed before next summer. Therefore, the priority must be the faster deployment of flexibility that the region already possesses.
This primarily means accelerating the connection of battery storage systems and their integration into balancing and ancillary service markets. Industrial consumption management, more accurate forecasting of renewable energy generation and electricity consumption, and closer coordination among transmission system operators should also gain a more prominent role.
Analysts note that batteries are not meant to replace pumped-storage hydroelectric power plants, but rather complement them. Battery storage systems can respond very rapidly and are suited for short-term fluctuations. Conversely, pumped-storage plants can serve to "shift" large volumes of electricity over a longer time horizon and stabilize the system.
From a long-term perspective, Pappas argues it will be necessary to strengthen cross-border transmission capacities and make more efficient use of European balancing energy trading platforms, notably PICASSO and MARI.
Commentary from Our Specialist
"This year's situation in Southeast Europe shows once again that with the growing share of renewables, power system flexibility will be an increasingly critical topic. At Grant Thornton, we participate in this transformation, for example, in the CARMEN project in Romania and Bulgaria, where we support the preparation and implementation of investments in the modernization and digitalization of transmission and distribution grids. We are also involved in the Czech-German GABRETA project, and under the TUNE project, we are supporting the preparation of a CEF grant application for a cross-border transmission grid project involving Slovenia, Slovakia, and Hungary. These projects clearly demonstrate that enhancing flexibility is not just a matter of battery storage, but also of higher-capacity, digitalized, and better-interconnected grids," says Jiří Dvořák, Partner, Advisory.
This text was originally published on oenergetice.cz.
This text was translated by AI.
