At Principia, we remain firmly committed to accelerating the energy transition through innovation, technology and sustainable investments. As part of this strategy, we are completing our first Battery Energy Storage System (BESS) - a landmark project not only for our company, but also for the entire Greek energy market. The unit, commercially named “Themelio”, is located in Polygyros, Chalkidiki, and is one of the first BESS projects implemented in Greece, aligned with the national plan for grid stability and system electrification.
A Foundation for the Future
The name “Themelio” (meaning “foundation”) is no coincidence—it symbolizes the beginning of a new era for Principia, in which we expand beyond renewable energy generation and strengthen our technological diversification. At the same time, we reaffirm our commitment to sustainable investments and energy innovation, with the goal of maximizing the value of Renewable Energy Sources.
The “Themelio” Project in numbers
Construction began in April 2025 and was completed in September of the same year. The project has a power capacity of 49MW, an installed storage capacity of 127.04MWh, and a guaranteed storage capacity of 98MWh for two hours, delivering significant flexibility to the grid. This capability enables better balancing of supply and demand, enhancing the stability and efficiency of the power system.
The system consists of 26 Sungrow battery containers, each with a maximum capacity of 5,015 kWh and equipped with advanced CALB 314Ah cells. It also includes 13 Sungrow power stations with 5,140 kW transformers and 33kV medium-voltage switchgear, as well as two medium-voltage terminal substations that ensure smooth and secure grid interconnection.
Of particular importance is the fact that over 20,000 work-hours were completed with zero accidents, confirming our strict adherence to health and safety standards.
Benefits for the Energy System
Principia’s “Themelio” energy storage unit delivers tangible benefits to Greece’s energy system and market. First, it helps reduce curtailments from wind and solar plants-especially in grid-congested areas-by absorbing excess generation and injecting it back into the system when needed. It also enhances system stability by providing power during peak demand and ensuring smooth grid operation. In addition, the unit promotes energy decentralization, as it is located close to renewable energy production sites, contributing to the creation of a more flexible and intelligent energy environment.
Looking Ahead
With “Themelio”, we are taking on new technology, but this is just the first of many steps. We continue to invest in energy storage solutions and innovative technologies that will increase the value of renewable energy, ensure grid reliability and shape a clean, sustainable and resilient energy future.
