Chalkidiki is becoming the heart of Greece’s energy transition

Published: Updated: Estimated reading time: 3 minutes
grecja
Source: Shutterstock

Greece completes milestone 49 MW battery storage project in just six months

In just six months, Greece has taken one of its most significant steps toward building a modern, flexible power system. In the Chalkidiki region, in the picturesque mountain area of Vouno near Polygyros, the Themelio energy storage project has been completed — the first fully operational Battery Energy Storage System (BESS) developed by Principia.

This 49 MW / 98 MWh facility carries importance that extends far beyond its local scale.

“Themelio” — laying the foundation for a new energy era

The name Themelio is no coincidence — in Greek, it means foundation. The project indeed represents the cornerstone of Principia’s strategic shift toward energy storage and advanced grid technologies.

The company, a joint venture between Italy’s Enel and Australia’s Macquarie Asset Management, has so far focused mainly on renewable energy generation. Now it is expanding into a sector that is crucial for grid stability and flexibility.

Construction of the entire battery infrastructure was completed between April and October 2025, with commercial operation scheduled for December 2025. The six-month timeline demonstrates that BESS projects can be deployed faster than most traditional energy investments.

Technical parameters and system architecture

The Themelio system offers 49 MW of power and an installed capacity of 127.04 MWh, with 98 MWh guaranteed availability for two hours of operation. It uses Sungrow’s PowerTitan technology, known for its high reliability and scalability.

The installation includes:

  • 26 battery containers, each with a maximum capacity of 5,015 kWh, using CALB 314 Ah cells
  • 13 Sungrow power stations with 5,140 kW transformers
  • 33 kV medium-voltage switchgear and two main substations ensuring stable grid integration

An impressive safety record underscores the project’s execution quality — over 20,000 working hours without a single incident. This is not only a mark of strong HSE standards but also a reassuring signal for investors and policymakers planning similar projects.

Financing and business model

The investment is valued at €28 million, with Principia funding half from its own capital and the remaining half through a Eurobank loan. The project received government support under Greece’s second energy storage auction (2024) via a Contract for Difference (CfD) mechanism.

This structure provides revenue predictability and financial stability, both essential in the still-developing Southern European BESS market. Themelio belongs to the first wave of projects implemented under a new, more flexible regulatory framework that promotes subsidy-independent investments and simplifies grid connection processes.

Strengthening the power system

Beyond the impressive figures, the true strength of Themelio lies in its system-wide impact. A storage facility of this scale helps to:

  • Reduce curtailment losses from wind and solar plants during periods of excess generation
  • Stabilize the grid during peak demand
  • Increase autonomy and resilience of networks in areas with high shares of distributed generation
  • Support energy decentralization, especially in regions with significant renewable penetration

Its location near renewable energy sources shortens energy transmission paths, reduces losses, and improves local system reliability.

A cornerstone for Greece’s energy transition

Greece aims to deploy 3.55 GW of BESS capacity in the coming years — a key part of its broader energy transition strategy to increase renewable energy penetration and phase out fossil fuels.

Recent regulatory changes in 2024–2025 — including simplified grid connection procedures and a stronger role for market mechanisms — have positioned Greece as one of the fastest-growing energy storage markets in Southeastern Europe.

According to Principia representatives, Themelio is only the beginning. The company plans further storage investments across the country, integration of advanced energy management systems, and active support for policies accelerating BESS development.

“Themelio marks the start of a new era. Our ambition is to build a bridge between renewable energy generation and system flexibility,”
said a Principia spokesperson.

Change consents