5 MW of thermal energy and computing power – scaling to a new level with hydro technology
Summary
In 2025, MinersLoop carried out a strategic expansion at the Rajatie data center in Seinäjoki, with the goal of doubling both computing capacity and heat production. The expansion was based on water-cooled hydro technology, efficient heat recovery, and MinersLoop’s in-house design expertise.
The project was completed in early December 2025 and brought into operation within the same heating season. As a result, the data center’s heat output increased to 5 megawatts, making it one of the most significant producers of renewable heat in Seinäjoki.
Initial Situation
A Proof of Concept (POC) carried out in 2024 clearly demonstrated that the immersion solution did not provide as high efficiency or thermal capacity as the hydro system implemented later that same year.
Three development drivers formed the basis for the expansion:
- Seinäjoki’s growing demand for renewable heat
- Rapid growth of MinersLoop’s hosting services
- Lessons learned from the hydro POC, which made it possible to build a scalable, standardized solution
Based on these factors, it was a natural step to begin designing the next scale of operation.
Project Objectives
- Increasing capacity
• Doubling hosting capacity
• Doubling heat production - Building an energy-efficient hydro system
• Low heat losses
• High efficiency - Optimized integration with Seinäjoki’s district heating network
• Operating in support of the network - Laying the foundation for the 2026 expansion
• Pre-installed main pipelines and connection points
Solution
The expansion was implemented in close cooperation with Calefa and other key partners. The overall solution was built around three main elements:
- Calefa Ambiheat – heat pump
• Heat pump sizing, delivery, and installation
• The selection was based on positive experiences from the previous phase - Hydro cooling – the foundation of high efficiency
• The core concept was adapted to meet higher power requirements
• Server racks were sourced from a European manufacturer as part of evaluating alternative supplier technologies - MinersLoop’s in-house design and manufacturing
• Piping, critical cooling components, and system integrations
• Production environment
• Automation system developed in collaboration with Schneider Electric
The solution was designed with the future in mind, enabling the 2026 expansion to be implemented without major modifications.
Project Implementation
The project progressed through three phases.
Design:
Technical specifications and interfaces were reviewed in detail. Calefa designed the heat pump scope, while MinersLoop was responsible for the cooling network and automation.
Construction:
Piping, electrical work, site preparation and automation were carried out in stages.
The piping was fabricated on site according to the plans. At the same time, transformer installations and feeder cable routing were completed. The overall system architecture began to take shape well in advance, even though delivery delays extended the schedule. The heat pump and liquid cooler arrived as agreed at the end of November, allowing the final connections to be completed.
Testing and Commissioning
- All system components underwent the required pressure resistance and leak-tightness testing
- Sensors and measurement devices were calibrated
- The expansion was started up for the first time in early December
Project Team
- Pekka Kytömäki, Project Manager
- Roni Karjalainen
- Mikko Rantanen
- Pete Karjalainen
- Miro Kankaanpää
Subcontractors and Partners:
Sähkötyö Haapala Oy, Schneider Electric Finland Oy, Seinäjoen Energia Oy / Seiverkot Oy, Calefa Oy.
Results
✓ Capacity doubled
The data center’s mining capacity increased significantly and enables future growth.
✓ Heat production exceeds 5 MW
MinersLoop is now one of the region’s most significant producers of renewable heat.
✓ Completed on schedule at the start of the heating season
Ensured immediate utilization of thermal energy during winter peak demand.
✓ Energy efficiency improved significantly
Lower heat losses and higher output temperatures from the servers.
✓ Readiness for the 2026 expansion
Heat pump capacity reservation and preparatory work on the main pipeline, automation center, and cable routes will accelerate the 2026 expansion.
Next Steps
MinersLoop will continue optimizing the system and analyzing real-time data to further improve thermal efficiency.
During 2026, the plans include:
- Commissioning new systems
- Adding additional capacity without major modifications
- Creating a scalable process for future data centers
The goal is to use the Seinäjoki data center as a model for new data centers in Finland and internationally.
– MinersLoop