The Hallanvahti project is 100% owned by the Taaleri SolarWind III fund, managed by Taaleri Energia, a Finnish-based wind, solar and battery energy storage developer and fund manager.

The 129 MWp Hallanvahti project is situated approximately 6.5 kilometers from Joroinen in east-central Finland. Spanning around 200 hectares of wet peatland with a lightly dense forest, the site features a thick layer of peat, ranging from 500mm to 7000mm in depth. The project’s goal is to preserve the peat layer throughout its construction and lifecycle while effectively managing the water flow.

This project includes over 206,000 solar panels on an east/west tracking system, making it the largest of its kind in Finland. It is expected to generate between 130 and 145 GWh of electricity annually, sufficient to power thousands of homes and businesses. Over its projected 40-year lifespan, the project will produce a total of 5,200 to 5,800 GWh of clean energy. During its lifetime the project will supply energy to nearly 300,000 single-family homes or nearly 1.5 million apartment buildings. With the energy produced by the project, it would also be possible to drive an electric car for up to 25 billion kilometers.

Extensive environmental, soil, and hydrological investigations have been conducted to ensure the sustainability and efficiency of the site. The project has been developed by Etec Automation Oy and 3Flash Finland Oy. As part of the process, Etec Automation Oy and 3Flash Finland Oy worked with Pelastakaa Sysmäjärvi ry, Joroinen municipality, and Pohjois-Savo ELY Centre on a locally important water protection project, aiming to significantly improve the water quality of Sysmäjärvi in the long term.

When realised, the project will be a significant employer, creating up to 290 person-years of work with annual maintenance work for at least 30 years.

This operation benefits from support from the European Union under the InvestEU Fund. This project has received funding from the European Union's NextGenerationEU campaign.

Sustainability Initiatives at Hallanvahti

Hallanvahti sets a benchmark for biodiversity work in solar power projects

Hallanvahti is a significant project also thanks to its environmental and nature solutions. Hallanvahti has been built on the drained Tervajoensuo peatland, the drainage of which has led to the area drying out and the loss of peatland habitats. One of the project's starting premises has been to avoid further draining of the peatland. The panel foundations have been implemented using piling, which does not require soil replacement or drying out the area. The power plant's road structures in the peatland area have mainly been built as reinforcement mesh structures laid on top of the peat, which help avoid or minimize the need for soil replacement and drainage, allowing water to move underneath.

Additionally, special attention has been paid to water management in the project area. The discharge routes have been equipped with basins that delay runoff and act as sedimentation basins. If needed, the water level can be controlled using flow control weirs. This makes it possible to increase the retention time of runoff water and adjust the water level to the desired level. During construction, disturbance of the peatland was avoided wherever possible, and ditches were not cleared unnecessarily. Trees felled on the peatland have partly been used in floating road structures. The project area has not been fenced, in order to safeguard recreational use and minimize disturbance to animal habitats.

Local long-term improvements

The condition of the nearby Sysmäjärvi lake has been improved by rerouting a ditch near the project area. The flow of water has been redirected into its old channel, and all discharge water from the project area is led through a wetland area, which acts as a natural filter.

After construction, monitoring of the recovery of the peatland ecology has been launched. Dozens of vegetation plots and measurement points for tracking groundwater levels have been established in the area. Leaving the vegetation plots and water level measurement points in the project area enables further monitoring, for example after two, five, or ten years. Water body impacts have been monitored in the project since October 2025.

‍