Some 71,000 steel screw piles hold up Finland’s newest large solar park, driven into peat that in places runs seven metres deep. On 5 October, Taaleri Energia formally opened the 129 MWp Hallanvahti plant in Joroinen, North Savo, three months after it started generating at the end of June.
The numbers are substantial for a country better known for wind. Hallanvahti’s 204,000 bifacial panels sit on single-axis trackers and are expected to produce about 140 GWh a year, roughly what 18,000 Finnish households use. Renewables Finland, the industry association, describes it as the country’s first utility-scale solar farm with trackers. Its contractors rank it second in size only to the 206 MWp Kalanti park near Uusikaupunki.
Building on a bog
The site is the unusual part. The roughly 200-hectare plot is the drained Tervajoensuo peatland, which had been drying out since it was ditched. Instead of excavating and replacing the soft ground, the builders chose to pile through it, keeping the peat layer in place for the plant’s lifetime and managing how water leaves the site.
Helicasol, a subsidiary of Paalupiste, ran pull-out tests before settling on a pile design, then installed up to 3,500 piles a week using six or seven rigs at once. The project’s own documentation lists other measures: no perimeter fence, so wildlife and walkers can still cross the land; settling basins to catch sediment; discharge routed through wetlands; and a diverted ditch intended to improve water quality in nearby Lake Sysmäjärvi. Felled trees became floating road foundations.
Kai Rintala, Managing Director of Taaleri Energia, said the project had “progressed on schedule, with particular attention paid to environmental considerations throughout the construction process.”
Who paid, who buys
Taaleri’s SolarWind III fund invested in February 2025, and funds managed by Taaleri now own the project outright. Etec Automation and its subsidiary 3Flash Finland developed it with Taaleri. Eltel Networks held the €73.5 million turnkey construction contract, the largest single order in Eltel Finland’s history, and will handle maintenance.
The financing mixes public and private money. SEB provided project debt, the EU supported it through the InvestEU Fund, and Finland’s Ministry of Economic Affairs and Employment awarded a grant of about €17 million. NextGenerationEU money is also in the mix. A long-term power purchase agreement with Oulun Energia covers the output, though its terms have not been disclosed.
A fast-filling market
Hallanvahti arrives during a sharp build-out. According to Renewables Finland, the country added 478 MW of utility-scale solar in the first half of 2026, taking the total to 842 MW across 45 plants, more than double the end-2025 figure. Alight and Autoliv opened the 101 MWp Eurajoki park only last month.
That pace raises a familiar question. Finnish solar produces most in summer, when wind is often also generous and prices can collapse. Hallanvahti’s trackers, which follow the sun from east to west, spread output into mornings and evenings, and that may prove worth more than the headline capacity. Petri Isotalus, Investment Director at Taaleri Energia, called rising electricity demand “an increasingly important investment theme.” Whether that demand arrives quickly enough to absorb all of this new capacity will decide how well the peatland bet pays off.
