World's largest sand battery starts slashing emissions in Finnish town

Euronews

15-06-2025

The world's largest sand battery has started working in the southern Finnish town of Pornainen.
Capable of storing 100 MWh of thermal energy from solar and wind sources, it will enable residents to eliminate oil from their district heating network, thereby cutting emissions by nearly 70 per cent.
'Our goal is to be climate neutral by 2035, and the sand battery is a major step toward that,' says Mikko Paajanen, CEO of Loviisan Lämpö, which runs the district heating network.
The industrial-scale solution from Finnish company Polar Night Energy is now the primary production plant for the network. The consumption of wood chips is set to drop by around 60 per cent as a result, while the existing biomass boiler will continue to serve as a backup and support the sand battery during peak demand periods.**
The new 1 MW sand battery has a precursor. In May 2022, Polar Night Energy rigged a smaller design to a power station in Kankaanpää town.
Launched just as Russia cut off gas supplies in retaliation for Finland joining NATO, the project was a timely example of how renewable energy could be harnessed in a new way.
Euronews Green previously spoke to the young Finnish founders, Tommi Eronen and Markku Ylönen, who engineered the technology.
'We were talking about how - if we had the liberty to design a community for ourselves - how could we solve the energy problem in such a confined environment?' Markku said of the inspiration behind Polar Night Energy in 2018.
'Then quite quickly, especially here in the north, you run into the problem of energy storage if you're trying to produce the energy as cleanly as possible.'
The friends started playing around with ideas, landing on sand as an affordable way to store the plentiful electricity generated when the sun is shining, or the wind blowing at a high rate.
Finding a way to store these variable renewables is the crux of unleashing their full potential. Lithium batteries work well for specific applications, explains Markku, but aside from their environmental issues and expense, they cannot take in a huge amount of energy.
Grains of sand, it turns out, are surprisingly roomy when it comes to energy storage.
At 13 metres high and 15 metres wide, the sand battery in Pornainen is around 10 times larger than the one at Vatajankoski power plant in Kankaanpää. Polar Night Energy also previously connected a pilot plant to the district heating network of Tampere city.
It's quite a simple structure to begin with, Polar Night Energy said of its prototype. A tall tower is filled with low-grade sand and charged up with the heat from excess solar and wind electricity.
This works by a process called resistive heating, whereby heat is generated through the friction created when an electrical current passes through any material that is not a superconductor. The hot air is then circulated in the container through a heat exchanger.
The sand can store heat at around 500C for several days to even months, providing a valuable store of cheaper energy during the winter. When needed, the battery discharges the hot air - warming water in the district heating network. Homes, offices and even the local swimming pool all benefit in Kankaanpää, for example.
'There's really nothing fancy there,' Markku says of the storage. 'The complex part happens on the computer; we need to know how the energy, or heat, moves inside the storage, so that we know all the time how much is available and at what rate we can discharge and charge.'
Having refined its charging algorithms, Polar Night Energy has now successfully scaled up the storage tech in Pornainen.
'This project has gone very smoothly," says Mayor of Pornainen Antti Kuusela.
Many of the town's buildings, including the comprehensive school, town hall, and library, rely on district heating.
"Pornainen wants to be a front runner in sustainable energy solutions, and we welcome all innovations that support that goal. One of the key targets in our municipal strategy is carbon neutrality, and the sand battery plays an important role in achieving it."
In total, the sand battery is expected to knock off 160 tonnes of carbon dioxide equivalent emissions per year.
The battery's thermal energy storage capacity equates to almost one month's heat demand in summer and a one-week demand in winter in Pornainen, Polar Night Energy says.
'We wanted to find something that can be sourced nearly everywhere in the world,' Markku said. But is sand as ubiquitous as we might think?
Demand for the construction material is set to soar by 45 per cent in the next 40 years, according to a recent Dutch study. Building sand is typically extracted from rivers and lakes, and 'sand pirates' are speeding up its loss from these ecosystems.
But as far as the Finnish engineers are concerned, it doesn't really matter where the sand comes from. Though builders' sand was used initially (to limit transport emissions), sand batteries work with any sand-like material that has a high enough density, within certain thermodynamic parameters.
In Pornainen, Polar Night Energy has found a sustainable material in crushed soapstone; a by-product of a Finnish company's manufacture of heat-retaining fireplaces.
"Tulikivi is a well-known and traditional company,' says Naskali. 'The soapstone they use is a very Finnish thing.'
"We always choose the thermal energy storage medium based on the customer's needs. Examining and testing different materials is crucial for us to use materials that are suitable in terms of properties, cost-effectiveness, and promotion of circular economy," she adds.
Polar Night Energy has big ambitions to take its technology worldwide, and is currently in "active discussions" with both Finnish and international partners. Earlier this spring, the company announced a pilot in Valkeakoski to explore the conversion of stored thermal energy back into electricity.
As Markku told us back in 2022, 'we want to build a hundred times larger storages around the world as fast as possible.'
The ocean is essential to limiting global temperature rise. It captures about 30 per cent of all carbon dioxide emissions, and 90 per cent of the excess heat generated by these, but has been overlooked in the conversation about how to curb climate change.
This is increasingly concerning as oceans suffer from the results of excess carbon dioxide, including acidification and rising sea temperatures. These have significant impacts on ecosystems, the communities that rely on them, and the ocean's role as a climate regulator.
'The globe is burning. Our oceans are boiling. Scientists speak of effects that we're having, heatwaves even in our oceans, and as we have the rising sea levels, submersion threatens us,' said French President Emmanuel Macron at the opening plenary of the United Nations Ocean Conference (UNOC) in Nice this week.
The conference saw what Macron called 'unprecedented mobilisation' for oceans, with over 120 countries, 50 world leaders and 10,000 people in attendance. It also included a strong push to start including oceans in climate and biodiversity talks, including the COP30 climate conference to be held in Brazil in November.
That would mark a big change from previous discussions. Even the Paris Agreement - the landmark treaty that aimed to keep global warming below 1.5C - has just one mention of the ocean, noting the importance of ensuring the integrity of all ecosystems.
'We're very, very late. We're at UNOC3 - the climate COPs are at COP30. Unfortunately, the climate COPs, much like other conferences of the like, have not really properly integrated the ocean. So on the science, we're picking up, but on the political side of things, it's still very, very much catching up,' says Louis Lambrechts from the Oceano Azul Foundation.
Speaking at the beginning of the summit, Marcon pointed to the ocean's carbon capture potential and its role as a climate regulator, highlighting the need to act to protect this, particularly ahead of COP30. Lambrechts tells Euronews Green that it is crucial to create coherence between climate, biodiversity, and ocean silos.
'What should come out of this conference [...] should be very clear messages towards the next climate COP happening in Brazil later this year, about why it's so critical that the ocean should be properly addressed and considered in the debates,' he says.
'Any objective or action we're trying to have on climate would be completely unrealistic if the ocean wasn't there to play the game with us,' he adds.
Isabella Lövin, former Swedish climate and environment minister and now Green member of the European Parliament described how, during her time in government, she fought to get oceans into the climate conversation, but said this shift has taken a long time.
'People have so much to think about - what's happening on land and with the forests and the atmosphere and the cryosphere and so on, but the oceans are really one of the two major climate regulators, so we need to have much more conversations on how we can preserve the ocean in order to stay below 1.5C,' she explains.
Similarly, Ana Vasconcelos, a member of the European Parliament with centrist group Renew Europe, warned that, politically, ignoring the ocean in climate and economic negotiations is a failure.
'Europe must go to COP30 with a clear message: the ocean is not a backdrop - it's a frontline climate actor. I want the UNOC to produce real and concrete commitments that reflect the scale of the crisis and the ocean's role in solving it,' she says.
That includes establishing clear and actionable guidelines for global ocean governance, recognising that the ocean is a common resource that needs to be safeguarded through global cooperation, she adds.
Ahead of COP30, France and Brazil also launched the Blue NDC Challenge, calling on countries to place the ocean at the centre of their plans to reach the goals of the Paris Agreement. Countries need to submit updated versions of these plans by September ahead of COP30.
The ocean's role as a climate regulator is increasingly being chipped away.
At the start of the conference, on 8 June, scientists released the first Starfish Barometer - an assessment of ocean health aimed at providing reliable evidence to inform policymakers and track the restoration of ocean health. It warned of rising sea levels, record temperatures, and rapid acidification.
This is worrying given the climate disaster the ocean has, so far, held back.
'If the ocean wasn't there, it could be 50C warmer on land, but you don't get anything for free in this world, and the ocean is changing as a result of all of that excess heat going into it, and its capacity to continue absorbing heat is not something we can count on into the future,' says Robert Blasiak, Associate Professor at the Stockholm Resilience Centre.
Lambrechts likens the ocean warming to a kettle boiling: taking a long time to warm up - much longer than the air - but staying hot for a long time.
The world is heading towards that boiling point, he says, creating dead zones where marine life cannot survive, hindering ecosystems' ability to store carbon, as well as affecting fish populations and impacting those communities who rely on them.
While some damage to the ocean may take centuries to recover from, there are measures we could take today to help prevent further harm.
Banning bottom trawling and deep sea mining would be decisions with immediate results, says Lévy. These damage ocean ecosystems and, in the case of deep sea mining, a lot of the potential impacts are still unknown.
The EU's 2023 Marine Action Plan called on member states to phase out bottom trawling in all marine protected areas by 2030, due to the importance of the seabed for healthy marine ecosystems and climate change mitigation.
While 37 countries, including 15 EU nations and the UK, have signed a pause on deep sea mining as part of a political effort to prevent the practice until the implications of it are understood.
According to Lövin, the most important thing to consider when protecting the ocean is the precautionary principle - the idea of avoiding activities that might cause harm that is not yet known.
'We need to really take the precautionary approach seriously because we are the decision makers. We are the ones that are going to be held accountable. We have the responsibility for future generations,' she tells Euronews Green.
Vasconcelos also called on the EU to take a 'central and credible role' in International Seabed Authority (ISA) negotiations in July to ensure that ocean governance aligns with its climate and geopolitical priorities.
Ahead of UNOC, the European Union released its Ocean Pact, pledging €1 billion to support ocean conservation, science and sustainable fishing. It also announced that it will propose an Ocean Act in 2027 aimed at strengthening and modernising maritime spatial planning to help achieve the pact's priorities, like restoring ocean health, building a blue economy, and advancing research and knowledge.
While it was not as ambitious as some would have liked, with Vasconcelos saying it is unclear where the €1 billion will come from and leading ocean NGOs saying it lacks concrete protection measures, it has been widely welcomed as a way of bringing oceans back into the conversation and linking different ocean policies.
However, not everyone is on board. One of the notable absences from the conference was the US government, which under President Trump has pulled out of the Paris Agreement and is unilaterally trying to push ahead with deep sea mining.
Lövin called the lack of US presence a scandal, contrasting it with the efforts of the EU and other world leaders to work against planetary collapse and pointing to the need to work together to protect the world for future generations.