From Sand Batteries to Sewer Heat: The Future of Urban Energy is Here

WASHINGTON, DC – February 19, 2026 – While world leaders debate climate targets, a quiet revolution is unfolding in the pipes and power plants beneath our cities. This week, the most innovative projects driving this change were honored at the 2025 Global District Energy Climate Awards (GDECA), announced at the International District Energy Association’s (IDEA) CampusEnergy2026 conference. The winners, spanning from Finland to India, showcase a powerful and practical array of solutions—from storing heat in giant sand batteries to capturing energy from urban sewers—that are actively decarbonizing heating and cooling for entire communities.

Presented by IDEA and Euroheat & Power, with support from the International Energy Agency (IEA) and the UN Environment Programme, the biennial awards celebrate the unsung heroes of the energy transition: district energy systems. These networks, which pipe hot or chilled water from a central source to multiple buildings, are proving essential in the shift away from fossil fuels. “The Global District Energy Climate Awards shine a spotlight on practical, proven projects that help communities reduce emissions while improving energy resilience, infrastructure, and long-term affordability,” said Rob Thornton, president and CEO of IDEA.

The New Frontier of Thermal Energy

This year’s winners demonstrate that the future of energy is not just about generating clean electricity, but also about cleverly managing heat. In Finland, two awards highlighted the country’s pioneering work with sand batteries—a groundbreaking technology that stores renewable energy as high-temperature heat in large silos of sand.

Receiving an Award of Excellence for modernization, Vatajankoski’s project in Kankaanpää, Finland, has created a remarkably advanced system. It features the world’s first operational sand battery, a digital twin for network optimization, and new e-boilers, achieving a 72% cut in carbon emissions between 2019 and 2024 while maintaining 99.94% delivery reliability. Further validating the technology, Polar Night Energy, the company behind the sand battery, earned a Certificate of Merit for a new, even larger installation for the Loviisan Lämpö utility. This new battery can store 100 MWh of thermal energy, ten times more than the Kankaanpää original, and is expected to slash local district heating emissions by nearly 70% by phasing out oil and reducing biomass consumption.

Meanwhile, in Canada, Markham District Energy is tapping into a different, yet ubiquitous, source of thermal energy: wastewater. The utility, which received a Certificate of Merit, is building the world’s largest Wastewater Energy Transfer (WET) plant. This 31.45 MW system will extract thermal energy from a large sewer main to provide heating and cooling, a process expected to reduce the utility’s carbon emissions by over 30,000 tonnes annually. This project highlights a key trend in modern district energy: viewing the entire urban environment as an integrated system where waste from one process becomes a valuable resource for another.

From Local Grids to Global Climate Action

The GDECA winners underscore a powerful message: global climate goals are achieved through tangible, local action. In Groningen, Netherlands, the Warmtenet NoordWest project, which earned a Certificate of Merit, is methodically replacing natural gas connections for 27,000 homes. The network is already 60% sustainably powered, using a mix of waste heat from data centers, one of the world's largest solar thermal parks, and seasonal underground heat storage that captures summer warmth for winter use. This project exemplifies a holistic approach that combines technical innovation with public ownership and strong community engagement.

In Asturias, Spain, an Award of Excellence went to a project that turns a relic of the fossil fuel age into a source of clean energy. The HUNOSA utility is using geothermal energy from the water of a defunct coal mine, hybridized with biomass boilers, to provide heating and hot water to buildings in the town of La Felguera. The success of the Fondón Colliery system is now serving as a model for developing more mine-water-based district heating networks across the region, transforming a legacy of coal into a sustainable future.

This global collaboration extends to developing nations facing immense energy challenges. In India, where cooling demand is projected to skyrocket, Tabreed’s Cooling-as-a-Service (CaaS) project in Gurugram received an Award of Excellence. By providing district cooling as a utility service, Tabreed eliminates the high upfront capital costs for developers, making efficient, centralized cooling more accessible. This model is critical for managing peak electricity loads, reducing grid stress, and curbing emissions in one of the world’s fastest-growing economies.

“The Global District Energy Climate Awards represent a powerful example of international collaboration for a more sustainable future, which is much needed in our fragmented world,” noted Aksana Krasatsenka, Knowledge Transfer Director at Euroheat & Power and GDECA coordinator.

Building the Blueprint for Sustainable Cities

Beyond individual technologies, the winning projects provide a blueprint for sector coupling—the intelligent integration of the power, heat, and transport sectors to create a more efficient and flexible energy system. Enwave’s project at “The Well,” a massive mixed-use development in Toronto, received an Award of Excellence for its innovative use of thermal storage. An 8-million-liter thermal battery, hidden deep underground, charges with low-cost energy at night and discharges during the day, providing low-carbon heating and cooling while easing strain on the city’s electrical grid.

Similarly, in Brescia, Italy, A2A Calore e Servizi earned a Certificate of Merit for its comprehensive decarbonization efforts. By integrating large heat pumps, thermal storage, and waste-heat recovery from a new data center, the utility has dramatically reduced its reliance on fossil fuels. In 2024, the system was 83% fossil-fuel-free, achieving a 73% reduction in CO₂ emissions compared to 2016 levels.

These projects demonstrate that modern thermal networks are the key to unlocking the full potential of renewable energy. They can absorb surplus wind and solar power, balance the electrical grid, and recycle waste heat that would otherwise be lost. As cities around the world strive to meet net-zero targets, the lessons from these award-winning systems offer a clear and proven path forward.

Robin Wiltshire, Chair of the GDECA assessment panel, praised the quality and diversity of the submissions. “It is testament to the commitment and skills of all those who have contributed to making these systems such a success,” he said. “We thank them wholeheartedly for displaying their achievements, which I am sure will inspire others in their quests for excellence.”