As the adoption of renewable energy accelerates globally, there is an increasing focus on improving efficiency and developing robust systems. energy storage solutions to ensure reliable supply. Existing technologies include water tanks, compressed air storage and large-scale batteries. However, Finland is pioneering an innovative approach to underground thermal storage that has significant potential for the energy transition. This system can store up to 90 GWh of energy from renewable sources.
What will I read in this article?
Energy storage caverns
To grasp this initiative, one must first understand the nuances of the Finnish energy system. In towns like Vantaa, vast networks of pipes distribute hot water to domestic heat exchangers, heated by industrial waste heat and thermal power plants. The objective, however, is to move towards the storage of heat from renewable sources, such as summer solar energy, to achieve carbon neutrality by 2030.
The construction, scheduled for construction in 2024, includes three vast underground caverns, each measuring 300 meters long, 40 meters high and 20 meters wide, capable of storing more than one million cubic meters of water at depths of up to 140 meters. This depth keeps the water under enough pressure to heat up to 140°C without vaporizing.
During summer and periods of low electricity costs, these caverns will be filled with water heated by two 60 MW electric boilers powered by renewable sources. Once fully operational, the system can provide up to 60 GWh, enough to power a medium-sized Finnish city for a year or recharge 1.3 million electric vehicles, according to the public company behind the project. All of these factors will make it the largest storage facility of its kind in the world.
In addition, the project will integrate AI-controlled systems manage hot water inlets and outlets throughout the year, optimizing the use of resources. Project proponents note that in addition to reducing emissions, energy storage will help stabilize consumer prices.
With an estimated investment of 200 million euros, the Vantaa thermal energy storage complex is expected to enter service in 2028.
Megabatteries: the future of energy storage
Megabatteries represent the most versatile and scalable energy storage solution today. Typically using lithium-ion technology, they store energy generated by solar and wind installations, ensuring availability at all times, regardless of weather conditions. For example, the Cunningham battery farm in Texas can store 380 MWh on a six-hectare site.
This technology offers many benefits, including consistent energy supply, the ability to meet peak demands, and reduced investment in energy infrastructure. For more information on megabatteries as an energy storage solution, we recommend This item for a detailed analysis.
The era of waste heat
The Finnish initiative is just one of many initiatives exploiting thermal energy in urban areas. Another important area of focus is sewage systems, which are significant consumers of energy. Daily activities like taking a shower or using a washing machine send hundreds of liters of hot water down the drain.
This energy is recoverable through a method known as wastewater heat recovery (SHR), used either to generate electricity or to provide heating, thereby contributing to the transition to a fully renewable electricity system. The process involves passing hot wastewater through heat exchangers, which transfer heat without direct contact with the secondary fluid, and then redistributing the heated water to homes via a network of pipes. This method does not store energy but maximizes the energy initially used to heat the water.
A notable example is a pilot project in Vancouver, Canada, where more than 6,000 apartments are heated using recovered heat, saving up to 80% energy. Other cities like Chicago are also expected to soon adopt SHR technologies, not only for heating homes but also for public swimming pools, as seen in Raalte, Netherlands.
Sources:
Pictures: