Under the streets of Vasteras, a southern Swedish city, lies a network of man-made tunnels and caverns that were originally constructed during the Cold War to store oil. Today, these caverns serve a new purpose – storing hot water. A visit from the Swedish king highlights the significance of this giant heat battery, designed to keep the city warm, especially during harsh winters when temperatures can drop to -20 degrees Celsius.

The city’s district heating system, run by the locally-owned energy company Malarenergi, connects to several huge boilers housed in a local power plant, which produces electricity and heat. This system is highly efficient, utilizing 90% of the energy consumed.

Although the plant must run all year round to provide hot showers even in summer, there are occasional struggles to produce enough heat during the winter, resulting in the use of fossil fuels and CO2 emissions. The caverns offer a solution by storing excess heat generated during the summer, which can then be accessed in winter to keep the city warm for up to two weeks.

Malarenergi invested around $15.5 million in this project, which is expected to generate returns within five to ten years due to fuel savings. Additionally, this heat storage system reduces CO2 emissions by approximately 1,600 tons annually.

Experts believe that similar heat storage solutions can be adopted in other locations, not just in cities with existing underground structures. Countries like Finland, Norway, and Sweden have favorable conditions for building such cave storage due to their crystalline bedrock. Other areas may need to explore alternative methods, such as drilling wells to heat fractured rocks or constructing artificial pits for water storage.

Source: https://www.dw.com/en/can-caverns-of-piping-hot-water-heat-our-cities/a-71756844?maca=en-rss-en-all-1573-rdf