Denmark’s use of pit thermal energy storage provides cost-effective solution: Ambassador Jakob Linulf
Staff Writer
Islamabad: Denmark’s Ambassador to Pakistan Jakob Linulf said this week that Denmark’s use of pit thermal energy storage provides a cost-effective solution for storing energy.
“Denmark’s use of pit thermal energy storage provides a cost-effective solution for storing energy. @Ramboll’s work on the largest PTES in Vojens supplies 45% annual district heat consumption, reducing CO2 emissions by 6k tonnes annually,” he tweeted.
Denmark is recognised for pioneering the use of wind energy technology, it may surprise some to know that the country also utilises solar heating as a plank in its objective of greening its heating system.
Given that Denmark is not exactly known for a plethora of warm, sunny days, there is a need to store water that has been heated by the sun during the summer at solar heat plants so it can be utilised for heating during the winter as part of the country’s district heating system. This is achieved through pit thermal energy storage (PTES).
The way that PTES works is through the creation of an underground pit that is surrounded by soil or sand and lined with water-proof plastic that ensures heat is retained and water doesn’t leak out. The pit is then filled with water and stored.
By covering the pit with a lid, heat is retained and the intrusion of rainwater into the pit is prevented. The water is then stored seasonally and subsequently sent to consumers in the district heating network so that it can be used for heating in the winter. By using solar power to heat water and then store it, a percentage of heating needs can be met, depending on how large the storage capacity is and the efficiency of the storage.
Since the establishment of several PTES demonstration plants in the 1990s/early 2000s, Denmark is now home to several commercial PTES plants. In the town of Vojens in Southern Jutland, the local district heating company has expanded its existing solar heating plant to 71,000m2 of solar panels and built an accompanying 203,000m3 pit thermal heat storage facility in 2015 in order to meet its district heating needs as sustainably as possible. The size of the pit and the expanded solar heating plant mean that the pit is the largest of its kind on a global scale, and the solar heating plant is among the largest.
The pit in Vojens has a depth of 13 metres and a maximum capacity of 200 million litres. It takes approximately five months to fill the pit, which has a pumping capacity of 50,000 litres of water per hour. An insulating floating lid covers the entire surface of the pit. The lid enables the storage of hot water, which is then made available to consumers during the Danish winter.
