The heat storage facility comprises of an insulated water tank built from steel and has a capacity of around 10,000 cubic meters. It is 45 meters high, with a 17-meter diameter.

Heat consumption fluctuates throughout the day. In the fall and the spring for instance, temperatures are generally warmer during the day, so less heat is consumed, while at night, rooms get cold.

"The logic is that if there is surplus heat during the day, it will be stored as hot water, and at night, when more heat is needed, it is taken from that storage and fed into the district heating network," said Margo Külaots, head of Gren's business operations in Estonia.

Without the storage facility, boilers, which often run on gas, are left switched on during the cold hours of the night. Külaots pointed out that not only is gas expensive, but it is also an imported fossil fuel, and the storage facility means Gren can use wood chips instead of gas. According to Külaots, reducing the use of gas means that the company will cut down on its CO2 emissions by 2,000 tonnes a year.

"In addition to that, the boilers don't have to be constantly switched on and off to cover specific hours. Switching boilers on and off is very inefficient and also causes boilers to break down," he said.

According to Külaots, the new system will reduce the annual gas consumption by  around the same amount used by 18 large apartment blocks in Tartu's Annelinn district.

Up to now, no other similar facilities have been installed in Estonia. According to Külaots, this may partly be due to the fact that, prior to last year, gas had been cheaper and district heaters are also used to switching boilers on and off during peak periods. However, the main reason for building new storage facilities relate to more recent developments in both construction and insulation technology, which make it possible to build them to a higher standard.

As for district heating customers, the impact on their bills will not be too noticeable, said Külaots. "It will certainly help to stabilize prices. If we use less gas and we replace it with wood chips, because gas is more expensive, it will certainly have a downward effect on prices. However, it is more likely to improve the security of supply," he said.

--

Follow ERR News on Facebook and Twitter and never miss an update!