The invention relates to a method for optimizing a district heating network (1) comprising outgoing supply pipes and incoming return pipes, wherein a heat carrying fluid is circulated to be utilized for residential and commercial heating requirements. For storing excess thermal energy available at the district heating network. the method involves the steps of implementing more than one ground-based borehole thermal energy storage (4) as distributed heat storages at different locations of or along the district heating network (1). Each heat storage (4) is adapted to receive thermal energy from various forms of heat sources. which heat sources may be found at different locations of or along the district heating network (1) such, that the heat sources and the heat storages forming nodes in the district heating network (1). Excess thermal energy available to one node of the district heating network (1) is used to charge a borehole thermal energy storage (4) at one or several nodes, and thermal energy available from the borehole thermal energy storages (4) is at disposal to be used to heat the heat carrying fluid circulated in the supply pipes of the district heating network.

Disclosed herein, is an integrated thermal management system that efficiently manages the heat or cold flows while minimizing the energy loss and the space requirements with lower operational costs. The system herein comprises a distributed network of heat exchanging means with a flowing heat collector, the heat collector adapted to collect the waste heat from a plurality of sources through a thermal connection between each of the sources and the heat collector and the consumers. A centralized control unit is embedded in the system to control the extraction and absorption of heat between the heat collector and the sources and a centralized dissipation unit for releasing the extracted waste heat to the ambient air.

Thermal network comprising at least one plant, at least one end-user location (14,15), a pipe system (11-13) and a medium contained within said pipe system (11-13) said plant and said end-user location; said end-user location(s) (14,15) being connected to the plant through the pipe system (11-13). The thermal network according to the invention is characterized in that it comprises three main pipes (11-13) that are each connected to said plant(s) and wherein the medium is in a liquid state in the first and the third main pipe (11,13), and in a gaseous state in the second main pipe (12).