A newly started annex on implementation of underground thermal energy storage is described. The scope of the annex is to conserve energy, improve the environment by facilitating a broader use of Underground Thermal Energy Storage, UTES, in the building, into industrial, agricultural and aquaculture sectors. The objectives are to document successful and promising system applications and to identify boundary conditions, which make UTES economically feasible. The objectives also include proof of UTES environmentally benign by demonstration and information. The work-plan will be performed in several steps from state-of-the-art studies to R and D projects in the way to carry out user-friendly engineering tools and setting market barriers aside. The annex, which will be operated by task sharing, is divided into five sub-tasks with an estimated overall time schedule of three years