To cover the heat requirements of villages and towns with as little CO2 as possible, large heat storage systems are increasingly required. The most economical construction method is the so-called earth basin heat storage system, which consists of a water-filled earth basin. In Denmark, several of these heat storage tanks with a water volume of 35,000 to over 200,000 m³ are already in operation. In Germany, the demand for underground heat storage tanks is now also increasing. The storage covers built since then are insulated, float on the water basin and cannot be used. Individual requirements such as the drainage of rainwater and the ventilation of the storage tank have not yet been reliably solved. The aim of the seminar is to design high-quality architectural solutions that demonstrate synergies for solving the existing problems while at the same time utilising the storage area. At the beginning of the seminar, lectures on renewable energies, the seminar topic and the task are introduced. Building on this, each participant will develop a concept for a pit cover.