The transition of our electrical grid from a centralized controlled grid to a decentralized grid, with plenty fo renewables sources, will increase the volatility on the different electricity markets. In order to react to these fluctuations, many devices can steer their energy production and consumption. In order to guarantee comfort settings, many heating devices will profit from thermal energy storage. Today large thermal energy storage tanks are mostly constructed of reinforced concrete, pre-stressed concrete or steel. The latter results in low flexibility and high installation costs, thus preventing a widespread break-through in hospitals, office buildings, green houses, schools, apartment blocks, etc. The FLEX2 project targets a low-cost and flexible hermal energy storage system. Its solution consists of a flexible thermal buffer made of vessels of coated textiles, insulation material and an integrated control systems.