In 2016 ALACAES successfully built and tested the world-wide first pilot plant of an advanced adiabatic compressed air energy storage (AA-CAES) technology. The pilot plant, located in the Swiss Alps near the city of Biasca, exploited a disused transportation tunnel of the AlpTransit project as its pressure cavern, by constructing two 5-m thick conical concrete plugs to seal the pressure zone. The plant was a 120 m section of the 5m-diameter tunnel and had a capacity of 1 MWh. The hot pressurized air entered the pressure zone through a feeding pipe in the plug and was carried directly to the thermal energy storage (TES), that was placed inside the pressure zone. The air cooled down to ambient temperatures by flowing through the TES and was subsequently stored in the empty volume tunnel section. For discharging, the process was reversed by opening the control valves, allowing the cool pressurized air to enter the TES, heat up, and leave the plant through the same pipe it entered (See graphic below).
With the pilot plant, ALACAES has verified the flawless functioning of its proprietary technology and gathered valuable know-how for the design, construction, and operation of future plants.
Due to the national relevance of the project, the Swiss Federal Office of Energy financed 40% of the costs of the pilot plant.