Engineering

Switzerland is using compressed air tunnels as energy storage

There is just dedicated to the new Gotthard Base Tunnel, since the Switzerland uses one of the old supply tunnel as energy storage. 100 m of the tunnel are a compressed air storage now test basis to compensate for energy spikes. Thereby, the Swiss want to achieve amazing efficiency.

Through the tunnel digging out has been created until a few years ago outside the Gotthard Base Tunnel to just, inaugurated on June 1. The German company Herrenknecht tunnel drills had started in 2003 to drill through the massive rocks of the Gotthard. The discovery came on October 15, 2010.

air tunnels as energy storage
The engineers Giw Zanganeh (left) and Andreas Haselbacher, both of the ETH Zurich, in the compressed air storage power plant in the Gotthard. Photo: Swiss Federal Office of energy

And now the tunnel on the outside was make the broken Rock after, will be used to test a compressed air storage power station. Engineers of ETH Zurich have the lead. 100 m of the tunnel have been hermetically sealed and equipped with high-performance pumps that use excess electricity to compress the air in the tunnel.

100 m tunnels are now a compressed air storage

“With the extra energy a generator is operated, which presses air in a tunnel”, depicts engineer Giw Zanganeh, head of the project funded by the Swiss Federal Office of energy named Alacaes in an interview with the Swiss news agency. “When there is a demand for electricity, the flow is reversed, that is, the compressed air will be drained and generates electrical energy with a turbine.” The Switzerland for the test mode emits four million Swiss francs.

Swiss Federal Energy
For its compressed air storage, engineers of ETH Zurich use an old supply tunnel, was acquired by the the overburden of the Gotthard Base Tunnel to the outside. Photo: Swiss Federal Energy

In the 100 m-long pressure Chamber in the middle of the tunnel, which is sealed off with steel doors, the air at up to 33 bar is condensed. Just past test mode is investigating how the mountain deals with the high pressure, whether he throws such as vibrations or shocks.

Swiss want to meet efficiency of 72%

The special feature of Swiss air space but is less of the tunnel and the pressure, but the high efficiency, the engineers trying to do. You are planning an efficiency of more than 70%. The only two in operation under commercial compressed air storage power plants in Germany and the United States are around 50%.

The world’s oldest air power is located in Huntorf in Wilhelmshaven. It was commissioned in 1978 as a combination of compressed air storage and gas turbine power plant and uses two cavities in a brine at a depth between 650 and 800 m. The air is condensed on 65 to 72 bar, so about twice as strong as in the compressed air reservoir in the Gotthard.

KBB underground technologies
The compressed air storage power station in Huntorf went into operation in 1978. The two salt caverns are located at a depth between 650 and 800 m. Photo: KBB underground technologies

Through modernization, Huntorf arrives to a capacity of 321 MW. The efficiency is only slightly more than 40%. This is because that the air heated by compression must only be refrigerated before it is stored in the sole. Before being discharged into the turbine, the air with the use of natural gas has to be heated again.

A heat storage are built into the Gotthard

Right here, the Swiss put engineers. You have installed a room in the tunnel, which is filled with stones and retains heat, which occurs during the compression of the air, and later returning when needed. The Swiss process the air in two stages will occur compacts, temperatures of up to 550 ° C with. By storing this energy and later use, the engineers want to achieve an efficiency of up to 72%.

Energy storage is important, because a consistent temperature of air is necessary for the reliable operation of the turbine with compressed air. Therefore, the compressed air is heated by Huntorf with gas, which lowers the efficiency.

Swiss Federal Energy Office
The compression of the air temperatures of up to 550 ° C. By storing this energy in a room, which is filled with stones, the energy can be use again later. As a result, Swiss engineers want to achieve an efficiency of up to 72%. Photo: Swiss Federal Energy Office

In the second commercial compressed air storage power plant, which in 1991 went to McIntosh in the United States in operation, the efficiency is just above 50%. There waste heat from the gas turbine is used compressed air to heat, which improves efficiency when compared to Huntorf.

Water pressure is suitable for energy storage

Also an other engineering works to save energy with pressure. Prof. Eduard Heindl of the Hochschule Furtwangen pursues the idea of a gravity current store: a Round Rock cylinder diameter to one kilometre from below due to water pressure in the height be raised thereby save energy.