Patented Compressed Air Technology

How Green-Y works: Compressing air creates heat and consumes electricity. Expanding air creates cold and generates electricity. These two main steps are performed separately in time. Therefore, Green-Y unifies the functionalities of a heat pump and a battery by storing electricity and generating heat and cold. The compressed air is stored in commercial pressure tanks which is a durable and inexpensive solution to store electricity.

Innovation: We essentially advanced the well-known compressed air energy storage technology by increasing the energy density by a factor of three and double the heat & cold extraction. This reduces the required storage volume by a factor of three and makes the decentralized application possible. Further, efficient heating and cooling is enabled directly in the building where the thermal energy is needed. The heat energy can be used to provide e.g. hot water for domestic use and room heating and the cold for e.g. cooling the building.


Our highly efficient tri-generation energy storage system aims for an electrical round-trip efficiency of 65%* while extracting heat and cold with a combined COP of 4.6*


* current estimate


Excess electricity is used to fill the compressed air electricity storage. The compression generates heat which is e.g. directly used or stored in a thermal energy storage


During electricity demand the expansion of the air drives a generator to produce electricity and generates cold



Air & water as working fluids

100% recyclable


65% electrical efficiency

COP of 4.6


More than 20'000 cycles

Lifetime >50 years


Electricity storage far below

1 ct/kWhel

Solution: Sector coupling

Green-Y provides a unique and eco-friendly approach to couple the electricity and heating & cooling sector by combining the electricity storage together with renewable heat and cold generation in one device.

2. Renewable heating and cooling: Fossil fuels in the energy intensive heating and cooling sector have to be replaced by providing the heat and cold from renewable electrical energy.

1. Renewable electricity: The production of renewable electricity, for example with wind and solar, is already today cost-competitive. However, low-cost electricity storages are required to provide it around the clock.

The energy transition can only be realized with the expansion and integration of renewable energy sources: