A new class of renewable power infrastructure.

As renewable penetration increases, electrical systems require technologies capable of storing and delivering clean electricity across much longer durations.

Airengy’s CAPP platform combines AirBattery technology with underground storage infrastructure to create a new category of renewable power plant.

The system captures surplus renewable electricity, stores energy underground in the form of compressed air, and converts it back into electricity on demand.

Unlike conventional fossil-fuel generation, CAPP delivers dispatchable power without combustion and without dependence on fuel supply.

AirBattery energy storage system

Designed to enable total renewable integration. Providing grid-scale, ultra-long duration storage.

As the energy transition advance, dependence on intermittent renewable energy grows, leading to grid vulnerability during long periods of undersupply.

Traditionally, fossil fuel power plants provided backup during these times. Augwind's AirBattery offers a sustainable alternative, replacing fossil fuel generation with a cost-effective, eco-friendly energy storage asset.

In 2021, an AirBattery system was installed at pilot scale in southern Israel, reaching a round-trip efficiency (RTE) of 21%. In early 2024 the system was re-commissioned with upgraded machinery and processing.

The current pilot capacity is 250kW/1MWh, with current a RTE greater than 47%.

The project is a small-scale viability demonstration of Airengy’s AirBattery energy storage technology. Airengy is now ready to further advance the AirBattery towards commercialization.

The experiments in Yahel validate the company’s roadmap targeting >60% for a fully commercial AirBattery system.

The program is a cooperative effort alongside the Israeli Ministry of energy and the communal settlement of Kibbutz Yahel.

Round-Trip Efficiency Roadmap

The AirBattery is a closed loop, bi-directional system, meaning that all elements run at one direction for charging, and work in reverse when discharging. At the core of the process is Airengy’s proprietary near-isothermal liquid piston, responsible for both charging and discharging procedures.

A liquid piston process describes compression of gas using fluids. In our case, we use water to compress air. To host this liquid piston process, Airengy developed the “AirX”- our patented, underground vessels. When coupled, two or more AirX vessels serve as a liquid piston, with a pump delivering water from one vessel to the other.

Liquid piston mechanism

The compression process begins with one AirX vessel that is full of water and one AirX vessel that is full of air.

Water is pumped from the water filled vessel into the air-filled vessel. As the water level rises in the air-filled vessel, it compresses the air like a piston. Once the air pressure is high enough, the air is sent for storage and the vessel that was initially full of air is now full of water.. On the other hand, the vessel that was originally full of water is now full of air. Now, the water can be pumped back into the first vessel for another compression cycle. The process is repeated as long as there is excess electricity and room in the storage reservoir.

During expansion, a bubble of stored compressed air is released into the water filled AirX vessel. The expanding air streams the water though the same set of reversible pumps (this time operated as turbines) to regenerate electricity. The streamed water is transferred from the pump into the other vessel. Once all of the water has been transferred, the other vessel is full of water and another expansion cycle can begin.

Compressed Air Power Plant (CAPP)- Powered by AirBattery technology

The AirBattery combines the strengths of Compressed Air Energy Storage (CAES) with those of Pumped Hydro Energy Storage (PHES) to offer grid-scale, multi-day energy storage. It utilizes cost effective geological compressed air storage, along with efficient hydroelectric turbomachinery.

The system uses a closed-loop liquid piston mechanism to compress and expand air in an underground, near-isothermal process. Once compressed, the compressed air is stored in underground salt caverns (which are prevalent in the natural gas industry throughout the world), waiting for discharge.

The AirBattery is designed to store and dispatch energy for long durations-
Days, weeks or monthes, depending on the cavern's volume.

Key Advantages:

Cost Efficiency

The cost of increasing storage duration is only the cost of increasing the cavern volume. As opposed to other CAES technologies (such as A-CAES) there is no need for thermal storage (in the form of heat or fossil fuels). This enables the AirBattery to provide much lower capex per kWh installed at multiday/weekly duration.

Environmental Impact

AirBattery has minimal land footprint, does not require rare raw materials, does not consume water, and does not emit anything but fresh air- Contributing to a safer and cleaner energy supply.

Supply Chain

Onsite construction that is based on local materials (steel, concrete and polymers) and labor- The AirBattery contributes to local economies where it is deployed.

European CAPP Development Pipeline

Airengy is developing CAPP through a structured, phased approach. We start in markets where the need is clear. These are countries leading the energy transition with increased renewable penetration and suitable geological conditions.

Our first commercial projects aim to assure regulators and financial institutions of the technology robustness and reliability. This will allow to devise regulation and financing schemes which will make grid scale CAPP facilities bankable.

To build on that, together with leading strategic partners, we are already developing a pipeline of grid-scale CAPP projects across Europe. This pipeline positions Airengy for the growing role of long-duration energy storage in future power systems.

Denmark is one of the world's most advanced renewable energy markets. In 2024, renewable sources generated more than 80% of the country's electricity, with wind power alone contributing nearly 60%. Such high renewable penetration creates growing demand for long-duration energy storage to manage variability, reduce curtailment and strengthen grid reliability. Combined with extensive salt formations and well-established subsurface infrastructure, Denmark offers ideal conditions for commercial CAPP deployment.

Partner

Nobian is one of Europe's leading producers of salt, essential chemicals and renewable hydrogen. The company is also a leading developer of underground salt caverns, supporting natural gas, hydrogen and future large-scale energy storage projects across Europe.