energy storage

Compressed Air Systems: Efficient Renewable Energy Storage

As energy systems become increasingly distributed, localized, and reliant on intermittent clean sources, storage options are gaining importance for ensuring stable supply and stable grids. One technology that remains under-utilized is Compressed Air Energy Storage. Israeli company Augwind has developed a concept that is both simple and sophisticated.

For grid operators, the rise of renewable energy sources over the past two decades has not been an unmitigated success story. The old model of energy generation in large, centralized power stations is increasingly shifting toward decentralized assets, which feed power into the grid at irregular intervals that are hard to predict. The resulting instability and challenges associated with grid management are among the main drivers of the search for efficient, sustainable, and economical energy storage solutions.

Some of these, such as battery storage or pumped hydropower, are based on conventional technologies that are well understood and already in widespread use, and simply need to become more efficient. Others, including green hydrogen, are not yet mature, but are attracting enough attention and investment to indicate that they will be ready to enter general use in the near future. However, given the urgency of mitigating climate change, experts say all avenues should be explored and all storage options utilized to ensure the energy transition takes place without disruptions to consumers.

One of the technologies whose potential has yet to be fully mobilized is electricity storage using compressed air. Compressed Air Energy Storage (CAES) is not a new concept: Some of the oldest projects in the US and Germany go back to the 1970s, but commercialization has been hampered by the cost and size of tanks as well as the large spatial footprint. Today, the need to stabilize the grid is generating renewed attention for these solutions, while market forces and regulation of carbon emissions are bringing them closer to commercial viability.

Sun, Air, Water, and Earth

One of the companies exploring and fine-tuning CAES technology is Augwind Energy, Israel’s fastest-growing energy efficiency company. Founded in 2012, Augwind aims to offer an alternative solution for energy storage, but also for the use of compressed air in industrial manufacturing. The AirBattery concept is a simple, yet effective variation on pumped hydropower: During the day or when conditions are right, renewable energy (mainly solar or wind) powers a water pump within a closed water loop to compress air, which is stored with minimal efficiency loss, close to the green power source, in an array of Augwind’s AirX storage vessels, buried in the soil a few meters underground and lined with polymer to prevent leakage.

When the energy is needed – for example, at night or to facilitate peak shaving in response to grid conditions – the compressed air is used to power a hydroelectric turbine, with an expected round-trip efficiency of between 70 and 80 percent. It is essentially the same concept as pumped hydro storage, but with compressed air replacing the gradient of a mountain slope (e.g., 60 bar of pressure is equivalent to a 600-meter incline). The system is safe, scalable, and can be installed almost anywhere due to its relatively small footprint above surface.

energy storage
Aerial view of Augwind facilities for energy storage

Under Pressure

In comparison to traditional pumped hydro storage facilities, the AirBattery does not require major construction work, which is a particular advantage on AugWind’s home turf, as Ido Ben Yehuda, the company’s Head of Marketing, told Supertrends in an interview: “There are very little geographical constrains to installation of the AirBattery system, although here in Israel, if you’re going to start digging, you need to make sure that you’re not on some kind of archaeological site or a cemetery from earlier centuries.” But there are other reasons why this technology has been developed to maturity in Israel. The country has set itself renewable integration goals, along with supportive regulations, and many renewable energy projects are underway.

Furthermore, Israel has vast solar potential, but is subject to “land constraints”, in Ben Yehuda’s words: “It’s a small country, there is no vast geography for implementing renewable energy resources at will.” Not only that, but due to the political situation in the region, it currently can’t rely on an interconnection architecture with all of its surrounding neighbors. Israeli engineers have long been working to make their state self-sufficient and resilient in energy supply. This means developing alternative energy sources and the means for their grid integration, but also improving the energetic efficiency of its industrial consumption as well as energy storage solutions.

“What’s nice about this solution is that it’s simple and basic in some respects, but highly sophisticated and technological in other respects.”

Ido Ben Yehuda, Head of Marketing at Augwind

As such, Augwind is also deploying the same technology to optimize compressed air use in industrial manufacturing, where about 7 percent of energy usage can be attributed to air compression. The AirSmart Energy Efficiency System can boost the efficiency factor of compressed air generation, reducing electricity consumption by up to 35 percent and improving security of supply and production yield. Augwind has already installed more than 25 AirSmart systems in Israel at some of the major manufacturers in numerous industries including the metal, cement, plastics, and food and beverage sectors. It has also completed its first installation in Italy and plans to develop new projects in the US and Europe soon.

Simple, But Sophisticated

Even though the technology is new, it relies on two mature energy storage categories – CAES and pumped hydro storage – that are proven to be highly reliable and economical. Both AirBattery and the AirSmart energy efficiency system use the same core components for storage, and both benefit from Augwind’s special expertise and experience in deployment of compressed-air solutions.

“What’s nice about this solution is that it’s simple and basic in some respects, but highly sophisticated and technological in other respects. The technical approach is simple – a combination of pumped hydro for power and compressed air for energy – but the high-tech parts and Augwind’s proprietary software layer, which controls the overall operations, are embedded in the system’s architecture, integration, and brain,” says Ben Yehuda. “It uses traditional industrial components and construction-grade raw materials in a novel technical approach, with no dependency on scarce materials or other elements that could potentially create a bottleneck due to supply chain issues, to provide a long-term solution for distributed renewable integration.”

Compressed air for energy storage is just one of several options for storing renewables, and one whose full potential has yet to be exploited. As the global clean energy transition progresses, such innovative improvements, approaches, and uses of CAES will have a bigger role to play in a distributed and sustainable energy system wherever conditions are suitable.

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