Long duration energy storage (LDES) is storage that can supply power to the grid for greater than four hours, without requiring any recharge. Typical LDES applications are at least 8 hours in duration, which allows for reliable replacement of grid capacity and dealing with much of the intermittency of renewables.  While commercially available lithium-ion batteries are a good solution for shorter duration applications, low cost technologies are needed for long duration applications that the grid requires. Advanced-Compressed Air Energy Storage (A-CAES) can cost-effectively store energy for much longer periods than batteries (6+ hours), has a longer life cycle (50+ years) and lower environmental impact (being both flexibly-sited and emissions free, with a low overall environmental footprint).

Advanced-Compressed Air Energy Storage (A-CAES) is a long-duration energy storage system that provides reliable, emissions-free energy storage where the grid needs it. A-CAES uses proven components from mining and gas operations to create an advanced and scalable energy storage system that is low-impact and cost-effective.

Hydrostor’s A-CAES system works by converting excess grid energy into compressed air. This compressed air is then sent into purpose-built underground caverns, where it displaces water to create storage capacity (in other words, stored energy in the form of pressurized air). This compressed air can then be run through an air turbine to generate electricity, with no additional fuels, when the grid needs it.

Megawatt (MW) is a term used for the amount of power supplied to the grid given at any single point in time. Megawatt Hour (MWh) is the term used to describe energy – in other words, a given amount of power supplied for one hour in time. If an energy storage system is 10 MW and 100 MWh, it means the system will give 10 MW for 10 hours (100 MWh).

Hydrostor’s systems typically range between 200-500+ megawatts (MW) in power and 6-24+ hours in duration. A-CAES can be smaller in select cases, particularly where pre-existing caverns are repurposed.

A-CAES systems are very long-life power infrastructure, that provide a future-proof backbone to the decarbonized electricity system.  A-CAES uses off-the-shelf equipment in proven mechanical processes, with known reliability for 50+ years, coupled with 100+ year caverns constructed in bedrock. This enables A-CAES to achieve a reliable lifespan of at least 50 years, with normal equipment maintenance, and even longer-term application with refurbishment of the topside facilities.

Our closed-loop water reservoir contains approximately 170 m³/MWh of storage capacity (or 40 gallons per kWh). This is roughly 20 times less than the water required for an equivalent capacity pumped hydro facility (with a dam height of 120m).  This water use is non-consumptive – it is a one-time draw that can be provided from a variety of sources, including recycled water, making it suitable for an array of different geologies and conditions.

All A-CAES systems are designed to seismic standards required by the jurisdictions in which they operate – this is true for both the surface and subsurface facilities.  The subsurface facilities are only minimally impacted by earthquakes.  Just like waves on the ocean, the shaking caused by an earthquake is much stronger at the surface than underground. Below 60-90m from the surface little-to-no damage generally occurs to underground facilities during an earthquake, and A-CAES caverns are ten times deeper at 600m. This is why mining and tunneling still occur in earthquake prone zones, and why being deep underground is actually one of the safest places to be during an earthquake.

Hydrostor works with reputable Tier 1 OEM suppliers to deliver the equipment, including its turbomachinery and thermal management systems. The above-ground facility is constructed by best-in-class EPC firms, which multi-decade experience delivering directly analogous systems on-time and on-budget, while the subsurface component is delivered by world-class cavern construction specialists, who deliver identical caverns for more rigorous applications.

Project development takes 1-2 years; construction takes 2-4 years.

A-CAES facilities require normal maintenance that would be expected of any power infrastructure facility. Operating and maintenance expenditures (excluding charging costs) are typically 1-1.5 per cent of total project Capex. Unlike chemical batteries, A-CAES does not require costly augmentation or experience degradation and efficiency losses during its life cycle. Maintenance procedures are synonymous with longstanding mechanical equipment operations in the oil and gas industry – providing immense opportunity to transfer direct skills from the fossil fuel industry into alternative energy solutions.

Yes, Hydrostor exclusively sources its equipment from proven equipment manufacturers that offer best-in-class warranties on their equipment. In addition, multiple insurance products are available as a further backstop to deliver investors and customers a fully de-risked and bankable solution.  These include construction bonding and performance guarantees that cover on all aspects of A-CAES operation.