Sea Bed Air Batteries- long term, cheaper energy storage

[Sparty]

Summary of https://cleantechnica.com/2024/05/05...ust-add-water/

BaroMar, an Israeli company, is testing a new approach to grid-level energy storage that it claims will be the most cost-effective way to stabilize renewable grids over longer periods. This innovative system leverages the power of water.

The future zero-carbon energy grid will be complex, with solar, wind, and other renewable energy sources contributing power when possible. However, this won’t always align with demand, necessitating energy storage and release measures. These measures will be needed for various time scales, from smoothing out daily peaks and troughs to compensating for periods of poor solar output due to overcast weather.

Long-duration storage, which aims to store electrons for the winter when there’s a seasonal dip in solar generation, is the area BaroMar is targeting with its unique take on Compressed Air Energy Storage (CAES).

CAES uses excess energy to run compressors, typically pumping air into large, rigid tanks where it can be stored at high pressures. The stored air can then be released through a turbine to drive a generator and recover the energy. While CAES is already a cost-effective energy storage option, BaroMar believes it can outperform traditional systems for long-duration energy storage using a low-tech solution.

BaroMar’s plants will be located near coastlines with access to deep water. Instead of using large high-pressure tanks, BaroMar uses the pressure of the water column to store compressed air in cheaper enclosures. These enclosures are large, inexpensive concrete and steel tanks, weighted down with cages full of rocks and submerged at depths between 200-700 meters. The tanks, initially filled with seawater, have several water-permeable valves. When there’s excess energy to be absorbed, a compressor feeds ambient air down to these tanks through long hoses, forcing water out of the tanks.

The hydrostatic pressure of the external water equalizes against the internal air pressure, meaning the tanks don’t need to be as strong or expensive as land-based tanks that must hold high-pressure internal air against regular atmospheric pressure.

When it’s time to recover the energy, the system allows air to run back up the hose into a thermal recovery system, followed by a turbo-expander that drives a generator. Water then rushes back into the tank, ready to be displaced again when the compressor is running.

Engineering consultancy Jacobs, appointed to design a pilot project in Cyprus, aims for a round-trip efficiency of around 70%, similar to the world’s largest CAES plant in Zhangjiakou, northern China. This underwater pilot will be much smaller, storing just 4 MWh.

BaroMar claims it should outperform competing long-duration energy storage (LDES) options on cost, thanks to its durable, very low-cost tanks and minimal underwater maintenance costs. Running a 100 MW/1 GWh installation 350 days per year for 20 years, BaroMar says it can deliver a Levelized Cost of Storage (LCoS) of US$100 per MWh, compared to “other LDES technologies” which, it claims, come in closer to $131/MWh.

However, there are challenges with anything designed to operate for 20 years under the sea. Jacobs, tasked with designing the system to a buildable standard, hints at the hurdles ahead, including extensive geophysical, geotechnical, and bathymetric surveying, investigation, feasibility studying, and permitting for tank installation at deep depths for onshore mechanical and electrical equipment needs.

Despite these challenges, cost-effective and scalable solutions will prevail in the new renewable grids. If BaroMar’s idea delivers as claimed, it will be relevant to many locations, given the proximity of cities to the coast.