Examining Unique Alternatives to Conventional Energy Storage

In most cases relating to renewable energy sources, energy storage is considered solely in terms of conventional batteries. While this electrochemical form of storage is the industry's mainstay, recent years have seen significant interest in other forms of energy storage. Specifically, compressed air energy storage (CAES) and buoyancy work energy storage systems (BWES) offer unique alternatives to conventional energy storage.

Researchers from the University of Sharjah in the United Arab Emirates have assessed the viability of different buoyancy work energy systems. This article reviews CAES and BWES systems and examines the details of the research studies.

 

Compressed air energy storage. Image used courtesy of Wikimedia Commons

 

Compressed Air Energy Storage

Compressed air energy storage represents a promising avenue for efficient and sustainable energy storage solutions.

CAES systems store energy by compressing air using surplus electricity, usually generated from renewable sources during times of low demand. This compressed air is then stored in underground caverns or tanks. When electricity demand peaks, compressed air is released, driving a turbine connected to a generator and converting the stored potential energy back into electricity. This offers a viable solution, particularly in grid stabilization, where large amounts of energy need to be stored and released quickly to balance supply and demand. 

 

A compressed air energy storage system. Image used courtesy of Pacific Northwest National Laboratory

 

Compared to traditional battery-based storage, CAES systems have an advantage in scalability and capability. CAES systems can scale up to store large amounts of energy, making them well-suited for grid-scale storage applications. This contrasts with traditional batteries, where scaling up can significantly increase cost and complexity​.

CAES is also particularly advantageous when integrated with renewable energy. Renewable energy integration requires the power grid to be flexible and capable of accommodating fluctuations in energy generation. CAES contributes to this flexibility by providing a way to balance energy supply and demand over various timescales, from short-term fluctuations to longer-term shifts in energy production and consumption patterns​​​​. By doing so, CAES can help reduce the reliance on conventional fossil-fuel power plants, traditionally used to meet peak demands and balance the grid, thus supporting a more sustainable and low-carbon energy system.

 

Buoyancy Work Energy Storage

In addressing the challenge of renewable energy storage, the research team focused on a buoyancy work energy storage system. A BWES differs from traditional CAES by using the buoyancy force in fluids for energy storage. In a BWES, a buoyant object, such as a polyvinyl chloride (PVC) float, is submerged to store potential energy and released to ascend, converting this energy into mechanical work. 

The study examined the impact of different buoy materials, gases, and coatings on system performance. Their experimental setup involved a plastic buoy and a PVC float, common in buoy construction, filled with either air or helium. The investigation extended to assessing the effect of a lubricating silicon coating on these buoys.

The study revealed that PVC floats, particularly when filled with air or helium and coated with silicon, demonstrated superior energy output compared to the uncoated plastic buoy. Specifically, the silicon-coated, air-filled PVC float exhibited a notable 15.44% increase in energy output and a 4% overall efficiency improvement. However, researchers observed the silicon-coated, helium-filled PVC floats required more energy to submerge, leading to some efficiency losses, with peak efficiency recorded at 24.18%. In contrast, the silicon-coated, air-filled PVC float achieved a higher efficiency peak of 29.61%.

 

The working principles of a BWES. Image used courtesy of Klar et al.

 

Building on these results, the researchers proposed scaling up the BWES for use alongside the London Array offshore wind turbine farm. This larger-scale implementation aims to leverage the buoyancy system's enhanced performance characteristics, projecting a levelized cost of electricity (LCOE) of just 0.978 ¢/kWh. 

 

Energy Storage Research Impact

The research findings could have notable implications for the future of renewable energy storage. For example, the cost-effective rate of the resulting system indicates these systems could be commercially viable. Overall, the success of this research could pave the way for broader adoption of buoyancy work energy storage systems, offering a sustainable and efficient alternative to traditional energy storage methods​.