Academics have patented new concepts on electric power energy storage using gravity, with the concept of gravity energy storage using soil batteries being promoted by two University of Nottingham academics – European Academy of Sciences fellow and World Society of Sustainable Technologies president Professor Saffa Riffat and Marie Curie research fellow Professor Yijun Yuan.

The academics filed a patent application in May for a gravity energy storage technology based on drums filled with soil.

The GravitySoilBatteries technology uses storage cores – large drums filled with compacted soil – that can be shifted between lower and higher points. The soil for the storage device can be obtained locally by digging the ground to create deep channels for the system.

The soil is also used as a filler for the central concrete support structure. Pulleys are mounted on the top of central concrete structure. The drums are fitted with axial shafts and bearings and are mounted on a metal frame similar to tarmac rollers.

The drums can then be pulled on the sloped central concrete structure using cables and a motor or generator. The motor or generator is mounted on the ground to provide good stability and ease of maintenance.

When the heavy drums move down, they release potential energy (i.e. electricity generation) to the main grid system.

During the discharge phase, the drums are moved upward to store energy supplied by photovoltaic solar power or wind turbines, using power when not needed by the grid, storing the energy for later use.

GravitySoilBatteries can be used for large-scale storage in conjunction with main grid systems, the academics say.

The technology is environment-friendly and simple to construct, the World Society of Sustainable Energy Technologies says.

The estimated cost of the GravitySoilBatteries is about $50/kWh or lower depending on the depth of the channels and height of the central support structure. The cost of pumped storage hydropower, without considering land costs, is about $200/kWh, while the cost of battery storage is about $400/kWh.

The energy storage capacity of GravitySoilBatteries for small-scale storage could be 300 kWh, while that of high-scale storage could be 30 000 kWh or higher, depending on the drum weight and stack height, with an estimated system efficiency of about 85%.

GravitySoilBatteries can be applied widely with simple siting and construction, the academics say.