Bioinspired Storage

The growth of solar energy as a mainstream source of power generation has so far been limited by the uncertainty and variability associated with its integration into the grid network. While battery storage is an option, its high capital cost and bulkiness have prevented it from becoming a viable solution.

Australian scientists and professors at the RMIT University, Melbourne, Litty V. Thekkekara and Min Gu, have invented a new technology that has the potential to solve solar energy storage challenges. The technology uses electrodes made of graphene, an allotrope of carbon that has two-dimensional atomic hexagonal lattices. Its structure makes graphene one of the strongest materials in the world, with highly efficient heat and electricity conduction properties. These electrodes can improve the solar energy storage capacity by up to 3,000 per cent.

The multiple-electrode network is designed to imitate an American sword fern, which is extremely efficient in storing energy and water for transporting through the plant. The veins of the plant fill in the spaces through self-repeating patterns known as fractals. This has been replicated by the two scientists in the storage solution they have developed. It helps improve solar energy storage at the nano level.

Moreover, when the technology is combined with super-capacitors, as developed in the prototype, the energy storage capacity of these super-capacitors can be increased by 30 times the current limit. Super-capacitors help provide long-term reliability and release a quick burst of energy that can particularly help during overcast weather or a long-drawn monsoon season. Graphene-based electrodes, when combined with super-capacitors, result in long-term energy storage with minimum leakage.

The prototype has been developed based on flexible thin-film technology. Flexible thin-films are sheets of amorphous silicon or cadmium indium gallium selenium solar cells that have high efficiency and can be installed anywhere. Such flexible sheets are ideal for rooftop solar generation as well as for potential usage as fuel for transportation. With the integration of graphene-based energy storage technology into flexible thin-film solar cells, the boundless applications of solar energy can be unlocked.

The new energy storage technology aims at developing an independent solar cell that can not only generate but also harvest, store and transfer energy to the device as required. Small applications include charging stations for phones, laptops, electric vehicles and other devices. As flexible thin-films can be installed on any surface such as windows, car panels and buildings, with the help of the graphene-based storage technology, harvesting solar energy for any application will no longer be restricted to the daytime or sunny weather. It can also be potentially integrated into wearable devices.

The cost of developing graphene-based storage system is, however, a limiting factor at this stage. The cost of graphene at the beginning of 2016 was around $100 per gram, making its use in energy storage technology unaffordable. Also, flexible thin-films cost more as compared to conventional thin-film solar modules, making the integrated technology even more expensive.

Graphene-based solar energy storage systems with their unlimited applications have the potential to transform the Indian solar market. The government’s efforts to increase solar installations are now becoming increasingly dependent on proper power evacuation infrastructure, and the integration of variable and uncertain solar energy into the grid. However, as the demand on the grid requires a constant supply of power, the integration of renewable energy is proving to be difficult. While the prevalent lithium-ion batteries allow solar systems to harness solar power as required, their use is limited to small residential systems and is not extended to grid-based power. The lean new storage technology could help store large amounts of power that can be fed into the grid without interruption or uncertainty.

The new solar storage technology has the potential to completely disrupt the battery storage market for solar applications. When combined with super-capacitors and flexible thin-film solar technology, the complete independent system could help solve energy issues in most developing countries, especially in remote areas with no access to grid-based power. Also, it will help better integrate solar into the mainstream energy grid. Its applications are, however, subject to the scalability of the technology and the cost reduction achieved as a result, which would make this product affordable for the masses.