Energy storage technologies are being developed at lightning speed with extensive ongoing research. For example, the Journal of Energy Storage published 2,500 research papers in 2022.
This article addresses recent advances (new members) of the growing “house of energy storage.”
The following are the upcoming successors in energy storage technologies.
Graphene batteries. Graphene batteries can be used as a subset of air batteries and lithium-ion (Li-ion) batteries. These batteries utilize chemically processed graphene in the electrodes. Graphene is used in creating hybrid materials for battery enhancement like vanadium oxide and graphene (for enhancing conductivity) and lithium iron phosphate with graphene (lightweight and fast-charging capacity).
R&D is ongoing in graphene nonflammable Li batteries (operating temperature increase by 5°C and reducing fire risks) such as Lyten Inc.’s first automated battery pilot on graphene-enhanced lithium-sulfur batteries; niobium-graphene batteries with 30-year life cycles; and graphene-enhanced polymer battery by PolyJoule Inc. (discharge up to 1 MW of power in less than 10 seconds and recharge in less than 5 minutes).
Graphene has significant advantages over conventional batteries by improving safety, energy density, conductivity, and reducing weight, size, and charge-discharge time (Fig. 1).
Nuclear batteries. Nuclear batteries convert radioisotope energy to electrical energy. They have high energy density (10,000 times more than conventional batteries), reliability, and longevity (power output for decades to 100 years).
Fission batteries use microreactors generating 1 to 20 MW of thermal energy that can be converted to heat/power. Various advanced microreactor designs are presently being supported, including gas, liquid metal, molten salt, and heat-pipe-cooled designs. This system can be integrated plug-and-play and function without operations and maintenance staff (Browning, et al., 2022).
The safety assurance of these batteries is essentially inherent as they are exceptionally robust, residual heat is very small, nuclear fuel is cool in all circumstances, and the steel structure prevents any external contact with the biosphere (Fig. 2). They can be located below grade to ensure protection from external forces.
Another class of nuclear batteries doesn’t rely on fission for power production. Radioisotope decay can be harnessed to yield electricity using thermal/nonthermal conversion.
In the nonthermal conversion, the radioactive particles fall on semiconductors, or the particles are used to produce photons and are then converted to electricity. The challenges that remain are the expensive radioactive particles and low power-density application. There are research groups in Idaho National Laboratory, Los Alamos National Laboratory, NASA, and Westinghouse, which offer more information on nuclear batteries (Chandler, 2021; Singh, et al., 2016).
Supercapacitors battery hybrid. Individually, batteries have high energy density, and capacitors have high power density. Supercapacitors are “electrochemical capacitors.” The capacitance is between the electrode and a layer of ions on the electrode.
Supercapacitors are simply capacitors employing plates with extremely large surface areas, providing a high storage capacity. They typically store 10 to 100 times more energy per unit volume or mass than electrolytic capacitors.
There are three major types of supercapacitor battery hybrids: double-layer capacitors, pseudocapacitors, and asymmetric electrolytic capacitors (Fig. 3). Metal-ion capacitors (like Li-ion, Si-ion, and K-ion) with carbon-based materials are used in these hybrid battery-capacitors for high energy density, high-rate performance, cyclability, and long-term application for energy storage.
The development of such hybrid capacitors is at an early stage and the progress has benefited from development of advanced carbon-based materials (Benoy, et al., 2022).
FlyGrid. FlyGrid is a high-performance flywheel energy storage system integrated into a fully automated fast-charging station or grid. It consists of a flywheel with a spinning rotor, a motor generator, and power converter. The excess power is supplied to the flywheel (more than 100 kW) and can be transmitted to a vehicle automatically.
This serves as an integration to the volatile renewable energy resources and the electricity grid. Enhanced grid stability and power quality through the introduction of inertia in the grid are positives. The integration of energy storage, demandside measures, and grid reinforcements like the FlyGrid can benefit the overall cost infrastructure of energy storage.
FlyGrid is a German research project with consortium members Graz University of Technology and EVT–Montanuniversität Leoben, the electricity grid operator Energienetze Steiermark, and industry partners like myonic GmbH, Thien eDrives, Secar, Energie Steiermark, and DAU (TU Graz, 2018; Thormann, et al., 2021).
There are significant research efforts for development of new flywheel composite materials (high-strength and high energy-storage density), superconductive magnetic suspension bearings (to reduce the frictional losses during the rotation and self-discharge loss and increase the rotor speed), high-speed permanent magnet motors, and a state-of-art operation and control technology (automated system response and system efficiency control) (Bamisile, et al., 2023).
BIO-CAES. Compressed air energy storage (CAES) uses excess power to compress the air, which is further cooled for underground storage. When power is required, the air is heated to power a gas turbine.
The diabatic CAES requires a recuperator and a heater for heating the cooled, pressurized air post-underground storage. This is inefficient because there is only one power output and two input power requirements for compression and heating of the cooled, compressed air.
There is also an adiabatic CAES with thermal energy storage. The waste heat is captured in thermal energy storage after the compression stage. This stored heat is further utilized to heat the air before power generation. But the thermal energy storage time duration is limited.
A novel CAES system with an anaerobic digester will use the generated heat during compression to produce and store biogas. The biogas will be used in the air-expansion stage to maximize the efficiency of the overall process. Therefore, the BIO-CAES concept has a theoretical energy efficiency of over 80%. This hybridization of technologies will benefit by providing sufficient thermal energy from the biogas, high energy storage in chemical form instead of thermal energy storage—avoiding thermal energy storage investment, and reducing heat losses (Llamas, et al., 2020).
Pumped thermal energy storage (PTES). This technology stores electrical energy in the form of thermal energy by employing a heat pump and heat engine cycle during charging and discharging, respectively. The technology is at an embryonic stage with a theoretical estimate of the roundtrip efficiency of 52%. Experimentation and studies are required for performance evaluation in different configurations of PTES such as Brayton-PTES, Rankine-PTES, and compressed heat energy storage (Sharma & Mortazavi, 2023).
The Way Ahead
The developments in BIO-CAES for bulk storage will help increase the efficiency of mature compressed air energy storage. The supercapacitor battery hybrid will widen its usage curve from reserve and response to transmission and distribution for worldwide cost-effective deployment. FlyGrid and graphene batteries are enhancements in the currently established energy storage technologies for improving safety, efficiency, compactness, life, and energy density. Nuclear batteries offer a novel look into the future.
For Further Reading
Development and Prospect of Flywheel Energy Storage Technology: A Citespace-based Visual Analysis by Bamisile, O., et al. Energy Reports.
Recent Trends in Supercapacitor-battery Hybrid Energy Storage Devices Based on Carbon Materials by Benoy, S. M., et al. Journal of Energy Storage.
Foundations for a Fission Battery Digital Twin by Browning, J., et al. Nuclear Technology.
Why “Nuclear Batteries” Offer a New Approach to Carbon-free Energy by Chandler, D. MIT News.
Journal of Energy Storage News
Development of an Efficient and Sustainable Energy Storage System by Hybridization of Compressed Air and Biogas Technologies (BIO-CAES) by Llamas, B., et al. Energy Conversion and Management.
Graphene Batteries Explained, NanoWerk.
Pumped Thermal Energy Storage: A Review by Sharma, S., et al. International Journal of Heat and Mass Transfer.
Nuclear Batteries: Harnessing Energy of Radioactive Materials for Long Lasting Low Power Applications by Singh, A., et al. Bhabha Atomic Research Center.
Graphene Batteries: Introduction and Market News, Graphene Info.
FlyGrid–Integration of Energy Storage Systems into EV Fast Charging Infrastructure by Thormann, B., et al. International Energy Economics conference.
Who is Working on FlyGrid?Flywheel Energy Storage for EV Fast Charging and Grid Integration.
Are Graphene Batteries the Future? AZO Nano.
Preparation of Graphene by Exfoliation and its Application in Lithium-ion Batteries by Wen, Y., et al. Journal of Alloy and Compounds.
