Technology Overviews
The Technologies
In-depth overviews of the five technology categories tracked on this site — what they are, how they work, and where deployment stands today. Each overview covers the underlying science, the leading developers, and the projects currently in development or operation.
Iron-Air Battery
Iron–air batteries promise affordable, multi-day energy storage for the grid by harnessing abundant, eco-friendly iron, but face challenges with efficiency and material durability at scale. Ongoing innovations in materials and system design aim to unlock their potential as a safe, sustainable solution for firming renewables and boosting grid resilience.
Vanadium Redox Flow Battery
Vanadium redox flow batteries (VRFBs) are a unique energy storage technology that stores power in liquid vanadium electrolytes, allowing independent scaling of power and energy for cost-effective, long-duration storage. With lifespans exceeding 20,000 cycles and virtually no capacity loss, VRFBs are gaining traction worldwide—especially in China—despite higher upfront costs, thanks to their robust performance and recoverable electrolyte value.
Refractory Brick Heat Battery
From ancient kilns to cutting-edge grid-scale solutions, Thermal Energy Storage systems are revolutionizing industrial decarbonization and renewable energy integration with high-temperature, low-cost, and modular technologies that surpass conventional batteries. As innovations drive material sustainability and system flexibility, overcoming technical and market barriers will be key to unlocking TES’s full potential for deep decarbonization and grid resilience.
Geopressured geothermal storage
Geopressured geothermal storage (GGS) is a breakthrough energy technology that stores and dispatches electricity by harnessing the immense pressure of deep underground rock, offering grid-scale storage without the geographic limits of traditional hydropower. With commercial deployments already underway, GGS delivers high efficiency, low fluid loss, and cost-competitive power, positioning it as a game-changer for renewable energy integration and grid resilience.
Liquid Air Energy Storage
Liquid air energy storage (LAES) is a cutting-edge, long-duration energy storage technology that turns ambient air into liquid at -196°C, storing it for later use to generate electricity with no reliance on lithium or rare-earth materials. With commercial-scale projects underway in the UK, China, and Japan, LAES offers a high-density, geographically flexible alternative to traditional storage methods, boasting a 30–50 year design life and efficiencies up to 90% in hybrid systems.
Compressed Air Energy Storage
Compressed Air Energy Storage has transformed from basic mechanical applications to cutting-edge systems like adiabatic and isothermal CAES, which boost efficiency and eliminate fossil fuel use by capturing and reusing compression heat. Despite innovations in storage architecture and media, CAES must overcome high costs, geological constraints, and regulatory hurdles to realize its potential as a scalable, zero-emission solution for long-duration energy storage.
Solid Oxide Fuel Cell
Solid oxide fuel cells (SOFCs) are high-efficiency, fuel-flexible electrochemical devices that generate electricity directly from a variety of gaseous fuels at elevated temperatures, offering a promising pathway for clean power and hydrogen production. Despite rapid market growth and major deployments by companies like Bloom Energy, SOFCs face challenges such as high costs, durability issues, and the need for advanced materials to achieve long-term reliability.
CO2 Battery
CO₂ Batteries are a breakthrough long-duration energy storage technology that stores electricity by compressing and liquefying carbon dioxide, achieving higher energy density than air-based systems using only standard industrial components. Pioneered by Energy Dome, these batteries offer a scalable, lithium-free solution deployable anywhere, with commercial plants already operating in Italy and the U.S.
Millimetre Wave Drilling
Millimetre wave (MMW) drilling, pioneered at MIT and commercialized by Quaise Energy, uses high-power electromagnetic waves to vaporize rock and could unlock superhot geothermal energy from depths far beyond the reach of conventional drills. After achieving a record 100-meter granite bore in Texas, the technology promises terawatt-scale clean power but faces major engineering hurdles before reaching its 15–20 km commercial targets.
Advanced Geothermal (Closed Loop)
Closed-loop geothermal systems (CLGSs) are revolutionizing geothermal energy by using sealed wellbores to extract subsurface heat without fracking, water consumption, or seismic risk, as demonstrated by GreenFire Energy and Eavor Technologies. While CLGSs offer vast global potential and reliable performance, their widespread adoption for electricity generation hinges on significant reductions in drilling costs, making district heating their most promising near-term application.
Enhanced geothermal system
Enhanced Geothermal Systems are revolutionizing clean energy by unlocking heat from deep, hot rocks using advanced drilling and reservoir engineering, making geothermal power possible in regions previously out of reach. Despite their promise for scalable, reliable energy, EGS must overcome high costs, technical challenges, and environmental concerns to achieve widespread adoption.
Lead Cooled Fast Reactor
Lead-cooled fast reactors (LFRs) are next-generation nuclear systems that use molten lead as coolant, offering major safety advantages over sodium-cooled designs and ranking highest among Gen IV reactors for sustainability and security. With Russia’s BREST-OD-300 nearing completion and several international projects advancing, LFRs are poised to transform nuclear energy by the 2030s—if engineers can overcome the challenge of lead corrosion at high temperatures.
Sodium-cooled fast reactor
Sodium-Cooled Fast Reactors promise a leap in nuclear sustainability by maximizing fuel use and minimizing waste, thanks to their innovative use of liquid sodium coolant and closed fuel cycles. Despite their potential for safer, more efficient power, SFRs face hurdles from high costs and engineering challenges, but global efforts in Russia, India, and China are pushing the technology toward commercial reality.
Lightwater SMR
Light-water small modular reactors (LW-SMRs) promise safer, factory-built nuclear power using proven pressurized water technology, but their economic viability hinges on achieving large-scale deployment to drive down costs. With leading designs like Westinghouse AP300 and Rolls-Royce SMR vying for market share, the world watches to see if these compact reactors can deliver affordable, low-carbon energy by the early 2030s.
High-temperature gas-cooled reactor
High-Temperature Gas-cooled Reactors (HTGRs) have advanced over 75 years, offering robust safety, high efficiency, and unique industrial applications thanks to innovations like TRISO fuel and helium coolant. While recent international projects highlight their transformative potential for clean energy and decarbonization, HTGRs must still overcome challenges in fuel supply, regulation, and waste management to achieve widespread deployment.