Episode Summary
Executive Summary: The episode argues that as grids decarbonize, storage needs will grow far beyond today’s battery base, but no single technology will win. Shail Khan and Andy Lubershane compare lithium-ion, thermal storage, Form’s long-duration iron-air batteries, hydrogen, and fossil fuels with CCS, concluding the future grid will likely use a portfolio matched to different duration needs.
Main Topics: Current fossil-fuel storage on the grid (Priority: 5/5): Andy explains that the energy system already stores large amounts of energy in coal piles, oil tanks, gas pipelines, underground reservoirs, and strategic reserves—forming a de facto storage layer that supports reliability and resilience today. Lithium-ion batteries for short-duration balancing (Priority: 5/5): Lithium-ion is presented as the best fit for 2-8 hour daily peaks in net load because it is efficient, mature, increasingly cheap, and benefiting from EV-driven manufacturing scale, though its cost rises roughly linearly with duration. Thermal storage as cheap diurnal storage (Priority: 4/5): Heat storage is framed as a promising low-cost option for situations where end-use heat is the desired output, and potentially for repowering retiring coal plants; however, power-to-power thermal systems face efficiency and operational challenges. Form Energy and multi-day storage (Priority: 5/5): Form is highlighted as a rare player in ultra-long-duration storage, offering low-cost iron-air batteries for multi-day backup. The technology is less efficient than lithium-ion but valuable for capacity during extended low-renewable periods. Hydrogen as ultra-long-duration and cross-sector storage (Priority: 4/5): Despite skepticism about hydrogen’s poor efficiency and difficult handling, Andy becomes more open to its role because it can be produced at scale, stored underground, and used across power, heat, and industrial sectors. Fossil fuels with CCS as a competing alternative (Priority: 3/5): Carbon capture and storage is described as a potential substitute for many storage needs because fossil fuels already provide massive storage. If CCS becomes economical and proven, it could compete with other storage pathways.
Key Arguments: The grid already has substantial storage in fossil fuel inventories, so the challenge is not creating storage from zero but replacing and reconfiguring it. Lithium-ion is ideal for short-duration daily cycling because its efficiency and mature supply chain outweigh its cost limitations at low durations. Battery economics worsen as duration increases because capacity cost scales with kilowatt-hours, making lithium-ion less suitable for long-duration needs. Thermal storage can be extremely cheap and efficient when electricity is converted to heat and used as heat, especially for industrial applications. Multi-day storage requires different economics than daily balancing; Form-like systems can serve capacity needs during rare extended lulls in renewable output. Hydrogen is inefficient as a storage medium, but its future may be supported by the buildout of clean hydrogen production, underground storage infrastructure, and retrofit-ready gas turbines. A future low-carbon grid will likely rely on a portfolio of storage technologies rather than a single dominant solution, with each tranche serving a different duration need.
Data Points: Primary energy supply stored today: about 47 days - Estimated average amount of fossil fuel energy kept in stockpiles, pipelines, tanks, and reserves in the U.S. Natural gas in storage: about 9 days - Part of the 47-day fossil fuel storage total. Coal stockpiles: about 13 days - Part of the 47-day fossil fuel storage total. Crude oil storage: about 10 days - Part of the 47-day fossil fuel storage total. Strategic oil reserve: about 15 days - Historical strategic reserve included in the fossil storage estimate. Renewables-generated energy in 2021 if bottled as storage: about 5 days - Illustrates how small non-fossil storage is relative to current fossil stockpiles. Pumped hydro storage: about 9 minutes - Primary-energy-supply equivalent of the largest existing grid electricity storage resource. Battery storage capacity today: seconds level, possibly milliseconds - Comparison to primary energy supply equivalent; emphasizes how little grid-scale battery storage exists. Net load spike duration: 2 to 6 hours, sometimes up to 8 hours - Typical duration of daily peak periods that lithium-ion is well suited to address. Lithium-ion AC-to-AC efficiency: 80% to 90% - Round-trip efficiency advantage for power-to-power applications. Lithium-ion installed cost at 4 hours: about $300 per kWh - Approximate fully installed cost cited for today’s stationary lithium-ion systems. Thermal storage core material cost: about $5 per kWh or lower - Cheap materials such as rocks, brick, or carbon can store heat very inexpensively. Lithium-ion cost floor: north of $100 to $150 per kWh installed - Andy’s estimate of the likely lower bound for fully installed lithium-ion systems. Form battery duration: approximately 100 hours - Described as roughly a four-day battery system for multi-day storage. Form cost relative to lithium-ion: around a tenth or less - Expected installed cost for Form’s 100-hour battery compared with lithium-ion. Hydrogen electrolysis loss: at least 30% - Initial efficiency loss when making hydrogen from electricity. Hydrogen transport/storage loss: another 10% to 20% - Additional losses from moving and storing hydrogen. Hydrogen power conversion efficiency: about 35% in a gas turbine; 55% to 60% in a fuel cell - Ways to convert hydrogen back to electricity. Hydrogen round-trip efficiency: about 20% to 35% - Overall power-to-power efficiency estimate for hydrogen storage. Hydrogen in current gas turbines: about 10% to 18% by annual energy content - Current blending level in retrofit-ready turbines. Hydrogen retrofit target: up to 100% starting around 2030 - Potential future capability of gas turbines to run on hydrogen. Renewable penetration benchmark: 50% to 60% - Level at which thermal storage becomes more attractive due to more surplus generation. Surplus renewable periods: 6 to 10 hours - Typical daily periods of excess generation in high-renewables systems.
Pivotal Quotes: "between the minutes of energy storage we have today and 47 days, I think we're going to fall probably actually ultimately closer to the 47 days level than even minutes, hours, or just a few days worth of storage" — Andy Lubershane: Core thesis that future grids will need far more storage than today, though not necessarily all fossil-based storage "heat storage is one of those concepts that, as soon as you sort of wrap your mind around it, just makes incredible amounts of sense" — Andy Lubershane: Introduction to thermal storage as a low-cost, high-efficiency option for heat applications "you have to believe that there's going to be a lot of surplus generation that you otherwise would be wasting if you're going to be doing something that inefficient with primary energy" — Andy Lubershane: Explanation of why hydrogen’s poor round-trip efficiency can still be rational in a high-renewables system
Implications: Utilities, investors, and policymakers should plan for a layered storage stack: lithium-ion for short peaks, thermal and form-style systems for longer gaps, hydrogen for ultra-long duration, and CCS as a wildcard competitor.