Decarbonisation Technology August 2025 Issue

Evaluating methanol, hydrogen, thermal, and battery storage Exploring the strengths and trade-offs in terms of efficiency, cost, scale, and practical deployment of multiple long-duration storage options

Ashish Gupta and Vaibhav Desai KonsciousPlanet

T he drive to decarbonise the electric grid has sparked a search for energy storage solutions beyond the familiar lithium-ion battery. A reliable, fully renewable grid will need storage that can last not just hours but days, weeks, or even seasons. In addition to lithium- ion, three promising approaches are being explored for long-duration storage: storing energy as heat in ‘Carnot’ thermal systems, using hydrogen as a renewable gas fuel, and synthesising methanol as a storable liquid fuel. Each of these options comes with unique strengths and trade-offs in terms of efficiency, cost, scale, and practical deployment. Batteries today offer unmatched efficiency and quick response, but they are best suited for short- duration needs. Thermal (Carnot) storage can economically handle medium durations (many hours to a few days) by using cheap heat storage, though it sacrifices energy efficiency. Hydrogen can bank massive amounts of energy for weeks or months, at the cost of more complexity and lower efficiency. Methanol, a liquid made from hydrogen and carbon oxides, is emerging as a versatile long-duration storage medium that leverages existing fuel infrastructure. This overview compares all four technologies at a high level, with a special focus on why methanol is gaining attention as a flexible solution for multi- day and seasonal energy storage. Lithium-ion batteries Lithium-ion batteries are the workhorse of today’s grid storage. They dominate applications from home solar backup systems to huge utility- scale ‘battery farms’. Their appeal lies in very high round-trip efficiency (around 85-90% of

the input electricity is returned on discharge) and fast reaction speed. Battery technology is mature, widely available, and its costs have plummeted over the past decade. Large battery installations are now commonly used to smooth out hour-to-hour solar and wind fluctuations and to provide fast frequency regulation. However, lithium-ion batteries have inherent limitations for long-duration storage. The cost per kilowatt-hour of capacity is still high compared to alternatives when scaling up to many hours or days of storage. Practically, most battery projects deliver only a few hours “ Methanol, a liquid made from hydrogen and carbon oxides, is emerging as a versatile long-duration storage medium that leverages existing fuel infrastructure ” of energy (often two to six hours) before the economics become unfavourable. Pushing to 10 or 20 hours of storage would multiply costs dramatically. Additionally, batteries gradually degrade: a lithium-ion system might last around 10-15 years before it requires replacement. This finite lifespan, along with the expense of building very large energy reserves, makes batteries ill-suited to serve multi-day backup or seasonal storage needs for the grid. Key points – lithium-ion: ● Efficiency: ~90% round-trip (very high, minimal losses). ● Best use: Short-duration storage (minutes to a few hours).