How does thermal energy storage compare to other energy storage technologies in terms of cost and efficiency

Thermal energy storage (TES) compares favorably to other energy storage technologies in terms of cost and efficiency, particularly for long-duration storage applications and industrial uses. Below is a detailed comparison based on recent data and analyses:

Cost Comparison

• Thermal Energy Storage Costs:
  Thermal energy storage costs range around $232/kWh installed capex globally on average, making it one of the least expensive long-duration energy storage (LDES) technologies available today[2]. For molten salt TES systems used at utility scale, capital expenditure (capex) is estimated at about $350/kWh with an estimated levelized cost of storage (LCOS) around 13.5 c/kWh-th under a 10% internal rate of return scenario, with possibilities to reduce costs to 5-10 c/kWh-th with improvements and lower capital costs[1].
  Thermal storage using materials like water, stone/rock, or molten salt can have capacity costs between 0.4 to 70 Euro/kWh depending on the medium, with water-based storage being the cheapest and molten salt somewhat higher but still competitive, especially for large-scale applications[5].

• Lithium-ion Batteries:
  Lithium-ion batteries have higher capex costs, about $304/kWh for four-hour duration systems globally, which is higher than TES for longer durations[2]. Cost predictions for 2025 estimate lithium-ion battery capacity costs between $308-$419/kWh, significantly higher than many thermal storage options[5]. Lithium-ion batteries also require extensive safety and monitoring systems that increase overall operating costs[3].

• Other Technologies:
  Other LDES technologies such as compressed air storage and flow batteries have capex costs around or slightly above TES costs, e.g., compressed air at $293/kWh and flow batteries even higher[2]. Mechanical storage like pumped hydro and compressed air generally have lower energy densities and different siting constraints but can also be cost-effective at scale[5].

Efficiency Comparison

• Thermal Energy Storage Efficiency:
  ThermalBattery™ systems demonstrate round-trip efficiencies over 98%, which is very high for thermal storage[3]. Thermal systems generally experience low thermal losses (~1-2% per day) due to good insulation[1]. They can store and release heat continuously over periods ranging from hours to days, offering reliable supply especially for industrial process heat and renewable integration[3].

• Lithium-ion Batteries Efficiency:
  Lithium-ion batteries typically have electrical round-trip efficiencies around 85-95%, slightly lower than some advanced thermal storage systems but still high[3]. Their capacity degradation and limited cycle life can reduce effective efficiency over time.

• Other Technologies:
  Compressed air energy storage and pumped hydro efficiencies vary widely, typically 70-85%. Flow batteries have efficiencies closer to lithium-ion but with larger footprint and cost concerns for long durations[2][5].

Other Considerations

• Durability and Maintenance:
  TES systems like ThermalBattery™ have longer service lives, minimal performance degradation, and are nearly maintenance-free compared to lithium-ion batteries which degrade over cycles and require fire safety measures[3]. Thermal storage is also based on abundant, recyclable materials, making it more sustainable and environmentally friendly[3].

• Applications and Scalability:
  TES is especially suited for industrial heat supply, grid-scale energy balancing, and renewable integration, providing flexibility in site location due to lower footprint constraints than pumped hydro or compressed air[1][4]. Lithium-ion batteries excel at short-duration, fast-response energy storage with high power density.

• Geographical and Market Differences:
  TES and other LDES technologies benefit from economies of scale in markets like China where gigawatt-hour scale projects reduce costs substantially[2]. Outside China, costs are higher but still competitive for long-duration needs where lithium-ion costs rise due to materials and scale limitations.

Summary Table

In conclusion, thermal energy storage offers lower costs, higher efficiency, and longer durability than lithium-ion batteries and many other long-duration energy storage options, especially for applications requiring storage of heat or long discharge durations. It is particularly advantageous for industrial heat storage and grid-scale integration of renewables where thermal output is directly usable. Lithium-ion batteries, however, remain preferred for short-duration, high-power storage needs despite higher costs and environmental concerns[1][2][3][4][5].