The costs of supercapacitors are tabulated in this data-file, with a typical system storing 15-seconds of electricity, for a capex cost around $10,000/kWh of energy but just $40/kW of power. Hence, for short-duration, but very frequent and fast-acting voltage regulation, supercapacitors may be highly competitive with lithium ion batteries and flywheels. Numbers can be stress-tested in this model.
Supercapacitors store energy electrostatically, as electrical charge builds up on two plates, made of material such as activated carbon or graphene, which is disposed on either side of a dielectric material. If the voltage falls below some threshold level, then the charge will flow off these plates. Hence capacitors and supercapacitors resist changes in voltage.
As opposed to lithium ion batteries, which tend to have 3,000 – 10,000 cycle lives, due to battery degradation, supercapacitors can have up to 1M cycle lives, and can be operated with several thousand charge-discharge cycles per annum.
Supercapacitors can also regulate voltage, and buffer against voltage drops very rapidly, with response times in the nanosecond range, which makes them particularly useful for buffering the kinds of transients of AI data-centers.
What are the costs of supercapacitors? This data-file captures supercapacitor economics, based on 20 examples and case studies, ranging from small battery-sized cells with <1kW of capacity (and <10Wh of energy storage) through to MW-scale systems to buffer grids or prevent voltage sags around electrical railways, which can store 10kWh+ in container-sized systems.
The capex costs of supercapacitors are contrasted with the costs of lithium ion batteries and the costs of flywheels in the chart below.
A typical supercapacitor stores about 15 seconds of energy, for a capex cost of $10,000/kWh, but just $40/kW of power. This is down to very high power density (10-25 kW/kg, 10-25x higher than a lithium ion battery), albeit quite low energy density (2-10 Wh/kg, which is 95-99% below a lithium ion battery).
Hence a supercapacitor system earns a 10% IRR if it charges a 6c/kWh spread and charges/discharges around 30,000 times per year. If say, 5-10%, of the electricity in a power-consuming system flows through the supercapacitor as part of voltage stabilization process, then this will inflate the total consumed cost of power by 0.3-0.6 c/kWh.
Supercapacitor costs in $/kW and $/kWh terms vary as a function of the system build, materials and energy storage duration (in seconds). Numbers can be viewed in the data-file. As supercapacitor companies scale up production, capex costs will likely fall further, as has been the precedent from the scale-up of other solid-state devices and semiconductors.
Please download the data-file to stress-test the costs of supercapacitors and the economics of supercapacitor-based voltage regulation.