Overview of lithium-ion capacitor-based system for compensation of short-term power disruptions
Overview of Lithium-ion Capacitor-based System for Compensation of Short-term Power Disruptions 1 System performance
Uninterruptible switching (Switching time: 2 ms or less)
99% or more (Excepting power for air conditioning systems㸧
2 External view of system (System used in field trials)
System for compensation of short-term power disruptions
6,600 V, 1,000 kVA, 600 kW×11 sec compensation
3 Outline of system operation Lithium-ion capacitor-based system for compensation of short-term power disruptions Normal operation Normal operation
㸦Connected㸧 Lithium-ion capacitor-based system for compensation of short-term power disruptions Power disruption Power disruption
㸦Disconnected㸧 4 Use of lithium-ion capacitors
Lithium-ion capacitors are hybrid capacitors, exploiting the fact that they function according to the
principle of operation of electrical double-layer capacitors*1 at their positive electrodes and the principle
of operation of lithium-ion batteries*2 at their negative electrodes to offer the characteristics of both.
They are able to store approximately three times as much energy as conventional electrical double-layer
The use of lithium-ion capacitors in the energy storage section of the newly developed system for
compensation of short-term power disruptions enables the system to respond to power disruptions of up
to 20 seconds in duration, meaning that its use in combination with fast-acting emergency generators is
able to ensure a complete absence of power disruption.
5 Other technologies applied in the system
The new system employs high-speed, high-capacity solid-state transfer switches developed for an
electrical double-layer capacitor-based instantaneous voltage drop compensation system which Chubu
Electric has already developed for commercial operation. The switches are highly reliable, and capable
of ultra-high-speed switching. This enables the system to switch from the commercial power supply to
inverter output in 2/1,000th of a second or less. In addition, the improvement of capacitor charge
management has resulted in the achievement of a 99% or greater level of efficiency in constant
operation (excepting power for air conditioning systems).
Because lithium-ion capacitors also require different forms of charge-discharge control to electrical
double-layer capacitors (management of lower limit voltage, etc.), circuit configurations and control
methods have been redesigned (for example through the use of DC circuit breakers in the charge storage
(Reference) Lithium-ion capacitors: Structure and principle of operation
Lithium-ion capacitors employ activated carbon in their positive electrodes. The adsorption and
desorption of charge-carrying ions across an extremely thin electrical double layer that forms on the
surfaces of the electrodes (the thickness of these layers is of the order of two molecules of the electrolyte
solution) enables energy to be stored as capacitance (capacity to adsorb charge). The negative electrodes
of a lithium-ion capacitor employ layered graphite, and store energy through adsorption of lithium ions
Separator Electrical double layer Discharge Electrolyte ion Lithium ion Positive electrode (Activated carbon) Negative electrode (Graphitic carbon)
Lithium-ion capacitors combine the characteristics of electrical double-layer capacitors*1 and lithium-ion
batteries*2. Their high voltage (3.8V) in comparison to conventional electrical double-layer capacitors
enables them to realize a level of energy density (amount of electrical energy stored per unit volume)
approximately three times higher, while also displaying a level of power density (electrical energy
output per unit time) and a cycle life (number of possible charge-discharge cycles: around 100,000)
rivaling that of electrical double-layer capacitors.
*1 Electrical double-layer capacitor
Electrical double-layer capacitors use porous activated carbon in their electrodes (the same material that the positive electrodes of
lithium-ion capacitors are made of), and adsorb and desorb charge-carrying ions across extremely thin electrical double layers that
form at the electrodes. This enables the capacitors to realize a higher level of capacitance than standard condensers, but because
their voltage is low at around 2.5V, they have a low energy density compared to other energy-storage devices.
However, because no chemical reactions occur at either the positive or negative electrodes, the capacitors also display the highest
power density and cycle life (100,000 cycles or more) of the three types of energy-storage devices.
*2 Lithium-ion battery
Like lithium-ion capacitors, lithium-ion batteries use graphite in their negative electrodes, but they use layered metal oxide lithium
in their positive electrodes. When the batteries charge, lithium ions are drawn out of the crystal structures of the positive
electrodes and inserted into the graphite layers of the negative electrodes. This gives the batteries a high voltage (4V or higher)
and energy density, but because charge and discharge involves chemical reactions, their power density is low and their cycle life is
N. 02403/2011REG.PROV.COLL. N. 07848/2010 REG.RIC. R E P U B B L I C A I T A L I A N A IN NOME DEL POPOLO ITALIANO Il Consiglio di Stato in sede giurisdizionale (Sezione Terza) SENTENZA sul ricorso numero di registro generale 7848 del 2010, proposto da: Sanitaria Scaligera Spa, rappresentata e difesa dagli avv. Renzo Cuonzo, Stefano Gattamelata, Giovanni Sala, Faust
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Overview of Lithium-ion Capacitor-based System for