The Tortoise & the Hare: Batteries & Ultracapacitors

The tortoise & the Hare: in Energy storage, they both win.

By Hanna Schroer

The energy sector is buzzing about the hidden potential of ultracapacitors. Ultracapacitors have less storage capacity than a battery, but are the fast-start companions for lithium-ion batteries. The market has grown to $350 million through 2012 and is expected to increase to over $400 million in 2013. This market growth has positive implications for the power grid and for automobiles.

Managing Power Quality

While batteries release energy slowly via a chemical reaction, ultracapacitors deliver a short, powerful burst of energy to supplement the slower battery.  This characteristic makes ultracapacitors ideal for handling the peaks and valleys in the power grid, known as surges and brownouts. The intermittent electricity experienced by residential consumers is not an option for digitally controlled  technologies that need a steady influx of power, according to Chad Hall, COO of Ioxus, a manufacturer of ultracapacitors.  He added that a building, with multiple appliances running simultaneously, puts enormous strain on the power grid, which negatively affects the power quality delivered to individual machines. For rate payers, this means paying costly peak prices. 

One way that large commercial energy users manage their need for quality power is through a new approach called distributed energy (see below). The advantage of distributed energy systems is that they incorporate energy management technologies that balance the load, regulating off-and-on-again solar and wind as well as grid fluctuations. A major tool for accomplishing this task is the ultracapacitor, which can deliver immediate energy when it is demanded, or rapidly store excess energy during power surges. As Mr. Hall said, “It won’t run your house for days, but it will reduce your peak demand.”

Distributed Energy

Distributed energy refers to a variety of small, modular power-generating technologies that can be combined with load management and energy storage systems to improve the quality and/or reliability of the electricity supply. They are “distributed” because they are placed at or near the point of energy consumption, unlike traditional “centralized” systems, where electricity is generated at a remotely located, large-scale power plant and then transmitted down power lines to the consumer. Implementing distributed energy can be as simple as installing a small, stand-alone electricity generator to provide backup power at an electricity consumer’s site. Or it can be a more complex system, highly integrated with the electricity grid and consisting of electricity and thermal generation, energy storage, and energy management systems.

UltracapcitorsThe Future of Vehicle Efficiency

The way that ultracapacitors deliver on their promise for fast starts is by using electric fields. In contrast, batteries rely on chemical reactions to store and release energy.  When immediate energy is demanded of a battery, the chemical reactions needed to release the energy take longer than may be practical (see “How Ultracapacitors Work”).

Battery support

What this has meant for cars is that the battery, which is a deep energy reserve, is now doing double and triple duty.  As cars have switched from hydraulic systems to electric systems, vehicles now come equipped with power steering, DVD players, air conditioning, electric seats, power windows and even power brakes.  Alternators, designed to take over once the battery starts the car, have not gotten bigger to meet the increased electric demand. As a result, new power claims on energy have begun to tap into battery reserves, resulting in the need for larger batteries.  Now, car manufacturers such as Toyota, Nissan, Mazda and Lamborghini use capacitors in some sense to help power emergency braking, electronics or engine pick-up.

“Think about steering,” Mr. Hall said.  “How many times do you steer [a car]?” 


When hybrids shut off at red lights, they require a large amount of power to cycle back up.  This drains the battery, leaving it lagging after only 6-8 months. However, capacitors can recharge quickly and remain active in a wider temperature range than batteries.

“Batteries are best at doing a little work for a long time, like running a radio,” added Mr. Hall.  “Capacitors, on the other hand, can do a lot of work for a short time.”

New technologies, like ultracapacitors from Ioxus, are paired with batteries for hybrid vehicles.  The combination can start the vehicle, help in braking and power steering, while it ensures that the battery never sees a high current peak. This means a longer life, less waste, smaller batteries, lighter vehicles and a solution 5-15 percent more efficient.

Ioxus - Market Leader

Ioxus is in the forefront of ultracapacitor technology.  The company focuses on making capacitors better by improving their energy density.  Manufacturing their products in the United States gives the company complete control from design to shelf, and allows the company to easily adjust its process to meet customer needs. To get to their position, Ioxus used a combination of strategic and equity investment.  Strategic investors such as General Electric were key to getting the product moving and implemented.  General Electric, uses Ioxus capacitors to help power its MRI machines in areas around the world with poor power quality.  The capacitors handle the machine’s initial turn around, providing energy to meet its high start-up demand so the power grid is not drained.

“Having a strategic investor like that makes a lot of sense,” Mr. Hall said.  “[A strategic investor] has access to different markets and suggestions you may not have as a small company.”

The ultracapacitor market is growing at 50%, despite an uncertain economy.  It is supported in part by market newcomers who make similar products. Target customers within the automotive industry need multiple sources before they consider investing in a technology. They need reassurance that a replacement part will be readily available if something goes wrong. 

Ultracapacitor prices continue to drop while performance increases.  By comparison, battery prices and performance power is staying steady.  In several years, the price and power behind ultracapacitors will set them apart as the new measure of the market. 

how ultracapacitors workHow Ultracapcitors Work

A basic capacitor is essentially two conductive surfaces — a metal plate, for example — separated by an insulating layer.  During charging, electrons gather on one conductor, which becomes negatively charged, and depart from the other conductor, leaving it positively charged.  Electrons from the negatively charged conductor are unable to cross the insulating layer to replace the missing electrons, polarizing the electrons.  This imbalance created during charging generates the electrical field that gives a capacitor its power. A conventional (basic) capacitor can carry more power than a similarly sized battery.  But calling any capacitor basic is a misnomer.  The storage capacity of any capacitor is a function of surface area and space.  A capacitor’s power capabilities increase both when a conductor’s surface area increases and when the space between polarized capacitors decreases.

The conductors inside ultracapacitors are made of active carbon.  While even the thinnest metal conductors have a smooth surface, active carbon conductors have a porous surface that gives ultracapacitors a much greater surface area.  The conductors in ultracapacitors are also pressed tightly together and coated with a liquid electrolyte that connects both conductors electrically, leaving them separated by as few as only several nanometers.  This generates a much higher electrical field than the standard capacitor.

In theory, an ultracapacitor should be able to harness and release huge amounts of energy.  Its conductive surface area, which resembles a sponge or crumpled paper, is up to 100,000 times greater than a standard capacitor’s. The electrolyte used in an ultracapacitor determines its current capabilities as well as its operating temperature and voltage ranges.  Past a certain voltage, however, the electrolyte breaks down. Without the electrolyte, an ultracapacitor cannot release or store energy.  Until scientists find a way to maintain electrolytes at high voltage, ultracapacitors are only capable of storing 1,500 times more energy than a standard capacitor.