Will Ultracapacitors Overtake Batteries in the Energy-Storage Race?
he short answer to the headline’s question is probably not. Perhaps this isn’t the answer you were expecting from the CEO of an ultracapacitor manufacturer. However, ultracapacitors and batteries are different technologies with different benefits for different applications. The idea a battle exists between the two is perhaps a bit of an energy-storage myth. What’s interesting, though, is the increasing number of applications where ultracapacitor technology unquestionably outperforms batteries, and the new solutions emerging as a result.
Understanding the difference between ultracapacitors and batteries
Ultracapacitor technology has been in development for several decades, but has progressed rapidly in recent years. This acceleration is the result of advances in nanomaterials (in our case graphene), the electrification of infrastructure and industry and increased concerns around fuel efficiency. The technology has already been adopted by a number of markets including motorsports, automotive, aerospace, heavy industry and transportation and renewables and grid.Unlike batteries, which rely on a chemical reaction, ultracapacitors
store energy in an electric field. This allows them to charge and discharge much faster than batteries. They can also survive up to a million charge and discharge cycles, whereas battery lifetime is restricted by degrading chemicals. Ultracapacitors have little or no internal resistance (down to 0,12 mΩ), allowing them to work at close to 100% efficiency. They are also significantly lighter than batteries, and generally don’t contain harmful chemicals or toxic metals.
Power density versus energy density
Crucially, the power density of ultracapacitors is up to 60 times greater than batteries. This high power density means it’s possible to recharge large banks of ultracapacitors in just three or four seconds. This means they are ideally suited for applications that require high bursts of power. These range from adjusting solar arrays on spacecraft, to powering kinetic energy recover systems (KERS); providing starting currents for trucks and other heavy transport, to dealing with short-term fluctuations caused by increased renewable generation in the power grid.
Where batteries win is energy density. (Remember power density affects how quickly a technology can release energy, while energy density affects how long it will run for). Ultracapacitors aren’t yet able to store the same amount of electrical energy as batteries, although breakthroughs have been made in recent months. Earlier this year, Skeleton Technologies released a product range with a capacitance of 4,500 Farads, marking the biggest increase in ultracapacitor energy density for 15 years.
Combining the two technologies provides the best of both worlds, and is the real key to unlocking the energy storage market.