Skeleton Technologies, the ultracapacitor start up firm, has launched a new range of ultracapacitors that it says offers the highest level of energy density on the market.

Through the use of patented graphene material, the new series boasts a capacitance of 4500 farads. “By contrast, the closest competitor product has a capacitance of only 3400 farads,” Taavi Madiberk, the chief executive told Batteries International. “This is the single biggest increase in energy density for ultracapacitors in the past 15 years.

“We’ve actually reached 5,000 farads already,” he says. “But for commercial purposes it’s better to show a consistently achievable figure even though it’s lower.”

Energy density is a key development challenge for the ultracapacitor market and is fundamental if the technology is to eventually replace battery storage. Madiberk says the firm, which was set up in 2009, is aiming to double its capacitance by 2017.

“This would give us an energy density approaching that of lead acid batteries,” he says.

The energy density achieved by the SkelCap 4500 series will allow Skeleton Technologies, it says, to maximize opportunities in the heavy transportation and industrial markets where weight and space are at a premium.

Skeleton Technologies’ ultracapacitors have already been chosen by the European Space Agency, where their use should lead to cost savings by reducing the volume of heavy batteries required for energy storage. This summer the company will be announcing the first ultracapacitor product for the hybrid truck market.

“Graphene has long been heralded as a wonder material for a range of applications, including energy storage. However, a mass-market, graphene-based product has been slow to materialize. Our ultracapacitors will be that market breakthrough,” says Madiberk.

“We are harnessing the power of graphene to make the most significant advances in ultracapacitor performance seen for years.

“Elon Musk has predicted that ultracapacitors will be the future for electric vehicles, replacing batteries in the longer term. We will fulfill that prediction.”

The new range has been designed for mass-market applications and the needs of systems engineers. The format has been developed to meet the industry standard of a 60 mm diameter cylindrical cell. Skeleton Technologies had previously offered prismatic cells, which are more compact in modular arrangements but more expensive to produce.

Skeleton Technologies has also achieved one of the lowest ESR (equivalent series resistance) levels on the market at 0.095 mΩ. This factor greatly increases the efficiency of the cells by reducing the amount of energy that is lost as heat. For example, if a 3900A current is run through the SkelCap 4500 cell, it will lose only 0.30 joules per farad, whereas competing products can lose as much as 1.00 joules per farad, the firm says.

“The ultracapacitor market is dominated by organic precursor carbon from coconut shell. It is the successful development of a graphene-based carbon that is allowing us to set new records for product performance,” says Volker Dudek, the newly appointed chief technology officer at Skeleton Technologies.

“We have set ourselves an ambitious technology development target of 20 Wh/kg by which is comparable with battery level energy density. With the launch of the SkelCap 4500 range we are already half way towards that goal.”

In June, Skeleton Technologies announced it had secured €9.8 million ($10.7 million) in a series B financing from a consortium led by Harju Elekter Group, which owns electrical equipment manufacturing plants in the Nordic-Baltic markets, and UP Invest, one of the largest investment firms in the Baltic region. The financing should allow Skeleton to ramp up the deployment of its graphene ultracapacitors.

Andrus Allikmäe, chief executive of the said: “We are convinced that ultracapacitor-based solutions will increasingly be used in electrotechnical and manufacturing automation applications for energy storage, control and high-power fast switching. Our participation in this field gives us the ability to cooperate in potential future applications and also creates a synergy in participating in the development of ultracapacitor modules.”

Skeleton is already working on incorporating ultracapacitors into smart grids and is involved in the EU funded Artemis Joint Undertaking Project. As part of this ultracaps are being installed at the electricity grid company NTE in Norway.

Skeleton is headquartered in Tallinn, Estonia where it conducts research and development as well as pilot production. It has opened up a plant in Saxony, Germany, where it has plans for mass manufacturing.

Skeleton Technologies raised €3.9 million in July 2014 in a Series A financing.