UltraBattery® with its Inventor, Dr. Lan Lam (Image courtesy of CSIRO)
Batteries pack a lot of energy into a small space, but they’re slow to charge, they lose their capacity after several charge-discharge cycles, and many are not environmentally friendly. Supercapacitors (also known as ultracapacitors) can be charged very quickly, can survive a near limitless number of charge-discharge cycles, and are made from relatively benign materials.
Electric and hybrid vehicles (EVs and HEVs) need the benefits of both technologies, and often employ a blend of batteries and supercaps, with the former providing a long driving range and the latter storing energy from regenerative braking and giving quick bursts of energy for rapid acceleration.
Grid-level storage combined with renewable energy has the potential to replace gas fired “peaker plants,” but like the EV, it requires the high energy density of batteries and the quick response time and long life of supercaps.
Using batteries and supercaps together requires control circuitry to move electricity to and from the different storage elements. But what happens if you combine the battery and the supercap in one package? You get the best of both worlds: the UltraBattery®, developed by a team from Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) and now produced by CSIRO spinoff company Ecoult. The UltraBattery is a lead-acid battery with a built in supercapacitor, as shown here:
Image courtesy of Ecoult
Conventional lead-acid batteries suffer from sulfation, lead sulfate crystals growing on the battery’s plates, causing a decrease in capacity and an increase in internal resistance. Sulfation occurs naturally with age, but it’s made worse by operating the battery at intermediate states of charge (somewhere between full and empty). Since that’s the normal condition for EV batteries and grid-level storage systems, you can see why many of those applications employ more costly NiMH or Li-ion batteries instead of inexpensive lead-acid batteries. According to CSIRO and Ecoult engineers, using a carbon-based supercap in parallel with the battery reduces negative plate sulfation. They don’t explain the chemistry behind that and I’m not a chemist, but independent testing by Sandia National Labs confirmed that the UltraBattery showed very little sulfation compared to standard deep-cycle lead-acid batteries under the same conditions.
Additional tests by Sandia National Labs showed that when subjected to cycles that are typical of grid-level storage applications, the UltraBattery lasted ten times longer than a conventional lead-acid battery. When tested under hybrid EV conditions, the UltraBattery once again outperformed its lead-acid counterpart by a factor of ten, performing at least as well as NiMH batteries but at a significantly lower cost.
UltraBatteries achieved a round-trip efficiency of around 90%, compared to 70% for conventional lead-acid batteries. This occurred under both low-current and high-current charge-discharge cycles. (For more details on the exact testing procedures and results, click the “Read More…” link at the end of this article and download the white paper.)
In addition to its superior electrical characteristics, the UltraBattery is non-flammable and made from materials that are abundant, non-hazardous, and fully recyclable. The UltraBattery is safe, clean, efficient, reliable, and inexpensive. What more can you ask for?
Renewable energy sources like solar and wind are intermittent, sometimes providing more energy than needed while other times not generating enough. Cost effective, efficient grid-level storage is the key to a renewable energy future. Electric vehicles and hybrids demand high capacity, inexpensive, and lightweight batteries. Likewise, storage is the main obstacle standing in the way of universal adoption of EVs. While research into alternative battery chemistry continues, it could be that the good old lead-acid battery, enhanced by a built-in supercapacitor, will satisfy both needs.