Monday, March 30, 2009

Nanotech Batteries - A New Energy Future

People want to use clean and green energy and live easy on earth’s resources. Many are changing to hybrid cars and using solar panels side by side with conventional sources of energy. But they hold a grudge. How to store large amount of energy in batteries?

Hybrid cars fit batteries for power storage. But this power is not enough to last long distances and takes many undesirable hours to recharge. The storage battery is not very helpful during acceleration. Solar and wind also don’t provide us with power at constant rate. They give us energy intermittently. Their storage devices also take lots of space and money as well and yet they don’t seem promising for surge demand. Gary Rubloff, who is the director of the University of Maryland’s NanoCenter is also voicing a common consumer’s concern, “Renewable energy sources like solar and wind provide time-varying, somewhat unpredictable energy supply, which must be captured and stored as electrical energy until demanded. Conventional devices to store and deliver electrical energy — batteries and capacitors — cannot achieve the needed combination of high energy density, high power, and fast recharge that are essential for our energy future.”

Scientists at the Maryland NanoCenter at the University of Maryland have produced new systems for storing electrical energy derived from alternative sources that are, in some cases, 10 times more efficient than what is commercially available.

Electrical energy storage devices can be categorized into three groups. Each group has its advantages and disadvantages. Batteries, mainly consisting of lithium ion, accumulate large amounts of energy but cannot afford high power or fast recharge. The second type is electrochemical capacitors (ECCs). Their advantage is they can offer higher power at the price of relatively lower energy density. The third storage device is electrostatic capacitors (ESCs). They store charge on the surfaces of two conductors. This way they are capable of high power and fast recharge, but at the price of lower energy density.

Scientists are using new processes to enhance the storage capacity of the devices. They are banking upon millions of identical nanostructures having peculiar shapes that will facilitate energy transport with the help of electrons. Electrons will move to and fro and store energy at a very large surface area. We all are familiar with the fact that materials behave according to physical laws of nature. The Maryland researchers are using this fact to their advantage. They are utilizing unusual combinations of these behaviors to produce millions and in the end billions of tiny, virtually indistinguishable nanostructures. These are supposed to receive, store, and deliver electrical energy.

Scientists are concentrating on self-assembly, self-limiting reaction, and self-alignment behaviors of nanostructures. Rubloff clarifies further, “The goal for electrical energy storage systems is to simultaneously achieve high power and high energy density to enable the devices to hold large amounts of energy, to deliver that energy at high power, and to recharge rapidly (the complement to high power).”

The Maryland research team is going for electrostatic nanocapacitors. They significantly increase energy storage density of such devices - by a factor of 10 over that of commercially available devices. This advance puts electrostatic devices to a performance level competitive with electrochemical capacitors.

The research team is right from the beginning building up the technology for commercial purposes. Their outward appearance would be like thin solar panels produced at economical costs. Multiple storage devices can be staked one over the other inside a car battery system. For the solar and wind energy storage they dream about the fully integrated with storage devices in manufacturing.