Archive for the ‘Battery technology’ Category

Ni-MH Batteries for PV & Wind

Thursday, June 4th, 2009

Nickel–Metal Hydride (Ni-MH) rechargeable battery modules specifically designed to meet the needs of off-grid photovoltaic (PV) and wind energy systems. This offers better performance, lower total cost of ownership (TCO), improved integration and better environmental profile than traditional batteries.

Stand-alone renewable energy sources are increasingly popular in applications ranging from street lighting and signage, water supply and irrigation, weather stations and environmental sensors, wireless local area networks and navigation aids. These applications benefit from reliable, maintenance-free and long-life energy storage. However, renewable energy storage in highly distributed, often remote locations in uncontrolled environments is characterized by a high number of shallow cycles, with erratic charge current and time, often under extremes of temperature. Today’s lead-acid storage batteries do not cope well in these conditions, and suffer from limited life, poor reliability and even sudden death – leading to high maintenance and replacement costs.

Despite its higher initial cost, the Ni-MH chemistry of the Smart VHT Module range has been shown to reduce total cost of ownership by 45 per cent, or more, when operating over a 15- year period in such applications. This is thanks to its longer life (typically 3–5 times), better failure resistance and wider temperature tolerance than lead-acid technology.

The design and production of the VHT range have been optimized to minimize water and energy consumption, reduce the production of greenhouse gases and toxic waste, diminish negative effects on global warming and the ozone layer, and curb the unnecessary depletion of natural resources. The Smart VHT Module enables direct integration of smart electronics – such as seamless charge/discharge management, battery condition logging and accurate state of health indicator – removing the need for separate PV controllers.

Available in 12V, 24V and 36V versions in 10Ah capacity increments (up to 80Ah). Modules can also be housed in a ruggedized aluminium casing providing added protection from the elements. They are directly interchangeable with traditional Valve-Regulated Lead-Acid (VRLA) battery modules.

Canadian Research Team Reports Major Breakthrough in Lithium Battery Technology

Friday, May 29th, 2009

A government-funded lab at the University of Waterloo has laid the groundwork for a lithium battery that can store and deliver more than three times the power of conventional lithium ion batteries.The research team of professor Linda Nazar, graduate student David Xiulei Ji and postdoctoral fellow Kyu Tae Lee is one of the first to demonstrate robust electrochemical performance for a lithium-sulphur battery. The finding is reported  in the on-line issue of Nature Materials.

The prospect of lithium-sulphur batteries has tantalized chemists for two decades, and not just because successfully combining the two chemistries delivers much higher energy densities. Sulphur is cheaper than many other materials currently used in lithium batteries. It has always showed great promise as the ideal partner for a safe, low cost, long lasting rechargeable battery, exactly the kind of battery needed for energy storage and transportation in a low carbon emission energy economy.

“The difficult challenge was always the cathode, the part of the battery that stores and releases electrons in the charge and recharge cycles,” said Dr. Nazar. “To enable a reversible electrochemical reaction at high current rates, the electrically-active sulphur needs to remain in the most intimate contact with a conductor, such as carbon.”

The Canadian research team leap-frogged the performance of other carbon-sulphur combinations by tackling the contact issue at the nanoscale level. Although they say the same approach could be used with other materials, for their proof of concept study they chose a member of a highly structured and porous carbon family called mesoporous carbon. At the nanoscale level, this type of carbon has a very uniform pore diameter and pore volume.

Using a nanocasting method, the team assembled a structure of 6.5 nanometre thick carbon rods separated by empty three to four nanometre wide channels. Carbon microfibres spanning the empty channels kept the voids open and prevented collapse of the architecture.

Filling the tiny voids proved simple. Sulphur was heated and melted. Once in contact with the carbon, it was drawn or imbibed into the channels by capillary forces, where it solidified and shrunk to form sulphur nanofibres. Scanning electron microscope sections revealed that all the spaces were uniformly filled with sulphur, exposing an enormous surface area of the active element to carbon and driving the exceptional test results of the new battery.

“This composite material can supply up to nearly 80 percent of the theoretical capacity of sulphur, which is three times the energy density of lithium transition metal oxide cathodes, at reasonable rates with good cycling stability,” said Dr. Nazar.

What is more, the researchers say, the high capacity of the carbon to incorporate active material opens the door for similar “imbibed” composites that could have applications in many areas of materials science.

The research team continues to study the material to work out remaining challenges and refine the cathode’s architecture and performance. Dr. Nazar said a patent has been filed, and she is reviewing options for commercialization and practical applications.

The research has been funded under a Natural Sciences and Engineering Research Council of Canada program

Source: National Research Council of Canada .