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REGENERATIVE BRAKING is widely practised, but there have to be other trains around to absorb the surplus power being fed back into the catenary or third rail. Processing the output from trains and pushing it back into the local grid is possible with an AC power supply, but very expensive with DC traction. Too often, power produced by traction motors in braking mode ends up heating resistor banks. The elegant alternative is to store the braking energy on the train. This not only avoids the electrical complications of regenerating through the traction power supply network. It reduces the rated power requirement of that network by lopping demand peaks during acceleration, saves energy by reducing losses in the catenary or conductor rail, and by limiting voltage drop it allows substations to be further apart. NiMH batteries have the necessary energy storage density in terms of kWh/kg, and are slightly more expensive, but their life in terms of charge/discharge cycles in no way matches the LRV requirement for 2million cycles over 10 years. Flywheels have been tried but never caught on for several reasons.

Not really good news for us...

Sure, regenerative braking - the process that converts the energy typically wasted as heat when slowing down and storing it as electrical power in batteries - is a terrific energy saving solution. Many hybrid cars, such as the Prius, use regenerative braking and it's starting to appear aboard hybrid diesel/electric trains as well. But more efficient still is to maintain your momentum and dispense with a train's need to make stops

Does it make sense to solar power everything? It leads to many small, and relatively expensive installations. Wouldn't it be more effective to go for a battery & plug-in concept where possible. One would loose the inflight recharging of the solar airplane, but for everything else, the plug-in concept probably provides benefits.

In addition, the lifetime of cars, for example, is much lower than the one for solar panels. Why integrate both?

Yes, I agree that there is too much emphasis on the novel in attempt to solve climate change. Creating technology for the designer label market to sell goods to the rich who want to tell their friends they are green. The same investment in a solid developed renewable method could yield a hundred times the reduction of carbon or more...

Charles Bremner, Times, UK offers up some great news for air travelers. The dream of inexpensive, ecofriendly aviation has come closer to reality after a French test pilot achieved the first flight in a conventional light aircraft powered by an electric motor. The Electra, a wood-and-fabric single-seater, flew for 48 minutes for 50km (30 miles) around the southern Alps, winning a global race to apply battery power to a fixed-wing standard aircraft….Electric power for larger aircraft, including airliners, is also on the horizon, with research by Nasa and Boeing into the holy grail of the field: hydrogen-fed fuel cells. These will drive electric motors with power like those on French high-speed trains.

Environ Sci Technol. 2003 Dec 1;37(23):5414-6. Global sustainability and key needs in future automotive design. McAuley JW. Basell USA Inc., 912 Appleton Road, Elkton, Maryland 21921, USA. john.mcauley@basell.com Abstract The number of light vehicle registrations is forecast to increase worldwide by a factor of 3-5 over the next 50 years. This will dramatically increase environmental impacts worldwide of automobiles and light trucks. If light vehicles are to be environmentally sustainable globally, the automotive industry must implement fundamental changes in future automotive design. Important factors in assessing automobile design needs include fuel economy and reduced emissions. Many design parameters can impact vehicle air emissions and energy consumption including alternative fuel or engine technologies, rolling resistance, aerodynamics, drive train design, friction, and vehicle weight. Of these, vehicle weight is key and will translate into reduced energy demand across all energy distribution elements. A new class of vehicles is needed that combines ultra-light design with a likely hybrid or fuel cell engine technology. This could increase efficiency by a factor of 3-5 and reduce air emissions as well. Advanced lightweight materials, such as plastics or composites, will need to overtake the present metal-based infrastructure. Incorporating design features to facilitate end-of-life recycling and recovery is also important. The trend will be towards fewer materials and parts in vehicle design, combined with ease of disassembly. Mono-material construction can create vehicle design with improved recyclability as well as reduced numbers of parts and weight.

"To see the future of solar power, take an hour-long train ride inland from Shanghai and then a horn-blaring cab trek through the smog of Wuxi, a fast-growing Chinese city of five million. After winding through an industrial park, you will arrive at the front door of Suntech Power, a company that in the few years since its founding has become the world's largest maker of crystalline-silicon solar panels. Solar panels cover the entire front face of the sprawling eight-story headquarters. Nearly 2,600 two-meter-long panels form the largest grid-connected solar façade in the world. Together with an array of 1,800 smaller panels on the roof, it can generate a megawatt of power on a sunny day. It's expected to produce over a million kilowatt-hours of electricity in a year--enough for more than 300 people in China. In 2001, when Suntech was founded, all the solar-panel factories in China operating at full capacity would have taken six months to build enough panels for such a massive array. Suntech's first factory, which opened in 2002, cut that time to a little more than a month. Today, the company can make that many panels in less than one 12-hour shift. By the end of this year, the workers could be done by lunchtime. Suntech's production capacity has increased from 10 megawatts a year in 2002 to well over 1,000 megawatts today. Chinese solar manufacturing as a whole has increased its capacity from two megawatts in 2001 to over 4,000 megawatts."

What if cutting greenhouse emissions could also save the lives of soldiers in Iraq, where fuel-laden convoys make them targets? The U.S. Army says it is happening now in a push to reduce its carbon "bootprint." From forward areas like Iraq and Afghanistan to training ranges in the United States, the Army has been working to limit its use of fossil fuels and make its operations more environmentally sustainable.

Great point, and one I've not heard before. Yet another benefit of going low-carbon. I suspect that there must be many linkages between sustainable energy and the military. Energy efficiency could be another one. It extends the range of equipment, It reduces demands on upstream logistics and so on.