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Batteries not included

Posted: 23 Jan 2009 ?? ?Print Version ?Bookmark and Share

Keywords:battery electric vehicle? blog? harvesting energy?

By Paul Westbrook

The Detroit auto show looked more like the consumer electronics show this year. Electricity was in the airor actually in the cars as electric vehicles were everywhere, at least in concept form. There appears to be only one thing impeding our transition from fossil fuelsthe right energy storage technology.

Gasoline has a relatively good energy density per unit of weight or volume. The race is on to find a cost effective energy storage alternative. Lead acid batteries, nickel metal hydride batteries (NiMH), lithium-ion batteries (Li-ion), hydrogen, compressed air, flywheels, and many more systems are being engineered in labs and factories across the world. So while the concept vehicles tried to wow shoppers they probably should have included a small disclaimer that said "affordable, reliable battery solutions not yet included." The pure electric vehicle hasn't quite moved from hype and hope to mainstream but more manufacturers are seeing the benefits of hybrids as a transition technology. Batteries can't yet go it alone, but the internal combustion engine and battery combo is a great intermediate step. Even at today's level of storage technology electric and hybrid vehicles operate at ? to ? the cost of a conventional gas or diesel powered car.

While we don't currently see many electric cars on the road, we have seen a great increase in the amount of electronics in our vehicles. Cars have become quite dependant on silicon to get from point A to point B with each vehicle carrying dozens of microprocessors to manage a myriad of functions. A few items made possible by electronics are airbags, anti-lock brakes, stability control, adaptive cruise control, emissions controls, and engine management. I won't even delve into the infotainment electronics like stereos, mp3 players, DVD players, navigation system, and Bluetooth. Electronics will be a big part of the energy storage solutions too. Electronic controls will manage the large energy flows to and from a battery system and optimize the charge/discharge rate and temperature to maximize the life of the battery system. The Toyota Prius only allows the battery to charge up to about 80% of capacity and won't let it discharge below about 40%. This greatly extends the operating life of the battery to over 180,000 miles and more than a decade.

And let's not forget efficiency. Tire pressure sensors can help you keep your tires inflated to the correct pressure. Better still those sensors could be designed to be powered by the movement of the wheels. Using ambient energy to power a device is known as "energy harvesting." US drivers are wasting about 1.2 billion gallons of gas per year driving on under-inflated tires. That savings represents about 1% of our total consumption.

There are other energy savings solutions that involve even more electronics. If cars could travel in tight packs it would increase the number of vehicles on the existing infrastructure and improve the mileage of each vehicle due to aerodynamic coupling. Recent innovations in vehicle radar, lane identification, and other collision avoidance systems might someday coalesce into vehicles that can automatically group into packs traveling at high speed just inches apartsort of a High Vehicle Occupancy (HVO) lane.

Of course there is an alternative. We could design automobiles out of the equation. Well planned cities built around walkable communities with good mass transit infrastructure would eliminate most people's need for a car. Preposterous you say? In New York City 54% of the households don't own a vehicle. In Manhattan the number is 77%. Population density may have trumped the race for energy density in some locations. That's the exception though as we have almost as many vehicles in the US as we have people.

At Texas Instruments we are not building battery systems, but we do design and manufacture all the electronic components that help them operate more effectively. With energy harvesting some of our devices may even say "batteries not included - because they aren't required."

- Paul Westbrook is sustainable development manager, SMTS, LEED AP. He is one of the power and energy experts featured regularly at TInergy.

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