Mobile computing's energy crisis

Battery technology hasn't kept up with twin demands of taking up less space and powering more features in disconnected computing devices.

When Dave Saltzman prepares for a business trip, he charges up the main battery in his notebook computer, removes the CD-ROM drive and fills the bay with a second battery, and then packs a third one in his bag. That's sufficient for long trips, says Saltzman, systems manager at United Parcel Service Inc. in Atlanta.

Like many users, Saltzman wants to be able to work continuously during extended flights, but he also wants to use power-hungry features such as wireless networking while traveling. These changing usage patterns and the demand for faster notebooks have created a power gap between what batteries can provide and what systems can deliver.

While notebooks continue to benefit from Moore's Law, batteries haven't kept up. The future of disconnected computing depends on century-old electrochemical technology that has improved only gradually.

It's not that batteries haven't gotten better. "If we were to put today's battery on a notebook built five years ago, you'd get eight hours of battery life," says Carl Pinto, director of product development for notebooks at Toshiba Corp. in Irvine, Calif. The problem is that mobile devices are demanding more power, he says.

Until recently, investment in battery technology has been relatively small. "In the last 100 years, there hasn't been enough work put into batteries. It's just not exciting stuff," says Rob Enderle, an analyst at Enderle Group in San Jose.

But battery life has risen to become one of the top three purchase criteria for notebook computers, says Mike Trainor, chief mobile technology strategist at Intel Corp., which produces logic boards and chip sets used by the majority of notebook makers. "IT shops want more performance, more wireless and slimmer systems, which cuts down the room for batteries," he says.

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Intermec Technologies Corp.'s prototype IP3 RFID scanner combines a PDA (top) with a scanner (left). The fuel cell system and fuel cartridge (front) are embedded within the scanner, along with a lithium ion battery to handle peak power demands. "It's produceable. The question becomes is there a viable market for this device?" says Dan Bodner, director of RFID products.

Intermec Technologies Corp.'s prototype IP3 RFID scanner combines a PDA (top) with a scanner (left). The fuel cell system and fuel cartridge (front) are embedded within the scanner, along with a lithium ion battery to handle peak power demands.
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Intel's Centrino mobile chip set has reduced power consumption, extending projected operating times from two to three hours into the five-hour range, which is still short of the all-day battery users want. Eight hours of life would require 100 watt hours (Wh) of power, but the best available battery technology—lithium ion—delivers less than 60Wh.

Trainor is confident that Intel can "give Moore's Law's worth of features" through the end of the decade while keeping consumption at the 100Wh mark. But that still leaves a power gap. "The other side of the equation has become equally important: How do we get more energy into the system?" he says.

Vendors have recently awakened to the problem, but government and private research and development dollars have poured into fuel-cell research rather than into basic battery designs. The direction of investment away from batteries has contributed to today's power gap, contends Donald Sadoway, a professor of materials engineering at MIT. "They put all of their eggs in one basket. Here we are, seven or eight years later, and fuel-cell applications are nowhere near to realization," he says.

Users are feeling the pain. Tony Scott, chief technology officer at General Motors Corp., says Centrino-based notebooks have improved battery efficiency 20% to 30%, but actual operating times remain under three hours. That's not always enough when people bring such computers to meetings, says Scott.

"If you get two back-to-back one-hour meetings and you're making any significant use of the machine at all, you can start running into problems. And three meetings in a row—forget it," he says. "We need eight-plus hours of use, and that's a struggle with a lot of the devices we have today."

For Saltzman, the battery issue goes beyond notebooks. He manages 200,000 battery-powered devices at UPS, including radio-enabled handhelds used in delivery trucks. The batteries don't charge well in hot or cold weather, so charging must be done at the dispatching location. And because drivers are on the road for up to 10 hours, UPS must use bigger batteries, which adds weight to the devices. Saltzman would like to see higher energy densities to reduce weight.

Extending the Batteries

Battery manufacturers have made incremental improvements in lithium ion batteries since they were introduced in the early '90s, says Kurt Kelty, director of business development at Panasonic Energy Solutions Lab, a unit of Princeton, N.J.-based Panasonic Technologies Inc. Over the past five years, lithium ion batteries have replaced nickel cadmium (NiCd) and nickel metal hydride (NiMH) technology in mobile computing devices. Lithium ion offers a higher volumetric energy density. It also doesn't suffer from the memory effects that shorten the life span of NiCd batteries. And it's environmentally superior to NiCd, which faces a gradual phaseout because cadmium is toxic, making it a hazard in the waste stream.

While nickel-based chemistry has reached its capacity limit, lithium ion continues to make small gains. In recent years, capacity has increased at a rate of about 10% per year, while competition has reduced prices at 10% to 20% annually, Kelty says.

Although lithium ion hasn't yet hit the theoretical capacity limit, the industry consensus is that future gains will be unlikely to close the power gap. That conclusion has spurred renewed interest in battery research.

A prototype external fuel cell power pack (shown attached to a cell phone) from Hitachi.
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A prototype external fuel cell power pack (shown attached to a cell phone) from Hitachi.
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Companies such as Mississauga, Ontario-based Electrovaya Inc. use lithium ion polymer, which uses a gel-like electrolyte. Despite early promise, the technology remains more expensive than lithium ion and hasn't improved energy density. But it does have one advantage: Polymer-based cells can be formed into flat shapes that fit into small devices, while lithium ion is limited to cylindrical cell designs.

Pionics Co. in Shiga, Japan, has shown a prototype battery with an energy density of 600Wh/liter. Most of today's lithium ion batteries fall into the 200Wh to 250Wh/liter range, says Atakan Ozbek, principal analyst at ABI Research in Oyster Bay, N.Y. Still other vendors are working on designs based on materials such as lithium sulphur and lithium phosphate.

Even the traditional alkaline battery may get back into the game. With zinc-based alkaline batteries, it has been difficult to get more than 10 recharge cycles, says Robert Zeiler, president of Zinc Matrix Power Inc. in Santa Barbara, Calif. The company has replaced the alkaline battery's traditional electrolyte solution with a polymer-based formula that extends the number of recharge cycles. "We can get hundreds of cycles," with an energy density of 600Wh/liter, he says. The company has an agreement with Intel and says it will have a commercial notebook battery in production by 2006.

While Intel has invested in the more promising companies, Trainor is realistic about early claims. "What we have not seen is anyone manufacture these cells in high volume," he says.

Fuel-Cell Frenzy

For the long term, most vendors have pinned their futures on fuel cells. Government and private investments in fuel-cell research have been substantial, and more than 60 companies are working on designs to power electronics, says Jim Balcom, president and CEO of PolyFuel Inc. in Mountain View, Calif.

Fuel cells combine a fuel such as hydrogen or methanol with oxygen in an electrochemical reaction. The most popular design, the direct methanol cell, uses methanol or a methanol/water mix. Fuel cells show promise in delivering dramatically higher energy densities, and the ability to swap out fuel cartridges could guarantee a virtually endless power supply. As little as 1cc of fuel can generate 1Wh of electricity—enough to power a cell phone for about two hours, says Alan Soucy, chief operating officer at MTI MicroFuel Cells Inc. in Albany, N.Y.

But the technology faces several challenges. Fuel-cell systems are complex, requiring an engine, or "stack"; tiny pumps, sensors and other electronics; a venting system; and a fuel tank (see diagram below). Squeezing them into something the size of a notebook battery that can be sold at a reasonable price and that works reliably is a major engineering hurdle.

Fuel cells are also relatively inefficient—turning 70% of the energy they produce into waste heat vs. 10% for batteries—which is a problem for notebook designers, who are already facing thermal challenges. And the systems vent small amounts of carbon dioxide and water vapor.

Fuel cells also don't respond well to sudden spikes in power demand, so early designs, such as Intermec Technologies Corp.'s fuel-cell-powered IP3 radio frequency identification (RFID) reader prototype, are coupled with a lithium ion battery. The IP3 fuel cell, an MTI design, trickle-charges the battery in addition to directly powering the RFID reader. The unit runs for 30 hours on a 55cc fuel cartridge compared with about 10 hours for a traditional battery. Other vendors are experimenting with ultracapacitors, solid-state devices that can deliver short bursts of supplemental power to handle peak loads.

Hitachi's prototype notebook computer with
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Hitachi's prototype notebook computer with "swap bay" fuel cell attachment on rear of case.
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"Toshiba's big investment is in fuel cells," says Pinto. Toshiba, Hitachi Ltd. and NEC Corp. have shown prototype "swap bay" designs that attach to a notebook or handheld, with internal units to follow. But real products won't come until standards are ironed out. A standard fuel mix and cartridge design is needed for broad acceptance, and regulators still need to approve its safety and use, particularly on airplanes. Getting Federal Aviation Administration approval to carry the flammable methane tanks onboard commercial flights may not be easy, given the agency's recent ban on butane lighters.

ABI Research's Ozbek says fuel-cell makers have made significant strides in the past six months, reducing the package size by 50% while surpassing the energy density of lithium ion in test units. Early fuel-cell power packs will ship this year and next, ramping up to a few thousand units in 2007. "Then it's going to be millions by 2010," he says.

In the interim, users will have to make do by dimming screens and using the power-saving features available to them. Those features can help, says GM's Scott.

But power-saving designs alone aren't going to close the power gap, he adds. "Batteries have been the boat anchor in terms of real progress."

 

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Battery Timeline

1802: First electric battery capable of being mass produced developed

1859: Rechargeable lead acid battery invented

1888: Dry cell battery debuts

1899: Nickel cadmium (NiCd) battery developed

1947: Sealed NiCd battery invented

1960: Alkaline battery created by Union Carbide

1990: Nickel metal hydride (NiMH) battery debuts

1992: Reusable alkaline battery developed

1999: Lithium ion polymer battery invented

2002: Early proton exchange membrane (PEM) fuel cells developed for powering vehicles

2004: Early trials of direct methanol fuel cells for mobile computing/portable electronics conducted

2010: Wide commercial adoption of direct methanol fuel cells (DMFC) predicted

Source: Cadex Electronics Inc., ABI Research.

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Power Gap for Notebook Computers

Improvements in the traditional six-cell lithium ion battery pack are projected to fall short of notebook requirements, so vendors are turning to new battery chemistries to improve energy density. Longer term, fuel cells are expected to take power densities well beyond what batteries can offer and will allow virtually unlimited operating time to be extended by refueling the system with a replaceable methanol cartridge or refillable tank.

Power Gap for Notebook Computers

Source: Intel Corp.

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