Power up! The hunt is on to extend battery life for mobile devices

battery crisis primary

Smartphone and tablet makers are on a mission to make their mobile devices the epicenter of a user's professional and personal life. One major obstacle stands in their way, though: The device's battery life.

The number of hours any given laptop or phone will stay powered on depends on the device itself, along with the number and types of applications being used at any given time. Location-based services such as Facebook are well-known battery drainers.

The situation has caused everyone from chip-makers to system providers to try to attack the battery problem as a competitive differentiator, with varying degrees of success.

Meanwhile, manufacturers, operating system creators and app developers have made strides to improve the mobile experience in many other dimensions. They've addressed issues such as the number of apps available, the usefulness of the device and the size and quality of the display. Other factors such as processor speed and device weight also have evolved.

In the fourth quarter of 2013, iPhone and Android owners used 26.8 apps per month, spending a total of 30 hours and 15 minutes with them, according to a July 2014 Nielsen report. That marks an uptick from the fourth quarter of 2011, when smartphone owners used 23.3 apps and spent only 18 hours and 18 minutes with them.

While users are certainly relying more heavily on their devices, some observers hold that until battery capacity and efficiency evolve, mobile devices will fall short of being the command center of users' lives.

"As personal devices like smartphones become more powerful, energy consumption is outpacing advances in battery technology," says Iqbal Arshad, senior vice president of engineering for global product development at Motorola Mobility. "The smartphone is increasingly used less as a phone and more as a screen to your online life. The trend towards larger, higher-resolution displays greatly increases the burden on the power delivery system."

Mobile device and battery manufacturers, app developers and researchers are scrambling to create new chemistries, re-evaluate how batteries charge and discharge, understand how components such as storage utilize the battery and figure out the impact that advanced energy harvesting -- akin to how solar calculators work -- could have on battery life.

Ranveer-Chandra Microsoft

"Anything we get, even if it's just 5% more, would be considered an improvement," says Ranveer Chandra, principal researcher at Microsoft Research. 

While all who are involved are hoping for a remarkable breakthrough, any advancement in battery capacity and life would be welcome, according to Ranveer Chandra, principal researcher at Microsoft Research. "Anything we get, even if it's just 5% more, would be considered an improvement," Chandra says.

Arshad says Motorola, which continues to work on its low-power architecture for smartphones and smartwatches, is investigating emerging technologies. "We are engaging with a range of startups and university labs to seek opportunities to invest in and accelerate promising cell, signal processing and power conversion technologies," Arshad says, although he didn't name specific targets or partnerships.

For its part, "at Microsoft Research we engage deeply with academia," Chandra says. "We are also working closely with universities through various internships and research grants," but didn't give specifics.

Here are five ways, among others in the pipeline, that researchers across the country propose to boost battery life and performance:

1. Change the chemistry

Forget a mere 5% improvement. At the University of California Riverside's Bourns College of Engineering, husband-and-wife professors Cengiz and Mihrimah Ozkan are hoping for a 300% boost in energy density.

With their graduate students, the team re-engineered a typical lithium-ion battery's chemistry to include sand (in other words: silicon dioxide). By replacing the graphite found in today's batteries with sand, they achieved three to four times the energy density currently available in the same design footprint.

Such improved performance could mean increasing the lifespan of batteries up to three times or more, which would be significant for many applications.

sand in the battery University of California Riverside

A team at the University of California Riverside's Bourns College of Engineering is hoping for a 300% boost in energy density, which they say they've achieved by replacing the graphite found in today's batteries with sand.

The types of materials typically used to manufacture batteries limit the total number of charges, which, in turn, "limits the energy density," says Cengiz, an expert in mechanical engineering and materials science. "One way to address this is to use new materials to add more energy storage and to speed energy storage," he adds.

Mihrimah, an electrical engineering specialist, says users who tend to shy away from smartphones or tablets for processor-intensive tasks such as number crunching would find the 300% increase in energy density a game-changer. "The way we've designed the battery, it will need to be charged three times less, so it's not always dying out on you," she says.

The university has applied for a patent for the silicon approach, and the technology has been licensed to Temiz Energy Technologies. Having successfully tested their sand theory with coin-sized cells, the team now plans to move to testing pouch-sized batteries, the type used in most smartphones.

2. Wrap a ribbon

Scott Elrod, vice president of the Hardware Systems Lab at research giant PARC, a Xerox company, agrees with the Ozkans' concern that, until mobile device batteries fundamentally change, uninterrupted productivity cannot be guaranteed.

To that end, researchers at PARC are homing in on the manufacturing process for lithium-ion batteries. And they're finding inspiration in a tube of toothpaste.

Scott Elrod, vice president of the Hardware Systems Lab at PARC, explains the striped-toothpaste approach to increasing battery life.

In today's battery technology, lithium ions are swapped back and forth between cathode and anode electrodes using flat layers of material. Elrod says the flatness, coupled with the inherent limits to the electrodes' thickness, prevents the lithium ions from penetrating deep enough to hold a better charge. He calls this "wasteful" when every bit of battery charge is needed.

Researchers used a process called "co-extrusion" to remodel the layers of the cathode and anode using a ribbon pattern that resembles striped toothpaste. "Instead of laying out a single material, we've created side-by-side ribbons that act as a highway or channels for the lithium ions to get in and out," he says, thereby allowing more ions to be exchanged faster, across a shorter span and with less waste.

"By structuring an electrode with conductive regions that are interleaved with storage regions, current paths can be shortened without compromising capacity," according to PARC's overview of the design (PDF).

Changing this dynamic will result in a 20% to 30% improvement in battery life for consumers, according to Elrod. PARC initially used co-extrusion on solar cells and realized its relevance to other batteries.

Pending qualification and reliability testing, the new printing technology could be available to manufacturers within three years, Elrod says. It will take more time for manufacturers to embed this new technology into their processes.

3. Look outside the battery

While the Ozkans and Elrod are focused on the battery's design, Microsoft's Chandra says operating system and application developers should take on more responsibility for extending battery life.

"Some people are waiting for the ultimate battery chemistry to be created" and the industry needs to "stop doing that," he says. "Instead, consider embracing new breakthroughs that happen outside of the battery makeup."

For instance, Microsoft Research has partnered with University of California San Diego researchers to study the impact of storage devices and storage management software on mobile devices' batteries. Included in their findings was a tool to help developers assess how their applications will use storage and, consequently, tap the device battery.

Through experimentation on several mobile platforms, researchers found that the storage software used up to 200 times more energy when compared to storage hardware. "The hardware itself is quite efficient; the software, however, consumes a lot of energy," Chandra says.

Hard drives Wikipedia

Different types of storage -- and most especially the software used with these devices -- can have varied effects on battery life.

Major factors in storage include the security and privacy requirements of mobile apps. The energy overhead of enabling encryption ranges from 2.6x for random reads to 5.9x for random writes, the researchers discovered.

Running applications using managed languages, like Java on Android, also drains power. Researchers found that on Windows RT, the energy overhead for storage systems ranged from 12.6% to 18.3% by running applications in a managed environment.

"We believe that most developers design their applications under the assumption that storage systems on mobile platforms are not energy hungry," the researchers noted. "However, experimental results demonstrate the contrary."

With Microsoft's EMOS (Energy Modeling for Storage) Simulator, developers can input a sequence of time-stamped disk requests and the total size of the file system cache to reveal details about energy consumption. Each I/O type (such as read/write, size or cache) is measured and assigned an energy value. The EMOS predictions have an 80% accuracy, according to researchers.

"Although profiling, understanding and modeling are not going to get us a big leap in battery life, it is essential to understand the energy each piece of a mobile device consumes," Chandra says. This is important for two reasons, he says.

First, it helps researchers identify, and ultimately fix anomalies and energy bugs, such as when a component is consuming an unexpected amount of power. Second, the models help researchers derive power-saving algorithms.

The EMOS model and algorithm are available in a research paper (PDF), which includes details to help researchers who want to try to implement the technology.

Microsoft's already shipping a tool called WattsOn, built using Visual Studio, that allows developers to estimate the amount of energy consumed by the phone or tablet app, and highlights parts of the code that consume more energy. The developer can then take steps to reduce the app's energy footprint.

4. Improve signal transmission

Eta Devices' CTO Joel Dawson, who was a professor of electrical engineering at the Massachusetts Institute of Technology for almost a decade, believes that something as mundane as the inefficiencies of a radio transmitter wouldn't have garnered attention were it not for the intense need nowadays for longer battery life.

"Until mobile devices stopped lasting a full day, consumers only cared about their capabilities," he says.

Eta Devices' chip Eta Devices

Eta Devices updated how mobile devices exchange signals with base stations. Its products include semiconductors.

To attack the problem, Dawson and his team updated how mobile devices exchange signals with base stations. Dawson and Eta co-founder David Perreault, who is still an MIT professor, realized that existing power amplifiers (PAs) within handsets and base stations leak a tremendous amount of energy because they are built with out-of-date analog technologies.

The company created what is essentially an automated digital gearbox, called ETAdvanced, to replace the traditional PA inside the mobile device and base station. The gearbox establishes the proper amount of power needed for communication, reducing potential waste. The company asserts that ETAdvanced enables high-efficiency performance for newer standards such as LTE Advanced and 802.11ac Wi-Fi.

ETAdvanced can provide up to a 50% improvement in battery life, according to Dawson.

5. Harvest ambient noise

Researchers at the Queen Mary University of the London School of Engineering, in coordination with Microsoft, announced that they had been able to harvest ambient noise and create enough energy to top off a mobile phone. In other words, it would be possible to charge mobile devices with sound, like rock music or cheers at a ball game.

According to the university, "The team used the key properties of zinc oxide, a material that when squashed or stretched creates a voltage by converting energy from motion into electrical energy, in the form of nanorods." The nanorods -- rod-shaped semiconductor nanocrystals -- were then manipulated to generate a high voltage.

sound-power Queen Mary University of London

While energy harvesting is not new -- think solar calculators -- being able to gather enough to keep a smartphone or tablet battery at capacity has proven challenging. Researchers were able to generate five volts -- enough to charge a Nokia Lumia 925.

PARC's Elrod is skeptical of energy harvesting as it stands today because of smartphones' and tablets' intense energy requirements. "For solar to work, your cell phone would have to be out in the light," he says. Other harvesting methods using water or heat -- or ambient sound -- still have to mature before they can supply ample power to top off a phone or tablet.

Microsoft's Chandra agrees and believes that, for now, magnetic resonance-based charging, such as that used by WiTricity's charging station, is the closest the industry will get to energy harvesting for quite some time. WiTricity claims that users can place the charging hub (a large mat) somewhere in a room and encase their devices in a special sleeve. When users are in proximity of the charging hub, their devices will automatically re-charge. (That said, individuals cannot yet buy a charging station from Witricity; the technology is currently available only to partners that will incorporate it into future products.)

While extending mobile devices' battery life is now on many inventors' radar, significant improvements are still a few years out. Experts say until these technologies hit the market, the onus is on device manufacturers, along with platform and app developers, to be transparent about energy consumption and to help users tweak settings to extend battery life.

Copyright © 2015 IDG Communications, Inc.

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