Energy’s next challenge


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The world’s energy future is painted in pictures of solar panels and fuel cells, but the story will be told in the language of storage  —  the cylinders, tanks and boxes where we can put the energy these evolving technologies will produce in abundance.

Right now, the demand for energy storage outstrips supply. It’s even built into the electric grid. Power plants have to be able to produce enough power to meet the highest possible demand, which happens on only a few days of the year. (Think July in west Texas, when everyone is running air conditioners at full blast.) If generating plants could run at a steady rate and store power to release on those few days when it’s needed, plants could be made smaller and more cheaply.

The storage problem has evolved along with our power sources. The most visible example erupted in California in April 2014. On a day when the state’s renewable-energy installations were churning out more electricity than the grid could absorb, utility companies asked solar and wind producers to cut production for 90 minutes to make room in the wires for their output. During those 90 minutes, the state lost more than a billion watts of electricity — enough to power 1,000 typical US homes for a month. 

“Two-thirds of energy from renewable sources is energy that we really don’t need when it arrives, and so it goes to waste,” according to Daryl Wilson, chief executive of the publicly traded Hydrogenics, a hydrogen energy-storage developer in Ontario. From 2009 to 2012, Italy reported losing 1,600 gigawatt-hours of wind-generated electricity — about €130 million worth — just because there was no place to put it until it was needed.  

Huge investment opportunity

This is an opportunity, and everyone from car makers and utility companies to the European Union is jumping in. The Washington-based Energy Storage Association forecasts a growth in its industry of 250 percent in 2015 alone. An April 2015 study from Navigant Research forecasts that the energy-storage market will grow from $605 million this year to $21 billion by 2024.  Panasonic, one of Japan’s foremost electronics firms, glimpsed that future in 2013 when it walked away from the plasma television business and invested in batteries and solar panels.

Now the company is harvesting the fruits of that decision with Tesla Motors’ announcement of its home-battery pack. Panasonic is making the cells for Tesla’s power system, about 3 feet (one meter) tall and available in either a 10-kilowatt-hour or 15-kilowatt-hour capacity. The pack can be charged from the electric grid and reserved for use as backup during power outages, or as an alternative to the grid during high-cost peak-demand periods. But the batteries also can be charged from a generator or solar panels, taking a household completely off the grid.

The 10kwh system will retail for about $3,500 plus installation and connection fees. In its California test market, Tesla is said to have negotiated an agreement with Pacific Gas and Electric Co. to rebate half the cost to each buyer. After a $1,500 downpayment, the buyer can opt to pay for the battery pack on small monthly installments. One beta tester noted that he charges the battery during off-peak usage hours, then sells some electricity back into the grid during peak demand times. The trick makes him enough money to cover the monthly payment.    

Like Tesla, other engineers — some quietly, some less so — have been testing new ways to keep power on tap. There are low-tech ways that work, such as using excess electricity to compress air in a tank and then expelling the air through a turbine when power is needed again. Other ideas are more exotic — and hold far more promise for a power-hungry planet.

It’s a lithium world

As the demand for storage climbed through the 1990s, lithium emerged as the battery medium of choice for holding electricity for personal use. It’s the lightest of metals, and can deliver the highest voltage or “amount” of electricity among metals. So, it stores the most electricity for its weight. It’s also plentiful; the oceans alone are estimated to hold as much as 270 billion tons.  Rechargeable lithium-ion cells are likely to drive everything from notebook computers to electric cars for at least the next decade.

As a result, engineers and entrepreneurs pay a lot of attention to making lithium-ion batteries better. And they should. Lithium batteries deplete their charges relatively quickly; they fail after about 1,000 charge cycles; and as they age, they can swell, even burst, and start fires. As with internal-combustion engines, the intricate science of lithium batteries is a field where small improvements can make a big difference.  

For instance, the most common lithium batteries contain graphite, a form of carbon. (A battery can contain as much as 30 times more graphite than lithium.) Researchers at the University of California’s Riverside campus recently have shown a way to replace graphite with a fabric of silicon microfibers that lengthen a lithium battery’s life and ease the problem of bulging. The discovery is crucial to the US for another reason: The nation imports 100 percent of the graphite it uses. China delivers 70 percent of the world’s supply, but began restricting exports in 2014.  (The publicly traded company Graphite One Resources is working to develop a 4-billion-ton graphite reserve inside the US.)

Engineers at Stanford University have demonstrated a battery with an electrode and cathode both of lithium, which could at least triple battery life. At the University of Michigan in January, a research team revealed a solution to lithium batteries’ habit of sprouting internal metal tendrils, which can short-circuit power production and shorten battery life. By embedding sheets of aramid, a synthetic fabric, through the battery, the team foiled tendrils’ growth, showing the way to a smaller, lighter battery. The university has spun off the private firm Elegus Technologies to commercialize the technology as early as the end of 2016.

Last October, scientists at Singapore’s Nanyang Technology University announced a lithium battery with an anode made of a gel holding titanium dioxide nanotubes a thousand times thinner than a hair. Researchers say the tubes speed electrons’ flow in and out of the battery, making it possible to charge a dead lithium-ion battery to 70 percent in two minutes and lengthening battery life to 20 years before its charge would begin to degrade.

Sakti3, a Michigan startup, is developing a solid-state lithium battery made by depositing thin films in layers, the way photovoltaic panels are made. The company claims energy densities more than double those of today’s lithium-ion batteries, and it plans to commercialize the invention in consumer electronics before 2018. Beyond that, Sakti3 envisions an electric car that can cost $25,000 and travel 300 miles per charge on its batteries.

But lithium isn’t the only basis for a power cell. Engineers at St. Andrews University in Scotland are making a battery out of carbon and air that, in theory, could deliver 10 times the energy of
today’s lithium-ion cells. In April 2015, a research team at Stanford University unveiled a prototype of what it contends is the first commercially viable aluminum battery. It unites a graphite cathode with an aluminum anode, and a proprietary liquid as the electrolyte, to carry the charge between poles. The metals are much less reactive than lithium, so an aluminum battery would be safer. The group also believes it will be cheaper, longer-lived and fast-charging; an aluminum battery for a smartphone or notebook computer could be charged in a minute instead of hours, it claims. However, the prototype doesn’t store much energy, so there’s much more engineering to do before the invention meets the market.  

The consumer-battery market is risky territory for investors. Battery-making is both knowledge- and capital-intensive, and one innovation can be rendered useless or obsolete by another. An effective strategy could be to bet early on spinoffs and startups and hope that one of the global battery giants subsumes them.

Future for batteries: think big

Better batteries for cell phones and electric cars are well and good, but sometimes batteries have to go big — for example, when capturing the vast output from photovoltaic farms or “load balancing,” jargon for smoothing out the peaks and valleys of demand on the electric grid. For these applications, several companies are jostling for space in the blossoming market for flow batteries.

The “flow” is the movement of liquid electrolytes through an electrochemical cell that converts this chemical energy into electricity. The electrolytes are stored in tanks and pumped back and forth through an electrochemical cell, discharging and recharging the system. Because flow batteries can be charged and discharged thousands of times a year with no loss of capacity, they’re the cheapest way to store large amounts of power for high-output, high-demand applications such as solar- or wind-power systems or even utility grids.  

EnerVault, a Silicon Valley development company backed by an international consortium of industrial corporations and venture capitalists, has introduced the world’s largest commercial flow battery based on an easy iron-chromium chemistry. Imergy Power Systems, backed by its own squad of venture funders, offers a competing battery using recycled vanadium. It can be scaled up in power just by increasing the size of the liquid-storage tanks. Primus Power has installed a zinc-based 1MWh flow battery tied to an existing 230kW solar installation at a US Marine Corps station in California. Japan’s Hokkaido Electric Power Co. Inc. installed a 60-megawatt-hour flow system to store power to even out demands on its grid. A December 2014 analysis from Lux Research sees a $190 million annual market for flow batteries by 2020, growing in tandem with the spread of renewable energy installations.

Venture capitalists don’t want to own companies forever, so, at some point, individual investors can expect flow battery makers to go public.  

To meet the large and small challenges of energy storage, including those that haven’t materialized yet, many look to hydrogen. In 2015, Toyota introduced its Mirai, Honda debuted the FCX Clarity, and Hyundai unveiled its Tucson, electric cars powered by hydrogen fuel cells.  British utilities are liberating hydrogen from water and mainlining it with natural gas. European wind farms are using excess electricity they produce to extract hydrogen from water, store the gas, then use it to make electricity when the wind dies down.

Indeed, hydrogen seems like the perfect fuel. It burns without toxic residue, contains more energy by weight than any other element — about 200 times more than in a lithium-ion battery — and is the most plentiful element in the universe.

But hydrogen confronts its own array of challenges, including how to store it. Liquefying hydrogen, the way we do natural gas, requires cooling it almost to absolute zero, which would take more energy than the hydrogen itself could return. Compressing hydrogen gas in a tank not only uses up to 15 percent of the energy the hydrogen would return, but the tanks also would take up disproportionate amounts of space for the energy stored. But no one is giving up.  

Producers as well as users have stored hydrogen in underground caverns, the honeycombed rock inside depleted oil and gas fields, and even in played-out salt mines. Chevron has stored as much as 2,500 tons of hydrogen gas in an old salt cavern in Texas since the 1980s, and Europe’s “HyUnder” project is planning case studies for storing hydrogen across the continent in subterranean salt caverns.  

But that’s not going to fill your fuel-cell car’s tank in Tacoma. For consumer applications, engineers are developing solid-state storage systems using materials called sorbents and hydrides.  

 

Conveniently, many metals absorb hydrogen. (Magnesium is especially good at it, able to take in the gas to about 8 percent of its own volume.) To store hydrogen, the gas can be floated above the surface of these metals; the metal sucks it in and stores the hydrogen atoms in spaces within the metal’s crystalline structure, becoming a hydride. Like sorbent materials (such as special treatments of carbon), hydrides release most of their absorbed hydrogen only when their temperatures change sharply  — another energy cost to calculate when judging the system’s practicality.

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