Aquion Energy, based in Pittsburgh and founded in 2007, is using basic materials like sodium and water to build modular batteries that will be able to provide energy storage services for the power grid. The technology was developed out of Carnegie Mellon University by founder and chief technology officer Jay Whitacre.

The company’s battery pairs a carbon anode with a sodium-based cathode, and a water-based electrolyte shuttles ions between the two electrodes during charging and discharging. Many batteries have solvent-based electrolytes.

Aquion Energy employees assembling batteries at a rotary dial table

The purpose of using basic materials is to make a battery that is super low cost. That’s one reason why Aquion is focused on stationary applications, like the grid, where lower energy density can be an acceptable trade-off for lower costs and longer life. The battery can also withstand a wide range of temperatures without losing storage capacity, so could be installed alongside a solar installation without sapping a lot of energy for air conditioning to keep the batteries cool.

Aquion Energy has been planning on building a factory in Pennsylvania that could make its sodium batteries starting this year. About a year ago Aquion said it had leased a facility from the Regional Industrial Development Corporation in Westmoreland County, Pennsylvania, and the company hopes the factory could create 400 jobs by the end of 2015.

Such a factory could cost between $75 million and $80 million to build, so it’s likely this funding will go towards moving into production. In the summer of 2011 Aquion raised $20 million. The Department of Energy has also supported Aquion’s technology development with a $5 million stimulus grant.

Kleiner Perkins’ David Wells played a key role in helping incubate this technology. Whitacre and Wells started talking in late 2007 and a year later Kleiner sponsored an incubator at Carnegie Mellon for Whitacre to develop the tech. Following that, Whitacre spun off the venture and began to work on commercializing the battery.

Bill Gates has also invested in battery startup Ambri (formerly called Liquid Metal Battery), which like Aquion is building a grid battery and looking to begin production in the coming years. Gates has backed at least 5 battery startups, according to a talk he gave back in 2010.

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Much of the battery innovation that has occurred over the years has happened in Japan and Korea (via giants like Panasonic) and much of the battery manufacturing happens in China. But California now has some 40+ battery companies, spurred by the Silicon Valley venture and startup ecosystem, through strong university research and through federal funds from the Department of Energy. Of the 13 battery startups I recently profiled, almost half of them are based in California.

The CalCharge accelerator launched last spring, and provides battery companies and entrepreneurs with a space to collaborate, share resources, find and recruit talent and coordinate on solving problems. A battery entrepreneur that has utilized CalCharge told me earlier this year that one of the great things about the accelerator program is that companies can share battery lab equipment, which can cut down dramatically on their startup costs.

Updated at 2:25PM on Friday to correct that CalCharge isn’t using a $120 million grant from the DOE. That $120 million grant was allocated for the Joint Center for Energy Research.

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Six-year-old startup Seeo — which is backed by Vinod Khosla, Google.org and others — has installed its first battery system to act as energy storage in conjunction with a solar panel system developed by SunEdison, according to Seeo CEO Hal Zarem, who I interviewed last week. The solar battery installation is a trial for now, but a sizable one: on the level of kilowatts and tens of kilowatts, explained Zarem. For comparison’s sake, the Nissan LEAF uses a 24 kilowatt hour battery, while an average cell phone will use 2,000 to 3,000 milliamp hour batteries (far smaller than a kilowatt hour of capacity).

Batteries, like the one Seeo has installed for SunEdison’s solar system, can act as storage for the energy produced by solar panels, so that when the sun goes down (or behind a cloud) the battery can then offer up the stored power. Utilities, building owners and even home owners are starting to see the benefits of having battery storage systems connected to solar systems, because power can be far more smooth and reliable. Likewise solar installer SolarCity has been working with Tesla’s batteries to sell a home battery system with its solar panels in certain markets.

The next-gen tech

So what makes Seeo’s batteries safer? It largely involves improvements to the electrolyte, or the medium that shuttles lithium ions back and forth between the cathode and the anode to charge and discharge the battery. Traditional lithium-ion battery electrolytes are mostly made of liquids, while Seeo is using a solid dry polymer based electrolyte, which feels like plastic to the touch.

The polymer is non-flammable and when combined with using lithium foil as the anode, the battery can be ultra light weight and also have a high energy density, or amount of energy that can be stored per a given weight. During an interview at Seeo’s headquarters last week I picked up and compared two battery packs — one made by Seeo, and one that used traditional lithium ion batteries — and the Seeo battery felt about three times lighter.

If traditional lithium ion batteries are overcharged they can have a margin of error in the danger zone of about 20 percent above the max voltage of the battery, explained Zarem. In contrast, Seeo batteries have a margin of error of 100 percent over the voltage. The batteries also won’t burst into flames if something penetrates it (for example, during a car crash).

Seeo isn’t the only one working on solid electrolytes for batteries. It’s actually a growing field for innovation, and startups like Sakti3, and Imprint Energy are working on this technology, as are researchers at Oak Ridge National Laboratory.

What’s next

Seeo has just started commercializing its technology and working with customers to test out its batteries. The company has built out a pilot production line at its headquarters in Hayward, Calif., which can make 4 MW hours worth of batteries using traditional manufacturing machines like coaters. I toured the company’s pilot line last week and the team is indeed heads down churning out small levels of Seeo batteries.

But to get to the next-level of manufacturing, which involves hundreds of megawatt hours — the kind that could start to actually change the game for solar energy storage, or electric vehicles — Seeo plans to build a new factory somewhere in the U.S. this year, close enough to the Hayward site to create easy collaboration. It could end up being built in Hayward, says Zarem, but the company is still in the process of figuring out the best location.

Seeo could have to raise some sort of funding to get such a plant built, and probably has already started raising such funding. But on that funding note Zarem wouldn’t comment. Raising funding could be difficult in 2013, after so many advanced battery companies, like A123 Systems, struggled in 2012. Eventually Seeo also wants to build an even larger plant, but that would likely be developed outside of the U.S., in a low cost manufacturing part of the world, said Zarem.

Along with Google.org, and Khosla Ventures, Seeo also has investors Chinese firm GSR Ventures, and Presidio Ventures, a fund managed by Japanese giant Sumitomo. So clearly, Seeo has some strategic connections in overseas markets.

Seeo’s Zarem has an interesting perspective on the past couple of years of battery innovation. A generation of large battery factories were built out in recent years, he said, some using U.S. government funds to meet an anticipated market for electric cars (like A123 Systems). Unfortunately that electric car market didn’t emerge as quickly as expected, but it’s coming, as is energy storage for clean power.

Sometimes the companies that are the first to market either aren’t the right ones, or they’re too early, says Zarem. Of course, he’s hoping that Seeo has timed it just right.

This article was updated at 10:15AM to correct that the company has an investment from Google.org, instead of Google Ventures.

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Leyden Energy was founded in 2007 (formerly called Mobius Power) with a patent acquired from chemical giant Dupont, and a $4.5 million investment from investors. Leyden’s original secret sauce is an innovation for the electrolyte part of the battery. A battery has a positive and a negative plate and then an electrolyte in between, which is the substance through which electrons transfer back and forth while the battery charges and discharges.

In addition to its electrolyte innovation, Leyden also has a new breakthrough technology for a silicon anode that boosts the energy density (amount of energy stored per volume) and enables the battery to be made in a very slim form factor. Many battery companies combine next-generation technology in each part of the battery to produce a better whole battery in production.

Making lithium ion batteries slim is a priority for Leyden. It’s recently been focused on tablets and consumer electronics and announced an effort with chipmaker NVIDIA to design tablets; it also has been courting makers of chargers for smart phones and devices for personal Wi-Fi hot spots. A couple years ago Leyden launched a replacement lithium-ion battery for laptops that won’t degrade (start losing its full charge) for at least three years, and will come with a three-year warranty.

Start-stop vehicle tech, which uses a battery to automatically cut off the engine of a gas-powered vehicle while it’s idling, is another target area for Leyden. Start-stop vehicle technology is starting to gain momentum in Europe, following carbon reduction regulations, and the technology can reduce fuel use by 5 to 12 percent.

These are difficult times for battery startups right now, particularly those that were hoping the electric car market would take off faster than it has. Lithium ion battery leader A123 Systems recently went bankrupt and then was sold to Chinese auto parts giant Wanxiang. Battery maker Ener1 also filed for bankruptcy last year.

But there’s still some rare next-gen battery startups looking to innovate around new materials, new production techniques, and nanotechnology. Here’s 13 battery startups to watch in 2013.

Leyden’s series C round of $10 million came from existing investors including NEA, Lightspeed Ventures, Sigma Partners and Walden International. The company has raised $48 million in venture capital since it was founded.

Images courtesy of Leyden Energy.

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But in a small, brightly-lit lab in an office park behind the Oakland Airport in Alameda, Calif., a young startup called Imprint Energy, is using research created at the University of California, Berkeley to develop just such a battery that could free gadget makers from the constraints of the standard lithium ion battery. Well, that’s the plan anyways.

Using zinc, instead of lithium, and screen printing technology, Imprint Energy is already churning out low volumes of its ultra-thin, energy-dense, flexible, and low cost rechargeable batteries for pilot customers.

The battery barrier

The problem is, it’s hard to make standard lithium ion batteries thin and flexible, explained Imprint Energy CEO Devin MacKenzie to me in an interview in the startup’s lab last week. There’s a “lot of packaging,” required to seal off the highly reactive lithium in the battery from the environment, said MacKenzie. If you’ve ever seen YouTube videos of lithium batteries that catch on fire in the air or water, you know why those barriers are needed.

But this architecture also makes lithium ion batteries rigid and potentially bulky. Even the slimmest laptops like the Macbook Air, or tablets like the iPad, faced design limitations created by the size and weight of the batteries. The Nike FuelBand uses a curved (called conformal in battery terms) lithium polymer battery, but if you look closely at the shape of the band (photo left), the battery is the only part of the bracelet that isn’t pliable.

Upsides of zinc

Imprint Energy’s battery tackles the problem of rigidity and bulkiness by simply throwing out the lithium. The company, which now has a staff of 8, was founded in 2010 by U.C. Berkeley PHD students Christine Ho and Brooks Kincaid, and more they recently raised seed funding from Dow Chemical and CIA fund In-Q-Tel.

The company uses zinc for the anode part of the battery, and combines that with a solid polymer electrolyte and a cathode made of a metal oxide. A battery is made up of an anode on one side and a cathode on the other, with an electrolyte in between — zinc ions (in Imprint’s case) travel from the anode to the cathode through the electrolyte, creating a chemical reaction that allows electrons to be harvested along the way.

MacKenzie tells me that while zinc has been used for years in batteries, it’s been difficult to make zinc batteries rechargeable. That’s because when zinc is combined with a liquid electrolyte it creates something called dendrites, which are tiny fibers that grow and get in the way of the charging reaction. Imprint Energy solved this hurdle by using an electrolyte made of a solid polymer combined with the zinc.

Using zinc means Imprint’s batteries can have far less “packaging” because zinc isn’t highly reactive with the environment. In other words, the batteries can be made much more thinly. They can also be made as tiny as a few hundred microns thick (the width of a couple human hairs). Batteries that small could power tiny digital smart labels, like freshness detector stickers on food.

Zinc also makes Imprint’s batteries more safe and less toxic than lithium-based batteries. The team at Imprint can work on the zinc batteries in the open air. And the zinc batteries are a safer option for creating devices that sit on — or even in — the body. Imagine a lithium battery powering a heart device inside a person’s chest cavity, and the battery leaks lithium into the person’s body. Yikes.

Printable batteries

The other innovation that Imprint Energy has developed is that it’s printing out its batteries using standard screen printing technology. Most batteries are made by coating the materials onto foils, which are then assembled into cells.

In Imprint Energy’s Alameda lab, CEO MacKenzie shows me one of two battery printing machines on site and a variety of screens that look sort of like t-shirt silk screening screens. The battery materials are printed like ink onto the screens in whatever shapes the client requires. Customers will pay a premium for batteries created to the custom shapes of their devices.

The company can churn out 100 cells a day on the machines in its lab. That’s tiny in the world of the battery giants in Asia, but it’s large enough to get samples out to potential customers. Down the road — potentially two to three years — the company will scale up manufacturing to a large commercial scale, but it won’t likely be building its own factories. More likely, it will work closely with manufacturing partners or license its technology.

An eye on wearables

While it’s still early days for Imprint Energy, the team’s end goal is the wearable electronics market, both for consumers (like Nike’s FuelBand and the FitBit line) as well as the health sector (such as implanted monitors). The wearables industry could reap the most benefits from the novel and thin shapes of the batteries, as well as the safe and less toxic materials.

Co-founder Kincaid is a wearables buff. He shows me his own Nike FuelBand on his wrist during the interview, and he says he’s eagerly awaiting the arrival of his Misfit Shine. For the wearables industry, Imprint Energy’s zinc poly batteries could enable an entirely new type of device that’s more hidden, more streamlined, or more functional. Given that wearable electronics is an emerging sector, and one that could become a lot more mainstream over the next few years, disruptive design could ultimately completely change the wearable industry.

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As Cleantech Group CEO Sheeraz Haji put it in a call with the media: the sector saw “a significant drop off.” That was caused by a variety of issues in 2012, including cheap natural gas (which makes solar and wind projects less economical), the commoditization of solar modules (which makes VCs less willing to invest in solar manufacturing innovation), and global government uncertainty, as many clean energy technologies have relied on government support to be competitive.

Haji also said that the sector has experienced “a cleantech cliff” of sorts, given that clean energy received so much support through the U.S. government recovery package, and will not likely see that same type of government support in the near future. In addition, the cleantech sector is suffering through its own startup and investor crisis as companies, entrepreneurs and investors have been burned by funding companies that required more capital and more time than expected, said Haji.

However, Haji said he is still bullish on the opportunities for innovations for some sectors like energy efficiency, clean web, water, agriculture, bio chemicals, and more. “A foundation has been built,” over the past few years in cleantech and that will grow in value,” he said.

But if you’re going to brave either building a cleantech startup, joining a cleantech company or investing in cleantech startups, here’s 5 things you definitely should not do:

1). No more capital intensive plays: Investors that put money into cleantech in 2012 put less money into individual cleantech startups. The average round size raised by a cleantech startup was $10.9 million in 2012, down from $14.4 million in 2011. The average Series B round size for a cleantech startup in 2012 was $16.3 million, down from $20.8 million in 2011. The average early stage round for a cleantech startup in 2012 was $2.7 million, down from $4.6 million in 2011. The days of startups raising hundreds of millions of dollars in VC funding for electric cars, electric car infrastructure, thin-film solar materials or new battery technologies is largely over (some exceptions remained in 2012).

2). Stay away from new solar materials and manufacturing: According to the Cleantech Group, investment in solar technology innovation represented almost 40 percent of all of the VC dollars that went into cleantech in 2008. In 2012, solar technology represented about 12 percent. As solar modules become commoditized, it’s hard to create innovation on a material and manufacturing level. Again, some companies are still doing this, but it’s just a lot more difficult.

3). Don’t rely on a cleantech IPO: O.K. SolarCity made it out in 2012, but over 2012 there were ten VC-backed cleantech IPOs that were pulled, according to the Cleantech Group. Even in China, which previously has been a hot clean energy IPO market, there were real challenges in 2012, said Haji. Don’t expect 2013 to get all that much better.

4). Corporate investors aren’t the savior: Now that VCs are pulling back from cleantech investing, a common mantra in the industry is to say that corporate investing is really ramping up. But according to the Cleantech Group, corporate investing — from the likes of GE, BP, Shell, Siemens etc — also dropped off significantly in 2012. Corporate investors put $31 million into cleantech startups in the fourth quarter of 2011, and that dropped to $26 million in Q1 2012, $24 million in Q2 2012, $20 million in Q3 2012, and $18 million in Q4 2012.

5). For new early stage cleantech companies, VCs are probably not your best bet: Not many VCs are doing investments in early stage — brand spanking new — cleantech deals any more. There’s a few, but they are the outliers. While cleantech investors back 344 early stage deals in 2011, only 282 early stage cleantech deals took place in 2012. On the other hand, if you can market your company not as a cleantech company, that’s a better way to get some VC dollars.

Image courtesy of huskyte77.

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The winning bid beat out Johnson Control’s bid to acquire A123′s automotive division. Johnson Controls previously had offered to buy the automotive division and two factories for $125 million.

One of the reasons Wanxiang’s offer to buy up A123 had been controversial was because A123 had some U.S. military contracts, which critics didn’t want to see in the hands of a Chinese company. But A123 decided to sell off its government business, including all its U.S. military contracts, to Illinois-based company Navitas Systems, for $2.25 million. Wanxiang acquired the rest of the assets including the grid storage business.

We’ll see if that move silences politician critics like U.S. Sens. John Thune (R-S.D.) and Charles E. Grassley (R-Iowa). The deal still has to be approved by the bankruptcy court as well as the Committee for Foreign Investment in the United States (CIFIUS).

If approved, the future of A123 System’s lithium ion battery tech will fittingly be owned by a Chinese auto giant, as China is increasingly becoming one of the most important markets for electric vehicles. Money from Chinese investors, conglomerates, cities and the government, continues to drive a significant amount of the future of next-generation electric car technology.

The deal also provides a future for A123′s technology, which had a promising beginning, but had suffered a series of setbacks in 2012. Venture-backed A123 held the largest IPO in 2009, raising some $371 million, and was trading at over $20 per share when it started trading. A123 also raised more than $350 million from private investors when it was still a startup.

Yet in recent months, it suffered from manufacturing problems, and also had only a handful of customers for its premium batteries. The company had been losing boat loads of money for years.

The Wanxiang deal still won’t make back enough to cover its debts. A123 says:

Because the total purchase price for A123’s assets would be less than the total amount owed to creditors, the Company does not anticipate any recoveries for its current shareholders and believes its stock to have no value.

Now that the A123 bankruptcy is moving forward, it will be interesting to see what Fisker Automotive, one of A123′s prime customers, will do. Fisker had told the media that it is waiting for the results of the A123 auction before it starts back up assembling its Karma cars.

This isn’t Wanxiang’s first cleantech and clean energy acquisition — it’s actually its fifth in 2012, says the company in a release. Wanxiang has been aggressively acquiring under valued American cleantech and clean energy companies.

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The companies actually called the move “a merger” in the press release, but the first thing you learn as a business reporter is that there are no mergers. Contour Energy Systems has raised a lot more money than ActaCell, and ActaCell is becoming a subsidiary of Contour, so I think it’s safe to call it an acquisition. The companies didn’t release terms of the deal.

I haven’t heard much about ActaCell in a couple years. The company was founded in 2007 and managed to raise a $5.8 million Series A round from well known investors including DFJ Mercury, Google.org’s RechargeIT program, Applied Ventures (the VC arm of Applied Materials), and Good Energies. That was back when Google was just starting to experiment with investing in some cleantech startups, and nowadays it has largely moved away from this strategy.

ActaCell also raised a $3 million grant from the National Institute of Standards and Technology’s Technology Innovation Program. According to SEC filings, ActaCell hasn’t raised any more funding since then.

ActaCell has been working on commercializing low-cost, high-power lithium-ion battery materials based on tech from professor Arumugam Manthiram at the University of Texas at Austin. The company holds exclusive patents for making a cathode from manganese spinel, and an anode from a “high energy nanocomposite alloy.”

Contour Energy Systems, on the other hand, closed a $20 million series C round back in October 2011 and had raised $30 million before that. Contour makes battery technology using the element fluorine, which is volatile but which could deliver longer lasting, higher power batteries for devices spanning from smart meters to pacemakers, and one day electric vehicles and laptops.

Contour says Actacell’s battery tech will allow it to enter new markets and provide new products. ActaCell says in the release that it will be able to speed up its technology to a commercial phase more quickly in partnership with Contour.

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But wait, there’s more . . . Add to their inevitable demise an overall lackluster performance in battery storage technology, and we have ourselves the makings of a blog post on the failure of batteries to live up to their promises.

To set the stage, the specific energy of gasoline — measured in kWh per kg, for instance — is about 400 times higher than that of a lead-acid battery, and about 200 times better than the Lithium-ion battery in the Chevrolet Volt. We should not expect batteries to rival the energy density delivered by our beloved fossil fuels — ever.

A recent article in APS News reported on an emerging view that batteries are failing to live up to our dreams in the electric car realm:

Despite their many potential advantages, all-electric vehicles will not replace the standard American family car in the foreseeable future. This was the perhaps reluctant consensus at a recent symposium focused on battery research.

I was somewhat stunned to see this article. I am accustomed to seeing articles emphasizing the possible — albeit often improbable, in my mind. Also appearing in the article is a quote from Paul Alivisatos, an accomplished physicist, summarizing the need for further research:

“It remains true today, as in the past, that we need a fundamental understanding of the physics of how energy-conversion processes take place, at a much deeper level, in order to achieve a truly sustainable energy future.”

Rephrasing: the physics we currently understand is not sufficient to deliver the kind of battery we need to make the future work without fossil fuels. Red flags go up for me when it is our understanding of physics rather than practical engineering challenges standing in the way — as serious as the latter can be. Physics limitations instantly present a much taller order to overcome.

Anecdotes

I’m sure everyone has tales of how batteries have let them down — ranging from the merely annoying to life-threatening situations. I find that I am more often disappointed than pleasantly surprised when it comes to batteries. Here are some examples:

• I frequently go for months without driving my truck. The battery is often dead when I try to start it. Lead-acid batteries only get worse if left in a discharged state, so it’s a runaway process. Fortunately, I live on a hill and can often roll-start my way back onto the road.
• The rechargeable NiMh batteries I use for small electronics devices are rated for 1000 charge cycles. I’ll bet I only get about 15–20 cycles before noticing a serious degradation in performance.
• The first set of lead-acid batteries I used with my home-built solar photovoltaic system only lasted two years before showing substantially reduced capacity. A newer set is still in good shape after 2.5 years, but the drop in performance can be pretty fast, I have found.
• Lead-acid batteries for cars tend to last 5–6 years, often failing with little warning, in many cases resulting in being stranded.
• New laptop batteries seldom fail to delight their owners in how much longer the charge lasts compared to the previous generation batteries. But give it a few years and it is not uncommon to be operating at half the original capacity.
• Batteries left in a device for a long time can develop corrosive crud around the terminals, often in hard-to-clean places.

A counter-example is the occasional amazement I experience when alkaline batteries in a device that has not been utilized in years crackle to life after all that time — if the batteries haven’t gooped themselves up, that is.

Energy-Power Tradeoff

The chief measure of a battery, in my mind, is how much energy it can store. But it makes sense to adjust this concept to the size or mass of a battery. Obviously, a more massive and voluminous battery can pack in more energy. So for a given mass (we’ll take a kilogram), we want to know how much energy a battery can store, called specific energy.

At low power demand (sipping rather than gulping), lead-acid batteries tend to hold about 30–40 Wh per kilogram (one Watt-hour is equivalent to 3600 J, or 0.001 kWh of energy). Ni-MH batteries score 45–60 Wh/kg, and Lithium-ion gets about 120–180 Wh/kg. Part of the reason for Li-ion’s better performance is that lithium itself is lightweight; by volume lead-acid has about 40percent the capacity of Li-ion. Gasoline, at 36.6 kWh/gal, has a specific energy of 13,800 Wh/kg. Off the charts!

As power demand increases, the battery flags, and will not offer as much total energy. Obviously, the battery discharges faster under heavier power demand, but the effect is exacerbated by less actual energy available. This is best shown on a Ragone plot, in which specific energy is plotted against specific power.

Note that the Internal Combustion Engine (ICE) exceeds both specific energy and power goals for vehicles (the mass must include engine weight, rather than the fuel by itself). Fuel cells provide decent specific energy, but typically insufficient power (per kilogram). Capacitors, including super-capacitors, discharge super-fast with lots of power, but have very low specific energy.

As useful as this plot is, it does not convey the whole story. While it looks like Li-ion meets the the goal for plug-in hybrid electric vehicles, this does not necessarily remain true if demanding 5,000 deep charge cycles, a ten-year lifetime, a moderately inexpensive product, etc.

Spider Diagrams

The U.S. Department of Energy teamed up with the automotive and battery industries to define benchmark performance targets for batteries that would result in electric vehicles being competitive with ICE vehicles on a mass-produced basis. The resulting coalition was called USABC/FreedomCAR, and their various target requirements are available here, with a useful summary presentation also available. Below is a subset of the target parameters pulled from these sources, and I have also thrown in the Chevrolet Volt for a side-by-side comparison to current capabilities.

The 300 mile (580 km) range for the pure electric vehicle (EV) comes from the presentation rather than the official USABC source, and does not look right to me based on the 40 kWh battery size. Electric cars typically need 30 kWh of storage for each 100 miles of driving (about what the Volt, Leaf, and Tesla achieve, based almost entirely on air resistance — not battery technology). So I would expect the 40 kWh battery pack associated with the EV goal to deliver half as much range as what’s in the table.

Some of the figures for the Volt deserve explanation, since many cannot be directly looked up, and require inference and calculation. Firstly, the 2013 model battery pack has a capacity of 16 kWh, but only 10.5 kWh are made available so-as to avoid potentially damaging deep discharges. Meanwhile, I have no choice but to use the entire battery pack mass and volume (197 kg; 100 L) in conjunction with the partial 10.5 kWh charge in calculating energy densities, because available energy density is what’s important.

For lifetime and cycle computations, I use the 100,000 mile, 8-year guarantee on the battery, together with the estimated 37 miles per gallon (MPG) on gas alone and 98 MPG for combined gas/electric. This implies an expectation that about 62,000 of the 100,000 miles will be driven under battery power. If recharges typically happen after 30 of the 38 miles are spent (corresponding to 80percent of available capacity), this translates to about 2,000 deep cycles. Perhaps this is pessimistic in the sense that most guarantees correspond to aminimum expected performance. But offsetting this is the fact that the USABC targets are specified for end-of-life performance, whereas I use the beginning-of-life numbers for the Volt. General Motors estimates a 10–30 percent degradation at the end of 8 years (100,000 miles).

A comparison between actual performance and target performance can be cleverly displayed graphically in a “spider chart,” as illustrated below for the plug-in hybrid performance as of May 2011 (I first saw such diagrams in a presentation by Venkat Srinivasan, in 2008).

We can make our own spider diagram for the Volt, based on the numbers in the table. Please excuse the sub-optimal placement of labels, etc.

Besides looking like some sort of cool fighter jet in a dive, the diagram highlights performance deficits on several fronts. It is not terribly hard to get lots of current out of a battery, translating to more-than-adequate power performance. But all other measures fall short of the goals by varying degrees. The APS article intones that we should not hold our collective breaths to see a march of progress in lithium-ion technology at a level that would satisfy this (still hungry) spider. In practice, improving one aspect of performance tends to decrease another somewhere else (see the piece by Srinivasan for more on this principle). So it’s not a simple matter of advancing on all fronts independently and incrementally.

Full Cost of Electric Drive

Let’s say you pay $0.10 per kWh for electricity delivered to your home. Charging the Volt battery with 10.5 kWh at 90 percent efficiency to replace the drain from 38 miles of driving will cost $1.17. If using gasoline alone, the same car uses about a gallon of gas to go the same distance. Let’s put the cost of that gallon at $4.00. Electric looks pretty good, at these rates!

Now figure in the estimated price of the Volt battery at $8,000 (a disputed number, but GM has not revealed the actual cost). If we get 62,000 miles of electric drive out of the battery, we will spend $1950 on electricity for charging, plus $8000 for the battery. That’s $9,950. The same distance on gasoline would cost $6500. Not an order-of-magnitude difference, but still gasoline currently wins.

If the price of gasoline goes up (it will; but so will electricity), and the cost of the battery goes down (it should), the two may cross. But there are other added costs to the Volt (or hybrids in general) besides just the battery. After all, hybrids can’t jettison the ICE, and require an electric drive train to boot. Even the fact that the space occupied by the battery forces bucket seats in the back of the Volt is a “cost” that must be paid.

Beyond Cars

Batteries are, of course, useful for purposes other than transportation. While transportation hardship may be the most pressing problem in the decades following peak petroleum production, solar and wind resources cannot scale to be very large without a viable storage solution.

I worked out in an earlier post how large a lead-acid battery would have to be to support the entire U.S. energy demand in the presence of solar/wind intermittency. It turned out that our estimates for recoverable lead in the world do not satisfy the need. Lithium and Nickel are even more constrained. It is possible that some other approach like sodium-sulfer or zinc-air can step in. But these are already relatively well-known options and have not blazed a wide path into storage over the past few decades.

Sigh

Don’t get me wrong: even though I dwell on the shortcomings of batteries in this post, I still hold a net positive view. When it’s dark at my house, my refrigerator, television, computers, and internet goodies are all powered by stored sunlight in lead-acid batteries. My laptop battery gets me through many a bus ride and an occasional airplane ride. Batteries really do work, and provide value. Moreover, electric cars are more than a notion or fantasy: they are actually on the road getting people where they want to go.  Despite their lackluster performance next to fossil fuel storage, batteries still beat the pants off of mechanical or gravitational storage.

And even though I might appear to be picking on the Chevy Volt by highlighting its deficiencies, I actually rather like the design point (electric vs. gasoline range hits the sweet spot, in my view). In fact, I was half way to buying one. By half way, I mean that if the price were cut in half, I would surely have one now.

The real point is that batteries fall pathetically short of our customary fossil fuel energy storage medium. When we wake up to a declining global availability of petroleum, we won’t just switch over to electric cars. We may not be able to collectively afford such a transition, given the huge up-front costs in both money and energy. Where will the prosperity come from? If oil shortages drive recession in the usual fashion, expensive options may be off the table.

ADDENDUM

The same author of the APS article referenced above wrote an extended version, worth a look.

This post originally appeared on Tom Murphy’s blog, Do the Math: Using physics and estimation to assess energy, growth, options.

Tom Murphy is an associate professor of physics at the University of California, San Diego. An amateur astronomer in high school, physics major at Georgia Tech, and Ph.D. student in physics at Caltech, Murphy has spent decades reveling in the study of astrophysics. He currently leads a project to test general relativity by bouncing laser pulses off the reflectors left on the moon by the Apollo astronauts, achieving one-millimeter-range precision. 

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