This weekend in New York city, dozens of developers gathered together for the second Cleanweb Hackathon, where programmers spent the entire weekend building mobile and web apps around new ways to manage energy, water, food and fuel. As Sunil Paul, the founder of the event and a partner with Spring Ventures, put it in a short talk on Sunday afternoon, the idea behind the project is that “Information technology is the most powerful lever we have to address resource constraints.”

Over the weekend the Cleanweb hackers created applications like NYC BLDGS, a web data base of the energy consumption of buildings in New York that pits the best and worst buildings against each other in friendly competition. Econofy, a web site created over the weekend that enables consumers to compare the energy consumption of appliances, won both the audience choice award and the judges award for best overall hack.

The first Cleanweb Hackathon was held in San Francisco in September of last year, and the New York event this weekend was a slightly more high profile affair. Judges of the hacks included investor Fred Wilson and Rachel Sterne, New York City’s Chief Digital Officer. The United State’s Chief Technology Officer Aneesh Chopra made an appearance as a special guest.

The event is the latest sign that the ecosystem around clean technology is changing. As investors look back at the mistakes that have been made and money lost in capital intensive investments like next-gen solar, biofuels and electric cars, some investors are taking a different route and looking to make cleantech investing look a lot more like web and mobile investing — literally. Paul’s firm Spring Ventures invests in Cleanweb companies like Solar Mosaic.

The Cleanweb is an attractive way to attack the problem of climate change and resource management for the age of 9 billion people. Information technologies are available now — compared to the science experiments in biofuels and parts of clean power — and thanks to Moore’s Law their cheap, and will get increasingly cheaper. Now it’s time to tap into the innovation of the developer community to try to create new ways to leverage IT to solve the world’s problems.

Check out the video of the event below and Paul’s explanation of the Cleanweb at our Green:Net 2011 event:

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Continue reading College students unveil the Kiira EV, Uganda’s first electric car (video)

College students unveil the Kiira EV, Uganda’s first electric car (video) originally appeared on Engadget on Fri, 04 Nov 2011 00:23:00 EDT. Please see our terms for use of feeds.

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Yeah, we’ve test driven a lot of electric cars on the Green Overdrive show, but we don’t usually get to spend all that long driving the cars. Most of the time it’s just around the block or a few minutes on the driving track. But for our latest episode, we took Mitsubishi’s all-electric i MiEV out for a full day of driving, running it through its paces on the highway, in the city, parallel parking, looking for a charge, and packing it with people (and stuff). Here are our impressions:

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Fisker has finally delivered some of the first Karma electric cars to its customers, including Kleiner Perkins Partner Ray Lane. While we already brought you photos and an interview with Lane earlier this week, we couldn’t resist making the Karma the subject of our latest GigaOM TV Green Overdrive show.

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The death of a battery: we’ve all seen it happen. In phones, laptops, cameras, and now electric cars, the process is painful and — if you’re lucky — slow. Over the course of years, the lithium-ion battery that once powered your machine for hours (days even!) will gradually lose its capacity to hold a charge. Eventually you’ll give in, maybe curse Steve Jobs, and then buy a new battery, if not a whole new gadget.

But why does this happen? What’s going on in the battery that makes it give up the ghost? The short answer is that damage from extended exposure to high temperatures and a lot of charging and discharging cycles eventually starts to break down the process of the lithium ions traveling back and forth between electrodes.

The longer answer, which will take us through a description of unwanted chemical reactions, corrosion, the threat of high temperatures, and other factors affecting performance, begins with an explanation of what happens in a rechargeable lithium-ion battery when everything’s working well.

Lithium-ion Battery 101

In a typical lithium-ion battery, we’ll find a cathode, or positive electrode, made out of a lithium-metal oxide, such as lithium cobalt oxide. We’ll also find an anode, or negative electrode, which today is generally graphite. A thin, porous separator keeps the two electrodes apart to prevent electrical shorting. And an electrolyte, made of organic solvents and lithium-based salts, allows for the transport of lithium ions within the cell.

During charging, electric current forces lithium ions to move from the cathode to the anode. During discharging (in other words, when you use the battery), ions move back to the cathode.

Daniel Abraham, a scientist at Argonne National Laboratory leading research into how lithium-ion cells degrade, compared this process to water in a hydropower system. Moving water uphill requires energy, but it flows downhill very easily. In fact, it delivers (kinetic) energy, said Abraham. Similarly, a lithium cobalt oxide cathode, “does not want to give up its lithium,” he said. Like moving water uphill, it requires energy to take lithium atoms out of the oxide and load them into the anode.

During charging, ions are forced between sheets of graphene that make up the anode. But as Abraham put it, “they don’t want to be there. When they get a chance, they’ll move back,” like water flowing downhill. That’s discharging. A long-lasting battery will survive several thousand of these charge-discharge cycles, according to Abraham.

When Is a Dead Battery Really Dead?

When we talk about “dead” batteries, it’s important to understand two performance metrics: energy and power. For some applications, the rate at which you can get energy out of the battery is very important. That’s power. In electric vehicles, high power enables rapid acceleration and also regenerative braking, in which the battery needs to accept a charge within a couple seconds.

In cell phones, on the other hand, high power is less important than capacity, or how much energy the battery can hold. Higher capacity batteries last longer on a single charge.

Over time, the battery degrades in a number of ways that can affect both power and capacity, until eventually it simply can’t perform its basic functions.

Think of it in terms of another water analogy: Charging a battery is like filling a bucket with water from a tap. The volume of the bucket represents the battery’s energy, or capacity. The rate at which you fill it—turning the tap on full blast or just a trickle—is the power. But time, high temperatures, extensive cycling and other factors end up creating a hole in the bucket (dear Liza, dear Liza…).

In the bucket analogy, water leaks out. In a battery, lithium ions are taken away, or “tied down,” said Abraham. Bottom line, they’re prevented from going back and forth between the electrodes. So after a few months, the cell phone that initially required a charge only once every couple of days now needs a charge every day. Then it’s twice a day. Eventually, after too many lithium ions have been tied down, the battery won’t hold enough of a charge to be useful. The bucket will stop holding water.

Why does this happen? Well, in addition to the chemical reactions that we want to happen in the battery, there are also side reactions. Barriers arise that impede the motion of lithium ions. So the electric car that went, say, zero to 60 in five seconds off the lot, will take eight seconds after a few years, and maybe 12 seconds after five years. “All the energy is still there, but it can’t be delivered fast enough,” said Abraham. The ions run into roadblocks.

What Breaks Down and Why

The active portion of the cathode (the battery’s source of lithium ions) is designed with a particular atomic structure, for stability and performance. When ions are removed, sent over to the anode, and then inserted back into the cathode, we ideally want them to return to the same spot, in order to preserve that nice stable crystal structure.

Problem is, the crystal structure can change with each charge and discharge. An ion from Apartment A doesn’t necessarily come home but could instead insert itself into Apartment B next door. So the ion from Apartment B finds her place occupied by this drifter and, not being one for confrontation, decides to take up residence down the hall. And so on.

Gradually, these “phase changes” in the material transform the cathode to a new crystal structure, with different electrochemical properties. The particular arrangement of atoms, which enabled the desired performance in the first place, has been altered.

In hybrid vehicle batteries, which only need to provide power during acceleration or braking, noted Abraham, these structural changes occur much more slowly than in electric vehicles, because only a small fraction of lithium ions in the system move back and forth in any given cycle. As a result, he said, it’s easier for them to return to their original locations.

Problem of Corrosion

Degradation can occur in other parts of the battery as well. Each electrode is paired with a current collector, which is basically a piece of metal (typically copper for the anode, aluminum for the cathode) that gathers electrons and moves them to an external circuit. So you have slurry made from an “active” material like lithium cobalt oxide (which is ceramic and not a very good conductor), plus a glue-like binder painted over this piece of metal.

If the binder fails, the coating can peel off the current collector. If the metal corrodes, it can’t move electrons as efficiently.

Corrosion within the battery cell can result from an interaction between the electrolyte and electrodes. The graphite anode is highly “reducing,” which means it gives up electrons easily to the electrolyte. This can produce an unwanted coating on the graphite surface. The cathode, meanwhile, is highly “oxidizing,” which means it easily accepts electrons from the electrolyte, which in some cases can corrode the aluminum current collector or form a coating on the cathode particles, Abraham said.

Too Much of a Good Thing

Graphite — the material commonly used to make an anode — is thermodynamically unstable in an organic electrolyte. What that means is the very first time our battery is charged, the graphite reacts with the electrolyte. This forms a porous layer (called a solid electrolyte interphase, or SEI) that actually protects the anode from further attacks. This reaction also consumes a little lithium, however. So in an ideal world, we would have that reaction occur once to create the protective layer, and then be done with it.

In reality, however, the SEI is a sadly unstable defender. It does a good job protecting the graphite at room temperature, said Abraham, but at high temperatures or when the battery runs all the way down to zero charge (“deep cycling”) the SEI can partially dissolve into the electrolyte. (At high temperatures, electrolytes also tend to decompose and side reactions accelerate.)

When friendlier conditions return, another protective layer will form, but this will eat up more lithium, giving us the same problem we had with the leaky bucket. We’ll have to recharge our cell phone more often.

Now, as much as we need that SEI to protect the graphite anode, there can be too much of a good thing. If the layer thickens too much, it actually becomes a barrier to the lithium ions, which we want to flow freely back and forth. That affects power performance, which is, as Abraham emphasized, “extremely important” for electric vehicles.

Building Better Batteries

So, what can be done to make our batteries last longer? In the lab, researchers are looking for electrolyte additives to function like vitamins in our diet, enabling the battery to perform better and live longer by reducing harmful reactions between the electrodes and electrolyte, said Abraham. They’re also seeking new, more stable crystal structures for the electrodes, as well as more stable binders and electrolytes.

Engineers at battery and electric car companies, meanwhile, are working on the battery pack and thermal management systems to try and keep lithium-ion cells within a constant, healthy temperature range. The rest of us, as consumers, can avoid extreme temperatures and deep cycling, and for now keep grumbling about those batteries that always seem to die too soon.

Image courtesy of Argonne National Labs, felixtsao, warrenski, MitchClanky2008, bizmac.

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No matter how hard Nissan tries to convince folks that driving an EV won’t leave them stranded on the side of the road gagging for electricity, that pesky range anxiety issue continues to permeate discussions about electric cars. So, what else to do but strap an EV charger on roadside service vehicles? The Japan Automobile Federation is trialing just such a scheme, with a Nissan-built prototype service truck helping to top up electrified transporters that have ended up bereft of juice at an inopportune moment. The trial’s gotten its start in Kanagawa Prefecture this week, which, incidentally, happens to be using a Nissan Leaf as its governor’s official car. So, even if you do figure out a way to use up your Leaf’s entire battery, you get the comfort of knowing you’re riding like a governor and that the good men in orange jumpsuits will be there to take care of your problemo.

Continue reading Japan trying out roadside service vehicles capable of charging EVs, soothing range anxiety

Japan trying out roadside service vehicles capable of charging EVs, soothing range anxiety originally appeared on Engadget on Thu, 09 Jun 2011 08:57:00 EDT. Please see our terms for use of feeds.

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