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How building a better battery would change the game for renewable energy

December 15, 2015 at 6:20 PM EDT
Wind can be a bountiful resource in Tehachapi, California, but not necessarily at the right time. There turbines generate the most energy at night, when the wind blows hardest, and the demand is the lowest. Science correspondent Miles O’Brien reports on the wider push for electricity storage solutions that may enable renewables to have a greater impact on the grid.

GWEN IFILL: The historic climate change accord in Paris is expected to give a further boost to wind, solar and other forms of energy that are less dependent on fossil fuels that cause greenhouse gases.

Some observers think it will change the business model for energy in the decades to come.

But when it comes to renewable energy, there’s a crucial technological gap that is no small hurdle.

Science correspondent Miles O’Brien has our report.

MILES O’BRIEN: A hundred miles north of Los Angeles, in Tehachapi, California, the wind can be a bountiful resource, but, unfortunately, not at the right time. It blows hardest at night, spooling up these wind turbines to their peak output, when the demand for electricity is at it lowest.

DOUG KIM, Southern California Edison: So, matching the output of wind to when customers really need it, that’s certainly one of the things that we’re looking at with this system that you see here, because you can store energy.

MILES O’BRIEN: Doug Kim is the director of advanced technology for Southern California Edison. The utility built this eight megawatt lithium-ion battery facility, designed to store electricity generated by the turbines.

DOUG KIM: We can certainly use this for an example, when the wind blows during the nighttime, capture that energy during the nighttime and then use it during the daytime, when the demand is high.

MILES O’BRIEN: The batteries, stacked in racks here, are equivalent to about 2,000 electric cars. It is the start of Edison’s effort to meet a state-mandated requirement to add 580 megawatts of energy storage into the grid by 2020.

It’s part of a big push to invent ways to practically store huge amounts of electricity, so that renewables so can become a more than fringe players on the grid.

DONALD SADOWAY, Massachusetts Institute of Technology: If we don’t treat the intermittency of renewables, they’re — they’re not really a solution.

MILES O’BRIEN: Electrochemist Donald Sadoway is a professor at MIT. He says lithium-ion batteries are not the answer; they pose a serious fire risk, and, as any laptop and cell phone user knows, their performance degrades fast as a speeding Tesla. In short, they are way too expensive and impractical for widespread usage on the grid.

But what are the alternatives?

DONALD SADOWAY: The issue is that we don’t have a battery technology that can meet the rigorous performance requirements of the grid, namely, super low-cost and super long service lifetime.

MILES O’BRIEN: Dr. Sadoway has spent 30 years working in electrometallurgy. So, no surprise that is where he found his inspiration, specifically in the aluminum smelting process.

DONALD SADOWAY: So, an aluminum smelter makes metal from dirt for less than 50 cents a pound and consumes huge quantities of electricity. And I looked at that and thought, man, if I could take that thing and teach it not to consume electricity, but to store electricity and then to give it back on demand, I know, at the end of the day, it’s going to be cheap.

MILES O’BRIEN: That was 10 years ago. Today, Dr. Sadoway is on the cusp of bringing a novel liquid battery to market through a startup he founded called Ambri.

DONALD SADOWAY: OK. So, let’s draw the battery.

MILES O’BRIEN: Dr. Sadoway gave me a chalk talk on how his battery works. It is layered like a parfait, with a low-density liquid metal at the top, a high-density liquid metal at the bottom, and molten salt in between.

DONALD SADOWAY: And the way the battery works is the metal on the top wants to form a solution with the metal on the bottom. We call it alloy.

MILES O’BRIEN: That interaction creates a flow of ions, electrical current. As it discharges, the top layer gets thinner and thinner. When the sun is shining on solar photovoltaic panels or the wind is spinning turbines, the process is reversed.

DONALD SADOWAY: It reconstitutes itself every time that it recharges, which means that, unlike other batteries, which will reduce their run time with use, our battery just keeps on running. Show me another battery that can do that.

MILES O’BRIEN: Actually, it might be just few miles down Massachusetts Avenue in a lab at Harvard.

MICHAEL AZIZ, Harvard University: We took one of these and we charged and discharged it 700 times — and if you think about doing that once a day, that’s two years — without any real sign of degradation of the molecules.

MILES O’BRIEN: Engineering professor Michael Aziz is developing a so-called flow battery. Flow batteries consist of two separate tanks filled with chemicals, one negative, one positive. The chemicals are pumped past each other into the battery.

When wind turbines or solar panels are generating power, they charge the battery, pulling electrons from the positive, and pushing them into the negative. When the battery is turned on, the flow of electrons reverses, generating electricity.

MICHAEL AZIZ: The advantage of a flow battery is, if you want more energy, you just have bigger tanks of chemicals. And that’s possibly a much cheaper way of getting the high amounts of energy than stacking up banks and banks of batteries.

MILES O’BRIEN: Flow batteries powered by a rare, expensive metal called vanadium have been around for a while. But Aziz is building his battery with benign chemicals that are cheap and plentiful.

MICHAEL AZIZ: They’re organic molecules. They’re made of carbon, hydrogen, oxygen, earth-abundant elements like that, and they’re really very inexpensive.


MICHAEL AZIZ: So, we noted in our publication that the molecule we’re using is very, very, very close to one that’s in rhubarb.

MILES O’BRIEN: So what on earth could be cheaper than a rhubarb battery? Maybe one that runs on air.

DANIELLE FONG, Founder, LightSail: This is version one. Version — this is it. This is version one. We — the technology, we’re calling it, regenerative air energy storage.

MILES O’BRIEN: Danielle Fong was all of 20 when she is co-founded a Berkeley, California, startup called LightSail. Eight years, and $70 million later, the company has developed a half-megawatt prototype system that pumps air into a tank when an intermittent power source is in operation.

DANIELLE FONG: By the time it gets to the end, it’s at 200 atmospheres. So that’s, in units of pressure, 3,000 pounds per square inch. It’s really a lot. When you want to get the energy back, you have a valve open. As the piston is drawing back, the valve closes, and then the air expands, and it drives the piston, which drives the crankshaft, which drives a generator, which produces AC power.

MILES O’BRIEN: LightSail is developing lighter, cheaper tanks made of composites to hold the highly compressed air. Up until now, the stumbling block for this idea has been managing the heat. Air at high pressure gets extremely hot.

LightSail’s breakthrough idea? Inject water droplets at the perfect size into the compression cylinder to cool the air. LightSail says it’s possible to store all the power required to run an average American home for a day, 30 kilowatt hours, in a tank of compressed air the size of a refrigerator.

DANIELLE FONG: There’s more than enough wind and more than enough solar to handle everything that we need. That’s for sure.

But the important question is, how do we, in parallel, build wind and solar resources along with energy storage, so that there is the right amount at every time? Right now, I would argue there is sort of like too much wind and solar, and not enough storage.

MILES O’BRIEN: Not even close. And the task is large. Bill Gates estimates all the batteries that currently exist in the world could power global electrical consumption for 10 minutes.

DONALD SADOWAY: People know that the battery is the missing piece. Without a battery, renewables are incomplete.

MILES O’BRIEN: But rising global demand for electricity, along with rising concern about climate change, may soon lead researchers to the missing puzzle piece, giving electricity some shelf life.

Miles O’Brien, the PBS NewsHour, Tehachapi, California.