New generation of flow batteries could eventually sustain a grid powered by

first_img Click to view the privacy policy. Required fields are indicated by an asterisk (*) Tanked up Because flow batteries store charge in tanks of electrolytes, they can be scaled up as a backup source of grid power. A new design relies on ferrocyanide to capture and release electrons. During discharge, ferrocyanide (green) loseselectrons, which travel through a circuit to aviologen-based electrolyte (orange). Ferrocyanide During charging, electrons reverse course. Ammonium ions (center) travel back and forth to balance charges. Viologen derivative Electrode Ammonium Energygeneration Energy storage Circulation pump + – C. Bickel/Science New generation of ‘flow batteries’ could eventually sustain a grid powered by the sun and wind Batteries already power electronics, tools, and cars; soon, they could help sustain the entire electric grid. With the rise of wind and solar power, energy companies are looking for ways to keep electrons flowing when the sun doesn’t shine and the wind ebbs. Giant devices called flow batteries, using tanks of electrolytes capable of storing enough electricity to power thousands of homes for many hours, could be the answer. But most flow batteries rely on vanadium, a somewhat rare and expensive metal, and alternatives are short-lived and toxic.Last week, researchers reported overcoming many of these drawbacks with a potentially cheap, long-lived, and safe flow battery. The work is part of a wave of advances generating optimism that a new generation of flow batteries will soon serve as a backstop for the deployment of wind and solar power on a grand scale. “There is lots of progress in this field right now,” says Ulrich Schubert, a chemist at Friedrich Schiller University in Jena, Germany.Lithium-ion batteries—the sort in laptops and Teslas—have a head start in grid-scale applications. Lithium batteries already bank backup power for hospitals, office parks, and even towns. But they don’t scale up well to the larger sizes needed to provide backup power for cities, says Michael Perry, associate director for electrochemical energy systems at United Technologies Research Center in East Hartford, Connecticut. By Robert F. ServiceOct. 31, 2018 , 2:10 PM Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Email Now, Liu and his colleagues have come up with a flow battery that operates at neutral pH. They started with an iron-containing electrolyte, ferrocyanide, that has been studied in the past. But in previous ferrocyanide batteries, the electrolyte was dissolved in water containing sodium or potassium salts, which provide positively charged ions that move through the cell to balance the electron movement during charging and discharging. Ferrocyanide isn’t very soluble in those salt solutions, limiting the electrical storage capacity of the battery.So Liu and his colleagues replaced the salts with a nitrogen-based compound called ammonium that allows at least twice as much ferrocyanide to dissolve, doubling the battery’s capacity. The resulting battery is not as energy-dense as a vanadium flow battery. But in last week’s issue of Joule, Liu and his colleagues reported that their iron-based organic flow battery shows no signs of degradation after 1000 charge-discharge cycles, equivalent to about 3 years of operation. And because the electrolytes are neutral pH and water-based, a leak likely wouldn’t produce environmental damage.”Overall, that’s an excellent piece of work,” says Qing Wang, a materials scientist at the National University of Singapore. Still, he and others caution that the battery is sluggish to charge and discharge. Liu says he and his colleagues plan to test other electrolyte additives, among other fixes, to boost conductivity.It’s too early to say which flow battery chemistry—if any—will support the renewable grid of the future. Another contender uses electrolytes made from metal-containing organic compounds called polyoxometalates, which store far more energy in the same volume than the competition. In the 10 October issue of Nature Chemistry, for example, researchers led by Leroy Cronin, a chemist at the University of Glasgow in the United Kingdom, reported a polyoxometalate flow battery that stores up to 40 times as much charge as vanadium cells of the same volume. The downside for now is that these electrolytes are highly viscous and thus more challenging to pump through the battery, Cronin says. “Today, no one flow battery fills all the needs,” Schubert says. That means there’s still plenty of room for innovation.*Correction, 21 November, 4 p.m.: This story has been updated to correct the name of the company ESS, Inc. Sign up for our daily newsletter Get more great content like this delivered right to you! Country Commercial flow batteries, such as this zinc-bromine system from Redflow, are helping back up renewables. That’s where flow batteries come in. They store electrical charge in tanks of liquid electrolyte that is pumped through electrodes to extract the electrons; the spent electrolyte returns to the tank. When a solar panel or turbine provides electrons, the pumps push spent electrolyte back through the electrodes, where the electrolyte is recharged and returned to the holding tank. Scaling up the batteries to store more power simply requires bigger tanks of electrolytes. Vanadium has become a popular electrolyte component because the metal charges and discharges reliably for thousands of cycles. Rongke Power, in Dalian, China, for example, is building the world’s largest vanadium flow battery, which should come online in 2020. The battery will store 800 megawatt-hours of energy, enough to power thousands of homes. The market for flow batteries—led by vanadium cells and zinc-bromine, another variety—could grow to nearly $1 billion annually over the next 5 years, according to the market research firm MarketsandMarkets.But the price of vanadium has risen in recent years, and experts worry that if vanadium demand skyrockets, prices will, too. A leading alternative replaces vanadium with organic compounds that also grab and release electrons. Organic molecules can be precisely tailored to meet designers’ needs, says Tianbiao Liu, a flow battery expert at Utah State University in Logan. But organics tend to degrade and need replacement after a few months, and some compounds work only with powerful acidic or basic electrolytes that can eat away at the pumps and prove dangerous if their tanks leak.Researchers are now in the midst of “a second wave of progress” in organic flow batteries, Schubert says. In July, a group led by Harvard University materials scientist Michael Aziz reported in Joule that they had devised a long-lived organic molecule that loses only 3% of its charge-carrying capacity per year. Although that’s still not stable enough, it was a big jump from previous organic flow cell batteries that lost a similar amount every day, Liu says.Iron, which is cheap and good at grabbing and giving up electrons, is another promising alternative. A Portland, Oregon, company called ESS, for example, sells such batteries. But ESS’s batteries require electrolytes operating at a pH between one and four, with acidity similar to vinegar’s. REDFLOW LIMITED last_img

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