{"id":13344,"date":"2017-10-12T10:15:37","date_gmt":"2017-10-12T10:15:37","guid":{"rendered":"https:\/\/www.revoscience.com\/en\/?p=13344"},"modified":"2017-10-12T10:15:37","modified_gmt":"2017-10-12T10:15:37","slug":"making-renewable-power-viable-grid","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/making-renewable-power-viable-grid\/","title":{"rendered":"Making renewable power more viable for the grid"},"content":{"rendered":"

\u201cAir-breathing\u201d battery can store electricity for months, for about a fifth the cost of current technologies.<\/strong><\/em><\/span><\/p>\n

\"\"
MIT researchers have developed an \u201cair-breathing\u201d battery that could store electricity for very long durations for about a third the price of current technologies, with minimal location restraints and zero emissions.
Courtesy of the researchers. Left photo: Felice Frankel.<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0Wind and solar power are increasingly popular sources for renewable energy. But intermittency issues keep them from connecting widely to the U.S. grid: They require energy-storage systems that, at the cheapest, run about $100 per kilowatt hour and function only in certain locations.<\/span><\/p>\n

Now MIT researchers have developed an \u201cair-breathing\u201d battery that could store electricity for very long durations for about one-fifth the cost of current technologies, with minimal location restraints and zero emissions. The battery could be used to make sporadic renewable power a more reliable source of electricity for the grid.<\/span><\/p>\n

For its anode, the rechargeable flow battery uses cheap, abundant sulfur dissolved in water. An aerated liquid salt solution in the cathode continuously takes in and releases oxygen that balances charge as ions shuttle between the electrodes. Oxygen flowing into the cathode causes the anode to discharge electrons to an external circuit. Oxygen flowing out sends electrons back to the anode, recharging the battery.<\/span><\/p>\n

\u201cThis battery literally inhales and exhales air, but it doesn\u2019t exhale carbon dioxide, like humans \u2014 it exhales oxygen,\u201d says Yet-Ming Chiang, the Kyocera Professor of Materials Science and Engineering at MIT and co-author of a paper describing the battery. The research appears today in the journal\u00a0Joule<\/em>.<\/span><\/p>\n

The battery\u2019s total chemical cost \u2014 the combined price of the cathode, anode, and electrolyte materials \u2014 is about 1\/30th the cost of competing batteries, such as lithium-ion batteries. Scaled-up systems could be used to store electricity from wind or solar power, for multiple days to entire seasons, for about $20 to $30 per kilowatt hour.<\/span><\/p>\n

Co-authors with Chiang on the paper are: first author Zheng Li, who was a postdoc at MIT during the research and is now a professor at Virginia Tech; Fikile R. Brushett, the Raymond A. and Helen E. St. Laurent Career Development Professor of Chemical Engineering; research scientist Liang Su; graduate students Menghsuan Pan and\u00a0Kai Xiang; and undergraduate students Andres Badel, Joseph M. Valle, and Stephanie L. Eiler.<\/span><\/p>\n

Finding the right balance<\/strong><\/span><\/p>\n

Development of the battery began in 2012, when Chiang joined the Department of Energy\u2019s Joint Center for Energy Storage Research, a five-year project that brought together about 180 researchers to collaborate on energy-saving technologies. Chiang, for his part, focused on developing an efficient battery that could reduce the cost of grid-scale energy storage.<\/span><\/p>\n

A major issue with batteries over the past several decades, Chiang says, has been a focus on synthesizing materials that offer greater energy density but are very expensive. The most widely used materials in lithium-ion batteries for cellphones, for instance, have a cost of about $100 for each kilowatt hour of energy stored.<\/span><\/p>\n

\u201cThis meant maybe we weren\u2019t focusing on the right thing, with an ever-increasing chemical cost in pursuit of high energy-density,\u201d Chiang says. He brought the issue to other MIT researchers. \u201cWe said, \u2018If we want energy storage at the terawatt scale, we have to use truly abundant materials.\u2019\u201d<\/span><\/p>\n

The researchers first decided the anode needed to be sulfur, a widely available byproduct of natural gas and petroleum refining that\u2019s very energy dense, having the lowest cost per stored charge next to water and air. The challenge then was finding an inexpensive liquid cathode material that remained stable while producing a meaningful charge. That seemed improbable \u2014 until a serendipitous discovery in the lab.<\/span><\/p>\n

On a short list of candidates was a compound called potassium permanganate. If used as a cathode material, that compound is \u201creduced\u201d \u2014 a reaction that draws ions from the anode to the cathode, discharging electricity. However, the reduction of the permanganate is normally impossible to reverse, meaning the battery wouldn\u2019t be rechargeable.<\/span><\/p>\n

Still, Li tried. As expected, the reversal failed. However, the battery was, in fact, recharging, due to an unexpected oxygen reaction in the cathode, which was running entirely on air. \u201cI said, \u2018Wait, you figured out a rechargeable chemistry using sulfur that does not require a cathode compound?\u2019 That was the ah-ha moment,\u201d Chiang says.<\/span><\/p>\n

Using that concept, the team of researchers created a type of flow battery, where electrolytes are continuously pumped through electrodes and travel through a reaction cell to create charge or discharge. The battery consists of a liquid anode (anolyte) of polysulfide that contains lithium or sodium ions, and a liquid cathode (catholyte) that consists of an oxygenated dissolved salt, separated by a membrane.<\/span><\/p>\n

Upon discharging, the anolyte releases electrons into an external circuit and the lithium or sodium ions travel to the cathode. At the same time, to maintain electroneutrality, the catholyte draws in oxygen, creating negatively charged hydroxide ions. When charging, the process is simply reversed. Oxygen is expelled from the catholyte, increasing hydrogen ions, which donate electrons back to the anolyte through the external circuit.<\/span><\/p>\n

\u201cWhat this does is create a charge balance by taking oxygen in and out of the system,\u201d Chiang says.<\/span><\/p>\n

Because the battery uses ultra-low-cost materials, its chemical cost is one of the lowest \u2014 if not the lowest \u2014 of any rechargeable battery to enable cost-effective long-duration discharge. Its energy density is slightly lower than today\u2019s lithium-ion batteries.<\/span><\/p>\n

Making renewables more reliable<\/strong><\/span><\/p>\n

The prototype is currently about the size of a coffee cup. But flow batteries are highly scalable, Chiang says, and cells can be combined into larger systems.<\/span><\/p>\n

As the battery can discharge over months, the best use may be for storing electricity from notoriously unpredictable wind and solar power sources. \u201cThe intermittency for solar is daily, but for wind it\u2019s longer-scale intermittency and not so predictable. When it\u2019s not so predictable you need more reserve \u2014 the capability to discharge a battery over a longer period of time \u2014 because you don\u2019t know when the wind is going to come back next,\u201d Chiang says. Seasonal storage is important too, he adds, especially with increasing distance north of the equator, where the amount of sunlight varies more widely from summer to winter.<\/span><\/p>\n

Chiang says this could be the first technology to compete, in cost and energy density, with pumped hydroelectric storage systems, which provide most of the energy storage for renewables around the world but are very restricted by location.<\/span><\/p>\n

\u201cThe energy density of a flow battery like this is more than 500 times higher than pumped hydroelectric storage. It\u2019s also so much more compact, so that you can imagine putting it anywhere you have renewable generation,\u201d Chiang says.<\/span><\/p>\n

The research was supported by the Department of Energy.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

\u201cAir-breathing\u201d battery can store electricity for months, for about a fifth the cost of current technologies. CAMBRIDGE, Mass. —\u00a0Wind and solar power are increasingly popular sources for renewable energy. But intermittency issues keep them from connecting widely to the U.S. grid: They require energy-storage systems that, at the cheapest, run about $100 per kilowatt hour […]<\/p>\n","protected":false},"author":6,"featured_media":13345,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22,17],"tags":[],"class_list":["post-13344","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-other","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/10\/MIT-Air-Breathing-1_0.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Other<\/a> Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/13344","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=13344"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/13344\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/13345"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=13344"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=13344"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=13344"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}