System deployed at Dutch centre for sustainability and innovation

Renewable energy sources are only as reliable as the natural world that fuels them. A cloud passing overhead cuts off solar power; the wind stops blowing and windmills stop working. In order for us to depend on undependable power sources, we need a grid-sized backup to acts of God.

In 2012, president Barack Obama’s energy secretary Stephen Chu issued a “5-5-5” challenge to those in the energy storage field, bring us a 5% reduction of cost, a five times increase in capacity, and do it in five years or less. Yet-Ming Chiang, MIT’s department of material science and engineering and founder of multiple battery-research startups, was the lead author on a study published earlier this week in the journal, Joule, that described a battery conceived and designed with a wary eye on that first five in Chu’s challenge. “We said, ‘If we want energy storage at the terawatt scale, we have to use truly abundant materials,’” Chiang told MIT News.

Chiang’s team knew from jump they wanted to use sulfur as the cathode, or negative terminal, and water as the electrolyte solution that holds the energy. After some false starts, the researchers fell upon oxygen as an anode, or the positive terminal, completely by accident when an incomplete seal in a prototype allowed for air to get in to the system. The final step was finding that adding salt to the water could help carry the charge back and forth between the two terminals more efficiently. All told, the total chemical cost of Chiang’s battery, comes to about $1 per kilowatt hour (kWh).

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If you live in Frankfurt, Germany and have solar panels on your roof, you might be able to generate enough energy to power your whole home throughout the day. But if you pull in too much energy for your needs, or not enough, you can trade power with another solar-powered home in Hamburg, or Berlin, or anywhere in the country. That’s the principle behind sonnenCommunity, a nationwide, cloud-based virtual power plant launched around three years ago and made up of around 8,000 homes equipped with solar panels and an interconnected SonnenBatterie—an energy storage unit developed in 2010 by the German company Sonnen. “What’s happening in Germany with peer-to-peer power-sharing is something that’s talked about in the U.S. as a great idea for future energy-storage solutions,” says Blake Richetta, VP of sales for Sonnen U.S.

The sonnenCommunitie facilitates its energy transfers using the grid infrastructure that already exists in the country, “What we do in Germany is we essentially cut out the middleman—the utility–and we work directly with the grid operator,” Richetta says. Generally, regional utility companies manage the sale, distribution, and flow of energy through the grid and into homes throughout the region in which it operates. But because Germany has just one interconnected grid system, Sonnen is able to bypass the various regional utilities and work with the grid operator to manage the energy flow into and out of homes connected in the sonnenCommunitie, essentially acting as a nationwide utility for its customers.

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Conductive metal-organic frameworks could form basis of storage systems for renewable energy, says US team

The biggest drawback to larger utilisation of renewable energy generation has always been their intermittency. The weather conditions that can be harnessed to generate electricity are, by their nature, transient, and unless energy can be stored and  put onto distribution grids when generation is not possible, renewables will struggle to displace power stations that are available around the clock, day in and day out. The search for materials that can effectively store the large amounts of energy necessary and discharge it efficiently has become more intense in recent years.

One promising candidate is the group of materials known as metal-organic frameworks (MOFs). These highly-porous materials have been used in many applications in recent years, from storing gases to catalysing reactions that convert carbon dioxide into fuels. The one barrier to their use in energy storage has been their inability to conduct electricity. The new discovery from chemists at the University of Southern California (USC) may change that.

A group from the USC’s Dornsife College in Los Angeles has published a paper in the Journal of the American Chemical Society describing a MOF containing cobalt and sulphur that, they claim, conducts electricity both like a semiconductor and a metal, with the greatest conductivity occurring at very high and very low temperatures (the semiconducting properties are most pronounced at around 180K (-93°C). This band-like conduction behaviour has never before been observed in a MOF, they state. The compound has a two-dimensional structure somewhat similar to graphene.

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Now MIT researchers have developed an “air-breathing” 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.

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.

“This battery literally inhales and exhales air, but it doesn’t exhale carbon dioxide, like humans—it exhales oxygen,” 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 Joule.

The battery’s total chemical cost—the combined price of the cathode, anode, and electrolyte materials—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.

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 Kai Xiang; and undergraduate students Andres Badel, Joseph M. Valle, and Stephanie L. Eiler.

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The electric industry is going through a period where long prevailing planning and operating assumptions are being upended. Significant, multi-faceted changes in energy supply and demand technology are compelling electric utilities to fundamentally rethink their legacy business models and develop profoundly different visions of their role in the energy market.With expected technological innovation, storage will grow in importance, making it imperative for planners to consider storage for energy, capacity, and ancillary service needs in all parts of the industry value chain.

Join Siemens in an exclusive 4 part mini- series with Energy Collective as we decipher the energy storage value proposition. For a full download of  our whitepaper on the energy storage value proposition, please visit our website.

Introduction

While energy storage has grown rapidly over the past couple of years and several hundred MWs of projects are under development, the value to investors of energy storage remains somewhat nebulous. This series identifies leading energy storage technologies, defines key applications, reviews current leading battery projects, and estimates investor returns for differing applications and markets. Further, this series also discusses the key factors driving storage economics and investor returns.

Today, in the right application and market, battery storage can provide attractive returns. Clearly, there are other applications where the economics today do not meet a minimum threshold. The storage economic proposition will improve in all applications as capital costs fall, which they are expected to do. By its very nature, storage offers multiple value streams. A rational investor would take advantage of all possible value streams, so long as each value stream in practice can be realized and there is no “double counting” of benefits.

Storage End Uses and Value Streams

As mentioned briefly, storage applications can range from very short duration requirements like frequency response and regulation, operating and planning reserves, to longer term needs of energy management (e.g., to store energy from renewable resources generated in off peak periods an consume it during on-peak periods). The graph below indicates the rated power and discharge time for each key storage technology available to meet the system frequency response and regulation, operating and ramping, and energy management needs. As shown, Li-Ion batteries are quite versatile in terms of the range of applications they capture. For example, such batteries can respond quickly (seconds) to cover frequency response and regulation needs with small storage sizes and at the same time cover longer duration storage needs where speed of response is less critical. Flywheels, on the other hand, can provide an even quicker speed of response and hence are ideal for frequency response applications but the storage duration or capability is much smaller.

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BEIJING, Oct 12 (Reuters) – China aims to boost its large-scale energy storage capacity over the next decade, the government’s central planner said, in a major push to solve the problem of stranded power in the west of the country as Beijing promotes the use of more renewable power.

While China has led the globe in pushing for greater reliance on wind and solar power in recent years, getting clean energy from western regions to urban users in the world’s top energy consumer has been a major headache.

China generated a total of 5.9 trillion kilowatt hours (kWh) of power in 2016, of which 25.6 percent came from hydro, wind, nuclear and solar power stations.

Storage technology like batteries can help preserve renewable power when demand is low and save it for distribution when consumption picks up. Sufficient storage would prevent power generation being curtailed due to surplus supplies.

A key part of the plan is to issue subsidies to energy storage companies to spur the construction of new power-saving facilities, according to a statement issued by the National Development and Reform Commission (NDRC) on Wednesday. Details of the subsidy were not disclosed.

The government will also launch some pilot projects to test advances in energy storage technology, such as pumped hydro storage, compressed air energy storage, superconducting magnetic energy storage and bulk storage with batteries using substances like lead-acid lithium-ion, the statement said.

Those programmes are expected to be completed by the end of 2020, with the aim of putting the projects into large-scale production five years after that, it said.

“The development of energy storage industry will offer significant support to China’s supply-side reform and the transformation of the energy structure,” the NDRC said.

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Elon Musk has gotten a lot of attention for his proposed efforts to rebuild Puerto Rico’s electric grid, which could prove how cheap and valuable solar and energy storage could be in the decades ahead. Musk’s plan isn’t public yet, but it would likely mean bringing Powerpacks to the island to help deal with outages that still affect 90% of consumers. And this may be an instance where Tesla (NASDAQ: TSLA) could build a solution faster than most utilities. 

But Tesla isn’t the only company eyeing solutions in Puerto Rico. Sonnen has said it will build microgrids on the island as well. This is potentially the first big test for solar plus storage as a fast solution to island infrastructure challenges. 

With a little help from energy storage, renewable energy could be just what Puerto Rico needs. Image source: Getty Images.

How solar and energy storage could help Puerto Rico

There are two main problems facing Puerto Rico’s energy infrastructure. First, when centralized power stations go offline during a hurricane they leave thousands, or millions, of people without power. Second, downed power lines can make an operational power plant meaningless because they aren’t connected to the grid. It’s this second problem that’s the main issue for Puerto Rico today and in the long term. 

A grid with more solar and energy storage could reduce both problems in Puerto Rico. Solar arrays all over the island would spread out energy generation across the island, reducing the risk that one plant will go down. And to generate enough power for the entire island, about 9.1 gigawatts of solar would need to be installed, requiring about 72,800 acres, or just 3.3% of the country’s land. Wind turbines, particularly offshore, could reduce that land usage as well. Puerto Rico could easily generate 100% of its own electricity, assuming it had enough energy storage. 

From a distribution standpoint, having a de-centralized grid would help the rebuilding process. It wouldn’t stop blackouts completely, but if transmission redundancies are built into a grid based on solar and energy storage it could make blackouts less likely. 

It’s not clear how much energy storage would be needed to keep Puerto Rico’s grid operations — since it’s never been done — but 55,000 megawatt-hours or about 250,000 Tesla Powerpacks would be a full day’s storage. That’s 426 times the size of the company’s Australia project, so it’s a lot, but not outside the realm of possibility. 

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