How Better Battery Storage Will Expedite Renewable Energy
“The worldwide transition from fossil fuels to renewable sources of energy is under way …" according to the Earth Policy Institute's new book, The Great Transition.
Between 2006 and 2012, global solar photovoltaic's (PV) annual capacity grew 190 percent, while wind energy's annual capacity grew 40 percent, reported the International Renewable Energy Agency. The agency projects that by 2030, solar PV capacity will be nine times what it was in 2013; wind power could increase five-fold.
Tesla's utility scale Powerpack batteries.
Electric vehicle (EV) sales have risen 128 percent since 2012, though they made up less than 1 percent of total U.S. vehicle sales in 2014. Although today's most affordable EVs still travel less than 100 miles on a full battery charge (the Tesla Model S 70D, priced starting at $75,000, has a 240-mile range), the plug-in market is projected to grow between 14.7 and 18.6 percent annually through 2024.
Ford C-Max Energi and Honda Fit EV at a public charging station in front of San Francisco City Hall.
The upward trend for renewables is being driven by concerns about climate change and energy security, decreasing solar PV and wind prices, rising retail electricity prices, favorable governmental incentives for renewable energy, the desire for energy self-sufficiency and the declining cost of batteries. Growing EV sales, also benefitting from incentives, are affecting economies of scale in battery manufacturing, helping to drive down prices.
Sun and wind energy are free, but because they are not constant sources of power, renewable energy is considered “variable"—it is affected by location, weather and time of day. Utilities need to deliver reliable and steady energy by balancing supply and demand. While today they can usually handle the fluctuations that solar and wind power present to the grid by adjusting their operations, as the amount of energy supplied by renewables grows, better battery storage is crucial.
Solar plant in the Mojave. Photo credit: Akradecki
Batteries convert electricity into chemical potential energy for storage and back into electrical energy as needed. They can perform different functions at various points along the electric grid. At the site of solar PV or wind turbines, batteries can smooth out the variability of flow and store excess energy when demand is low to release it when demand is high. Currently, fluctuations are handled by drawing power from natural gas, nuclear or coal-fired power plants; but whereas fossil-fuel plants can take many hours to ramp up, batteries respond quickly and when used to replace fossil-fuel power plants, they cut CO2 emissions. Batteries can store output from renewables when it exceeds a local substation's capacity and release the power when the flow is less or store energy when prices are low so it can be sold back to the grid when prices rise. For households, batteries can store energy for use anytime and provide back-up power in case of blackouts.
Batteries have not been fully integrated into the mainstream power system because of performance and safety issues, regulatory barriers, the resistance of utilities and cost. But researchers around the world are working on developing better and cheaper batteries.
Every battery consists of two terminals made of different chemicals (usually metals)—a positively charged cathode and a negatively charged anode—and the electrolyte, the chemical medium that separates the terminals. When a battery is connected to a device or an electric circuit, chemical reactions take place on the electrodes, causing ions (atoms with a positive electrical charge) to flow from the anode through the electrolyte to the cathode. Electrons (particles with a negative charge) want to move to the positive cathode too, but because the electrolyte blocks them, they are forced to do so via the outside circuit, creating the electric current that powers the device. After all the electrons move to the cathode, the battery dies. In rechargeable batteries, electricity from an outside source can reverse the exchange, but since the chemical reaction is not perfectly efficient, the number of times a battery can be recharged is usually limited.
Batteries vary in their attributes. The charge time determines how long a battery takes to get back to its charged state. Energy density is the amount of energy that can be put into a battery of a given size and weight, which matters depending on application. Cycle life refers to how many times a battery can be recharged before it drops below 80 percent of its ability to hold a charge, which is when it begins to be depleted. Other aspects of a battery include its toxicity, recycleability and how easily it can be kept in its required temperature range. Cost has been the major limiting factor for widespread use.
Duke Energy's large battery can store 500 kWh of electricity, enough to power 50 homes during peak demand.
There are many kinds of batteries available today and depending on the function a battery serves, many different requirements for storage capacity, charging and discharging performance, response time, maintenance, safety and cost. Here are a few examples of battery types.
Lead-acid batteries are already used worldwide to support renewable energy. Many have a short cycle life and last only three to four years. Nickel cadmium batteries have good cycle life and can discharge quickly, but the materials are more expensive than those in lead acid batteries. Lithium-ion batteries have high energy density for their size, which is why they are widely used for consumer electronics and electric vehicles. They are good for short discharge cycles and high power, but because of the energy density and combustibility of lithium, they can potentially overheat and catch fire. Sodium-sulphur batteries, with molten salt as the electrolyte, must operate at high temperatures, but can discharge for six hours or more.
Flow batteries, with the chemicals to produce electricity dissolved in water in separate tanks, can be charged and discharged limitlessly and can provide steady energy over time. Because the use of bigger tanks allows flow batteries to store more energy, they have great potential to help the grid deal with utility-scale electricity storage.
BASF experiments with cathode materials to improve lithion-ion batteries.
Battery researchers are trying to advance existing technologies and develop novel ones, as well as enhance materials and manufacturing processes. They are manipulating chemicals and experimenting with new ones, trying to improve the scale of batteries, the duration of their discharge, their efficiency, response time, sustainability and cost, as well as addressing safety issues. Japan and the U.S. are global leaders in the use of battery storage, with China and Germany close behind. India, Italy and South Korea are also implementing battery storage.
Some examples of new batteries being developed include Japan's dual carbon battery that charges 20 times faster than ordinary lithium-ion batteries with comparable energy density, doesn't heat up and is fully recyclable. Researchers at Stanford University are using nanotechnology in a pure lithium battery to hopefully triple the energy density and decrease the cost four-fold. At the University of Illinois at Chicago, lithium ions have been replaced with magnesium ions, which can move twice as many electrons; this allows the battery to be recharged more times before degrading. The Joint Center for Energy Research at Argonne National Laboratory is researching technologies other than lithium-ion that can store five times more energy at one-fifth the cost.
Eric Isaacs, a Columbia University Ph.D. candidate in Applied Physics, is studying how to improve cathode materials. Featured in the 2015 Earth Institute Student Research Showcase, his research focuses on lithium iron phosphate as a candidate for cathode material. It has high energy density and can be heated to hotter temperatures, so it is safer than typical lithium-ion batteries and since iron is abundant, it could potentially be used to produce a cheaper and more sustainable battery. But Isaacs explained that the basic material is unstable when it's partially charged and “playing tricks" in processing it to help stabilize it lowers the energy density. His research aims to understand and remedy the instability and could also eventually help identify and evaluate other new materials for cathodes.
More than $5 billion has been invested in battery development over the last decade. Bill Gates has backed MIT's liquid metal battery, made up of two common molten metals separated by a molten salt that is cheap, easy to assemble and long-lasting. The venture capital firm Kleiner Perkins Caufield & Byers invested in an aqueous-ion battery, an updated saltwater battery being developed at Carnegie Mellon with potential to become the cheapest non-toxic and long-lasting battery for homes and hospitals. Khosla Ventures is behind Berkeley Lab's dry lithium battery that uses porous material and has two to three times the energy density of today's liquid lithium battery.
“The issue with existing batteries is that they suck," said Elon Musk, Tesla's CEO when the company launched its new Powerwall and Powerpack products at the end of April. Tesla's solution is the Powerwall, a rechargeable lithium-ion battery, 7 inches thick and 3 feet by 4 feet, that can be mounted on a wall. The 7kWh version sells for $3,000, the 10kWh costs $3,500 and they are guaranteed for 10 years. Up to nine of them can be stacked in a home, providing up to 90 kWh of power. The 10kWh model could power the average American home, which uses about 30kWh per day, for 8 hours, according to one analyst. 38,000 Powerwalls units were reserved the first week after the launch and they are already sold out until mid-2016.
The Powerpack is a 100 kWh battery for utility scale use, which can be combined to “scale infinitely," said Musk. Ten thousand Powerpacks would produce 1GW of electricity. To move the world to sustainable energy and curb climate change, Musk envisions a scenario where 160 million Powerpacks could enable the U.S. to transition to renewable energy; 900 million Powerpacks could make it possible to make all electricity generation in the world renewable.
“The goal is complete transformation of the entire energy infrastructure of the world," said Musk.
To produce the Powerwall, Powerpack and its electric vehicle batteries, Tesla is building a $5 billion “gigafactory" in Nevada, the first of many. The factory will produce the energy it needs from geothermal, solar and wind and one expert projected that it will actually generate 20 percent more than it needs.
In the U.S., battery storage is already used in places like Notrees, Texas, where thousands of lead-acid batteries store wind energy. In Laurel Mountain, West Virginia, a lithium-ion battery storage plant with 32MW of capacity is so far the largest in the world. Southern California Edison has the nation's biggest battery storage system, with plans for an additional 264 MW of storage, using Tesla batteries. California's large utilities are required to collectively add 1,325 MW of storage by 2024.
A battery that costs $100 per kWh is the Holy Grail for battery researchers around the world. Electric vehicle batteries cost between $300 and $410 per kWh in 2014; analysts generally agree that batteries must reach $150 per kWh or less for those vehicles to be competitive with gasoline-powered vehicles. The cheaper the battery, the more electricity can be stored and the farther the car can go on a charge.
Last year, the cheapest utility scale batteries cost $700 or more per kWh. The Tesla Powerpack is currently estimated to cost $250 per kWh, with the “gigafactory" expected to cut battery prices by 30 percent. The Advanced Research Project Agency-Energy (ARPA-E) is funding 21 different grid-scale battery technologies, hoping to lower battery costs to $100 per kWh, the point at which storage becomes competitive with conventionally generated electricity.
According to the International Renewable Energy Agency, annual battery storage capacity is expected to grow from 360MW to 14GW between 2014 and 2023. Global sales of light duty electric vehicles are projected to go from 2.7 million in 2014 to 6.4 million in 2023. With so many striving for a significant battery breakthrough, more economies of scale and improved manufacturing processes, the world just might see a $100 per kWh battery within the next few years.
Columbia University's Earth Institute and School of Continuing Education developed the Master of Science in Sustainability Management to train professionals in sustainability. The program emphasizes skills and knowledge that are needed to integrate sustainability in business, and in public and non-profit organizations. The coursework combines the study of management and economic and quantitative analysis with classes in the state of the art in sustainability practice and science.
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By Eric Tate and Christopher Emrich
Disasters stemming from hazards like floods, wildfires, and disease often garner attention because of their extreme conditions and heavy societal impacts. Although the nature of the damage may vary, major disasters are alike in that socially vulnerable populations often experience the worst repercussions. For example, we saw this following Hurricanes Katrina and Harvey, each of which generated widespread physical damage and outsized impacts to low-income and minority survivors.
Mapping Social Vulnerability<p>Figure 1a is a typical map of social vulnerability across the United States at the census tract level based on the Social Vulnerability Index (SoVI) algorithm of <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/1540-6237.8402002" target="_blank"><em>Cutter et al.</em></a> . Spatial representation of the index depicts high social vulnerability regionally in the Southwest, upper Great Plains, eastern Oklahoma, southern Texas, and southern Appalachia, among other places. With such a map, users can focus attention on select places and identify population characteristics associated with elevated vulnerabilities.</p>
Fig. 1. (a) Social vulnerability across the United States at the census tract scale is mapped here following the Social Vulnerability Index (SoVI). Red and pink hues indicate high social vulnerability. (b) This bivariate map depicts social vulnerability (blue hues) and annualized per capita hazard losses (pink hues) for U.S. counties from 2010 to 2019.<p>Many current indexes in the United States and abroad are direct or conceptual offshoots of SoVI, which has been widely replicated [e.g., <a href="https://link.springer.com/article/10.1007/s13753-016-0090-9" target="_blank"><em>de Loyola Hummell et al.</em></a>, 2016]. The U.S. Centers for Disease Control and Prevention (CDC) <a href="https://www.atsdr.cdc.gov/placeandhealth/svi/index.html" target="_blank">has also developed</a> a commonly used social vulnerability index intended to help local officials identify communities that may need support before, during, and after disasters.</p><p>The first modeling and mapping efforts, starting around the mid-2000s, largely focused on describing spatial distributions of social vulnerability at varying geographic scales. Over time, research in this area came to emphasize spatial comparisons between social vulnerability and physical hazards [<a href="https://doi.org/10.1007/s11069-009-9376-1" target="_blank"><em>Wood et al.</em></a>, 2010], modeling population dynamics following disasters [<a href="https://link.springer.com/article/10.1007%2Fs11111-008-0072-y" target="_blank" rel="noopener noreferrer"><em>Myers et al.</em></a>, 2008], and quantifying the robustness of social vulnerability measures [<a href="https://doi.org/10.1007/s11069-012-0152-2" target="_blank" rel="noopener noreferrer"><em>Tate</em></a>, 2012].</p><p>More recent work is beginning to dissolve barriers between social vulnerability and environmental justice scholarship [<a href="https://doi.org/10.2105/AJPH.2018.304846" target="_blank" rel="noopener noreferrer"><em>Chakraborty et al.</em></a>, 2019], which has traditionally focused on root causes of exposure to pollution hazards. Another prominent new research direction involves deeper interrogation of social vulnerability drivers in specific hazard contexts and disaster phases (e.g., before, during, after). Such work has revealed that interactions among drivers are important, but existing case studies are ill suited to guiding development of new indicators [<a href="https://doi.org/10.1016/j.ijdrr.2015.09.013" target="_blank" rel="noopener noreferrer"><em>Rufat et al.</em></a>, 2015].</p><p>Advances in geostatistical analyses have enabled researchers to characterize interactions more accurately among social vulnerability and hazard outcomes. Figure 1b depicts social vulnerability and annualized per capita hazard losses for U.S. counties from 2010 to 2019, facilitating visualization of the spatial coincidence of pre‑event susceptibilities and hazard impacts. Places ranked high in both dimensions may be priority locations for management interventions. Further, such analysis provides invaluable comparisons between places as well as information summarizing state and regional conditions.</p><p>In Figure 2, we take the analysis of interactions a step further, dividing counties into two categories: those experiencing annual per capita losses above or below the national average from 2010 to 2019. The differences among individual race, ethnicity, and poverty variables between the two county groups are small. But expressing race together with poverty (poverty attenuated by race) produces quite different results: Counties with high hazard losses have higher percentages of both impoverished Black populations and impoverished white populations than counties with low hazard losses. These county differences are most pronounced for impoverished Black populations.</p>
Fig. 2. Differences in population percentages between counties experiencing annual per capita losses above or below the national average from 2010 to 2019 for individual and compound social vulnerability indicators (race and poverty).<p>Our current work focuses on social vulnerability to floods using geostatistical modeling and mapping. The research directions are twofold. The first is to develop hazard-specific indicators of social vulnerability to aid in mitigation planning [<a href="https://doi.org/10.1007/s11069-020-04470-2" target="_blank" rel="noopener noreferrer"><em>Tate et al.</em></a>, 2021]. Because natural hazards differ in their innate characteristics (e.g., rate of onset, spatial extent), causal processes (e.g., urbanization, meteorology), and programmatic responses by government, manifestations of social vulnerability vary across hazards.</p><p>The second is to assess the degree to which socially vulnerable populations benefit from the leading disaster recovery programs [<a href="https://doi.org/10.1080/17477891.2019.1675578" target="_blank" rel="noopener noreferrer"><em>Emrich et al.</em></a>, 2020], such as the Federal Emergency Management Agency's (FEMA) <a href="https://www.fema.gov/individual-disaster-assistance" target="_blank" rel="noopener noreferrer">Individual Assistance</a> program and the U.S. Department of Housing and Urban Development's Community Development Block Grant (CDBG) <a href="https://www.hudexchange.info/programs/cdbg-dr/" target="_blank" rel="noopener noreferrer">Disaster Recovery</a> program. Both research directions posit social vulnerability indicators as potential measures of social equity.</p>
Social Vulnerability as a Measure of Equity<p>Given their focus on social marginalization and economic barriers, social vulnerability indicators are attracting growing scientific interest as measures of inequity resulting from disasters. Indeed, social vulnerability and inequity are related concepts. Social vulnerability research explores the differential susceptibilities and capacities of disaster-affected populations, whereas social equity analyses tend to focus on population disparities in the allocation of resources for hazard mitigation and disaster recovery. Interventions with an equity focus emphasize full and equal resource access for all people with unmet disaster needs.</p><p>Yet newer studies of inequity in disaster programs have documented troubling disparities in income, race, and home ownership among those who <a href="https://eos.org/articles/equity-concerns-raised-in-federal-flood-property-buyouts" target="_blank">participate in flood buyout programs</a>, are <a href="https://www.eenews.net/stories/1063477407" target="_blank" rel="noopener noreferrer">eligible for postdisaster loans</a>, receive short-term recovery assistance [<a href="https://doi.org/10.1016/j.ijdrr.2020.102010" target="_blank" rel="noopener noreferrer"><em>Drakes et al.</em></a>, 2021], and have <a href="https://www.texastribune.org/2020/08/25/texas-natural-disasters--mental-health/" target="_blank" rel="noopener noreferrer">access to mental health services</a>. For example, a recent analysis of federal flood buyouts found racial privilege to be infused at multiple program stages and geographic scales, resulting in resources that disproportionately benefit whiter and more urban counties and neighborhoods [<a href="https://doi.org/10.1177/2378023120905439" target="_blank" rel="noopener noreferrer"><em>Elliott et al.</em></a>, 2020].</p><p>Investments in disaster risk reduction are largely prioritized on the basis of hazard modeling, historical impacts, and economic risk. Social equity, meanwhile, has been far less integrated into the considerations of public agencies for hazard and disaster management. But this situation may be beginning to shift. Following the adage of "what gets measured gets managed," social equity metrics are increasingly being inserted into disaster management.</p><p>At the national level, FEMA has <a href="https://www.fema.gov/news-release/20200220/fema-releases-affordability-framework-national-flood-insurance-program" target="_blank">developed options</a> to increase the affordability of flood insurance [Federal Emergency Management Agency, 2018]. At the subnational scale, Puerto Rico has integrated social vulnerability into its CDBG Mitigation Action Plan, expanding its considerations of risk beyond only economic factors. At the local level, Harris County, Texas, has begun using social vulnerability indicators alongside traditional measures of flood risk to introduce equity into the prioritization of flood mitigation projects [<a href="https://www.hcfcd.org/Portals/62/Resilience/Bond-Program/Prioritization-Framework/final_prioritization-framework-report_20190827.pdf?ver=2019-09-19-092535-743" target="_blank" rel="noopener noreferrer"><em>Harris County Flood Control District</em></a>, 2019].</p><p>Unfortunately, many existing measures of disaster equity fall short. They may be unidimensional, using single indicators such as income in places where underlying vulnerability processes suggest that a multidimensional measure like racialized poverty (Figure 2) would be more valid. And criteria presumed to be objective and neutral for determining resource allocation, such as economic loss and cost-benefit ratios, prioritize asset value over social equity. For example, following the <a href="http://www.cedar-rapids.org/discover_cedar_rapids/flood_of_2008/2008_flood_facts.php" target="_blank" rel="noopener noreferrer">2008 flooding</a> in Cedar Rapids, Iowa, cost-benefit criteria supported new flood protections for the city's central business district on the east side of the Cedar River but not for vulnerable populations and workforce housing on the west side.</p><p>Furthermore, many equity measures are aspatial or ahistorical, even though the roots of marginalization may lie in systemic and spatially explicit processes that originated long ago like redlining and urban renewal. More research is thus needed to understand which measures are most suitable for which social equity analyses.</p>
Challenges for Disaster Equity Analysis<p>Across studies that quantify, map, and analyze social vulnerability to natural hazards, modelers have faced recurrent measurement challenges, many of which also apply in measuring disaster equity (Table 1). The first is clearly establishing the purpose of an equity analysis by defining characteristics such as the end user and intended use, the type of hazard, and the disaster stage (i.e., mitigation, response, or recovery). Analyses using generalized indicators like the CDC Social Vulnerability Index may be appropriate for identifying broad areas of concern, whereas more detailed analyses are ideal for high-stakes decisions about budget allocations and project prioritization.</p>
By Jessica Corbett
Sen. Bernie Sanders on Tuesday was the lone progressive to vote against Tom Vilsack reprising his role as secretary of agriculture, citing concerns that progressive advocacy groups have been raising since even before President Joe Biden officially nominated the former Obama administration appointee.