Monday, November 29, 2010

Chu Touts Metal-Air-Ionic Liquid Battery

In a speech at the National Press Club, U.S. Energy Secretary Stephen Chu highlighted an electric vehicle battery technology being developed by Fluidic Energy and Arizona State University that could enable cars to be driven 500 miles on a single charge. Fluidic Energy, a spinoff from ASU founded by Professor Cody Friesen, recieved $5.13 million in DoE funding in 2009.

Fluidic and ASU are working on a Metal-Air Ionic Liquid (MAIL) battery technology that is designed to be measurably safe, earth-abundant and geo-politically sustainable, while also delivering ultra-high energy density at a low cost. MAIL batteries offer a high level of safety because the oxidant and reductant are not stored in the same space. In the event of a crash involving an electric vehicle, the risk of catastrophic energy release and fire is non-existent. The MAIL Battery will have a minimum energy density of 4-11 times that of Li-ion, and a long-term cycle life goal of 2600 cycles (according to the DoE website).

The new generation of “metal-air” batteries can store many times more energy than standard lithium-ion batteries. Metal-air batteries contain high energy metals and literally breathe oxygen from the air, giving them the ability to store extreme amounts of energy. To date, the development of these batteries has been blocked by the limitations of using unstable water based solutions that break down and evaporate out of the battery as it breathes. Fluidic Energy’s approach involves ionic liquids – extremely stable salts in liquid form -- using no water at all.

According to a previously published report, ionic liquids (also known as ionic fluids, liquid salts, and liquid electrolytes) don’t evaporate like water because they are formed from salts which remain liquid at room temperature. This includes sodium chloride and potassium nitrate that, when heated, melt and undergo a phase change into a liquid comprised almost entirely of ions. Such batteries could also offer better electrochemical stability (of up to 5 volts, compared to water’s 1.23 volts per cell), which means they could use metallic materials that have a greater energy density than zinc.

Chu also took the opportunity to suggest that the energy race was resulting in a "new Sputnik" moment, comparing concern over China's emerging prowess in energy to the alarm caused by the Soviet Union's Sputnik satellite flying over the U.S. in the '50s -- but that seems to be a bit of a stretch. China still has a long way to go in terms of its energy policies.

Friday, November 26, 2010

PV and Energy Storage Project Launched in New Mexico

PNM, an energy holding company based in Albuquerque, N.M., is moving forward on a smart grid energy storage demonstration project that involves the installation of a utility scale battery and 500 kilowatt solar photovoltaic plant. The project was recently approved by the N.M. public regulatory commission. PNM is New Mexico's largest utility.

The goal of the "Prosperity Energy Storage" project is to create a firm, dispatchable, distributed renewable generation resource, says Steve Willard, project manager.

The project, which received more than $2 million from the DoE, is a collaborative effort between PNM, the University of New Mexico, Northern New Mexico College and Sandia National Labs. In addition to developing storage applications for solar PV, the project funds New Mexico based research, helping to move New Mexico to the forefront of national renewable energy research.

UNM will conduct system modeling and design development for the project. Northern New Mexico College will perform data collection, analysis and management. Sandia National Labs will perform system testing and algorithm development.

The project will also complement the efforts of two other PNM projects: the smart grid demonstration project with the Electric Power Research Institute and the Japanese New Energy and Industrial Technology Development Organization project at Mesa del Sol.

Tuesday, November 23, 2010

High Performance Cathodes Focus of Energy Storage Research

Energy storage research – specifically high performance cathodes made of low-cost nanocarbons -- will be part of the focus on a new collaborative effort between The Dow Chemical Company and the University of Queenland's Australian Institute for Bioengineering Nanotechnology (AIBN). Dow will contribute approximately $AU1.74million ($UDS1.7million) in the three-year alliance. In addition to improved energy storage systems, AIBN will conduct research on sustainable sources for chemicals and new-generation circuitry.

Caption: PhD student Sean Muir, AIBN’s Dr Denisa Jurcakova, Dow chairman and CEO Andrew Liveris and Professor Max Lu.

The research into high performance cathode materials based on low-cost nanocarbons will involve the research group led by Professor Max Lu and Dr. Denisa Jurcakova. The objective of the project is to develop improved cathode materials with high energy and power densities for applications in hybrid vehicles and renewable energy storage systems.

Research in the project will involve novel material design, synthesis, electrochemistry and fundamental chemistry. The improved nanoparticles developed will find use in batteries with potential use not only in portable devices, but for hybrid vehicles and energy storage for renewable resources such as sun and wind.

Research into new-generation circuitry for electronics will be completed by Professor Andrew Whittaker's and Dr. Idriss Blakey's research group. Researchers will use organic synthesis, physical chemistry and electrical engineering to craft functional plastics and polymers for the manufacture of integrated circuits. The new generation of circuits will increase performance, decrease size and cost and have potential uses in computers, cameras, smart phones, hand-held gadgets and even fridges.

Escalating oil costs and concerns about carbon dioxide emissions make it imperative to develop new manufacturing processes based on renewable substrates rather than diminishing fossil fuels. Research carried out in the third project will be led by Professor Lars Nielsen and Dr. Jens Kromer, and will use scientific advances in the biosciences to genetically reprogram bacteria to produce the chemical building blocks of the future.

Energy Storage Crucial Step for Renewable Electricity, Says APS

U.S. policymakers must focus more closely on developing new energy storage technologies as they consider a national renewable electricity standard, according to one of the principal recommendations in a newly released report, Integrating Renewable Electricity on the Grid, by the American Physical Society’s Panel on Public Affairs (POPA).

The report notes that as renewable generation grows it will ultimately overwhelm the ability of conventional resources to compensate renewable variability, and require the capture of electricity generated by wind, solar and other renewables for later use. Transmission level energy storage options include pumped hydroelectric, compressed air electric storage, and flywheels. Distribution level options include: conventional batteries, electrochemical flow batteries, and superconducting magnetic energy storage (SMES). Batteries also might be integrated with individual or small clusters of wind turbines and solar panels in generation farms to mitigate fluctuations and power quality issues.

According to APS, cnergy storage for grid applications presently lacks sufficient regulatory history. Energy storage on a utility-scale basis is very uncommon and, except for pumped hydroelectric storage, is relegated to pilot projects or site-specific projects. Some states such as New York categorize storage as “generation,” and hence forbid transmission utilities from owning it. In addition, utilities do not know how investment in energy storage technologies will be treated, how costs will be recovered, or whether energy storage technologies will be allowed in a particular regulatory environment.

Another challenge facing the grid involves the long-distance transmission of renewable electricity from places that receive a lot of wind and sun to those that do not. “We need to move faster to have storage ready to accommodate, for example, 20 percent of renewable electricity on the grid by 2020,” said George Crabtree, co-chairman of the POPA study panel and a senior scientist at Argonne National Laboratory. “And, by devoting the necessary resources to the problem, I am confident that we can solve it.”

The report addresses variability and transmission issues by urging the U.S. Department of Energy (DOE) to increase research on materials to develop energy storage devices and by encouraging the DOE to focus on long-distance superconducting direct current cables to bring renewable electricity to load centers, lessening the chance that power will be disrupted. The report also calls for examining renewable electricity in light of a unified grid instead of one that is fragmented and improving the accuracy of weather forecasts to allow for better integration of renewable electricity on the grid.

The APS report says the DoE should develop an overall strategy for energy storage in grid-level applications that provides guidance to regulators to recognize the value that energy storage brings to both transmission and generation services on the grid. The DoE should also conduct a review of the technological potential for a range of battery chemistries, including those it supported during the 1980s and 1990s, with a view toward possible applications to grid energy and storage. Another recommendation is that the DoE should increase its research and development in basic electrochemistry to identify materials and electrochemical mechanisms that have the highest potential use in grid-level energy storage devices.

The American Physical Society is the leading physics organization, representing 48,000 members, including physicists in academia, national laboratories, and industry in the United States and internationally. APS has offices in College Park, MD (Headquarters), Ridge, NY, and Washington, DC.

Saturday, November 20, 2010

Energy Storage and PV Tied to EV Charging

John Gartner of Pike Research reports that two charging companies, Eaton and AeroVironment, are working to incorporate energy storage solutions into the charger (see EVs a Portal to Distributed Storage). "Putting storage into the charger rather than using the vehicle for power to the home will preserve the life of the EV’s batteries and can capture cheaper energy even if the vehicle is not plugged in," he says. The storage batteries could be lithium ion (in the future from the vehicles after their useful life), as well as less costly nickel metal hydride or advanced lead acid batteries.

These batteries could also be integration with a photovoltaics/solar power installation. Earlier this year, Eaton announced that is was working on a prototype integrated solar-assisted electric vehicle charging station to be erected at the Electric Power Research Institute (EPRI) research laboratory in Knoxville, Tenn. The project also involved the Tennessee Valley Authority (TVA). Additional stations are planned for Oak Ridge National Laboratory, Nashville, Chattanooga and another site in Knoxville.

“Solar-assisted electric vehicle charging stations are a crucial step toward the development of a regional system of clean fuel for electric vehicles,” said Tom Schafer, vice president and general manager, Eaton’s Commercial Distribution Products Division.

The collaboration comes on the heels of Eaton’s creation of a new business unit that will be responsible for the overall direction and profitable growth of the emerging electric vehicle and transportation infrastructure business within Eaton’s Electrical Sector. Eaton has named Tim Old the new business unit manager of this new Electric Transportation Infrastructure unit.

The prototype charging station used by EPRI and TVA, also known as a Smart Modal Area Recharge Terminal, or SMART™ station, will provide information on energy usage, the time when the equipment is used, the amount of solar-generated electricity produced and stored, and the potential impact of load clusters - when several vehicles are refueled at the same time - on distribution system reliability.

The collaboration will create a model charging facility that will charge electric vehicles quickly and reliably, and it will produce data to assist in implementing key components of a smart electrical grid. These components could include integrating renewables onto the grid, utilizing a battery storage system, assessing the impact on reliability of a distributed resource generation, testing advance metering infrastructure and analyzing electric vehicle supply equipment.

Eaton recently announced a deal with Mitsubishi Motors North America, Inc., (MMNA) and tech services provider, Best Buy. For residential electric vehicle customers, Best Buy's Geek Squad will provide site analysis and work to manage electrical home infrastructural upgrading and installation by licensed electrical contractors of Eaton's advanced Level 2 (220V) charging hardware for Mitsubishi's "i" powered by MiEV electric vehicle, which goes on sale in fall of 2011.

In addition, Eaton will provide both the electrical infrastructural support and Level 2 chargers to MMNA's dealerships. These 220V (15A) charging stations can be installed in a home's garage and help reduce the charging time of Mitsubishi's lithium-ion battery-powered vehicle by 50% versus a standard 110V electrical outlet. Given its battery size, Mitsubishi "i" customers can have the choice of only applying existing Level 1 (110V outlet) equipment, or the faster Level 2 charging which can affect a complete charge in about 7 hours.

Some basics on charging (courtesy of AeroVironment): You’ll often hear a particular charging regimen described by its charge “level” – Level 1, Level 2, or Level 3. These different charging schemes are distinguished by their utility requirement and total time for a full charge – and each fills an important niche.

“Level 1” AC charging uses a standard 120V outlet and takes 11 to 20 hours to charge a depleted EV. Level 1 charging systems are designed to be portable and used in the case of an on-road emergency, when the driver is running low on charge and needs to plug into a readily available outlet.

“Level 2” AC charging docks and stations deliver AC power reliably and safely to the electric vehicle. The power from the Charging Dock is fed to the car’s on-board charger. An on-board charger is small enough to be integrated into the car and, with the Level 2 off-board Charging Dock’s help, can power up the battery in 3 to 8 hours – usually at home when the driver is sleeping. This convenient charging regimen is often called opportunity charging, because it calls for recharging during "opportune" down time such as sleep, work, or play. Some charging docks feature robust communication capability and can “plug in” to the Smart Grid.

“Level 3” DC charging stations use greater amounts of power and current to bypass the vehicle’s on-board charger with a fast and reliable DC charge in minutes instead of hours. According to the AeroVironment website, the company's DC charging solutions have been vetted for more than a decade in heavy-duty industrial applications – including auto plants, airports, and retail distribution. They say level 3 DC charging is suited for public charging infrastructure; charging large vehicles with big batteries such as buses; and commercial or service fleets with very little recharging downtime.

Pike's Gartner notes that for commercial fast DC chargers, incorporating battery storage could be a way around impacting peak demand. "In addition to also storing excess solar power, commercial customers could use the charger/storage system as emergency power and to similarly purchase energy when it is the cheapest and quick charge their fleets on demand without worrying about cost or impact on the grid," he writes. "Charging just one vehicle at this rate is equal to approximately 43 vehicles being charged via Level 1 (aka standard household current) or 9-18 vehicles at Level 2 using charging equipment. Complicating matters is that DC charging is by necessity immediate – delaying a 15-30 charge defeats the entire purpose. Plus, these charge locations are likely to be at truck stops, gas stations, or mini-marts, which aren’t places that most folks plan on spending a lot of time."

Friday, November 19, 2010

Korea's POSCO Develops NaS Battery

POSCO, a large steel-maker in Korea, says it has succeeded in developing a sodium sulfur (NaS) battery for large capacity energy storage. With the goal of commercializing by 2015, POSCO has been developing a large capacity energy storing battery since January with RIST (a research institute wholly owned by POSCO).

This is a first for Korea, although, NaS battery technology is already in widespread use in Japan at more than 190 sites, totaling more than 270 MW (according to the Electricity Storage Association) and POSCO. The largest NAS installation in Japan is a 34 MW, 245 MWh unit for wind stabilization. U.S. utilities have deployed 9 MW for peak shaving, backup power, firming wind capacity and other applications; and project development is in-progress for an equal amount, according to the ESA.

POSCO claims its NaS battery has more than 3 times higher density than existing batteries with a lifespan of more than 15 years. In addition, unlike lithium ion batteries used as secondary batteries, materials are not particularly high in cost.

Prior to POSCO, Japan`s NGK has been the sole provider. As you can see in the chart, courtesy of NGK, NaS compares favorably to other energy storage systems.

As the smart grid business expands, the energy storage battery market which includes core technologies such as NaS batteries is forecasted to grow from approximately 450 million USD in 2010 to 10 billion USD in 2020, an average yearly growth of more than 35%, according to POSCO.

A NAS battery consists of liquid (molten) sulfur at the positive electrode and liquid (molten) sodium at the negative electrode as active materials separated by a solid beta alumina ceramic electrolyte. The electrolyte allows only the positive sodium ions to go through it and combine with the sulfur to form sodium polysulfides. During discharge, as positive Na+ ions flow through the electrolyte and electrons flow in the external circuit of the battery producing about 2 volts. This process is reversible as charging causes sodium polysulfides to release the positive sodium ions back through the electrolyte to recombine as elemental sodium. The battery is kept at about 300 degrees C to allow this process. NAS battery cells are efficient (about 89%).

Caption: NaS compared to other battery types, such as lead-acid, lithium ion and NiH. (Source: NGK).

Click here for a "feel good" movie about NaS produced by NGK.

Thursday, November 18, 2010

EnerG2 Focused on Electrodes for Ultracapacitors

EnerG2 is focused on customizing electrode materials to enhance energy and power density in ultracapacitors. The company is using nano-structured materials to optimize the electrodes' surface area, which they say will help performance and cycle life. A good story today at on supercapacitor-electrode-maker ENERG2, titled " The Story of an Energy Storage Startup."

In August, EnerG2 broke ground on what they claim to be the world’s first facility dedicated to the commercial-scale production of synthetic high-performance carbon electrode material. The plant was made possible by a $21.3 million Federal stimulus grant allocated by the US Department of Energy for makers of advanced automotive batteries and energy storage technologies. EnerG2 will partner with Albany-based Oregon Freeze Dry, Inc. (OFD).

In addition to the federal stimulus funding, EnerG2 since inception seven years ago has raised over $14.5 million in equity financing. Institutional investors OVP and Firelake led a Series A financing and additional strategic investors added new equity funding in April of this year.

Caption: EnerG2's carbons demonstrate a spectrum of pore size distributions and surface morphologies. The technology is based on molecular self-assembly and produces nano-structured carbon materials that are finely controlled and offer ultra-high surface areas.

The company uses nano-structured carbon materials that are finely controlled and offer ultra-high surface areas. These materials are extremely conductive and are tremendously attractive to energy-storing molecules such as electrolytic ions, methane, natural gas and hydrogen.

What's interesting is that it is exactly this kind of technology development that a DoE panel called for in 2007. In their findings, published in the Basic Research Needs for Electrical Energy Storage, the panel said the capability to synthesize nanostructured electrodes with tailored, high-surface-area architectures offers the potential for storing multiple charges at a single site, increasing charge density. The addition of surface functionalities could also contribute to high and reproducible charge storage capabilities, as well as rapid charge-discharge functions. They predicted that the design of new materials with tailored architectures optimized for effective capacitive charge storage will be catalyzed by new computational and analytical tools that can provide the needed foundation for the rational design of these multifunctional materials. "These tools will also provide the molecular-level insights required to establish the physical and chemical criteria for attaining higher voltages, higher ionic conductivity, and wide electrochemical and thermal stability in electrolytes," they said.

Ultracapacitors are a type of electrochemical capacitors (ECs), which differ from conventional dielectric and electrolytic capacitors in that they store far more energy. As energy storage devices, ECs have a number of potentially high-impact characteristics, such as fast charging (within seconds), reliability, large number of charge-discharge cycles (hundreds of thousands), and wide operating temperatures. Because of their very fast charging rate, ECs may be able to recover the energy from many repetitive processes (e.g., braking in cars or descending elevators) that is currently being wasted. Large-scale ECs can perform functions of a different kind, such as power quality regulation of the electrical grid, which can avoid the costly shutdown of industrial operations as a result of intermittent outages and power fluctuations.

While ECs are related to batteries, they use a different energy storage mechanism. Batteries move charged chemical species (ions) from one electrode via an electrolyte to the second electrode, where they interact chemically. Thus batteries store chemical energy. EDLCs store electrical charge physically, without
chemical reactions taking place. Because the charge is stored physically, with no chemical or phase changes taking place, the process is highly reversible and the discharge-charge cycle can be repeated virtually without limit. Typically, an EDLC stores electrical charge in an electrical double layer in an electrode-electrolyte interface of high surface area. Because of the high surface area and the extremely low thickness of the double layer, these devices can have extraordinarily high specific and volumetric capacitances. A striking dissimilarity between batteries and ECs is the number of charge-discharge cycles each can undergo before failure. The dimensional and phase changes occurring in battery electrodes represent one of the key limitations in attaining longer charge-discharge cycling. In contrast, no inherent physical or chemical changes occur in EC electrodes during cycling because the charge is stored electrostatically. As a result, ECs exhibit cycle lifetimes ranging from a few hundred thousand to over one million cycles. Most notably, however, ECs have the ability to deliver an order of magnitude more power than batteries.

Originally working in collaboration with the University of Washington Department of Materials Science & Engineering, EnerG2 has developed and commercialized unique sol-gel processing technologies to construct its carbon materials (from the EnerG2 website). Sol-gel processing, which creates optimal structure and purity in the finished carbon product, is a chemical synthesis that gels colloidal suspensions to form solids through heat and catalysts.

EnerG2 has invented a patented ability to control the hydrolysis and condensation reactions within the gelling process, allowing the materials' surface structures and pore-size distributions to be shaped, molded and customized. The company says it has developed these processing capabilities with an explicit and aggressive focus on cost control. To avoid the expensive processing typically associated with nanotechnology, the company has leveraged large-scale commercial processing technologies from established industries to design a production approach that is both relatively inexpensive and inherently scalable.

In addition to ultracapacitor electrodes, the company is targeting fuel cell and hydrogen storage applications.

International Battery Receives Pennsylvania Grant

International Battery was awarded an Alternative Fuel Incentive Grant (AFIG) by the Pennsylvania Department of Environmental Protection (DEP). Pennsylvania Governor Edward G. Rendell awarded the grant at a ceremony at the State’s Capitol building where he announced nearly $8 million for 21 projects promoting biofuels, natural gas and electric powered vehicles.

International Battery will use the grant proceeds, totaling $235,000, to purchase test equipment for the company’s Allentown, PA facility in order to evaluate the performance of its energy-dense, large-format, prismatic lithium-ion storage solutions under conditions that simulate actual electrical load profiles for large hybrid electric vehicles (HEVs). International Battery’s sustainable energy storage systems are based on large-format cells, which are proving to be ideal for electric bus applications where large amounts of energy must be stored in a relatively lightweight battery, placed within a compact space on the bus. Going forward, the test equipment will also advance the company’s capability to configure its flexible, modular battery system for customer-specific requirements, including retrofit applications, in order to address a broad spectrum of HEV bus manufacturers and vehicle sizes, each with different space and energy requirements. The equipment that International Battery can now acquire with the AFIG grant will expedite the design and validation of these very large battery systems, thereby reducing the time needed to get an HEV bus on the road.

“We are very pleased to receive the AFIG grant to further our commercialization of lithium-ion battery systems for larger alternative fueled vehicles,” said International Battery’s Executive Vice President of Business Development and Engineering, David McShane. “We have had great success with our lithium technology for HEV buses as large-format prismatic cells result in a less complex system with fewer thermal management issues. Coupled with active cell balancing, the lithium-ion technology enables optimal usage of the battery, allowing better system energy density. This grant is an important step to capitalizing on the full potential of our large-format prismatic lithium-ion cells for large HEV applications."

The $7.9 million Governor Rendell announced at the ceremony is through the Alternative Fuel Incentive Grant Program that will spur innovation in Pennsylvania’s advanced energy economy, while also making it easier for consumers and businesses to use home-grown biofuels and rapidly expanding technologies such as hybrid and electric plug-in vehicles, as well as those powered by natural gas. "Just recently, the Natural Resources Defense Council named Pennsylvania as the 7th least vulnerable state in the nation to oil price spikes because of our work to build a green economy here,” said the Governor. “In doing so, it noted 'America's addiction to oil continues to threaten not only our national security and global environmental health, but also our economic viability.'"

In making the announcement about the 21 AFIG awardees, Governor Rendell was joined by David McShane, Executive Vice President of Business Development and Engineering for International Battery, Andrew Daga, Principal Founder & CEO of Momentum Dynamics and Sarah Wu, Outreach & Policy Coordinator for the City of Philadelphia Mayor’s Office of Sustainability.

Wednesday, November 17, 2010

Energy Storage: The Basics

Welcome to Energy Storage Trends. In this first post, I'll provide a basic overview of energy storage trends with plenty of links to more in-depth reports and features. Subsequent blogs will focus on new developments. A few words about me, Pete Singer: armed with a degree in electrical engineering from the University of Illinois, I've been reporting on high tech topics for 26+ years, primarily focused on the semiconductor industry and related fields in electronics. I'm now the editor-in-chief of Solid State Technology and Photovoltaics World, which is part of PennWell's Renewable Energy World network.

So what's so cool about energy storage? Analysts see a strong, upcoming demand for energy storage as part of the grid. This will likely be a combination of some kind of central storage (i.e., a 20MW flywheel installation near a power generation station) and distributed storage (i.e., batteries or supercapacitors next to the familiar green transformers in people’s yards). These types of energy storage are primarily driven by a need on the part of utilities for load balancing, since it's expensive for them to constantly adjust the output of traditional power generation systems as the load varies. Energy storage may even allow them to offset or delay the requirement of additional power plants, such as a gas-fired "peaker" plants.

According to a report from Pike Research, the demand for energy storage is driven by several trends, including the proliferation of intermittent renewable energy sources such as wind and solar, the move toward smart grids, and the coming rise of plug-in hybrid and electric vehicles, to name just three. While storing electricity was once thought a practical impossibility, a variety of technologies have now emerged to disprove that theory, and the global energy storage market is poised to grow from $329 million in 2008 to $4.1 billion by 2018, according to Pike.

“About a dozen technologies are currently vying for a piece of the utility-scale energy storage market,” says managing director Clint Wheelock. “In our analysis, the greatest potential for growth lies with advanced battery technologies, especially Lithium Ion (Li-ion). Sodium Sulfur (NAS) batteries, Pumped Hydro, and Compressed Air Energy Storage (CAES) will also be important technologies in the years ahead.”

In some markets, there may also be value for companies and people on "the other side of the meter" to buy and store power when it is least expensive, and use the stored power during peak demand when prices are highest. Called “time shifting,” this is an interesting concept, although it may be a bit ahead of its time. Jaime Smith of SunEdison (Beltsville, MD), who runs the installer/developer’s North American PV commercial operations, said “as far as taking a solar curve and shifting it and it being worth the value of that shift for the cost of the storage, we have not seen that yet. We’re keeping our eyes and ears open for the right technology but we haven’t seen anything yet that is cost-effective.”

To a lesser extent, the need for energy storage will also be driven by the inherently intermittent nature of many renewable energy sources, such as solar power and wind. As more of this kind of power generation comes on-line, it makes sense to store the energy for times when the wind isn’t blowing or the sun isn’t shining.

Proponents of solar power, however, like to point out that although PV is intermittent (due to clouds and of course darkness), it’s actually highly predictable. Clouds don’t cause that much variability if the PV is spread out over a wide enough area, and because they are visible, it’s relatively straightforward to predict the impact on power generation on a short-term basis and even easier to predict the amount of power that will be generated the next day based on weather reports. That’s fine because power markets operate on a day to day basis. Dan Shugar, CEO of Solaria (Fremont, CA), a supplier of PV modules, said: “In PG&E’s territory alone, which is pretty much north of LA up to Oregon, there’s about 30,000 solar plants. If you look at a 10 x 10 mile area, statistically there’s no variability.”

Also, depending on location, peak demand is often in near-perfect sync with demand, since it’s the heat of the sun that creates the need for air conditioners which are the primary source of demand. “Solar is not available when you want it, but it’s available when you need it,” quips Smith of SunEdison. “It does have intermittency, but the reality is when the demand is the highest – which is when air conditioning demand is the highest – we are the strongest,” he said. Shugar agrees: “Do we need storage today? No. Solar is generating in a very high correlation with when the grid is needing power.”

While that’s true in most of California, it can be a little different in other States. “We’re not perfectly correlated because people come home and flip on their air conditioning in Western States at 5:00 and we’re peaking earlier than that, so storage could be very interesting for us to try to shift that curve,” Smith said.
In the future, 5-10 years from now, when PV and other renewables come to represent a significant percentage of the overall power generated for the grid, energy storage could play an increasingly important role. “As you go from a scenario where 2% of the peak load is generated by PV to 20-30-40%, you start to get into a situation where you need storage,” Shugar said. But he also points out that there are many other ways to control demand with a smart grid in place. “Instead of building dedicated storage systems, there are other things you can do. For example, all the commercial buildings with over 50 kW/h of load have time of use metering now. It’s very simple to install some demand response – there are programs that exist right now that are doing that – where you might let the temperature go from 71 degrees to 72 or 73 when electricity prices are highest.”

Electric vehicles will also come into play, in part by helping to advance battery technology, but also by becoming an integral part of the smart grid. Andy Chu, director of marketing at A123 Systems (Watertown, MA) envisions a time when utilities are so linked into the grid that they can monitor and control electric vehicle battery chargers, and charge them quickly or slowly so as to optimize the load/generation equation. “Electric cars already have a computer in there that can control the charging rate,” Shugar said. “My car is charging right now out in the parking lot from a solar array coupled with the building. I could easily control the rate at which that car is charging based on the availability of solar or a demand signal from the utility.”

Energy storage applications

The two main applications of energy storage technologies are for power – driven by the needs for power quality and bridging power – and for energy management. In power applications, stored energy is only applied for seconds or less to assure continuity of quality power, or it might be used for slightly longer (a few minutes) to assure continuity of service when switching from one source of energy generation to another. For energy management applications, storage media is used to decouple the timing of generation and consumption of electric energy, as previously described. A typical application is load leveling, which involves the charging of storage when energy cost is low and utilization as needed.

Table 1, developed by the Electricity Storage Association, lists various types of energy storage technologies, describes main advantages and disadvantages, and provides a rough measure of relative feasibility.

A new report issued earlier this year by Sandia National Labs, titled, “Energy Storage for the Electricity Grid: Benefits and Market Potential Assessment Guide,” goes even further, describing five main applications for energy storage, with 17 subcategories.

• Electric supply (electric energy time-shift, supply capacity)
• Ancillary services (load following, area regulation, reserve capacity, voltage support)
• Grid Systems (transmission support, congestion relief, upgrade deferral, substation on-site power)
• End user/utility customer (time-of-use energy cost management, demand charge management, service reliability, power quality)
• Renewables Integration (energy time-shift, capacity firming and wind generation grid integration).

Figure 1 shows financial benefits and maximum market potential estimates for the U.S. for each of the 17 subcategories. Clearly, renewable energy sources represent one driver for energy storage, but they will not be the primary driver.

When it comes to renewables, the report notes that one of the main objectives of energy storage is “capacity firming.” Here, the goal is to get a fairly constant output from combination of renewable energy generation and storage. The resulting firmed capacity offsets the need to purchase or ‘rent’ additional dispatchable (capacity) electric supply resources. Depending on location, firmed renewable energy output may also offset the need for transmission and/or distribution equipment.

One important challenge associated with intermittent renewable energy generation is that the generation’s power output can change rapidly over short periods of time. Photovoltaic (PV) output can drop quite quickly as clouds pass. Wind generation output can change rapidly during gusty conditions. These rapid changes (also known as ramping) can lead to the need for dispatchable power sources whose output can also change rapidly. Most non-renewable energy generation facilities (i.e., coal, nuclear, natural gas) are best operated at a constant output. Rapid changes from intermittent renewable energy generation can lead to ramping of these sources, which increases wear, fuel use and emissions. In some regions, there may not be enough dispatchable generation capacity to offset renewable energy generation’s ramping, which creates addition problems – again, potentially solved by energy storage.

An example of the daily operation profile for wind generation plus storage on a summer day is shown in Fig. 2. For the scenario depicted, winder generation output occurring at night, when the energy’s value is low, is used to charge storage. In this example, about ½ of the energy used on-peak is from wind generation that occurs off-peak. The result is constant power for five hours.

The utility factor

The vision of the smart grid with renewable sources and energy storage working in harmony is complicated by one main factor: The U.S. electric industry includes over 3,100 electric utilities. Investor owned utilities are privately-owned, represent 8% of the total, approximately 75% of generation capability and revenue. There are 2,009 municipal utilities, supplying approximately 10% of the generating capability and 15% of retail revenue. There are 912 cooperatives, operating in 47 States, accounting for 9% of total revenue and around 4% of generation.

Some utilities have embraced the concept of energy storage and already implementing it. New York Independent System Operator published a published a paper earlier this year, titled “Energy Storage in the New York Electricity Markets,” in which they note that integration of all types of energy storage technologies into the modern electric grid is becoming a priority. Storage resources can complement intermittent renewable resources such as wind and solar power by storing excess power for delivery when it is most needed. Some storage resources, particularly limited energy storage resources (LESRs) where energy output is measured in minutes, are well suited to providing regulation service that has traditionally been supplied by conventional hydroelectric and thermal units. “The use of storage for services that require fast response helps to improve system efficiency while reducing the need to burn fossil fuels to provide this service,” the report notes.

Beacon Power (Tyngsboro, MA) is constructing a 20-megawatt flywheel energy storage facility designed to provide regulation service to the electric grid. Beacon’s system utilizes 1 megaWatt flywheel modules consisting of 10 individual 25kWh flywheels integrated into a plant that can provide up to 20 megaWatts of regulation service. Beacon received a conditional commitment for a $43 million loan guarantee from the U.S. Department of Energy and broke ground in Stephentown, New York on November 19, 2009.

AES Energy Storage (Arlington, VA) has proposed three 20-megawatt battery storage facilities in the upstate New York counties of Broome, Onondaga and Niagara. AES has previously developed a 2 x 1 megawatt grid-scale energy storage system constructed with battery cells manufactured by Altair Nanotechnologies. The system has the capability to deliver one megaWatt of power to the grid for 15 minutes.

Energy storage also made notable progress recently in California, with the passage of AB 2514 legislation at the end of September by the California State Assembly. The bill requires the Public Utilities Commission by March 1, 2012, to “open a proceeding to consider establishing investor owned utility procurement targets for viable and cost-effective energy storage systems to be achieved by December 31, 2015, and an additional target to be achieved by December 31, 2020.” Publicly owned utilities would have comparable requirements, and would be required to develop plans to maximize shifting of electricity use for air-conditioning and refrigeration from peak demand periods to off peak periods. "Energy storage improves the overall efficiency of our electric power system which will lower costs for consumers," said Assembly Member Nancy Skinner.

Janice Lin, Director of the California Energy Storage Alliance, said “This landmark bill puts California at the forefront of a growing global market that will spur economic development. Given major advances in energy storage, the industry is now ready to provide affordable, reliable products for California's utilities and consumers.” The California Energy Storage Alliance is an association of companies committed to the rapid expansion of energy storage to promote growth of renewable energy and a cleaner, more affordable, reliable and secure electric system. Members include a diverse group of companies ranging from mechanical, thermal and chemical storage companies to system integrators and renewable energy component manufacturers and developers.

Another element that is essential to widespread use of energy storage in the grid (and renewable energy in general) is standardization. One standard of importance is IEEE P1547.8, which is focused on high-penetration, grid-connected photovoltaic technology, including energy storage aspects.

Suggested Additional Reading:

Solar and energy storage - a perfect match

Energy Storage takes on the Variability Conundrum

Basic Research Needs for Electrical Energy Storage

Grid Scale Frequency Regulation Using Flywheels Free whitepaper (registration required)