Electrical Energy storage (EES) is crucial to manage the grid with large renewable energy penetration. What have been the promising developments in the recent past in grid scale energy storage technologies?

In the US, most developments in EES for grid applications during the past few years are focused on the following areas:

  • Evolution of Favorable Regulations and Policy Framework:

At the federal level, there have been a number of favorable regulations which enabled the participation of energy storage systems (ESS) in electricity markets. For example, in 2011, Federal Energy Regulatory Commission (FERC) issued Order No. 755 that requires RTOs/ISOs to compensate the frequency regulation resources based on the actual regulation service provided. This rule promoted the participation of fast-response ESSs in regulation markets, with a significant amount of ESS deployments intended for serving the frequency regulation market. In 2013, FERC issued Order No. 784, which revised the accounting and reporting requirements for public utilities to better account for the use of ESS. In 2018, FERC issued Order No. 841 that requires RTOs/ISOs to establish market rules that recognize the physical and operational characteristics of energy storage resources. These regulatory changes have allowed opportunities for deployment of ESSs to provide grid services that hitherto have not been compensated.

There have also been significant policy changes in many states, with mandates and incentives for energy storage. For example, in 2013 the California Public Utility Commission passed a mandate for 1.3 GW of grid storage to be installed by 2020. Similarly, other states including New York and Massachusetts have announced initiatives and adopted policies adding a significant amount of energy storage resources in their electricity infrastructure. In states with significant behind-the-meter solar, there have been a number of favorable state level policy initiatives that provide further opportunities for large scale deployment of energy storage. For example, in March 2018, Colorado State passed Bill 18-009 that declares the right of customers to install, interconnect and use energy storage on their property. In April 2017, California Public Utility Commission approved $196 million in new rebates for 2017-2019 for customers who install behind-the-meter energy storage. Recently, New Mexico, Virginia, and Maryland also introduced a tax credit for behind-the-meter storage. Similar to behind-the-meter solar, installation of energy storage at residential and commercial installations is becoming routine and economical.

The above-mentioned regulations and policies have resulted in the dramatic increase in energy storage deployments in the US grid. According to Wood Mackenzie US Energy Storage Monitor, in the first quarter of 2019 about 149 MW/271 MWh, was deployed. Forty-six percent of that was behind the meter. These numbers represent an over 200% increase in MW and 100% increase in MWh in ESS deployment over the same period in 2018.

  • Energy Storage System Cost Reductions

The growth in the rapid increase in the deployment of ESS has been aided by significant cost reductions in the overall cost of energy storage system installation. Large amounts of new lithium-ion battery (LiB) manufacturing has come up during the last two to three years, primarily to support the growing demand for LiB batteries for electric vehicles. This is having a positive effect on the deployment of energy storage in the grid and behind the meter applications. With the increasing scale of Li-ion manufacturing capacity, there has been a rapid drop in the cost of energy storage systems for grid applications. For example, the cost of LIB systems has seen steady declines averaging over 8% a year. According to annual updates of the Energy Information Administration in the U.S. Dept. of Energy, from 2008 to the present the cost of residential and grid-scale batteries has declined by 80%, and these trends are projected to continue. In some markets, large Solar PV + Energy Storage systems are beginning to replace new and existing natural gas peaker plants, and with energy storage providing value streams for energy arbitration, frequency regulation, and transmission and distribution deferral.

  • Battery Safety and Reliability

Increasing energy density and storage capacity, especially of LiB ESS, is leading to increased fire risk due to potential thermal runaway in energy storage systems. Therefore, a lot of recent research and development work is focused on improving safety and reliability of existing battery technologies including Li-ion, NaS batteries, and vanadium redox flow batteries. The most critical areas of this research is focused on developing accurate tests and models for predicting and controlling the complex electrochemical, thermal, and mechanical behaviors of battery energy storage systems and the development of safety protocols/standards to enhance protection and mitigate safety concerns of the industry. There has been increased coordination between R&D community, manufacturers, standards development organizations, and regulatory bodies.

  • Improvements in Battery Technologies

The need for energy storage in the electric grid is predictably large given that more and more states and local communities are targeting a cleaner generation mix, with some states legislating the need to move towards 100% renewable grids. Even though Li-ion batteries currently have the biggest market share, there is continued focus on the development of alternate battery technologies and non-electrochemical energy storage solutions with reduced cost and materials availability. Furthermore, safety concerns of Li-ion battery technologies often increase the engineering costs and limit their applications for behind the meter customer applications.


What are the challenges in integrating Energy Storage to the grid?

The challenges of integrating ES to the grid are similar to but more complex than integrating PV and wind resources. Like PV and wind, ES is new to customers, utilities, regulators, and electric system operators. This creates a kind of inertia that must be overcome with a significant amount of outreach from manufacturers and system integrators on the role energy storage can play as a flexible resource that can improve the reliability and resiliency of the electric grid. Furthermore, the fact that ESSs can serve the dual function of generation and load make existing regulatory policies and interconnection standards not readily applicable for large scale ESS deployments. In the US, at present, only 15 states have legislative mandates in place to include ES in utility operations. Thus, development of a more unified regulatory framework is required for making ES universal across all electricity markets. And on a more technical level, interconnection standards vary from utility to utility and from state to state. Therefore, connecting battery energy storage systems is currently a complicated technological and policy-level challenge.

Currently, energy storage is a relatively expense asset and grid operators are judicious in where they deploy it. When the cost of energy storage drops significantly along with increased cycle life of energy storage technologies, we will see a situation where storage would be everywhere in the grid, in cars, and in individual homes.


Considering that integrating energy storage to the grid infrastructure involves additional cost how is the storage size optimized for a grid?

Currently, sizing and optimization of energy storage systems are easy problems. As ES is relatively expensive, storage systems have to be optimized based on the most beneficial applications. This will likely change with decreasing system costs. Thus, for now, sizing and optimization have to be analyzed for applications and markets. At a high level, mostly in regional long-term resource planning, the total amount of energy storage for a region must be specified to meet the renewable energy target. It must be co-optimized with the sizes of renewable resources such as solar PV and wind in order to fully power the load at the lowest cost. In transmission planning, the locations and sizes of energy storage systems must be specified in such a way that energy storage minimizes the cost for transmission expansion. In system design and project planning, the size of an energy storage system must be specified in order to maximize the benefit of the system providing some specific services.

At Sandia we have developed software tools for sizing and optimization that allow users to identify optimal solutions based on their locations, applications, and market structures. We recently released an open source software suite called QuESt. This is a Python-based application suite for energy storage simulation and analysis developed to provide energy storage analytics research on the desktop. QuESt currently consists of three distinct yet interconnected applications that individually and collectively help project engineers and researchers evaluate energy storage systems for different use cases. Future releases will include applications such as front-of-the-meter analyses, microgrid operation and control, and a toolset for energy storage project planning.

We have also been actively working on developing resources to reduce the complexity of project planning, especially with regards to financing. During the last three years, we have hosted workshops for project finance and developed resource guides for the industry. The success of solar PV was based on reliable cost and performance metrics, and the development of Power Purchase Agreements (PPA) have enabled project financing with long-term off take agreements. To succeed, an energy storage project must adequately address three fundamental challenges around technological, economic, and contractual risks, and mitigate both real and perceived project risk factors. Also, there is a critical need for the development of performance metrics so that projects can be financed. Our workshops and resource guides address these issues.

Energy storage is not just about batteries. The cost of the energy storage component – the battery, for instance, is roughly a quarter to third of the overall cost of the system. Power electronics and Power Conversion Systems (PCS) form a significant part of the cost and performance of energy storage systems. While there has been significant cost reductions in battery costs, similar cost reductions are not occurring with PCS technologies. The role of power electronics in the electric grid infrastructure will only grow. Approximately 30% of all electric power currently generated uses power electronics somewhere between the point of generation and  distribution. By some estimates, 80% of energy will flow through power electronics when renewable penetration reaches 50% or more. In the future grid, operations based on power electronic conversion would become pervasive throughout the system. Grids interconnected through high voltage direct current (HVDC) links, SSTs connecting different distribution levels, multi-port power electronics serving both AC and DC loads and sources, and energy storage distributed throughout the system will become significant within the next ten to twenty years. So far, cost reductions in power electronics and power conversion systems have been slow to come. Future utility grids will lean heavily on power electronics. As the role of power electronic energy conversion expands, there is a greater need for improving the cost structure, reducing complexities in system integration, and improving overall system reliability. Thus, there is a greater need for modular architectures.


Which among the current grid scale energy storage projects do you consider as the most significant and what have been the learnings so far?

Every week brings news about another grid scale ES project that sets new standards, either in size, price/kWh, or in virtual power plant or demand response innovations. As part of the DOE Energy Storage Program, we have been involved in a number of demonstration projects that have provided validation of energy storage for applications ranging from frequency regulation to resiliency. Lessons learned from DOE demonstration projects are available at: Another valuable resource is the Global Energy Storage Database (GESDB) that is accessible at: This knowledge hub is a resource with a comprehensive database of energy storage projects that are operational. In addition to providing a summary of energy storage deployments based on categories such as technology, location, and applications, the database has a number of visualization tools that are widely used by the industry. While the information on the GESDB is mostly related to utility class energy storage, it is rapidly developing data related to distributed energy resources (DERs) and behind the meter storage projects.

DOE, through Sandia National Laboratories, has developed Energy Storage Technology Advancement Program (ESTAP) as a platform to facilitate dissemination of lessons learned through a web-based information delivery platform ( This resource helps state energy offices develop a robust understanding of Energy Storage with the goal to help them in the development of Energy Storage (ES) policy and state supported projects. In addition to technical support for development and implementation of ES projects, the program continues to deliver informational webinars on energy storage technologies and disseminate knowledge from various DOE supported projects to state level energy offices, project planners, and other relevant stakeholders.


How do you visualize the electrical grid evolving and its impact on the global economy and environment?

We are beginning to see the grid edge changing rapidly. In many areas behind the meter solar is disrupting utility business models. Solar is now coupled with energy storage to ignite the rapid evolution of microgrids and potential off-grid solutions. Load profiles and demand management at residential, commercial and industrial scales are also changing rapidly. DC electronic loads, solid state lighting, roof top solar, and battery storage all examples. Electrification of transportation is at a point of take off with rapid charging infrastructure being installed in more and more places. Air-conditioning loads continue to grow globally. Changes at the grid edge pose challenges for grid operators including grid stability, unpredictability of loads, and how to manage a growing intermittent resource mix without causing major operational problems.

The question is: are we at the cusp of a major transformation in how the electricity grid is evolving and how electricity markets operate? Of the 6 TW of worldwide generation capacity, renewables have reached 20% mark in many markets with over 1 TW of cumulative renewable capacity already installed and growing. Whether we call the changes we are in as transformative, the pace of change is faster than anticipated. For example, in 2000, IEA forecasted that renewables would reach ~4-5% of generation mix by 2030, but in fact we have reached 20% in many markets already. At the center of the changes in the electric grid are renewables, energy storage, and electric vehicles, with power electronics and communications as key enablers. How the future grid architecture will look will be determined by advances in these areas, along with the adaptation of large scale energy storage, infrastructure for electrification of the transportation fleet including EVs and aviation, and the ability to control variable and bi-directional flows in the system.

If we look back at the last 200 years of industrialization, energy transition cycles have been long, with major transitions occurring every 50-60 years or more. With the rapidly decreasing cost of renewable generation, energy storage, and power electronics, one would anticipate the current cycle may be faster and changes may be coming sooner than anticipated. In the near term, the  changes may seem incremental with increasing amounts of renewables and ES, and replacement of coal fired generation replaced with a mix of combined cycle natural gas and renewables. In the longer term, the changes are more dramatic -- towards a smarter grid with cleaner generation and a far greater mix of renewable and distributed generation.


UN has set a goal of Universal Access to Electricity by 2030 and the World Energy Outook 2018 has reported that the people without access to electricity fell below 1 billion in 2017. Do you think the UN goal being realized earlier and how will energy storage technologies enable this watershed moment in the history of civilization?

Providing universal access to electricity by 2030 is of course a worthwhile and important goal. The technology exists now for this to occur, and as technologies improve and prices continue to decrease, the ability to meet those goals will become easy. For example, solar panels plus battery systems can provide better access to electricity in the remote rural areas where it is not economical to build and maintain transmission and distribution lines.  However, meeting that challenge requires much more than availability of technology. The greatest challenges are good governance, the availability of project financing, education and workforce development, infrastructure, and supply chains for delivery of systems and maintenance.

We have been involved in a number of rural demonstration projects in Native American communications that integrate energy storage with other resources to provide reliable power to rural communities. I also would like to highlight the IEEE Empower a Billion Lives campaign, that is providing a global platform to develop low cost, regionally relevant solutions to electricity access for 1 billion people without access to electricity.


Energy Storage systems are also central to the transition from fossil fuel driven vehicles to EVs. How does the storage system for EV different from those of grid scale energy systems?

Batteries for EVs have different attributes than stationary storage. Light weight, higher energy density and higher voltage are required for electric vehicles. There is limited flexibility in the size and shape required for EV batteries. Size is a major factor with most EVs requiring nothing larger than 100 kWh battery. For EVs, the industry is converging towards using Li-ion batteries. For grid applications, the need is for a range of solutions that scale in size from kW to multi-MW systems, with a span of applications that cover energy and power markets that range from the residential to multi MW/MWh grid applications.

From a grid perspective, the major question is how we handle large scale electrification of transportation and the upgrades needed in the distribution system infrastructure needed to accommodate fast charging. With major auto companies committing to electrify large portions of the fleet, there is a wide ranging expectation that we may see electrified passenger car fleet reaching 130-230M vehicles globally. There is also significant drive to electrify bus and other public transportation systems. Electric vehicles will drive electricity demand growth. If the forecast of fleet growth is anywhere close to projections, we may overload distribution systems and cause serious transmission congestion. In some markets, we may see total load doubling. Strengthening the distribution systems and providing additional flexible resources for large C&I customers and also integrating significant ES resources at distribution substations would be necessary.

Electricity demand under large scale electrification of vehicles will see increase in peak demand, though this could be somewhat mitigated under ideal vehicle charging conditions. Even if we see 20-30% electrification in the US, that represents 50-80M vehicles, and 5-10 TWh energy storage capacity on the vehicles. Thus, providing rapid charging infrastructure would require significant investments in distribution systems, including large amount of energy storage, and improved communications infrastructure to reliably manage power flows.


What are the emerging new EES technologies and how would they compare with Lithium ion batteries?

We have a range of battery technologies for short duration energy storage from seconds to days. These include Li-ion, advanced lead acid, NaS and other mature battery chemistries. Flow batteries are beginning to be deployed for longer duration (>4hr) energy applications. However, we do not have any ready solutions for long duration and seasonal storage needs. At Sandia, we are working on developing lower temperature sodium batteries, rechargeable alkaline zinc-manganese oxide batteries, and higher energy density electrolytes for flow batteries. We do a lot of research on the safety and reliability aspects of lithium ion batteries. Our work on safety of Li-ion batteries is laying the ground work for the development of significant professional and industrial standards. Results of our work in this area are well documented and reports are available at DOE’s Energy Storage Collaborative at: We are also involved in several pilot scale demonstration projects based on the above technologies. Results from these projects are available at:

We are quite excited about our on rechargeable zinc-manganese oxide batteries. This work in collaboration with several universities has the potential for significantly lower cost. Zn-MnO2 alkaline batteries, traditionally primary batteries at <$20/kWh with long shelf life, have the lowest bill of materials cost, low manufacturing capital expenses and an established supply chain for high volume manufacturing. These batteries can be produced in large format cells with sizes that are inherently well suited for grid energy storage. Alkaline batteries also do not have the temperature limitations of Li-ion or lead-acid batteries, thereby removing the need for complicated thermal management systems, and providing simpler systems with lower integration costs. Our work in  this area is focused on improving energy density and cycle life.

Traditional Na-based batteries, such as NaS and Na-NiCl2 have been deployed in the grid infrastructure for many years. Reducing the cost of these batteries is a critical challenge to make these technologies more competitive. These batteries typically operate near 300oC to maintain suitable ionic conductivity of solid state ceramic separators and to ensure the molten state of both the Na anode and the molten salt catholytes. These elevated temperatures, though, require relatively expensive sealing and packaging and increase operational and maintenance costs. Our current work in this area is on the development of a lower temperature of molten Na-halide batteries that operate near or below 100oC, a dramatic change that would extend battery life while facilitating the use of low cost, widely available packaging, and safe, new, highly cyclable battery chemistries.Flow batteries are being deployed for longer duration storage. There are still a number of challenges with this technology. Further improvements are needed in improving energy density and improved system reliability. Our current research is on the development of electrolytes with improved energy density and development of lower cost polymeric membranes. We are also involved in extensive field testing of deployed flow batteries at utility sites around the country.

As stated above, reducing the cost of power converters is also a significant challenge in making the overall cost of energy storage systems more competitive. We work on modular power converters, and we also do significant research on using power electronics to improve the safety and reliability of energy storage systems at the cell and module levels.


Between Swapping Batteries and Bulk Charging infrastructure, what in your assessment would be better option for driving the EV transition?

Both have advantages and disadvantages and the best option for driving EV transition will be to have both those infrastructures available, and probably along with others. It is also important to keep in mind that EVs are not just electric cars, the existing urban train systems are often electric too. Making those systems smarter and more efficient are also critical for public transportation and energy storage can also a feasible option for that.  


How do you think the EES market would evolve five years from now and how big it would be?

Future grid will need large amounts of storage across all market segments. For example, Wood Mackenzie projects that energy storage deployments will grow thirteenfold over the next 6 years, from a 12 GWh market in 2018 to a 158 GWh market in 2024. Barring large scale economic or political dislocations in the world, these numbers appear likely to be met.  

How much storage do we currently have in the grid? Very little. Most of the energy storage capacity is in the pumped hydro reservoirs that we were built to support the expansion of nuclear fleet in the 70s and early 80s. In the US, we have 22 GW of pumped hydro, and battery energy storage reached 1 GW this year. US installed energy storage capacity represents only 15 minutes of ride through. The energy storage needs for a rapidly changing grid are far greater. So far, firming up renewables has not been a requirement. However, that might change soon. In many markets, demand charges are significant, but with lower cost energy storage, demand charges could be entirely avoided. Power quality issues are real and energy storage can improve power quality and mitigate commercial losses from outages. We have a 1 TW grid in the US; even an hour of energy storage capacity would represent 1 TWh, equivalent to 4 to 5 years of all existing Li-ion battery  manufacturing capacity around the world. This underscores the magnitude of the challenge.

The future grid must be instrumented to be able to handle bi-directional power flows on a scale that we have not thought through. This not only includes the need for a robust communication infrastructure at every point of generation, delivery, and end use, but also reliable market mechanisms to account for complex power flows. We are still in an early stage in getting storage deployed in the grid on a large scale. We still have a number of technical challenges that need to be addressed. What is needed to connect and manage all of these individual systems and components effectively? What software and hardware platforms should be used? Can a standard architecture be developed and used for the majority of applications? What needs to be designed differently for a power system with an increasing number of distributed resources?


What is the significant developmental work taking place in the EES space in Sandia National Labs under your stewardship? Could you recommend some of your recent reports that would be of interest to many stakeholders in this space?

At Sandia we are working on all aspects of energy storage technology, from materials R&D, safety of energy storage systems, power converters, analytics and controls, project support and significant outreach and support to the industry, utilities and policy makers. The range of activities at the lab can be found be at the DOE Energy Storage website:


Is Sandia Labs jointly working on any project with any of the Indian Universities or Industries? If not is there any plan of doing so?

We currently have no collaborative projects with Indian institutes or companies. We had interactions with a number of Indian universities with other projects, but not in energy storage. We are open to explore opportunities for future collaborations.


Dr. Babu Chalamala is Head of the Energy Storage Technology and Systems Department and Laboratory Program Manager for Grid Energy Storage at Sandia National Laboratories, Albuquerque, NM. Prior to joining Sandia in 2015, he spent twenty years in industry R&D, mostly recently as a Corporate Fellow at MEMC Electronic Materials/SunEdison where he led R&D and product development in grid scale energy storage. Before that, he was involved in two startup companies for eight years. He spent early part of his research career at Motorola and Texas Instruments where he made contributions to electronic materials and display technologies. He received his B.Tech. in Electronics and Communications Engineering from Sri Venkateswara University and PhD in Physics from the University of North Texas. An IEEE Fellow, he served on the editorial boards of Proceedings of the IEEE, IEEE Access and IEEE Journal of Display Technology. He currently serves as Vice Chair of IEEE PES Energy Storage and Stationary Battery Committee. He has also been active in the Materials Research Society, where he served as a General Chair of the 2006 MRS Fall meeting and in several society leadership positions. He authored 120 papers, edited volumes, and was awarded 10 US patents.