the unpredictable operation of wind power has created a new need for interactive demand response, where the utility communicates with the demand. Historically this was only done in cooperation with large industrial consumers, but now may be expanded to entire grids. For instance, a few large-scale projects in Europe link variations in wind power to change industrial food freezer loads, causing small variations in temperature. If communicated on a grid-wide scale, small changes to heating/cooling temperatures would instantly change consumption across the grid. A report released in December 2013 by the United States Department of Energy further describes the potential benefits of energy storage and demand side technologies to the electric grid: "Modernizing the electric system will help the nation meet the challenge of handling projected energy needs—including addressing climate change by integrating more energy from renewable sources and enhancing efficiency from non-renewable energy processes. Advances to the electric grid must maintain a robust and resilient electricity delivery system, and energy storage can play a significant role in meeting these challenges by improving the operating capabilities of the grid, lowering cost and ensuring high reliability, as well as deferring and reducing infrastructure investments. Finally, energy storage can be instrumental for emergency preparedness because of its ability to provide backup power as well as grid stabilization services". The report was written by a core group of developers representing Office of Electricity Delivery and Energy Reliability, ARPA-E, Office of Science, Office of Energy Efficiency and Renewable Energy, Sandia National Laboratories, and Pacific Northwest National Laboratory; all of whom are engaged in the development of grid energy storage. Energy storage for grid applications Energy storage assets are a valuable asset for the electrical grid. They can provide benefits and services such as load management, power quality and uninterruptable power supply to increase the efficiency and supply security. This becomes more and more important in regard to the energy transition and the need for a more efficient and sustainable energy system. Numerous energy storage technologies (pumped-storage hydroelectricity, electric battery, flow battery, flywheel energy storage, supercapacitor etc.) are suitable for grid-scale applications, however their characteristics differ. For example, a pumped-hydro station is well suited for bulk load management applications due to their large capacities and power capabilities. However, suitable locations are limited and their usefulness fades when dealing with localized power quality issues. On the other hand, flywheels and capacitors are most effective in maintaining