Project Drawdown defines grid flexibility as a portfolio of practices and technologies (system operation, markets, load, flexible generation, networks, and storage) that increase grid efficiency, resilience, and ability to integrate variable renewable energy sources. The practices and technologies that constitute grid flexibility are in varying states of maturity: each one contains both elements that have existed since the beginning of electrification—such as governors on generators to keep frequency steady as load varies—and cutting-edge innovation just commercialized or on the horizon (e.g. advanced batteries, software platforms to enable dynamic trading of energy services).
Every electric power system has some degree of flexibility built in to provide a buffer between supply and demand. Adding variable renewable energy to a system increases the need for flexibility; fortunately, many means of providing it are inexpensive or have collateral benefits that offset their cost.
Adoption of grid flexibility is driven by incorporation of variable renewable energy into the electric grid; the age of existing infrastructure and its ability to manage two-way power flows (i.e., from a utility to a household and back); and the need to make the grid more resilient in the face of increasing natural disasters. In general, the practices and technologies that make the grid more flexible are challenging to quantify in a meaningful way, since there are many intertwined factors contributing to a more flexible grid. Metrics for this quantification are being developed (e.g., Cochran et al., 2014), though this solution has not been modeled.
Flexibility tools that rely on changes in law, changes in behavior, and changes in standards only reduce carbon dioxide emissions insofar as they increase the penetration of variable renewable energy sources of electricity generation.
Barriers to adoption of grid flexibility include public objection to new infrastructure such as transmission lines; reluctance on the part of regulated utilities to share data about system needs with unregulated competitors; privacy issues with regard to two-way communications between households and utilities; and the slow pace of changing regulations, as regulators face the challenge of encouraging innovation that benefits the system while protecting the interests of all rate payers.
Three trends stand out that will accelerate adoption of grid flexibility. The first relates to the availability, communication, and processing of data. As information technology has become more and more accessible, available, and cost effective, it has begun to transform the way that electricity is metered, billed, and valued, and made way for a host of new data-based services. Information and communication technologies provide utilities and energy providers with new opportunities to optimize energy systems management, which in turn enables new business models that promote investment in variable renewable energy sources and the infrastructure to integrate them. What began as an investment in automated meter reading in the 1990s has evolved into advanced metering infrastructure, which is expanding to include the exchange of many kinds of grid data over multiple communication networks (radio, cell, fiber, and conductor).
The second trend relates to energy storage and is discussed in detail in the utility scale energy storage and distributed energy storage solutions. The acceleration in advancement of lithium-ion batteries beginning around 2010 and their recent rapid decline in cost have made them increasingly useful and cost-effective.
The third trend, closely related to the second, is the uptake in adoption of electric cars. Wherever infrastructure allows electric vehicles to support the grid with energy and ancillary services (i.e., through smart charging and vehicle-to-grid systems), the grid will become more flexible. If battery costs remain high, then once past their useful life in cars they will be available for a second life in buildings. If battery costs fall enough to make battery second-life use impractical, then energy storage will have become cheap enough to be widely deployed and support a high penetration of variable renewable energy sources.
Better, more detailed and comprehensive methods of quantifying costs and benefits of the various practices and technologies would enable policymakers, regulators, and market operators to craft optimized solutions for integrating variable renewable energy sources into the grid.