The grid is the dynamic web of electricity production, transmission, storage, and consumption that 85 percent of the world relies on. It was designed for constant, centralized power production, not for the variability of solar and wind power. For electricity supply to become predominantly or entirely renewable, the grid needs to become more flexible and adaptable than it is today.
Many technologies contribute to grid flexibility:
- Constant renewables, such as geothermal;
- Utility-scale storage, such as pumped hydro and molten salt;
- Small-scale storage, such as batteries; and
- Demand-response tools, such as smart thermostats and smart appliances, to mediate peaks in demand.
Flexibility also depends on strong transmission and distribution networks—the connective tissue between generation and consumption. Where the grid spans larger geographies and more electricity sources, it can essentially even out the total output of renewables, reducing extremes in variability. Weather forecasting and prediction are also important tools to manage wind and solar generation.
While photovoltaic panels and towering turbines may garner most of the attention, flexibility is the means for renewables to become the dominant form of energy on the planet. Together, they will make the global energy transition possible.
“hitched to everything else in the Universe”: Muir, John. My First Summer in the Sierra. Boston: Houghton Mifflin, 1911.
85 percent of the world relies on [the grid]: World Bank. “Access to Electricity (% of Population).” Sustainable Energy for All (SE4ALL) database. 2012. http://data.worldbank.org/indicator/EG.ELC.ACCS.ZS.
November in Germany…low wind and sun: Martinot, E. “Grid Integration of Renewable Energy: Flexibility, Innovation, and Experience.” Annual Review of Environment and Resources 41 (2016): 223-251.
Spain…grid operator Red Eléctrica de España: Martinot, “Integration.”
[connected] power systems…in northwestern Europe: IEA. The Power of Transformation: Wind, Sun, and the Economics of Flexible Power Systems. Paris: International Energy Agency, 2014.
renewable generation [in 2050]: IEA. World Energy Outlook. Paris: International Energy Agency, 2015.
already reaching 20 to 40 percent share: Martinot, “Integration.”
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, etc.).
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: adoption 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 impact the reduction of carbon dioxide emissions insofar as these tools 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). This trend is discussed in depth in the Smart Grids solution.
The second trend relates to energy storage and is discussed in detail in the energy storage (utilities) and energy storage (distributed) 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 vehicles. 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 policy makers, regulators, and market operators to craft optimized solutions for integrating variable renewable energy sources into the grid.