Grid Services and Wind

With so much talk about the impact of wind on the need for various operating reserves, the U.S. Department of Energy Wind Energy Technologies Office recently asked me, along with my co-authors Trieu Mai and Yinong Sun, to prepare a brief overview of various services needed by the grid, and how wind might provide some of them.

What Services Does the Grid Need?

Our recently published paper provides (we hope) a nice overview of the services that the grid needs to balance supply and demand and remain stable. We focus on “essential reliability services” (which used to be called ancillary services) and discuss how much we need and how much they cost. We highlight how many of these services are conceptually quite similar. All types of operating reserves are simply designed to stabilize frequency; however, the ability for generators to provide the different reserve types depends on “how much” headroom is available, “how fast” the response needs to be, and for “how long” (see the graphic above).  

Can Wind Provide Them—Technically and Economically?

Using these basic concepts, we describe the opportunities and challenges for wind to provide multiple reserve services.  For the most part, wind plants can change output much more rapidly than thermal generators but for many reserves it all goes back to wind’s capacity credit (is the wind available over the duration when services are needed?) and economics (what is the opportunity cost to provide reserves vs. energy for zero-marginal-cost electricity?).  

Finally, we wade through some of the evolving terms being thrown around regarding resources that automatically respond to system frequency (synthetic inertia, fast frequency response, etc.). We expect that these terms will keep changing, but hope that by discussing the underlying grid requirements, our paper will provide a conceptual overview of different types of reserves. This can facilitate an understanding of how to reliably keep the lights on even in a future with high shares of wind (and other renewable) energy.