Inter-annual variability of wind and solar electricity generation and capacity values in Texas

Wesley Cole,Michael T Craig,Andrew Kumler,Ignacio Losada Carreño,Carlo Brancucci,Bri-Mathias Hodge

doi:10.1088/1748-9326/aaf935

Abstract

As power systems shift towards increasing wind and solar electricity generation, inter-annual variability (IAV) of wind and solar resource and generation will pose increasing challenges to power system planning and operations. To help gauge these challenges to the power system, we quantify IAV of wind and solar resource and electricity generation across the Electric Reliability Council of Texas (ERCOT) power system, then assess the IAV of wind and solar electricity generation during peak-load hours (i.e. IAV of wind and solar capacity values) for the current ERCOT wind and solar generator fleet. To do so, we leverage the long timespan of four reanalysis datasets with the high resolution of grid integration datasets. We find the IAV (quantified as the coefficient of variation) of wind generation ranges from 2.3%–11% across ERCOT, while the IAV of solar generation ranges from 1.7%–5% across ERCOT. We also find significant seasonal and regional variability in the IAV of wind and solar generation, highlighting the importance of considering multiple temporal and spatial scales when planning and operating the power system. In addition, the IAV of the current wind and solar fleets’ capacity values (defined as generation during peak-load hours) are larger than the IAV of the same fleets’ capacity factors. IAV of annual generation and capacity values of wind and solar could impact operations and planning in several ways, e.g. through annual emissions, meeting emission reduction targets, and investment needs to maintain capacity adequacy.

Highlights

In the United States, the installed capacity of solar and wind generators has grown rapidly in recent years, reaching a cumulative 423 and 88 GW in 2017, respectively (US Energy Information Administration 2018)
As power systems shift towards increasing wind and solar electricity generation, inter-annual variability (IAV) of wind and solar resource and generation will pose increasing challenges to power system planning and operations
We find the IAV of wind generation ranges from 2.3%–11% across Electric Reliability Council of Texas (ERCOT), while the IAV of solar generation ranges from 1.7%–5% across ERCOT

Summary

Introduction

In the United States, the installed capacity of solar and wind generators has grown rapidly in recent years, reaching a cumulative 423 and 88 GW in 2017, respectively (US Energy Information Administration 2018). Several factors have driven this growth, including falling wind and solar costs (Barbose et al 2016, Lazard 2017, Wiser et al 2017) and federal and state policies (US Department of Energy 2017, 2018). Due to economic and policy drivers, wind and solar installed capacity will likely continue to grow (Wiser et al 2015, Cole et al 2018a, 2018b), with some deep decarbonization scenarios envisioning wind and solar penetrations greater than 60% (Ribera et al 2015, Loftus et al 2015, Mileva et al 2016). Variability and uncertainty impact the amount of capacity needed to meet planning and operating reserve requirements, and can impact the cost of financing as higher variability can lead to higher project risk. Here we quantify long-term variability, inter-annual variability (IAV), of wind and solar resources and generation, and assess how this IAV might impact system planning and operations

Methods

Results

Discussion

Conclusion