Full Title: Bringing Variable Renewable Energy (VRE) Up To Scale: Options for Grid Integration Using Natural Gas and Energy Storage
Author(s): Energy Sector Management Assistance Program, World Bank
Publisher(s): Energy Sector Management Assistance Program, World Bank
Publication Date: February 1, 2015
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By the end of 2013, 144 countries—both developed and developing—had established plans for the expansion of power generation from renewable energy (REN 21). In setting these goals, countries are driven by a number of strategic considerations, including energy security, reducing pollution and greenhouse gas emissions, the need to expand and improve energy services for growing populations, and industrialization and job creation.
Among renewable energy sources, solar and wind resources stand out as having high inherent resource variability and limited predictability. For this reason, solar and wind generation technologies are often referred to as Variable Renewable Energy (VRE). Ten years ago, VRE technologies appealed primarily to those willing to pay a premium to move away from fossil fuels for environmental reasons. Today, due to equipment cost reductions, VRE is becoming competitive, putting the possibility of achieving high shares of VRE within reach of a growing number of countries.
To achieve a reliable, stable power supply, power system operators must continuously balance supply and demand. Power systems are designed to handle a certain amount of variability and uncertainty to accommodate fluctuations in demand and unexpected equipment outages. At modest levels of VRE contribution (i.e., below 5 to 10 percent, depending on the characteristics of the power system), the variability and uncertainty introduced by VRE are about the same order of magnitude as those due to normal fluctuations in demand. At this level, VRE integration can usually be managed with adjustments in operational strategies without significant investment.
But as the share of VRE increases, the higher levels of generation variability and uncertainty exceed the range that can be accommodated through operational adjustments. Additional measures are needed to avoid negative impacts on grid performance. With the promise of deriving a high share of power generation from VRE comes the challenge of integration: managing increasing levels of variability and uncertainty while maintaining performance and keeping costs down.
This report looks at the nature of VRE and the resulting challenges associated with the integration of VRE technologies into a power system. It provides an overview of the measures available to limit and manage these challenges. This report highlights the importance of increased flexibility when integrating high levels of VRE, and focuses on two sets of options to provide such flexibility: natural gas-fired power generation technologies and energy storage. Finally, this report provides some insight into the implications of VRE expansion for planning and regulation, and finishes with some recommendations for planners and policy makers.
A recent study (IEA, 2014) shows that if appropriate measures are taken to address VRE integration issues, it is possible to integrate levels of VRE even above 30 percent at modest incremental cost. To achieve this, power system planning, regulatory, and policy measures will need to be undertaken with the objective of minimizing total system costs, rather than minimizing VRE generation costs.