The electricity grid of the future needs to be flexible in order to integrate growing use of renewables, a new book from the International Energy Agency (IEA) says.

In Harnessing Variable Renewables: A Guide to the Balancing Challenge, the agency uses case studies of eight geographic regions, each facing unique energy challenges, to develop a four-step Flexibility Assessment (FAST) method.

The book focuses on variable renewable energy (VRE) technologies, such as wind, solar, wave and tidal, which have posed a unique challenge to utilities that need to provide customers with steady around-the-clock baseload power.

“The results from these case studies demonstrate that variability needs not be an impediment to deployments,” said IEA Deputy Executive Director, Richard Jones. “As long as power systems and markets are properly configured so they can get the best use of their flexible resources, large shares of variable renewables are entirely feasible from the balancing perspective.”

The FAST method recognizes that utilities have always had to face variability and uncertainty in terms of energy demand and required output. It lays out a four-step method by which the challenges stemming from the integration of renewables, a newly intensified uncertainty, can be minimized (see figure 1, below):

Step 1: Technical Ability – Assess flexible resource and its ability to ramp up and down

Step 2: Availability – How much of the flexible resource is available?

Step 3: Flexibility – How much does the system fluctuate? How much flexibility is required?

Step 4: VRE Penetration Potential – Looking at need for flexibility and availability of flexible resource, how much room is there for integration of renewables?

When the FAST method was applied to eight case studies, the book reports that a surprisingly large share of VRE could actually be integrated into the grid: The results ranged from 19% capability in Japan to 63% capability in Denmark (see figure 2, below).

These numbers take into account renewables that are already connected to transmission lines.

The book further recommends that power markets should take VRE into account, allowing “sufficient response from supply-side and demand-side flexibility assets.”

Ultimately, it will take a combination of economic incentives and the removal of political barriers, which exist “for historical and institution reasons,” for countries to incorporate the largest amount of possible VRE.

With larger grids that are distributed over a wide geographic region, VRE integration will be even smoother, the book says. Current technology could then be used, minimizing economic impacts, while fluctuation of renewables would be staggered throughout the day.

“Decision makers should plan for the widest possible dispersal of VRE plants within the bounds of grid and resource considerations.”