What happens when the wind doesn’t blow?It’s likely you’ve heard the argument that renewable energy is unreliable because the wind doesn’t always blow and the sun doesn’t always shine. It’s true that renewable resources are variable. We can’t make the wind blow and the sun shine 24 hours a day. That’s just nature. But, does this mean that large amounts of solar and wind can’t be incorporated into the grid?

It’s time to set the record straight.


Renewables, like solar and wind, are already providing clean, reliable electricity across the country. At the second half of 2014, the U.S. had nearly 16 gigawatts of solar photovoltaic (PV) installed. The U.S. currently has over 62 gigawatts of wind energy installed with about 13,600 megawatts currently under construction. In 2013, Iowa and South Dakota produced more than 25% of their total electricity from wind energy. In Europe, countries are taking renewable energy to a new level. Denmark, with ambitious goals to reach 100% renewable energy by 2050, currently produces over 40% of its energy from renewables. In April 2013, Spain produced 54% of its electricity from renewable sources. Solar met over 50% of Germany’s total electric demand on an afternoon in June of this year. This demonstrates that it is possible for renewable energy to pay a key role in our electricity sector.

Wind and solar can integrate effectively and reliably into the grid regardless of the variability of the resource. Grid operators have various tools to maintain the balance of electricity supply and demand. The variability of wind and solar resources are typically pretty predictable. With accurate forecasts and years of data, grid operations are equipped to balance diverse resources and can adjust as needed. Additionally, while the wind isn’t always blowing in one area, it’s typically blowing somewhere. Geographic diversity of wind resources helps lower the variability of the resource. Wind and solar resources are also very compatible. Solar tends to peak in the daytime, while wind typically blows the hardest in the mornings and evenings (although the sea breeze effect in coastal areas flips this thinking on its head).

In many cases, renewable energy can actually strengthen the grid and lower costs for ratepayers. Recent extreme weather events have proven that wind energy can provide very valuable electricity and avoid power outages. According to the American Wind Energy Association(AWEA), during the Polar Vortex with its record-breaking freezing temperatures this winter, “wind energy’s output provided the critical difference that allowed grid operators to keep supply and demand in balance and the lights on.” At times in the Mid-Atlantic during January’s Polar Vortex, wind energy was estimated to save ratepayers to the tune of $1.5 million to $2 million per hour. Recently in the U.K., wind energy filled the gap in generation when a fire at a gas power plant and four nuclear reactors unexpectedly shut off. Just last week, the Georgia Public Service Commission unanimously approved Georgia Power’s plans to build solar arrays at three military bases. The Army stressed the importance of access to power in times of emergencies.

Wind energy has also proven to help utilities avoid costly spikes in electricity during peak demand hours. A recent SACE report demonstrated that wind energy could supply cost effective electricity for high electrical demand across the Southeast during the summertime. North Carolina, South Carolina, and Georgia’s costal and offshore wind resources are positively correlated with peak electricity demand hours in summer months because of the sea breeze effect. Replacing peaking generation, which can be very expensive, with a zero-fuel-cost resource like wind or solar may be able to reduce ratepayer costs.

It’s clear solar and wind can rapidly expand across the U.S. by using existing technologies. Wind-integration studies have shown that the current grid can handle a much greater amount of wind energy without jeopardizing reliability. PJM, the world’s largest utility, released a study last year highlighting that 30% more renewables could be reliably added to the grid and could save the utility up to 15 billion a year. Future innovations, like creating energy storage technologies and building new transmission lines, will help to further boost renewables energy down the road.

Using large quantities of renewable energy is no longer theory, it’s fact in places like Iowa and Texas. When the wind doesn’t blow, or the sun doesn’t shine, other power sources are used. A report from the National Renewable Energy Laboratory suggests that the United States could power itself with approximately 80% renewable energy, relatively easily. Utilities do have to ensure reliability and so far, so good, when it comes to incorporating renewable energy.

This blog entry focuses more on wind energy. To find out what happens when the sun doesn’t shine, check out an earlier blog post by SACE’s Renewable Energy Manager, Charlie Coggeshall, here. It appears courtesy of SACE.