Another Myth Dispelled: Intermittent Solar, Wind Means More Emissions From Fossil Fuels

One of the arguments often used to minimize the value of renewable energy is that fossil-fuel plants are still needed for back-up.

That means renewable energy projects still produce significant emissions, they say, while adding costs for utilities that still have to rely on fossil fuel plants.

Research from National Renewable Energy Lab (NREL) disarms this argument, however. True, utilities have to ramp fossil fuel plants up or down more frequently as more wind and solar is added to the grid. This practice, called "cycling," ensures customers receive reliable energy whether the sun is shining or the wind is blowing.

Carbon emissions, however, from increased cycling are negligible at less than 0.2%, especially when compared to the huge emission reduction benefits of wind and solar. 

Using fossil fuels to fill in for intermittent wind or solar also doesn’t increase utility’s costs, it decreases them. Using high levels of solar and wind obviates the need for fossil fuels by about $7 billion a year in the Western US, compared to cycling costs, which range from $35 million to $157 million a year.

"Grid operators have always cycled power plants to accommodate fluctuations in electricity demand as well as abrupt outages at conventional power plants, and grid operators use the same tool to accommodate high levels of wind and solar generation," notes Debra Lew, project manager for the study. "Increased cycling to accommodate high levels of wind and solar generation increases operating costs by 2-5% for the average fossil-fueled plant. However, our simulations show that from a system perspective, avoided fuel costs are far greater than the increased cycling costs for fossil-fueled plants."

These calculations are based on renewable energy producing up to 33% of the energy on the Western grid (Western Interconnection) – a quarter of the total power. NREL finds that amount of solar and wind bring carbon emissions down 29-34% for the grid as a whole. 

The study focuses only on fossil fuel plant operations, not on capital costs to build various kinds of power plants or transmission lines. 

Operators can forecast solar availability pretty easily because they know the path of the sun each day, but it can be more challenging for wind. Despite these differences, NREL finds the impacts of solar and wind on system-wide operational costs are remarkably similar.

This second phase of NREL’s Western Wind and Solar Integration Study (WWSIS-2) follows a study released in 2010 which analyzed the viability of integrating high levels of wind and solar power into the western electricity grid.

Other myths recently dispelled are that wind farms lower property values and cause health problems for people that live near them.

Here’s the NREL study:

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