Dealing With The Variability of Renewable Energy Forces Us To be Smart

Dealing With The Variability of Renewable Energy Forces Us To be Smart
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The thing about fossil fuels is that they enable utilities, planners and policy-makers to, in effect, be dumb. Because fossil fuel is essentially stored solar energy, the fuel can simply be pulled out of the ground, transported to a large power plant and burned. No attention needs to be paid to wind speeds, cloud cover or tides. Of course, we know that the entire supply chain of conventional energy--from extraction, to processing, to transportation and on to burning the fossil fuel--lead to social, political and environmental degradation, the costs of which are getting higher and higher.

Moving to renewable energy sources helps mitigate those costs, yet it also forces societies to be smart about energy. To put it simply, that's because renewable energy sources are variable, and different regions can posses vastly different renewable resources. This variability can be a problem for utilities, because they need to constantly supply enough power to meet demand. According to a recent study by the Rocky Mountain Insitute (RMI), "In the past, utilities believed that they had to compensate for this variability by installing more traditional, fossil-fueled power plants. The more wind or solar power on the grid, the thinking went, the greater the need for backup generating facilities to be there when the wind or sun wasn't."

Rocky Mountain Institute Re-Thinks Variability
To prove that thinking wrong, a team of researchers at RMI began looking at wind turbines and solar panels as stocks in a diversified portfolio. In this case, diversification means spreading out the various renewable power plants geographically so that, in aggregate, all of them are producing a given amount of base load power even if at a specific site the sun isn't shining or the wind isn't blowing. Lena Hansen, the director of the study, put it this way: "By diversifying the portfolio of sites, you mitigate variability. . .Put another way, the wind blows differently in different locations. So spread out your resource to reduce total variability."

The team looked at 43 wind and solar sites in the midwest and modeled how much power would be produced from them, and at what times. In the end, "they found that variability in the whole system went down by 55 percent compared to the average of all sites studied." This is significant for several reasons. For one thing, if we are to meet Al Gore's challenge of 100% renewable energy within a decade, renewable energy sources are going to have to be able to provide both peak and base load power. These findings show that geographic distribution of different energy sources can provide a steady supply of energy. When combined with energy storage technologies--such as molten salt, which is currently used in many concentrating solar plants--renewable energy can provide peak power as well.

Being Smart About Energy
Equally importantly, the study underscores what being smart about energy really means. Moving forward, electricity generation will require an understanding of micro-climates, biomass availability, bird migration patterns and even local culture and politics. The days of constructing massive power plants that are out of site and out of mind are over. In our future renewable energy economy, large solar and wind farms will co-exist with distributed generation on rooftops, bridges and backyards.

Ultimately, while the variability of renewable energy makes it more challenging to harness, it also ensures that we don't repeat the mistakes of the last century. For instance, given that no one owns the sun or the wind, it's unlikely that there will be an Exxon Mobil of solar photovoltaics. Additionally, having a diversified energy supply reduces the risk of massive (and costly) blackouts; creates more jobs (since there are more individual sites to be installed and maintained); and opens the door for more innovation around control, monitoring, demand side management and forecasting technologies.

So yes, the variability of clean energy is an issue, but it should be viewed as an opportunity, not a problem. As the RMI report demonstrates, changing the way we think about energy is essential to eliminating the harmful effects of our energy system.

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