Renewable electricity could significantly offset the use of traditional coal or gas-fired power plants in the long term. But moving a meaningful percentage of our power use to a renewable source will require a degree of redesign.
There are three broad issues that need to be addressed. First, the US electrical grid is meant to carry electricity to people, as opposed to absorbing electricity being generated by people. Second, the variable nature of solar and wind power means that the grid needs to be able to load balance to account for variable generation. Third, peak load power occurs in the early evening, after solar plants have begun to go offline (solar generates the most power at high noon, when the sun is directly overhead). The eclipse next week will disrupt solar power, and is considered an important test of how to manage the electrical grid in such a situation.
The solar power “duck curve” shows that energy demand spikes late in the day, exactly when solar plants are going offline. The eclipse will create a similar effect. Image by Wikipedia
The New York Times reports multiple states are treating the eclipse as a test run for dealing with variations in power generation. While the eclipse is short, its impact will be felt, with solar power generation in North Carolina expected to dip from 2500MW to 200MW. It won’t do this for very long; the maximum length of totality for this eclipse is 2 minutes, 40 seconds.
If you live off the path of totality, you won’t see full coverage at all, but the length of the eclipse you do see will be different depending on how close you are to the path of totality. Space.com has a nifty writeup on how and why eclipses move as they do, with a discussion of the rotation speed of the Earth, and how the moon’s shadow tracks across the Earth’s spherical shape. There’s also an amazing bit about how, back in 1973, scientists aboard a prototype of the Concorde SST managed to track a total eclipse for 74 minutes across the sky, compared with just 7 minutes and 4 seconds for a ground-based observer at the time.
Another fun fact: Eclipses last longer at the equator, where the Earth spins the fastest, and less time the further north or south you are from the tropical latitudes.
The path of totality across the US.
So far, electrical grids in states like California have drawn up plans to bring oil and gas turbines online to deal with the ramp, while simultaneously preparing to draw on electricity generated in Arizona, Nevada, and Oregon. Load balancing tests like this are important for evaluating the overall strength of the electrical grid.
Some of you may remember the Northeast blackout of 2003, where the electrical grid’s load-balancing capabilities — which are meant to prevent destabilization — actually blew the power grid across multiple states. This was rather obviously not the intended outcome. But as power grids failed across multiple states, the computers compensated by attempting to push more power across the remaining lines. These sudden demand surges exceeded what the system was designed to handle, and power plants automatically disconnected themselves in response, causing the system to pull even more power. That’s a simplified version of events, but it’s a good example of how important proper load balancing is for the entire system.
There’s another important question to be answered here. Renewable energy skeptics have questioned whether renewable power can ramp up to a meaningful percentage of power generation. Other groups have argued that they very much can, and that the electricity load can be balanced by building regional networks that offset any decline in one specific area.
While the wind may not be blowing or the sun shining at a given moment, on a continental scale (or in areas with very steady wind), this is not much of a concern. The Great Plains states, for example, have excellent results with wind power, and Iowa, South Dakota, Kansas, Oklahoma, and North Dakota all generate more than 20 percent of their power via wind. Across the United States, roughly 5.5 percent of total power generation is from wind power. That’s still a fraction compared with conventional power plants, but it compares well with hydropower, which currently generates about 6.1 percent of the United States’ electrical needs.
Now read: How do solar cells work?