The Cost of Intermittency

Costs and Consequences of Wind and Solar

by Matthew Formby

Wind and solar are great in their potential, and if it were possible for them to provide all (or even most) power throughout the world right now, there would be little use for any other energy source. But, as many European countries have realized(1), the issue of intermittency isn't so easily solved. The problems faced by the renewable industry are the same issues they've been trying to solve since the beginning: supply not following demand, the possibility of completely losing wind or solar energy at any given time, and similar consequences of unreliable production.

Even though some states and countries have a high percentage of renewables, while their neighbors don't, it tends to make adding more intermittent renewable energy harder for those neighbors. It's a problem with the physics of intermittency, which Dr. Emanuel discussed in a previous interview with EAContent. At the time, he noted that a grid could only have around 20-30% of total capacity from these renewable. After that point, intermittent power becomes impossible to utilize effectively, if at all.

The grid can accommodate some intermittent power, and some areas can boast 100% renewable energy for a couple key reasons. First is what has been referred to as the law of large numbers(3), which is a lot like rolling 1000 dice, instead of just one or two, and predicting possible results. So even if clouds cover some of your solar panels, others might still provide power. The other, bigger reason is using the grid. If you use more energy than the solar panels on your house give, you can pull from the grid until you even out or can start selling energy back into the grid. As long renewable energy production is more than total consumption, most places consider it 100% renewable--even if you buy coal power once in a while.

The problem is that the grid doesn't act like a magical battery. It can only transport energy, so any extra power is lost. And even with expensive changes to the grid to make the most use of sudden supply changes and transport energy farther, energy will still be lost if it must travel great distances. These limits are what bring us to a hard limit for intermittent renewables--because energy is still essential at night to, say, power a hospital.

The current limits create an uphill battle that, maybe, one day will be won by wind and solar. And it will be great when the "substantial structural changes" Michael Liebreich, chairman of the advisory board at Bloomberg New Energy Finance says leading European markets (Germany, Denmark, Spain, and the UK) are going through can be brought to developing nations and made affordable compared to other sources of energy (Harrington 2016). But the planet faces an immediate threat, one that many nations cannot afford to solve with renewable energy alone.