• To maintain steady electricity output while using intermittent, weather-dependent sources like solar, utilities must ramp up and down generation from fossil fuels
  • Ramping them up and down is expensive and produces worse greenhouse gas emissions
  • Advocates claim battery backup solves this problem, but they don’t realize just how little utility battery backup offers and at what costs, not just to ratepayers, but also to the environment

Under the new administration of Pres. Joe Biden, more attention will be paid toward replacing the world’s finest electricity generating and distribution system with one that does not emit greenhouse gases (GHG). This brief does not consider the question of whether such a change is warranted, since that’s not being considered by the administration. They’re proposing to make reflexive changes instead.

Some of their changes require relying more on intermittent energy sources such as solar and wind plants. The problem is, the new administration will be unable to change the laws of physics — and there’s no reaching a settlement out of that court. Having to deal with the swings in energy production from solar and wind is a hard reality.

Recently, however, the lay press has been discussing battery storage and the promises it holds. As this brief will explain, those promises are slight.

The challenge of dealing with intermittent power generators

North Carolina has become a leading state for solar plant electricity generation. The reasons are simple. Our government uses taxpayers and electricity customers to offer some of the nation’s most generous incentives, causing an otherwise uneconomical generating technology to flourish. North Carolina is now second in the nation for installed solar generators, with approximately 25 million solar panels currently deployed. The power generated by these panels, while typically only 20 percent of the stated capacity, is now significant, but the output is controlled by the weather rather than a system operator.

Instead of allowing the system operator to accept solar power when the system is most able to accept it, NC law and policy forces the operator to accept solar power whenever it is produced. Here is what the system operator must typically deal with:

Source: Dan Way, “Solar energy output ratings misleading if not deceptive, critics say,” Carolina Journal article, May 20, 2019

Study these actual examples of electricity generation and put yourself in the position of the system operator. You’re charged with balancing your system of electricity generators’ output very precisely with customer demand, or else risk catastrophic damage to houses and businesses across the state. You’re struck with one observation: The solar plant output is intermittent. To balance that output with your demand and prevent catastrophic damage, you have to ramp up and down other electricity generators at a rate sufficient to complement this intermittent source.

It turns out that the best and most affordable generation capable of giving you such flexibility is provided by the combustion of fossil fuel. In particular, thanks to hydraulic fracturing and existing pipelines that bring natural gas into North Carolina, natural gas combustion turbines work the best of all. These turbines are very similar, but larger, than the combustion turbines used for airplane propulsion.

These engines work most efficiently — and pollute the least — when they are operated in a steady fashion, like they do once an airplane has reached its cruising altitude. If you use them to fill the gaps created by solar plants, however, you’re making these engines operate in a more unsteady fashion. This usage creates many challenges, including that they cost more to operate this way. They are also made to pollute more — so much so that the plant owner has difficulty complying with her air permit limits.

The very limited utility of battery storage and other uncomfortable facts

Here is where “battery storage” may hold some promise. System operators such as Duke Energy have recognized that, if their combustion turbines were given a little more time to start up and shut down, then their engines operate better. They also pollute less. As a result, Duke offers solar plants a higher price — to be paid by you, the customer, of course — to solar plants utilizing a sufficient amount of batteries so as to smooth out the intermittency of the solar plant’s output. Duke only needs a few minutes longer to help the operation of its combustion turbines, which is good because just a few minutes is all the time battery storage can provide.

You might think that battery storage would provide power for the time when the sun doesn’t shine. You might think battery storage would eliminate the need for combustion turbines. You might think battery storage would lead to zero emissions of GHGs. In all cases, you would be very wrong.

You should recognize that you will be paying more for electricity. You should recognize that batteries are energy-intensive to manufacture, and they consume a large amount of our earth’s natural resources — even when only providing such miniscule amounts of power. You might even recognize that these batteries can be hazardous as they are prone to bursting into flames. In all of these cases, you would be correct.

The more you learn about the use of solar and wind plants to supply a large fraction of our electricity, the less these sources make sense. Under current state and now federal policies, instead of investing in long-term, zero-emissions solutions like nuclear power, you will continue to pay for more solar panels, more combustion turbines, and now more batteries instead.