Are There Batteries In the Grid's Future?

 

Texas has the largest installed capacity of wind generation of any U. S. state as of 2019.  But all those windmills did no good a year ago when historically low temperatures knocked out natural-gas production and generators, leading to the Big Freeze and the deaths of over 200 people.  The reason?  There was almost no wind associated with the cold snap, and no wind means no wind generation. 

 

In the debate about the Texas power grid that followed, some charged that our increasing reliance on wind power (and to a lesser extent, solar power) was destabilizing the grid.  Up to now, at least, power has to be generated on demand, so electric-utility operators have come up with a combination of base-load and peak-load generators to deal with the fluctuations in demand, which can go very low at 2 A. M. on a mild spring day, but soar to many times the minimum on a blazing August afternoon.

 

Base-load generators are most efficient when they run all the time.  Nuclear power is in this category, as are fossil-fuel plants that use steam turbines and large boilers fired by natural gas (or, decreasingly, coal).  These types of plants are used for base loads because starting and stopping them is a big deal and can take hours or even days. 

 

Peak-load plants, on the other hand, are designed to come on line in just minutes.  One example is the gas-turbine plant, basically a bunch of jet engines hooked to generators.  Peak-load plants are typically less efficient than base-load plants, but they can be started up quickly to meet soaring demand in emergencies. 

 

Solar and wind don't fit either of these categories, as they depend on whether the sun's out or the wind's blowing, respectively.  Fitting the fairly unpredictable output of these renewable types of energy into an existing grid can be challenging, because it adds fluctuations that weren't there before.  If the wind's blowing hard and Texas is getting up to 10% or more of its total electricity demand met by wind energy, and all of a sudden the wind stops, you have to be ready to jump in with peak-load plants and supply what's missing, and that isn't always easy.  So as more fluctuating renewables are added, the problem of managing the grid to meet fluctuating demand gets even harder.

 

Although experts determined that this issue was not a primary cause of the February 2021 Texas blackout, it's an ongoing concern, and one way of dealing with it is a very old one:  batteries.

 

Using batteries as electric-utility energy storage is not a new idea.  I have a 1910-era book on my shelves that describes how electric-streetcar power plants were supplemented by banks of lead-acid batteries attached across the lines at strategic places along the streetcar routes.  In periods of light demand with low traffic, the batteries were charged by the central power plant.  And during rush hour when there were more trolleys on the line than usual, the batteries would discharge into the overhead wires and supplement the base-load power generated at the central plant.

 

The problem with lead-acid batteries is that it takes a huge number of them to store enough energy to make a difference with a large-scale power grid.  Depending on the technology, a lithium battery of the same volume as a lead-acid battery can store up to ten times the energy, and the weight advantages are even better.  That's why electric cars had to wait until lithium batteries were fairly practical to compete with internal-combustion cars. 

 

In December of 2020, Vistra Energy connected what was then the largest battery-storage energy facility in the world to the California grid at Moss Landing in Monterey County.  The system can provide up to 300 MW of power and can store 1.2 gigawatt-hours, implying that it could provide its peak energy output for three or four hours before pooping out.  But that is plenty of time to tide a grid over an emergency until other more conventional sources can be put online.

 

Actually, because batteries can start supplying massive amounts of power in less than one cycle of the 60-Hz power frequency, they are very useful for damping out short-term instabilities in power grids that can otherwise trip relays and cause blackouts.  This type of operation can't be done with mechanical generation systems.  So a battery storage facility like this is one more tool in the power-dispatcher's toolbox to use in meeting fluctuating demand.

 

The Moss Landing facility was in the news recently because of a fire that destroyed ten of the nearly 100,000 battery packs at the facility, the second such fire in five months.  The first fire was caused by leaking water from cooling pipes, and so the second one may be due to similar causes.  The fire was contained and out before the fire department had a chance to do anything. 

 

The nice thing about battery systems is that failures can be isolated fairly easily, as the Moss Landing mishaps show.  Although the plant was shut down during the fire for safety reasons, repairs are fairly straightforward and the system was back online in short order.  This feature of gradual degradation is a big asset in the utility business, where shutdowns can cause big headaches.

 

It remains to be seen how significant a role battery storage will play in the future of the so-called smart grid.  Electric-car makers such as Tesla have dreams of distributed battery storage, in which thousands or millions of electric cars plugged in overnight could serve as a virtual storage facility controlled by the electric utility they're plugged into.  That would require massive changes in both hardware and regulatory structures that I'm not sure we're ready for.  But it's a nice dual-use idea that might evolve into a much more reliable, robust, and efficient grid than the fairly brittle things we have now. 

 

When I worked at an electronics repair shop one summer in college, I'd be amused when a customer would say, "This radio isn't electric, it runs on batteries."  In the future we may all be running on batteries more than we realize, and the grid will be more stable as a result.

 

Sources:  The website www.vice.com carried a story about the Moss Landing fires at https://www.vice.com/en/article/dypw5x/largest-lithium-ion-battery-in-the-world-meltdown-moss-landing.  I also referred to the Wikipedia articles on "Wind generation in the United States" and "Battery storage power station."

 

Tricks A Dumb Grid Can Play

Inauguration Day in Brookville, Pennsylvania arrived with a bang. Within minutes after Donald Trump swore to preserve, protect, and defend the constitution of the United States, the 911 calls began.  In one house, light bulbs were exploding.  Another resident reported that a power strip was smoking.  At another house, the siding was on fire, and at yet another the electric meter was engulfed in flames.  The main radio transmitter at the police station tripped out, so the 911 call center was unable to contact them until the dispatcher used his battery-powered radio to make contact.  In all, about 400 residents of the small western Pennsylvania town of 3800 suffered some type of damage, ranging from singed carpets to fried computers and exploding fluorescent light fixtures.

The power surge had nothing directly to do with Donald Trump.  A quick investigation by Penelec, the local electric utility, revealed that an insulator on a power line had failed.  What follows here is my extrapolation from the limited details in the Associated Press wire story, but represents what I think is a good guess.

Electric power networks are divided into transmission lines and distribution lines.  The transmission lines are the tall steel-framed towers that span many miles across the countryside, and are the interstate highways of the electric grid, transmitting megawatts of power from generating plants to substations many miles away.  To transmit this much power efficiently, the voltage of these lines is generally above 100,000 volts (100 kV).  For example, there is a 138-kV transmission line that connects Brookville with the rest of the power grid in western Pennsylvania, and there may be others at even higher voltages.

           

Once power arrives at a substation, it is stepped down in voltage with large, expensive units called transformers to a lower voltage suitable for distribution locally.  Distribution lines, the neighborhood streets of the network, carry voltages in the range of 12 kV to 35 kV, or occasionally higher in rural areas.  My guess is that Brookville has at least two or three separate distribution circuits with voltages in the 25-kV range.  The familiar wooden power poles that carry telephone and cable TV lines also support power-distribution cables, always suspended on the highest point of the poles.  Every few hundred feet, a "pole pig" (distribution transformer), usually a metal can a couple of feet tall, lowers the voltage still more to 240 V or less for delivery to commercial and residential customers. 

What probably happened was this.  One of the high-voltage insulators on a transmission line carrying in excess of 100,000 volts failed mechanically, dropping its conductor on or near enough to one of the town's distribution lines to allow a flashover (an arc) to jump from the 100+ kV transmission line to a 25-kV distribution line.  All power-line insulators are built with a safety margin.  That is, an insulator for a 25-kV line may be able to withstand 50 or even 100 kV, which can happen during situations such as lightning surges and so on.  This is good in normal circumstances, but in this case it backfired.

The insulation of the 25-kV distribution line held just long enough for the high voltage, four or five times normal, to get into the distribution transformers and ultimately the houses of about ten percent of the town.  So for a few seconds or maybe even longer, equipment designed for 120 V was receiving, say, 500 or 600 V. 

There are kooks on YouTube who delight in taking innocent electric appliances such as razors, clocks, toasters, light bulbs, and so on, and connecting them to high-voltage power sources just to see what happens.  They are never pretty.  Every electric appliance has a maximum rated voltage, and when you exceed it by 500% you either blow a fuse or, in the case of equipment that doesn't have fuses such as light bulbs, the excess heating makes something melt or vaporize or explode. 

Many power strips have surge-arresting devices in them meant to absorb fast transient surges caused by lightning.  But those surges usually last only milliseconds, and a surge of several seconds overheats such a device, making it smoke, which explains the reports of smoking power strips. 

Why didn't all the protective devices that a utility normally uses, such as fuses and circuit breakers, operate right away?  Because they are designed primarily for lightning strikes, not an overvoltage that lasts many seconds.  And the fuses probably didn't blow right away because a fuse only slightly over its rated current takes a considerable time to melt. 

Penelec has announced that they will compensate those who have suffered losses as a result of the surge.  Fortunately, no one was injured, but a considerable amount of property was damaged and the mess will take weeks or months to clean up. 

The "dumb grid" in the title refers to the fact that most electric utilities still use protective technology that was developed prior to World War I, for the most part:  fuses and electromechanical relays.  Innovative "smart grid" technology connecting the power grid to the Internet and replacing many electromechanical controls with faster-acting solid-state devices promises a number of good things, mainly pertaining to increased efficiency and reliability.  But it's also possible that if Brookville's grid was smarter—that is, if it could have figured out within milliseconds what happened and cut off the surge then—none of the bizarre damage might have occurred.

Admittedly, situations in which a transmission line arcs over to a distribution line are rare.  But as Brookville shows, they can happen.  If the new Trump administration wants to improve America's infrastructure, encouraging utilities to take the smart-grid path is one way to do it.  Whatever Washington does about it, though, it's too late for a few hundred residents of Brookville, who are still replacing siding, light bulbs, and computers as a result of a freak accident that shows we still have a ways to go in improving electric utility safety and reliability.

Sources:  The Associated Press report on the Brookville incident of Jan. 20, 2017 was carried by a number of news outlets, including  PressFrom.com at http://us.pressfrom.com/news/us/-21781-tiny-towns-power-surge-fries-computers-appliances-siding/ on Jan. 28, 2017.