Some critters may be cute, but when jellyfish gum up power plant cooling systems; birds, rats, snakes, or squirrels cause electrical shorts; or invasive mollusk species obstruct hydropower plant pipes, losses can be steep. Here’s how some power plant operators are dealing with their critter troubles.
There are countless cases of wildlife entering power plant areas where they don’t belong. Unlike trained workers, the animals can’t read warning signs and often end up learning the hard way about the danger lurking in high-voltage systems. The result isn’t just bad for the critter; it can be bad for the plant, resulting in equipment damage and unplanned outage time.
Not every power plant must deal with the exact same pests. Pigeons, mice, rats, and raccoons are fairly common throughout North America, but other parts of the world have other vermin. Snakes—some of which are very dangerous—pose problems for some plants, and even insects, such as termites and carpenter ants, can cause significant damage not just to buildings, but also inside panels and equipment. It used to be that jellyfish and mollusks were found mainly at plants utilizing ocean water for cooling, but now freshwater species have spread to many areas throughout the U.S.
Keeping Unwanted Guests Out
Damage caused to electrical equipment as the result of animal intrusion can cost a lot to repair, not to mention the cost associated with lost production. Karl Mosbacher, business development manager for Roxtec Inc.’s U.S. Power group, recalled one instance where a squirrel caused $300,000 worth of damage when it triggered a power surge that affected an Indiana community center’s heating and air conditioning system and some parts of its boiler system. Rats and mice are also regular troublemakers due to their propensity for gnawing on cable and wire insulation.
In order to prevent such damage, it is important to seal building and equipment penetrations to keep pests out. Mosbacher said some materials, such as metal and concrete, are less susceptible to infestation than others, but over time, deterioration, inadequate alterations, and poorly completed repairs can create openings, allowing infiltration of unwanted pests.
A good understanding of pest behavior and vulnerable areas is important. Mosbacher noted that some products and materials commonly used to seal openings, such as neoprene and spray-in foam, are not rodent-proof. On the other hand, he said Roxtec’s uniquely designed sealing solutions are capable of preventing a wide variety of pests from entering facilities.
According to Mosbacher, the Roxtec seals (Figure 1) not only protect against rodents and pests, but also against water, gas, fire, dust, electromagnetic interference, and explosion. They are adaptable to cables of different sizes, which simplifies maintenance and upgrades.
|1. Sealing out trouble. These seals, installed at a facility in Mexico, prevent rodents, water, and other hazards from entering buildings through cable and pipe penetrations. Courtesy: Roxtec Inc.|
Animals and power plant substations don’t mix particularly well either. Raccoons, squirrels, and even snakes can end up in areas where they shouldn’t be, triggering bad outcomes for the utility, as well as for the animal (Figure 2). In some cases, the result is a simple conductor failure, but a strong flashover can result in shattered bushings or even complete transformer meltdowns.
|2. Raccoons can’t read warning signs. This little critter crossed some wires that it shouldn’t have. Courtesy: TE Connectivity|
TE Connectivity is another company that has developed a wide range of covers, isolators, and insulation products designed to protect systems from animals. The solutions include bushing covers (Figure 3), conductor covers, squirrel guards (Figure 4), bus support covers, raptor covers, and heat-shrink tubes and tapes. The company estimates that the overall risk factor can be cut as much as 80% by incorporating its mitigation products.
|3. You’re covered. Bushing and conductor covers can prevent animals and others from touching things they shouldn’t. Courtesy: TE Connectivity|
|4. A well-rounded solution. Bus insulator squirrel guards—the circular, fan-shaped protectors above the workers—are installed in this substation along with bushing covers and other protectors. Courtesy: TE Connectivity|
Pigeons are a fairly common pest at power plants. They may seem like more of a nuisance, but these birds are not as innocent as they may appear. It’s no secret that harboring a flock of pigeons will create a housekeeping problem, but Erick Wolf, CEO of Innolytics LLC, believes that pigeons are also a safety risk.
Bird feces can create slip and fall hazards on concrete walkways and steel deck grating. In addition, the birds can spook personnel who may not be expecting them when transiting through areas where the birds have taken refuge. The surprise could result in a fall or the ill-advised placement of a hand on a piece of equipment.
There are also some health risks. According to New York City’s Department of Health and Mental Hygiene—which sees its fair share of pigeon problems—three human diseases are known to be associated with pigeon droppings: histoplasmosis, cryptococcosis, and psittacosis. People with compromised immune systems are most at risk from exposure to droppings, but anyone cleaning up after pigeons should wear protective clothing, such as disposable coveralls, boots, gloves, and respirators.
Netting, bird spikes, electrical track or wire systems, flight diverters, guards, and audio and visual repellents are available for bird control through a variety of companies such as Bird B Gone, Bird-X, and BirdBusters. Jack Wagner, president of BirdBusters, said that there are more than 80 of his company’s Bird Wailers installed in electrical substations throughout Alberta alone. The units incorporate up to 34 natural sounds, such as target bird alarm and distress calls, together with the calls of predators like hawks, owls, and others indigenous to the area. In Alberta, a master unit and two speakers at each site have been effective in controlling ravens for more than 15 years.
When it comes to pigeons, Wolf said it is very hard to completely rid a site of the birds. He suggested that the cost to do so is usually a limiting factor.
“The closer you get to zero, the more it costs,” Wolf said. “Cost is one thing, but nature abhors a vacuum, so driving things to zero is not necessarily a good thing.”
In other words, once you eliminate a flock, the site may remain free of pigeons for a period of time, but eventually a new flock will move in. Wolf said the birds are in search of three things: food/water, harborage, and warmth. Power plants are a prime location for at least two of those items.
In addition to the options offered by BirdBusters and others, Innolytics created a product called OvoControl for gaining control of a plant’s pigeon population. For lack of a better term, OvoControl is birth control for pigeons.
Pigeons are sexually mature at six months of age. The birds have two eggs per clutch and up to six clutches per year, so it is a rapidly reproducing species. Pigeons typically only live for two to three years, however, so the use of contraceptive technology is an effective control measure, according to Wolf.
The OvoControl system is set up to automatically dispense food for the pigeons, which includes the birth control additive. The feeders are capable of holding more than 120 pounds of bait, which is enough to last several months for an average flock size. The system activates automatically using a digital timer.
“Keeping a portion of the flock at the facility serves the purpose of keeping other flocks from moving in. As long as there is a base of pigeons, there is not another flock of pigeons moving in,” Wolf said.
According to Wolf, after a few seasons, most customers get down to about 5% to 10% of the starting population. The cost for OvoControl averages about $400 per month during the first year, about $200 per month the second year, and roughly $100 per month thereafter. Palo Verde Nuclear Generating Station (profiled in this issue as a Top Plant Award winner) initiated use of OvoControl in November 2010 with three feeders and experienced at least an 80% reduction in its pigeon population.
BirdBuffer offers another option. According to Jim Beaumont, national account manager for the company, BirdBuffer machines create small vapor particles from an oil-based fluid made up of 20% methyl anthranilate (MA). MA is an extract fluid—made from the skin of grapes—that has been used in bird control systems for more than 40 years.
MA causes an avian-specific pain sensation in a bird’s trigeminal nerve, located in their sub-mucous membrane. The pressure is in the center of their face and results in a mace- or pepper spray–like reaction. Humans experience a pleasant grape-scented fragrance, while birds experience a facial pressure, tearing of the eyes, and temporary pain, creating an immediate desire to leave the area.
The machine (Figure 5) distributes the vapor on a two-stage timing strategy that is designed to confuse birds and control the amount of fluid being used. The strategy trains birds to avoid areas. Birds cannot see the vapor or identify the source, but they sense pain when they fly through the target area. As they are trained to associate pain with the location, they learn to avoid the area. The process can take from three weeks to three months to gain control, depending on the type of bird and its history with the location.
|5. A machine for all seasons. The Q3 BirdBuffer model, shown here, can be installed outdoors, while the lower-priced TD model is designed for covered areas. Courtesy: BirdBuffer|
“Birds will never habituate or become accustomed to the vapor—it always works, unless a mother bird has a nest with eggs or fledglings,” Beaumont said. “Birds will suffer any pain to protect their young, just like us.”
Beaumont said maintenance could be done in about 15 minutes each month, which includes refilling the reservoir with about 1 gallon of fluid, changing filters, and wiping off any vapor blowback that may have collected on the machine. Utility companies that have used the BirdBuffer system include Pacific Gas & Electric (PG&E), NRG Energy, Nebraska Public Power District, and Lower Colorado River Authority. An all-weather machine costs $8,995, but BirdBuffer also offers a covered-area model for $5,495 and rental or leasing options. The fluid costs $175 per gallon.
Attack of the Blob
Scientists have been scratching their heads as to exactly why we periodically see sudden, rapid increases in the population, or “blooms,” of that ubiquitous ocean-dweller, the jellyfish. But they are certain that there might be a mechanism at work that involves warmer ocean temperatures and environmental changes. And for the power sector, that’s bad news, because when it happens—as it has dozens of times to power plants around the world that draw in ocean water for cooling systems—it can be expensive.
The squishy creatures have gummed up intake structures in the U.S., Canada, Scotland, Sweden, Japan, Australia, and France. In 2011, EDF Energy’s Torness nuclear power plant in Scotland was forced to shut down twice in one week because cooling waters were inundated with jellyfish. It cost the plant about $1.5 million a day in lost revenues. The same year, jellies caused similar issues at the Shimane nuclear plant in Japan and at Israel Electric Corp.’s Orot Rabin coal-fired plant on the Mediterranean coast.
It turns out that jellyfish blooms aren’t the only clogging sea creatures to worry about. Power plant operators also struggle to keep salps—small jellyfish-like creatures often seen as long gelatinous chains—at bay. In 2012, PG&E had to temporarily shut down Unit 2 of the Diablo Canyon nuclear plant in California (Unit 1 was already offline for refueling at the time) after salps rapidly clogged intake screens, even though the screens roll in a circular fashion to allow them to be cleaned.
Several solutions have been put forth worldwide to deal with the spineless swarms, but many have been unsuccessful. Experts conclude that relying on debris filters and safety protocols may be the soundest approach to the unpredictable problem.
South Korean researchers, meanwhile, have developed a robotic jellyfish exterminator that seeks out and then shreds up to 900 kg of jellyfish per hour. An innovative, less-grisly solution used at Diablo Canyon, and reportedly at the Ringhals Power Plant in Sweden, is a “bubble curtain.”
“When needed, a device underwater releases a sheet of bubbles in front of the intake structure. This curtain of bubbles helps displace the sea salps,” PG&E’s Blair Jones told POWER. The solution is actually recommended by the National Marine Fisheries Service as a safe and effective method to divert aquatic creatures away from underwater construction sites. (For more detail and a diagram of this sort of system, see “CWA 316(b) Update: Fish Guidance and Protection” in the October 2011 issue.)
Torness spokesperson Lindsey Ingram underscored how low the risk of a jellyfish-spawned shutdown is, but she added that plant water intakes at all of EDF’s nuclear plants are designed to deal with jellyfish issues safely. EDF is “exploring the use of equipment to improve resilience of the filtration system, for example, screen-washing facilities, design, measuring equipment, and visuals to monitor the performance of the equipment where needed,” she said.
Along with evaluating (in cooperation with external research groups) the drivers that lead to the increase in large jellyfish blooms, the company’s UK research and development team is modeling the cooling water intake area to show what happens under various conditions. That will help the company “predict when this phenomenon is more likely to happen and if it is likely to pose any risk to our sites. In this way additional measures can be implemented on site in order to safely mitigate any risks,” Ingram said. (For another sort of unwelcome bloom and examples of positive plant-animal interactions, see the sidebars.)
A Green Attack: Algae Blooms
Problems with cooling water intake systems can also be caused by marine grass and other aquatic life. Operators of reactors in the Great Lakes region, for example, are concerned with the proliferation of Cladophora, a taxonomic grouping that includes species of green algae. Fertilizer runoff was blamed for Cladophora blooms in the 1960s and 1970s, but blooms have reappeared recently, despite restrictions on phosphorus.
The resurgence of Cladophora has been particularly costly and cumbersome to operators of nuclear plants on Lake Ontario. In 2005, algae buildup clogged cooling water intakes and forced Ontario Power Generation (OPG) to temporarily shut down Units 5, 6, and 8 at Pickering B, and Unit 1 at the Darlington generating station was taken offline later that year for similar reasons. In 2007, an algae event prompted another shutdown at Pickering—and, later, of Entergy Corp.’s FitzPatrick nuclear plant in New York for nearly a week. OPG said that between 1995—when the algae began to clog water intakes—and 2005, the company lost C$30 million in revenue from those and related Cladophora events.
Beyond calling for more vigilance regarding how much phosphorus enters the lake from agricultural and wastewater runoff, OPG has installed—with mixed success—a vertical mesh barrier anchored to the lake bottom near the end of the water-intake canal to block the flow of the dense green mass.
Perhaps the most insidious of power plant pests are the fingernail-sized quagga (Figure 6) and zebra mussels. The invasive species originating from the Black and Caspian Sea region have caused millions of dollars in damage in the Great Lakes region, where they were discovered in 1988. Now, they are making their way through U.S. waterways. Their discovery at Lake Mead in 2007, and subsequent colonization of Lake Powell and parts of Central Arizona Project’s water-delivery system has put the U.S. Bureau of Reclamation (USBR), Salt River Project, and other Western power generators on high alert.
It’s because, as the USBR says, they can cause steep losses through increased operation and maintenance costs as well as interruption in water delivery and power generation functions. Depending on levels of infestation and facility operating conditions, mussel-related impacts stem from “fouling” (live mussel attachment) and “clogging” (due to fouling or release of mussel shell debris) that may occur in a number of water delivery and hydropower systems, says the USBR, which is part of the Department of the Interior and also the second-largest hydropower producer in the U.S. “This includes intakes and penstocks, gates and valves, bypasses and air vents, cooling water systems, raw water fire protection systems, service and domestic water systems, instrumentation, and drainage, and unwatering systems.”
The attention on this problem has been good. Many entities have been battling the critters using traditional chemical control options—aqueous application of chlorine, in particular—as well as physical removal and mechanical controls; however, they complain that these increase corrosion initiated by the invasive mussels. But new solutions are emerging. Marrone Bio Innovations in 2007, for instance, developed Zequanox, an environmentally compatible molluscicide that does not corrode equipment and does not require detoxification before water discharge. The newly commercialized product is based on research conducted by a consortium of New York State’s power generators and the State Field Research Laboratory in 1991, which found a naturally occurring, harmless North American strain of bacteria that is lethal to the mussels.
While Zequanox sounds promising, the USBR isn’t stopping there. It continues to research mussel-resistant coatings, UV light treatment for quagga mussel larvae, and new ways to detect mussels early.
The Insect Threat
Though minuscule, insects can’t be ruled out when it comes to making an impact on power plants. Carpenter ant and termite infestations can be a nightmare, and swarms of bees and wasps can pose dangers to operators. Even seasonal swarms can be devastating: In 1984, mayflies caused a power transformer to short out, disconnecting the La Crosse nuclear plant in Wisconsin from the grid.
In the Gulf Coast states, meanwhile, the Rasberry crazy ant—native to Brazil—has been causing alarm. The ants—named for their rapid, erratic movement—have a reputation for swarming into electrical equipment, chewing through insulation, and causing overheating, mechanical failures, and short circuits. Around Houston, they have plagued NASA and shut down units in at least three chemical plants (Figure 7). Tom Rasberry, an exterminator from Pearland, Texas, who first noticed them in 2002 and has since dedicated years to studying them, says they are spreading at an alarming rate.
Because they tend to wander in aimless movements instead of a straight trail, they are difficult to locate and treat. Exterminators recommend spraying nonrepellent insecticide such as Taurus SC or FUSE around infested perimeters, setting up ant baits, sealing all possible entry points, and trimming vegetation away from structures. ■
—Aaron Larson and Sonal Patel are POWER associate editors.