New Study Concludes Net Effect of Human-Made Reactive Nitrogen (Nr) is a Cooling Effect

     I have written on this blog about the global warming potential (GWP) of nitrogen oxides, including nitrous oxides (N2O) from fertilizer, and about the photochemical smog (ozone) precursor nitrogen oxide (NOx) gases. It has been recently shown via a paper in Nature by scientists from the Max Planck Institute for Biogeochemistry in Jena, Germany, that the fine suspended particles of reactive nitrogen compounds mostly from combustion, which are short-lived in the atmosphere, are the biggest contributor to a net cooling effect of anthropogenic reactive nitrogen by shielding sunlight as does gaseous ammonia (NH3), also emitted by the agriculture sector. These gases are forms of reactive nitrogen (Nr) that appear in the biosphere on land and in the atmosphere. Nitrogen gas (N2), is non-reactive, or inert but all other nitrogen compounds are reactive (Nr).

     The global nitrogen cycle includes the growing amounts of anthropogenic nitrogen oxide gases (NOx, N2O) and gaseous ammonia (NH3) being emitted into the atmosphere. The authors of the paper summarized the results in the abstract:

 

“This net cooling effect is the result of increased aerosol loading, reduced methane lifetime and increased terrestrial carbon sequestration associated with increases in anthropogenic Nr, which are not offset by the warming effects of enhanced atmospheric nitrous oxide and ozone. Future predictions using three representative scenarios show that this cooling effect may be weakened primarily as a result of reduced aerosol loading and increased lifetime of methane, whereas in particular N2O-induced warming will probably continue to increase under all scenarios. Our results indicate that future reductions in anthropogenic Nr to achieve environmental protection goals need to be accompanied by enhanced efforts to reduce anthropogenic greenhouse gas emissions to achieve climate change mitigation in line with the Paris Agreement.”

 

 

     Combustion of fossil fuels and application of fertilizers are the two biggest sources of Nr. The study involved modeling the chemical reactions in the land biosphere and atmosphere to arrive at a flow chart or Nr cycle. They utilized terrestrial biogeochemistry and atmospheric chemistry. The authors admit, however, that there is still considerable uncertainty in the calculations and potentially a high margin of error since net warming and cooling effects can vary considerably in different regions.    

     It is well known that NOx, N2O, and NH3 form aerosol particles in the atmosphere and that these aerosol particles block sunlight thereby decreasing solar radiative forcing. They also contribute to smog in the lower atmosphere that has a similar effect. N2O remains long in the atmosphere like CO2, while NOx and NH3 are short-lived in the atmosphere, more like methane. Thus, N2O has a net warming effect but the shorter-lived gases have a net cooling effect due to the aerosol particles. All of these factors are accounted for in the models. Nr gases also have different individual aerosol effects and affect one another in different ways. The paper gives the equations and reactions used as model assumptions in the study. Lest we forget, air pollution does indeed slow global warming, but only for a short time. This includes the considerable aerosols from burning coal and biomass. Thus, it should perhaps be pointed out that this study only considers Nr aerosols and not all aerosol particles which also include particulate matter and sulfur oxide and sulfate compounds. When the world finally moves away from coal after China’s and India’s consumption peaks and begins to drop, the amount of combustion aerosols in the atmosphere will drop as well. Better pollution abatement equipment on coal and wood power plants, especially, but also natural gas plants can decrease aerosol production as well.

 

 

References:

Net effects of man-made nitrogen attenuate global warming, researchers find. Eberhard Fritz. Phys.org. July 24, 2024. Net effects of man-made nitrogen attenuate global warming, researchers find (msn.com)

Global net climate effects of anthropogenic reactive nitrogen. Cheng Gong, Hanqin Tian, Hong Liao, Naiqing Pan, Shufen Pan, Akihiko Ito, Atul K. Jain, Sian Kou-Giesbrecht, Fortunat Joos, Qing Sun, Hao Shi, Nicolas Vuichard, Qing Zhu, Changhui Peng, Federico Maggi, Fiona H. M. Tang & Sönke Zaehle. Nature (2024). Global net climate effects of anthropogenic reactive nitrogen | Nature

 

Stormwater Management and Compliance: Issues, Data, Trends, and Updates

Stormwater Management

     Stormwater management is mostly but not always an urban issue where excess water runoff from storms can cause environmental damage and pollution. Good runoff management can include well-designed culvert and drain systems to keep runoff away from places where it can cause damage. Temporary water catchment systems can be utilized for construction. Storms can create pollution events via soil saturation, runoff, and flooding, which can collect and transport contaminants. Stormwater management involves several activities, including planning and measurement, monitoring and control, and pumping and treatment. “It includes infrastructure such as gutters, conduits and trenches, in addition to detention tanks, large and small pump stations and treatment plants.”

     Maureen Harris, P.E., Stormwater Team lead for AECOM noted in a LinkedIn post:

“A 2,000 square foot house with a 400 square foot driveway can generate up to 1,500 gallons of stormwater in a one-inch rainfall.”

     Most stormwater falls under the EPA’s National Pollutant Discharge Elimination System (NPDES) program under the Clean Water Act of 1972. 47 of the 50 U.S. states were given primacy by the EPA to regulate stormwater pollution. This means that different states may have slightly different regulations that companies that operate in multiple states must manage and integrate.

     Polluted stormwater runoff often makes its way through municipal storm sewer systems which commonly discharge without treatment into waterways. The nation’s municipalities must build, maintain, upgrade, and sometimes replace their stormwater infrastructure. EPA mentions watershed-based stormwater planning as a current need.

     Two major sources of stormwater are construction stormwater which makes up nearly half of all facilities regulated by EPA’s National Pollution Discharge Elimination System (NPDES), and industrial stormwater, which makes up almost a quarter.  

 

 

     Stormwater management is one way to reduce the occurrences and impacts of urban flooding events. Planning involves initiatives such as creating “sponge cities,” designed to reduce runoff by allowing more rainwater to infiltrate the soil below. According to Xylem’s Complete Guide to Stormwater Management, sponge cities apply:

 

“… ecological principles, landscape architecture approaches and key techniques of infiltration, pumping, storage, purification, utilization and discharge. These techniques are applied through best management practices (BMPs) and green stormwater infrastructures (GSI) with low impact, as decided by each municipality.”

 

     Storms can cause combined sewer overflows (CSOs) which overwhelm the local sewer systems. Combined sewers have been discouraged since the 1950s but older systems remain in use. This can result in raw sewage being released into the environment along with contaminants from stormwater runoff. In these cases, disinfecting stormwater runoff can be desirable if feasible. Chlorine may be used. According to Xylem, ozone and UV treatment are among the most efficient disinfection methods for water and better than traditional chlorine-based methods. They do not form disinfection by-products (DBPs) as chlorine does.

     Stormwater runoff flow can be modeled with the goal of optimizing its management. Overflow mitigation is one of the most serious issues to address. For cities, stormwater pump station design can be a big factor in preventing overflows and pollution events. The following graphics depict some of the hydraulics and sedimentation issues facing urban stormwater pumping systems. There are several pump sizes and designs that may be used for these pumping systems. Debris management is very important as well. This often involves screens of different sizes and in different places in the system. Sand management is important as well, since sand is abrasive and can damage pumps. Two ways of dealing with sand in stormwater sewers are pumping it away and sand traps. If the stormwater is pumped to a treatment plant that can deal with solids, then pumping it there is usually the best method. If not, then sand traps can be used to collect the sand. Pumping the sand to the treatment plant involves keeping flow rates high enough to keep the sand in suspension. Trapping involves lowering the flow rate below a settling velocity for the sand particles. After the sand is trapped it may be pumped off to a discharge area or it may be cleaned out manually. Pumping effluent with solids and sludge is more difficult and maintenance-intensive than pumping clear water. Detention systems such as underground infiltration tanks are often utilized in these urban runoff systems. Boring new larger and deeper tunnels to collect stormwater is a management solution as well, as shown below.

 

     There are several strategies for cleaning these detention tanks: manual cleaning, tipping buckets, flushing, bulk flow and flushing with submersible mixers, and ejectors of several types. These are shown and described below from Xylem’s Complete Guide to Stormwater Management. What methods are used for transporting and cleaning depend on the sediment and solids encountered in that specific local environment.

 

     Stormwater management grades into flood management as these pumping systems may also be designed to lower the impacts of flooding events.

     Stormwater management benefits from stormwater monitoring. According to Xylem’s guide:

 

“Stormwater monitoring sites encompass a broad range of parameters from simple rainfall and turbidity measurements, typically encountered during construction practices, to complex multiparameter sites including open channel flow, level, rainfall, pH, temperature, conductivity, dissolved oxygen, turbidity, and even nutrients.”

 

     Groundwater management is another aspect of stormwater management. Drainage and pumping systems can help as well with groundwater management.

 

     Roadside or highway drainage is another important stormwater management strategy as is airport drainage.

 

     Retention ponds are another strategy. These include wet retention ponds, dry detention ponds, and polder pumping stations, all shown below.

 

 

     Rain storage systems might be an option for some applications. The Rainstore3 systems “are described:

 

“… as a modular, stackable, underground water containment system. This innovative solution was designed by a landscape architect for subsurface detention basins, retention/harvesting systems, water/rain gardens, green roofs, and sports field drainage.”

 

   

 

Construction Stormwater Management

 

     Sediment, debris, and chemicals in the loose soils of construction sites are picked up by runoff water and conveyed to sewer systems, streams, rivers, lakes, or coastal waters. Construction operators are required to install stormwater controls onsite. Sediment, solid and sanitary wastes, phosphorus, nitrogen, pesticides, oil and grease, concrete truck washout, construction chemicals, and construction debris are pollutants common at construction sites. Sediment is the biggest component of stormwater pollution. Concrete waste, chemicals and paints, oils and grease, and anything spilled onsite are other components. Sediment can collect in water bodies, reducing their depth and may lead to a need for dredging. According to EPA:

 

“A Clean Water Act permit is required for stormwater discharges from any construction activity disturbing:

 

“1 acre or more of land, or

 

“Less than 1 acre of land, but that is part of a common plan of development or sale that will ultimately disturb 1 or more acres of land.”

 

“Construction activity includes earth-disturbing activities such as clearing, grading, and excavating land and other construction-related activities that could generate pollutants.”

 

The permit requirements for construction and development. Known as C & D permits are as follows:

 

1)        Design, install, and maintain effective erosion and sediment controls, and pollution prevention measures, to minimize the discharge of pollutants;

2)        Stabilize disturbed areas immediately when construction has  ceased and will not resume for more than 14 days;

3)        Prohibit the dewatering discharges unless managed by appropriate controls;

4)        Prohibit the discharge of:

A)       Wastewater from concrete washout (unless managed by appropriate control), or washout/cleanout of stucco, paint, form release oils, other wastewater materials;

B)       Fuels, oils, or other pollutants used for vehicles; and

C)      Soaps or solvents to wash vehicles and equipment.

 

 

 

Erosion and Sediment Control

 

     Erosion and sediment control (ESC) is very important at construction sites and stormwater management is key to that control. In Pennsylvania, timber harvesting and road maintenance activities involving 25 or more acres of earth disturbance require an erosion and sediment control permit instead of NPDES permits. Oil and gas activities in the state that disturb more than 5 scres require a general erosion and sediment control permit. Measures are required to minimize erosion and sedimentation such as physical barriers to slow erosion caused by runoff. Local regulatory authorities may also have ESC requirements. EPA recommends that construction managers monitor weather and have ESC contingency plans and are aware of issues and conduct inspections before and after rainy weather events. EPA notes:

“At large sites, the developers may hire a firm with ESC expertise to implement an inspection, maintenance and repair program for the site. Some permitting authorities require construction sites to undergo inspection by a certified inspector and/or offer inspector certification programs.”

     A stormwater pollution prevention plan (SWPPP) is common, including ESC maintenance. This may involve “removing sediment before it accumulates to half of the above-ground height of any silt fence or other perimeter control.” Some permits require site ESC inspections weekly or every two weeks and must be well documented. This is required for EPA audits which basically ensure compliance. Those construction workers responsible for site ESC should be adequately trained. Microsoft Copilot with data from EPA, safetyculture.com, and others lists the following common ESC measures:

1)        Silt Fences: These are temporary barriers made of geotextile fabric that help to trap sediment while allowing water to flow through.

2)        Sediment Basins: These are designed to capture and store sediment-laden runoff, allowing the sediment to settle before the water is discharged.

3)        Mulching: Applying a layer of mulch to exposed soil helps to protect it from erosion by wind and water.

4)        Seeding and Planting: Establishing vegetation on disturbed soil can stabilize the soil and reduce erosion.

5)        Erosion Control Blankets: These are mats made of natural or synthetic materials that cover the soil and protect it from erosion.

6)        Check Dams: Small barriers placed in drainage channels to slow down water flow and capture sediment.

7)        Diversion Channels: These channels redirect water away from disturbed areas to prevent erosion.

 

     Some firms specialize in stormwater management. They contract with construction developers to handle stormwater compliance issues. They may do planning, permitting, inspection scheduling, inspections, monitoring, and installation oversight. Both site compliance and overall corporate risk management are focuses of these efforts. Corporations may see good stormwater management as an important part of their environmental compliance and sustainability programs. Strategies for managing stormwater compliance include inspections, visual assessments, analytical testing, and planning.

 

 Agricultural Runoff

   Agriculture is another source of stormwater runoff, especially when crops are not planted on a plot during off-seasons. Exposed soil during any season supports more runoff. Solutions range from cover cropping to sediment catchment strategies and drainage. Many of the ESC measures listed above are used to control agricultural runoff as well. The goal is to keep excess sediment out of streams, rivers, lakes, and wetlands. Agricultural runoff also carries fertilizer into waterways which can lead to harmful algae blooms.

 

 

Industrial Stormwater Management

     Parts of industrial activity that are exposed to weather are covered under NPDES industrial stormwater rules. Covered facilities include heavy manufacturing (including paper mills, chemical plants, steel mills, refineries, and foundries); coal and mineral mining and oil & gas processing; hazardous waste treatment, storage, and disposal; landfills and dumps; scrapyards, salvage yards, automobile junkyards, and battery reclamation facilities; steam electric power plants; transportation facilities that have vehicle maintenance, equipment cleaning, or airport deicing operations; sewage treatment plants with a design flow greater than 1 million gal/day; and constructions sites that disturb five acres or more (require a separate permit).

     A current issue of industrial stormwater pollution is with waters adjacent to large coal ash slurry ponds stored at coal-fired power plants. These have been shown to pollute local waterways with high levels of toxic heavy metals. They also have been shown to very often pollute local groundwater aquifers. Regulation is being ratcheted up as I explain in my post about coal ash cleanup.

    

 

Better Filtration for Storm Drains: Can it Reduce Surface Water Pollution?

      As mentioned, an important component of stormwater management systems is screening or filtration. Filters must be cleaned out regularly, often with vacuum trucks, which is expensive. A Florida company believes they have a useful solution. They are installing 50 drainage filters that utilize an "upper flow of water through the screen, which will allow it to continue to flow even as debris is collected,” according to an article in The Cool Down. The goal is to maximize water flow through while trapping debris such as plastics, leaves, and twigs. Their filters even include a QR code that community members can use to report clogs. The effort is focused on cleaning up pollution that makes its way into Biscayne Bay, which is considered quite polluted. The excess debris can also lead to localized excess nitrogen and phosphorus that can lead to algae blooms and some deoxygenation. The company has several videos on their website that model stormwater flow and filtration. The filters use Eddie Lopez patented technologies.

 

Testing Eddie Lopez Technologies' patented curb drainage filters - YouTube

I think that one of the amazing things the video shows is that these filters are very difficult to clog. This is a result of the upward flow of water through the openings. 

References:

Stormwater Management. Sara Meyer. ERM. August 2023. (24) Post | Feed | LinkedIn

Company develops high-tech solution to prevent major waterways from getting polluted: 'It's way easier'. Rick Kazmer. The Cool Down. May 5, 2024. Company develops high-tech solution to prevent major waterways from getting polluted: 'It's way easier' (msn.com)

Autodesk InfoWorks ICM: Plan, design, and operate stormwater, sanitary sewer, and flood infrastructure. Autodesk. Autodesk InfoWorks ICM | Get Prices & Buy Official InfoWorks ICM 2025 | Autodesk

Rainstore3: A Better Way to Contain the Rain. Invisible Structures. Rainstore3: Efficient Underground Water Containment System (invisiblestructures.com)

What is Stormwater Management? | The Basics | Part 1. Tully Consulting Group. Youtube Video. Bing Videos

The Complete Guide to Stormwater Management. stormwater-handbook-us_interactive.pdf (xylem.com)

National Pollutant Discharge Elimination System (NPDES). National Menu of Best Management Practices (BMPs) for Stormwater. U.S. EPA. National Menu of Best Management Practices (BMPs) for Stormwater | US EPA

National Pollutant Discharge Elimination System (NPDES). Stormwater Maintenance. U.S. EPA. Stormwater Maintenance | US EPA

Stormwater Management. U.S.EPA. Stormwater Management | US EPA

National Pollutant Discharge Elimination System (NPDES): Stormwater Discharges from Construction Activities. U.S. EPA. Stormwater Discharges from Construction Activities | US EPA

National Pollutant Discharge Elimination System (NPDES): Stormwater Discharges from Industrial Activities. U.S. EPA. Stormwater Discharges from Industrial Activities | US EPA

Construction Stormwater. Pennsylvania Department of Protection. Construction Stormwater (pa.gov)

Stormwater Best Management Practice: Erosion and Sediment Control Inspection and Maintenance. U.S. EPA. November 2021. Erosion and Sediment Control Inspection and Maintenance (epa.gov)

Ohio helping farmers keep water sources clean. WCMH Columbus. July 30, 2024. Ohio helping farmers keep water sources clean (msn.com)

How do we help contractors? | The Basics | Part 2. Tully Consulting Group. Youtube. How do we help contractors? | The Basics | Part 2 (youtube.com)

National Pollutant Discharge Elimination System (NPDES). Municipal Wastewater. U.S. EPA. Municipal Wastewater | US EPA

Stop Ocean Pollution Technologies. Website. Stormwater drainage inlet filters / screens — SOP Technologies - Environmental Solutions (soptechint.com)

Testing Eddie Lopez Technologies' patented curb drainage filters. Stop Ocean Pollution Technologies.  Testing Eddie Lopez Technologies' patented curb drainage filters (youtube.com)

 

Fish-Safe Hydropower Turbines: Another Important Example of Needed Wildlife Protection

 

     Reducing harm to wildlife or applying a wildlife impact criterion to assess harm and inform policy, is a worthwhile goal. Impact on biological species is a subset of environmental impact. Many human engineering and energy endeavors impact wildlife. Wind turbines kill migrating birds and raptors. Boats, underground blasts, and seismic air guns impact ocean life. Dams impact wildlife. Mining and oil & gas development can fragment forests, impacting species and habitats. Light pollution in urban areas impacts wildlife.

     I read about painting wind turbines black or with black stripes as a deterrent to birds that will prevent many deaths. I am not sure if this is being adopted (perhaps another post). The subject for this post is the development of fish-safe hydropower turbines. Harmful impacts of hydroelectric turbines on fish have long been known and there have long been strategies to lower impact.

     Hydropower is still by far the leading source of renewable electricity, producing more power than all other renewables combined in 2022, according to a July 2024 MIT Technology Review article. Hydropower is expected to have small growth or remain flat in many countries where it is nearly fully developed but in less-developed countries, there will be more hydropower plants built.

     Most dams were built many decades ago. According to the IEA, the average age of a hydropower plant in the U.S. is 65 years. Some are much older. When these were built, much less was known about environmental impacts and effects on fish. The fact is that many fish and other aquatic creatures are killed by hydropower turbines through direct hits or water pressure changes near dams with larger drops. As early as 1890, there were regulations on dams requiring infrastructure to allow fish to pass through. As well as harming fish through turbine strikes the dams prevent migrating fish from migrating and fragment their habitats. Fish can migrate upstream and downstream, and both are affected. Many of these hydro plants are coming up on their 50-year relicensing requirements which may include improving fish/wildlife safety. Hydropower relicensing, it has been argued in the past, has become cumbersome, expensive, and slow. While I agree it should be streamlined, there should be more focus on modernizing the old plants, and that could include making them safer for fish. The issue is not unlike requiring pollution abatement at coal-fired power plants. Perhaps a fish death abatement credit trading system could be developed similar to pollution credits. Of course, I don’t know the feasibility or plausibility of that. Around 17GW of hydropower facilities will be up for relicensing by 2035.

Fig. 7. Histogram showing the year in which a license will expire from a sample of 1038 FERC licensed hydropower projects across the United States.

 

 

 

Development of Guidance Systems to Allow Fish to Safely Bypass the Turbine Zone

 

     The EU project “FIThydro”, involved the research and industry partners studying the ecological impact of hydroelectric plants. Based on that research ETH Zurich’s Laboratory of Hydraulics, Hydrology and Glaciology (VAW) developed a protection and guidance system to migratory fish to safely bypass hydropower turbines. A model of that system is shown below.

 

  

      Fish migrate both downstream and upstream. Strategies like lift gates, basically elevators, are used to convey fish upstream. As the picture shows the fish are moving upstream. Those fish can’t pass through the turbine chamber so they must be accommodated with some type of conveyance system. Regarding downstream conveyance, the researchers noted:

 

“When descending over weirs, they can also be injured by the strong currents in the stilling basin or lose their orientation, making them easy prey for predators.”

 

      Predators include birds, which predate lots of juvenile fish at dams. Predation of disoriented juveniles may represent the largest number of fish kills at dams. Down the road from me here in Ohio there is a long-abandoned water mill in a very small river where the water level drops about 3 feet maybe, and I often see a grey heron there fishing the low side. The FITHydro researchers studied how different species of fish and eels pass along the guidance system. Based on that research they developed their curved-bar rack bypass system (CBR-BS), which is shown above.

 

“The core of the CBR-BS is a vertical bar rack with specially shaped bars; these create strong local eddies that steer fish away from the bar rack and towards a bypass. In this way, the CBR-BS is able to guide a variety of fish species of different sizes safely past the turbine. The bypass system is also designed so that the plant's operations are only slightly affected.”

 

     The researchers created a barotrauma detection system to detect and monitor dangerous changes in water pressure. It utilized sensors that are sent through or over the dams and retrieved. They also developed a bedload monitoring system (BMS) which enables qualitative and quantitative assessment of bedload transport in watercourses. This is a passive acoustic system that utilizes geophones and accelerometers.

 

     Solutions for protecting fish include fish ladders/spillways, installing screens, or lowering turbine blade speed. Fish ladders and other spillways have to divert some of the water so less can be used to power the turbine. They are like fish weirs that gather the fish. Screens can be very expensive to install and maintain, and lowering turbine speed can make power generation uneconomical. Thus, finding a means to allow fish to pass through the turbine chamber unharmed is a desirable problem to solve.

     Another strategy is to lower turbine speeds and runtime during fish migration seasons. Some dams shut down at night to allow eels to pass through. Changing operating parameters like this is always an option but also is weighed against economics. Trap and Haul is another strategy used more in the past. That is to use weirs to collect and trap the fish and transfer them to specialized tankers or barges that release the fish on the other side.

 

 

 

Fish Ladders and Spillways

 

     Fish ladders are a type of spillway that allows fish to pass around dams, avoiding the turbine. There are several kinds of them. Some use siphoning to guide the fish. Others use compressed air to guide them. Many use step downs to account for drop. There are quite a few designs. They have been around for centuries. They are often used for fish that swim upstream to spawn like salmon and trout. They can allow many species through at high rates, but other species can have much lower rates of passage. Dams commonly install screens to keep larger fish away from the danger zone near the turbines. “Leaves and debris can block these screens and reduce flow without constant maintenance. They also add about $1,000/kW in capital costs.”

 

     An informative video from Practical Engineering, How Fish Survive Hydro Turbines, shows how fish passage is managed at McNary Dam on the Columbia River which hosts a 1GW hydro plant. Splashing water is used to attract fish toward safe passage. Baffles, weirs, lift gates, screens, brushes to clean the screens, and step-down sections in the guidance systems help safe passage. An upstream guidance system also assists upstream migration. McNary Dam has ways to speed and slow the water currents and guide the fish in such a way as they get less disoriented and are less amenable to predatory birds. At McNary the small percentage of fish that pass through the turbine chamber are more endangered by changing water pressure than turbine strikes. This affects the swim bladders of fish that they use for buoyancy. The video also shows some interesting ways fish passage is studied in the lab and onsite at dams.

 

 

How Fish Survive Hydro Turbines | Watch (msn.com)

New Turbine Designs That Allow Safe Pass-Through of Fish

 

   These new fish-safe turbine designs are used for fish migrating downstream. Pass-around designs are still needed for upstream migration. Many older dams do not have fish bypass facilities. Adding a fish-safe turbine to these would still be beneficial. Natel Energy’s turbines, which are described below, have blunt leading edges and the turbine blades are curved to complement the curve of fish spines. The result, according to Natel, is safe passage for 98-100% of fish smaller than 20cm in length.

 

 

Natel Energy’s New Fish-Safe Turbine Designs

 

     Natel Energy was founded by two siblings, a brother and sister who are both MIT alumni. The MIT Technology Review article explains Natel’s new turbine designs through one of its cofounders:

 

“The company started with two big goals: high performance and fish survival, says Gia Schneider, Natel’s cofounder and chief commercial officer.”

 

“The company is making new designs for the turbines that generate electricity in hydropower plants as water rushes through equipment and moves their blades. Conventional turbine blades can move as fast as 30 meters per second, or about 60 to 70 miles per hour, Schneider says. When straight, thin edges are moving that quickly and striking fish, “it’s fairly obvious why that’s not a good outcome,” she says.”

 

“Natel’s turbine design focuses on preventing fast-moving equipment from making fatal contact with fish. The blades have a thicker leading edge that pushes water out in front of it, creating a stagnation zone, or “basically an airbag for fish,” Schneider says. The blades are also curved, so even if fish are struck, they don’t take a direct hit.”

    

     Natel started out designing Pelton Wheel Turbines, a kind of impulse turbine that extracts energy from the impulse of moving water instead of the weight of the water. These have been around since the 1870’s. When designing turbines for small river hydro projects they discovered that thicker turbine blades that were curved to match fish spine curves resulted in few to no deaths. The ratio of turbine blade thickness to the length of the fish is considered in the design. The blades are also slanted forward which results in glancing blows rather than direct blows. The design does require the turbine speed to be slowed to 7 to 10 m/sec but that is up to double the speed of 5 m/sec required for fish safety of conventional turbines. Turbines that run at lower speeds have less issues with cavitation, which is when high-speed bubbles make pits in the metal turbine blades. Natel used Alden Labs to study their turbine’s effects on passing fish. According to an article quoting the founders:

 

“You can expect 100 percent mortality for fish 20 centimeters long if struck by the leading edge of a rotating blade 10 millimeters thick,” Schneider said. That is the size of the blades for the conventional compact 1-MW turbines found on dams with 5 to 7 meters of head.”

 

“The expense of keeping out fish is high as it stalls or stops many small hydro projects since the solutions are so expensive. It is enough of a problem that the Electric Power Research Institute commissioned Alden Labs, a fluid engineering firm, {to} study the problem.”

 

“They found that fish do not notice spinning turbines. Once in them, the turbine accelerates the fish. When the thin turbine blades strike them, they break the fish’s spines.”

 

“Initial data showed that at 5 m head, 100 percent of 20 cm fish passed safely through the turbine. At 10 m head, 98 percent went safely through. That is close to Natel’s design goals and roughly as good as a fish spillway.”

 

     Natel also designs bypasses that attempt to optimize the natural features of rivers. This also allows for the passage of river sediment, something that dams can prevent that could even lead to coastal erosion downstream. As shown below, these designs mimic natural features like log jams, beaver dams, and rock arches.

     Thus far, Natel has installed two versions of its latest turbine, the Restoration Hydro Turbine, at existing plants in Maine and Oregon. By the end of this year, two more will be deployed, including one in Europe, a key market due to stronger hydropower regulation. The two installed turbines have been found to convert more than 90% of available water energy to power the turbine, which is comparable to conventional hydro turbines. The company estimates that 30GW of hydro capacity in Europe and the U.S. could be retrofitted with their turbines and that their turbines can avoid shutdowns and retirements at relicensing time. They also hope to build new plants on existing non-powered dams, noting that only 3% of the 80, 000 U.S. dams are powered. They estimate that this could result in up to 48GW of new hydropower in the U.S. and Europe. I include links to some of the testing and validation results in published papers in the references. 

 

 

 

Andritz’s Pass Through Fish-Safe Turbine Designs

 

     Another hydropower supply company that designs fish-safe turbines is Andritz. Some of their turbine designs, simulations, and mortality analysis are shown below.

 

 

     

     Regarding the study at the Xayaburi hydropower plant in Asia, shown above as the example of a fish ladder, the company noted:

 

“By implementing these technologies and developments, a 90% survival rate of the fish passing through a turbine can be ensured. It should also be noted that only about 20% of all migrating fish are affected by the turbine, since the majority of the fish population are protected by other measures, such as fish ladders and bypass passages.”

 

That is pretty good but Natel’s 98-100% is better. However, I am not aware of the details like turbine speeds and dam heights that would make comparisons equal.  

 

 

Other Fish-Safe Turbine Designs

 

     The DOE’s Office of Energy Efficiency and Renewable Energy notes two other turbine designs that achieved a 98% survival rate for fish passing through the turbine chamber. One the Army Corps of Engineers’ Ice Harbor Dam on the Snake River, which was installed in 2016. Another is the Alden Fish-Friendly Turbine which produced similar survival rates. Research is ongoing for fish pass-through and pass-around systems. Sensors are used to tag and track fish movement and to monitor the effects on different species.

 

 

 

References:

Company makes revolutionary development in hydropower with 'fish-safe turbines': 'Basically an airbag for fish'. Susan Elizabeth Turek. The Cool Down. July 23, 2024. Company makes revolutionary development in hydropower with 'fish-safe turbines': 'Basically an airbag for fish' (msn.com)

How fish-safe hydropower technology could keep more renewables on the grid. Casey Crownhart. MIT Technology Review. July 1, 2024. How fish-safe hydropower technology could keep more renewables on the grid | MIT Technology Review

How Do Fish Survive Hydropower Dams? U.S. Department of Energy. Office of Energy Efficiency & Renewable Energy. April 29, 2024. How Do Fish Survive Hydropower Dams? | Department of Energy

A path to fish-friendly hydropower. Yoana Cholteeva. Power Technology. January 25, 2021. A path to fish-friendly hydropower - Power Technology (power-technology.com)

Hydropower making sustainability gains with fish-safe turbines. Guest Contributor. Power Engineering International. November 16, 2023. Hydropower making sustainability gains with fish-safe turbines - Power Engineering International

Natel Energy: Making Hydropower Plants More Fish-Friendly and Sustainable. Zach Winn, MIT. Sci Tech Daily.  August 5, 2022. Natel Energy: Making Hydropower Plants More Fish-Friendly and Sustainable (scitechdaily.com)

Protecting fish and livelihoods: Fish-friendly assessment in practice. Andritz. Protecting fish and livelihoods - Fish-friendly assessment in practice (andritz.com)

Towards more fish-friendly hydropower plants. ETH Zurich. February 2021. Towards more fish-friendly hydropower plants | ETH Zurich

Estimated capital costs of fish exclusion technologies for hydropower facilities. Paul G. Matson, Kevin M. Stewart, Gbadebo A. Oladosu, Emrat Nur Marzan, and Scott T. DeNeale. Journal of Environmental Management. Volume 351, February 2024, 119800. Estimated capital costs of fish exclusion technologies for hydropower facilities - ScienceDirect

Design and validation of fishsafe hydro turbines for retrofit andnew-build applications. A.D. Schneider and S.M. Watson, Natel Energy, USA. International Journal on Hydropower and Dams. Issue 5. presented at the HYDRO 2023 conference in Edinburgh (October 2023). Layout 1 (website-files.com)

Improving survival: injury and mortality of fish struck by blades with slanted, blunt leading edges. Stephen V. Amaral, Sterling M. Watson, Abraham D. Schneider, Jenna Rackovan, and Andrew Baumgartner. Journal of Ecohydraulics. Volume 5, 2020. Pages 175-183. June 16, 2020. Full article: Improving survival: injury and mortality of fish struck by blades with slanted, blunt leading edges (tandfonline.com)

Fish-Safe Turbines Empower Small-Dam Hydro Projects. Alan Brown. The American Society of Mechanical Engineers. August 20, 2019. Fish-Safe Turbines Empower Small-Dam Hydro Projects - ASME

Pelton wheel. Wikipedia. Pelton wheel - Wikipedia

Innovative technologies from FIThydro. FIThydrowiki. Innovative technologies from FIThydro - FIThydrowiki

Bedload monitoring system. FIThydrowiki. Bedload monitoring system - FIThydrowiki