HydroVision International is the largest gathering of hydro professionals worldwide. Over 3,000 hydro professionals and over 300 hydro related product and service providers were on the exhibit floor. The participants are from 51 countries. The event highlights perspectives on the role of hydropower, explores issues affecting the hydropower industry, covers issues and concerns affecting hydro resources, publicizes current market opportunities and challenges, and facilitates development of a vision to meet challenges and to ensure sustainable development.
Alden is active in supporting the hydro industry, with physical hydraulic modeling, 3D and 2D numeric modeling, fish passage design and testing. We attend Hydrovision every year, and participate in the exhibit, as well as technical conference and training sessions.
I was able to meet with most of our dams and hydro clients and teaming partners. The attendance from the private power producers, utilities, consulting companies and equipment manufacturers were adequate but there was clearly less participation from the federal government, especially from the U.S. Army Corps of Engineers (USACE). I observed increased energy and optimism in developing renewable and small hydro with a hope of relaxed regulation and a faster FERC approval process. That being said, folks seemed to think the price of natural gas will remain low in the foreseeable future and the development of hydro assets may remain relatively less competitive in general. Overall, the need for hydraulic, environmental, and fisheries work appears steady, nonetheless.
The spillway failure at the Oroville Dam impacted the dam owners and hydro industry, overall. Most dam owners are concerned and are taking steps to ensure their dams are safe, irrespective of regulatory requirements. Clearly, the need for support in the area of dam safety will remain strong.
Here a few highlights of the conference I can share:
Attendees at the 2017 Alden Forum on Hydropower and Fish Passage
Based on presentations given by the various speakers, the primary takeaways from the forum include the following:
Cake consumed during a break at the 2017 Alden Forum, showing companies and agencies in attendance
The format and content of the forum was highly rated by the attendees and led to many in-depth and productive discussions. The setting appeared to be more conducive to open dialogue among all of the participants compared to typical relicensing meetings and agency consultations.
Planning for additional forums addressing other relevant topic areas related to fish passage and other environmental issues is underway by Alden staff, and may include hosting events in other regions of the U.S.
Testing of Flood Control America’s One World Trade Center flood protection barrier at Alden
During the first week in May, I attended the Association of State Floodplain Managers (ASFPM) Conference in Kansas City. This conference is generally recognized as the key floodplain conference in the U.S. In addition to floodplain managers, associated consulting firms and product vendors regularly attend.
We thought it would be a good idea to go, given Alden’s recent activity in flooding related testing and modeling. Given the nature of my interest, I primarily attended sessions on floodproofing and modeling, and also spent time in the exhibit. The sessions were well attended and had good quality presentations.
For me, the key takeaways from the conference were:
We welcome your comments on flood proofing, flood protection, and modeling.
Mixing between fluids of different properties goes on all around us every day (e.g., think of stirring milk into your coffee or smoke billowing from a chimney). In many flows of engineering relevance, velocity differences between fluid bodies generate turbulent motions that, in turn, greatly enhance the mixing process; small-scale chaotic eddies that characterize the turbulence are much more effective than molecular diffusion at mixing fluid properties such as momentum, heat, salinity, sediment load, or pollution concentration.
When fluid bodies are of different densities the effects of gravity weigh heavily on the turbulent mixing process (pun intended). For example, when warm air escapes from a chimney it accelerates upward in a turbulent billow because it is lighter (less dense) than the cooler air around it, and gravity acts to drive turbulence through buoyant convection. On the other hand, in a stably-stratified lake, gravity acts to suppress turbulence at the thermocline where lighter, warm water overlies heavier cold water.
The signatures of turbulent mixing in stratified flows are perhaps most obvious in the sky above us. Clouds provide a convenient flow visualization method! An anvil-shaped thunder head reveals convectively-generated turbulence in an unstably-stratified environment, whereas rolling billows – think of the sky in van Gogh’s Starry Night – indicate shear-generated turbulence in a stably-stratified environment. A great example of the latter type of cloud was recently observed outside Alden's Fort Collins office (Figure 1).
Figure 1: Lenticular cloud bands forming at the crests of atmospheric gravity waves in the lee of the Rocky Mountain Front Range (flow is toward camera).
The two parallel cloud bands seen in the photograph are occurring at the crests of atmospheric waves that are occurring in the lee of Colorado’s Front Range Mountains (wind is coming toward you in the picture). Flow over the mountains disturbs the stably-stratified atmosphere and generates a train of gravity waves similar to surface waves in a ship's wake. Low pressure at the wave crests causes water vapor to condense and form the "lenticular" cloud bands you see in the picture. Air is actually moving through the clouds rather than the clouds moving with the air! A good cross-section schematic of mountain lee waves is show in Figure 2 from Durran (2013).
Figure 2: Schematic of mountain lee waves and lenticular clouds (from Durran, 2013). Flow is from left to right.
While the lee waves themselves are not breaking into turbulence, it appears that a crosswind acting perpendicular to the main flow is doing something interesting to the cloud bands. See those curling billows in the photograph (close up picture in Figure 3)? Those are caused by shear between the lighter air above the cloud and the heavier air below. The fancy name for these shear-driven billows is Kelvin Helmholtz instabilities. "K-H" instabilities can be observed in many natural flows with density stratification and are common in thermally-stratified flows of oceans, lakes, and rivers. As the billows roll up, they lift heavy fluid up and push light fluid down – working against gravity. Eventually, the coherent billows collapse into smaller-scale, chaotic, turbulent motions that mix the two fluid bodies.
Figure 3: Zoomed photograph of Kelvin Helmholtz instabilities due to shear generated by a cross wind.
The computational fluid dynamics (CFD) models used at Alden can capture K-H instabilities as demonstrated in Figure 4 which shows a snapshot from a simple two-dimensional simulation of warm, lighter water (red) moving across cold heavy water (blue). In many cases of engineering relevance, however, domain size and complexity often preclude the resolution needed to explicitly model the flow structures such as K-H billows that ultimately drive mixing. Instead, numerical models rely on assumptions about what’s going on at the unresolved scales of the turbulence. These assumptions form the basis for turbulence models that approximate the mixing process.
Figure 4: Kelvin Helmholtz instabilities occurring on a density and shear interface between warm water (red) and cold water (blue) as captured in a highly-resolved (Δx = 0.50 cm) two-dimensional simulation. Each billow is approximately 10 cm tall.
Because no model is perfect, keys to a successful modeling effort include calibration and validation. A promising approach to calibration and validation using field data comes in the form of airborne thermal imaging. Alden is currently developing a drone-mounted infrared camera system that will provide overhead snapshots of mixing of water bodies of different temperatures – an application of focus being thermal plumes discharged from power plants. IR images taken recently from a power plant discharging cooling water into a major river are shown in Figure 5. IR imagery provides a valuable check on the lateral mixing predicted by a given CFD model and serves as yet another tool in Alden’s arsenal for understanding and solving mixing-related problems.
Figure 5: Aerial infrared image taken by Alden of a thermal plume discharged from a power plant on a major river.
Flow is from top to bottom of the image. Note the complex structure of the mixing/shear line and dilution of the plume in the downstream direction.
Durran, D.R. (2013, Jan. 29) Trapped lee waves over the western U.S. http://www.youtube.com/watch?v=P84WoxbDXCg.
The 26th Annual NUPIC Vendor Meeting was held June 21st and 22nd at the Hilton Riverside New Orleans and hosted by Entergy. This was Alden’s 4th time attending the event (see last year’s blog post for more information about the NUPIC organization). The meeting is an important opportunity for utility auditors and representatives to meet with suppliers outside of a NUPIC audit. As Oscar Limpias, the VP of Nuclear Oversight at Entergy noted in his keynote address, “vendor performance and the partnership between vendors and utilities is critical to the future of nuclear generation”.
A variety of topics were presented, including decommissioning, new plant construction, small modular reactors, equipment reliability, commercial grade dedication (CGD) and the revised CGD guidance, cyber-security considerations for suppliers, counterfeit items and delivering the nuclear promise. Copies of the presentations can be found on the NUPIC site (https://nupic.com/NUPIC/Home/HotTopics.aspx).
A common theme throughout the two days was the current state of nuclear power and its future. While NUPIC, itself, saves each utility an estimated $1 million per year, there are more opportunities to reduce cost in relation to NUPIC and vendor interfacing. The average cost for generating nuclear power in 2016 was $34 per MWh (down from a peak of $40 per MWh in 2012). Of this price, approximately $6 is the cost of fuel and $28 is the people and support systems. In order for nuclear to remain competitive with highly subsidized renewables and low-cost natural gas, the goal is to reduce the cost to $28 per MWh by 2020. This will be accomplished through the Delivering the Nuclear Promise initiative and the issued efficiency bulletins, which are the implementation of the initiative. All of the efficiency bulletins issued to date can be found on the NEI website (https://www.nei.org/Issues-Policy/Delivering-the-Nuclear-Promise/Efficiency-Bulletins). The four bulletins that currently relate to NUPIC and suppliers are EB 16-28a (Minimize NUPIC Vendor Audit Frequencies), EB 16-28b (Establish Common Finding/Deficiency Definitions Used During Vendor Audits), EB 16-29 (Optimize Strategic Sourcing to Deliver Savings), and EB 16-30 (Material Cost Reduction While Maintaining Quality). NUPIC is also considering additional savings possibilities such as graded scope audits, standardized purchase orders, reducing utility intervention in manufacturing and services and enhanced auditor training. (Refer to the presentations presented by Brian Mervak (NUPIC Chair, SCE&G) and David Kimball (Director of Nuclear Oversight at Cooper Nuclear Station) on Day 1 and Mark Mlachak (QA Manager, First Energy Nuclear Operating Company) and John Simmons (Consulting Nuclear Auditor, Luminant Power) on Day 2 for more information.)
The annual vendor dinner and social is always a highlight of the meeting. This year it was a dinner cruise aboard the Creole Queen Riverboat. We were treated to a creole buffet dinner with a lively jazz band and gorgeous views of the city (see photos below). As always, it was a very good meeting with a nice balance between informative presentations and networking between quality assurance professionals from utilities and nuclear suppliers. As Jeff Perry (Senior Project Manager, TVA) stated in his presentation on Small Modular Reactors, “QA in nuclear construction will make the difference between a project that is successful and one that is not.” An efficient and effective quality program including a robust corrective action program is of utmost importance throughout the supply chain.
Ice chunks the size of Volkswagens falling from the sky! Sounds like a Hollywood special effects scene in an action movie, right? Unfortunately, this is a real-life danger that can occur just about anywhere, but especially on wet stacks running in cold weather.
It should go without saying that ice falling from a tall stack can have damaging, even catastrophic effects on process equipment and personal safety. But with some situational knowledge and attention to design details, you can prevent ice build-up on wet-stacks before it becomes a problem.
Essentially, to operate an ice-free wet stack system, you need to properly handle the discharge of wet flue gas during prolonged exposure to cold temperatures. Units running at low loads on cold, windy days can see a dangerous icing develop from an effect called plume downwash.
Plume downwash occurs when a cross-wind at the top of the stack deflects the plume from its vertical path. This phenomenon is more likely to happen when flue gas exits at a lower velocity—like, for example, when units aren’t running at full capacity. As the wind impacts the plume, the plume is pushed downward onto the stack, causing the liquid within the flue gas to deposit on the stack’s surfaces.
And what happens when moisture is allowed to build up on cold surfaces? You guessed it—ice forms.
Ultimately, all stacks can experience downwash if wind speeds are high enough. The only questions are:
Thankfully, much of the guesswork can be eliminated by using computational fluid dynamic (CFD) modeling. CFD modeling is extremely well-suited to simulate the stack plume over a range of plant operating and atmospheric conditions to predict the potential for plume downwash. And if you haven't already identified icing with the naked eye, CFD simulations can be used to predict not only if icing can occur, but where it can form on the stack.
If conditions are right for plume downwash, the following areas are most likely to experience problems, including potential ice-buildup:
These areas are exposed directly to plume downwash, and therefore, icing in the right conditions— some more so than others. Heat tracing is often recommended for some of these surfaces to eliminate snow accumulation and excessive ice build-up, but care should be taken to ensure the drainage run-off doesn’t create a secondary icing problem.
More details about the icing potential in these areas can be found in the EPRI Revised Wet Stack Design Guideline, section 1.4.9.
According to the EPRI Revised Wet Stack Design Guideline, the potential for icing can be reduced by employing the following steps:
Any uncertainty in any of these recommendations can be discussed with our Gas Flow and Wet-Stack Design experts.
Icing can occur at below freezing conditions all winter long, every winter, creating potentially dangerous conditions for both people and property. If you're running a wet stack at a low load in cold, windy weather, icing is probably going to be a concern for you. Contact us for details and recommendations in order to ensure proper performance and reliable operation of your wet stack located downstream of a wet flue gas desulfurization system (WFGD).
And in any instances where ice is present, be careful!
As we discussed in our first blog post, there are many challenges facing the nuclear industry. One of the greatest is the current energy climate. There are many contributing factors to the general state of flux in energy production, which we would like to explore today. These challenges don’t just impact the nuclear industry, but also affect energy producers across generation types.
It may surprise you, but US energy consumption has effectively plateaued over the last 15 years. Below is a plot generated with the US Energy Information Administration Open Data Embedded Visualization Library. The EIA provides a wide range of information and data products covering energy production, stocks, demand, imports, exports, and prices; and prepares analyses and special reports on topics of current interest.
There are four sectors that are included when looking at total energy consumption. These include Residential, Commercial, Industrial, and Transportation, all of which are shown in the figure. As you can see, starting around the year 2000 the Total Energy Consumption has plateaued. The largest changes in trends have been experienced by the Industrial Sector, showinga significant decrease in consumption over that time. This is likely most attributable to a major focus on energy efficiency, which is improving consistently. There are still challenges, however, outlined in this US Department of Energy Report, which provides information on barriers to industrial energy efficiency.
The way energy is produced in the United States has changed dramatically over the last 15 years. Another plot from the EIA is provided showing the change in net generation for coal, natural gas, nuclear, hydroelectric and renewables. Each supply type is zeroed relative to its 2001 value for comparison.
It is obvious from this plot that while nuclear and hydroelectric production has remained relatively constant on an absolute basis, coal has suffered significantly while natural gas and renewables rise.
Solar Growth/Capacity Issues
Utility scale solar is the fastest growing renewable power generation source in the US on a percentage basis, as shown below. The figure shows the growth of various renewables as a percentage change from 2001.
The growth of solar, particularly in the Alden headquarters home state of Massachusetts, has been significant. Below is a plot from ISO New England showing the Projected Cumulative Growth in New England Solar Power. Starting in January of 2010, there was a minor amount of PV capacity in New England, however by 2025 they predict 3.27 Gigawatts of PV capacity.
Next week, we will continue this thread with a discussion of power prices and power storage, and how these effect the changing energy climate.