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.
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.
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.
In the last installment of this series, we discussed energy demand, energy supply, and the impact of the rapid growth of solar power on changing energy sources. Today, we continue with the effects of power prices, the importance of power storage, and offer some conclusions.
Price of Power
A significant portion of the United States electricity markets is split into hubs. Each hub is an independent energy market in which supply and demand set the price of electricity on a real time basis. A map of United States hub zones is shown in the following figure.
Daily electricity demand is primarily based upon the time of day and climate. As shown in Part I, more electricity is used during daylight and evening hours than night time. Very cold or very warm weather can add demand due to heating and cooling. Additional constraints on fuel costs and available supply add an extra layer of complexity. The cost of environmental mitigations for coal fired power plants, the lack of sufficient natural gas supply in certain markets like New England, and the recent addition of large amounts of intermittent renewables adds significant uncertainty and instability to real time power pricing. If supply exceeds demand in certain electricity hubs, negative power pricing can even occur.
These factors combine to create wide price swings in the cost of real time open market electricity pricing, as shown in the following plot from ISO New England. The figure shows the five minute open market pricing for the New England Hub for 03/02/2017. Prices for this day varied between -$150.13/MWh and $71.93/MWh.
For energy sources that have a high capital cost to construct and a marginal ability to throttle energy output in real time, highly volatile real time energy markets with negative pricing periods create a large amount of uncertainty. This uncertainty in the future price of markets makes new and continued investments in large power generating infrastructure unattractive.
In order to limit the impact of our changing energy demand and production, energy storage will need to be a major priority going forward. One major type of energy storage is hydroelectric pumped storage. This is a process by which water is pumped to a higher elevation during periods of high output and low demand, to be later sent through hydropower turbines to produce energy during peak demand periods. Alden has previously covered pumped storage on the blog so check that out for more information.
Massachusetts has an Energy Storage Initiative which intends to promote and support energy storage within the state. Late last year the state released the State of Charge, a Massachusetts Energy Storage Initiative Study. If the full length report seems daunting, there is an Executive Summary available which gives a good overview of the problem and some of the policy goals to help foster power storage in Massachusetts.
We have provided an introductory look into some of the factors that affect the changing energy climate in the United States. As we discussed in our first blog post, nuclear plants are facing major challenges with many shutdowns on the horizon. These closures will continue to change the landscape of how power is produced in the United States. Optimal solutions to this problem will need to include the growth of renewables and the next generation of nuclear, coupled with significant amounts of power storage if we are going to avoid the continued dependence on carbon emitting power options. Let us know in the comments below if there are any particular items you would like us to expand upon in future posts!
Recognition and Sources
All of our plots above came from either the US Energy Information Administration or ISO New England. They both have a wealth of information and we highly recommend you check them out if you are interested more information on these topics.
Special thanks to Will Fay for his assistance in the development of this post. He works in our Hydraulic Modeling and Consulting Group and is directly involved in Massachusetts power generation as an owner and operator of three hydropower plants.
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.
In June 2016, the Alden Quality Assurance department attended the annual NUPIC (Nuclear Procurement Issues Committee) vendor conference for the third year in a row. NUPIC is an organization that provides a cost effective method for NRC (Nuclear Regulatory Commission) licensee's to maintain their approved suppliers lists by sharing audits of suppliers. The vendor conference is an opportunity for utilities, suppliers and regulators to get together and discuss current issues which impact the processes of purchasing and supply of nuclear components and services. This annual event has been beneficial for Alden QA to stay abreast with current nuclear quality issues and to maintain a high quality product for our clients.
The NUPIC vendor conference is hosted each year by a different utility and in addition, the NRC sends representatives and holds a workshop on vendor oversight at the conference every two years. The 2016 event was hosted by Ameren in St. Louis, Missouri at a hotel adjacent to the Jefferson National Expansion Memorial (U.S. National Park featuring the Gateway Arch and Old Courthouse, see photos). Conference topics included an update on new nuclear plant construction, updates on NUPIC initiatives and activities, maintaining independence during internal audits, common audit findings, and nuclear safety culture. One particularly interesting presentation last year was given by Kenneth Koves of INPO (Instutite of Nuclear Power Operations). Mr. Koves talked about ways to improve nuclear safety culture including; making sure to step back and look at the big picture, the importance of human factors and remembering that you don't "fix" people, the importance of communication including communicating the "why" of a particular situation, listening is often more important than telling, and planning (you have to go slow to go fast). He also made sure to point out that completing a checklist does not mean you have accomplished anything other than completing the checklist! Copies of the presentations from the conference can be found on the NUPIC site (https://nupic.com/NUPIC/Home/HotTopics.aspx). The NRC workshop topics included commercial grade dedication, the development of guidelines for the implementation of 10 CFR Part 21, dedication of design and analysis software, and the expanded recognition of the ILAC accreditation process. Copies of the presentations from the workshop can be found on the NRC site (https://www.nrc.gov/reactors/new-reactors/oversight/quality-assurance/vendor-oversight/past/2016/).
Gateway Arch & Old Courthouse in St. Louis, Missouri