In this first-ever international product and technology guide, we present data on how several companies are helping owners of hydro plants and dams manage their facilities and maximize efficiency.
By Gregory B. Poindexter
Hydropower represents about 80% of the world’s installed renewable power generation capacity, according to the International Energy Outlook 2016. As such, the power source is a key ingredient in the world’s commitment for developed and developing countries to reduce greenhouse gas emissions in the coming decades.
A variety of methods are needed to efficiently manage and expand uses of this incredible resource. New software development for hydropower control and monitoring applications is essential for this industry, as well as hardware that is applied at projects in innovative ways.
HRW-Hydro Review Worldwide has identified new technologies; hardware that is in development, testing or deployment; and innovative applications for existing methods. What follows are short descriptions of each product and information on case studies and practical applications.
Cavitation monitoring software
Voith Hydro’s HyConMD cavitation monitoring module has been tested in Switzerland, Norway, Canada and Germany in seven hydropower plants that include 210 MW Wallsee-Mitterkirchen owned and operated by Verbund Hydro Power GmbH, according to Voith.
Two recently completed case studies from operational hydropower facilities and turbine prototypes indicate the HyConMD cavitation monitoring module provides reliable online information about the cavitation behavior of a hydraulic machine. Cavitation potentially limits the operational range of hydraulic turbines. It causes noise and vibrations and can even erode the surface of turbine components.
The monitoring system consists of a set of robust high-frequency sensors and amplifiers, a high-speed data acquisition and signal processing unit, and an analysis software module.
|The HyConMD cavitation module monitoring system can help prevent runner erosion.|
The sensors can be attached from the outside to the turbine.
Based on the measured acoustic emissions and commonly available machine data such as rotational speed, the software module calculates a characteristic value classifying the state of cavitation (no, acceptable, strong, severe). A key advantage of the method is the fact that no individual calibration of the system is necessary. This allows the user to assess the cavitation in different machines independent of machine size and speed and, most importantly, without prior knowledge of machine characteristics.
Both long-term and short-term observations are possible, each giving important insights into the machine behavior and providing directions for the operation of the machine. The instantaneous or short-term data can be used for an optimization of the operating range, while a long-term evaluation of the signal supports an individual, condition based adjustment of the revision intervals.
Seal management system
Wartsila’s REvolution digital management system can revolutionize sealing technology for hydropower customers. It incorporates machine learning, predictive modelling and model predictive control (MPC) techniques to provide hydropower plant owners and operators with intelligent, real-time active management of the sealing interface fluid film (pressurized water interface), minimizing wear and removing the turbine sealing components from the maintenance schedule critical path, the company says.
The application of advanced control techniques enables modern mechanical face seals to overcome operational issues such as excessive leakage and degradation of wearing components. Both are caused when the off-design-point operation of the seal occurs. This can be transiently, such as during start up or shut down conditions when the hydrodynamic lubricating film of a traditional mechanical face seal degrades and asperity (abrasive) contact occurs, or it can be a result of debris or abrasives entering or possibly occluding the interface.
The adaptation of a balanced mechanical face seal to incorporate an optimally controlled injection of clean lubricating water directly into the sealing interface mitigates excessive interface wear, eliminates abrasive contamination and optimally manages leakage. An adaptive MPC is used to manage the pressure and flow of the injection fluid. The analysis and predictive control action yields optimal sealing performance and can balance costs associated with leakage, wear and maintenance.
|The REvolution system collects performance data, including seal interface wear and pressure.|
The REvolution system combines the Wartsila REguard (a pump guard) mechanical shaft seal technology with a control and monitoring system package that includes pressure, flow, temperature and wear sensors within the seal.
Seal performance data are fed into a central controller running proprietary data analysis and control software. This enables the modification of the seal interface injection pressure in real-time. Data are accessed via a supervisory control and data acquisition system that can also operate as a standalone system.
The application of advanced digital controls and data acquisition provide the capability of optimizing performance throughout the seals’ entire operating envelope. The collection and use of historical data collected during operation through monitoring, local analysis and logging of the seal operating conditions enables real time predictive wear forecasting, which enables optimal maintenance routines.
Dam facing geomembrane
Carpi Tech B.V., established in 1963, works with geomembrane scientists and formulators to deploy watertight, flexible polyvinylchloride (PVC) geomembrane for specific site application. Carpi watertight geomembranes provide waterproofing and protection of all types of hydraulic, civil, underground and environment protection structures.
Typically, Carpi uses its patented geomembrane mechanical anchorage system and acts as a specialty contractor to install exposed PVC geomembrane on the upstream face of a dam.
Since 2006, Carpi has performed extensive research to adapt geomembrane systems for new installation and rehabilitation for several types of dams that include: roller-compacted concrete, concrete faced rockfill, rockfill, earthfill, thin arch, multiple arch, buttress, and gravity.
Carpi geomembrane installation can be performed in dry conditions and underwater, when dewatering is not an option.
A case study indicates an innovative use of the system in waterproofing the upstream face of the Nam Ou 4 Dam in Laos. The study, “Nam Ou VI: Geomembrane Face Rockfill Dam in Laos,” was presented at the 2015 Australian National Committee on Large Dams conference.
|The longevity of this patented system is one a the main benefits of Carpi geomembranes.|
The system is being constructed as part of the 1,156 MW Nam Ou River basin project. The entire river basin project will feature seven dams and powerhouses with projected installed capacity of 1,156 MW and annual generation of 5,017 GWh. The project is in the provinces of Phongsaly and Luang Prabang, and the total cost is expected to be US$2.8 billion.
According to Carpi, the Nam Ou 4 scheme includes an 88 m-high geomembrane faced rockfill dam (GFRD), which will be the highest GFRD in Laos. The only element providing watertightness to the dam is an exposed composite PVC geomembrane, installed according to an innovative design now being increasingly adopted to construct safe rockfill dams at lower costs.
The liner is a composite geomembrane (geocomposite), SIBELON® CNT, comprising a watertight PVC geomembrane that can withstand elongation exceeding 250% of its original shape and an anti-puncture geotextile heat-bonded to the geomembrane during manufacture.
Carpi geomembrane systems have been tested by the U.S. Army Corps of Engineers, Hydro-Quebec in Canada, the Technical University of Munich in Germany, and Italy’s Istituto Sperimentale Modelli E Strutture, which many in dam safety and the hydropower industry consider a top hydraulic research institute.
Ultrasonic flow measurement
Ultraflux has tackled accurate flow measurement at hydropower facilities (i.e., better than 1% accuracy) in tough hydraulic conditions (e.g., insufficient straight length). These applications used up to eight ultrasonic chords, and in some cases required the installation of probes inside pipe where external access for use of insertion probes was not possible. The resulting precision flow measurement was used to calculate turbine capacity.
Ultraflux installed products for hydropower generation applications in France and all over the world, including: Brazil, South Africa, Morocco, Georgia and in the UK. Ultraflux has been tasked with installing multi-chord ultrasound flow meters on existing pipes that have 1,800 mm to 2,700 mm diameter and, in one case, pipes exceeding 7,000 mm in diameter.
|Ultraflux is able to install probes for pipe diameters up to 10 m.|
In the South African hydroelectric plant operation for four penstocks at 7.4-m in diameter, the measurement system installed by Ultraflux uses clamp-on probes to regulate the plant’s flows and protect against the risk of flooding in the valley. The project combined an acoustic transmission test using a portable flow meter and SE 1599 probes in direct configuration that helped optimize system application.
Ultrasonic flow measurement is one of the technologies that still has the potential for improvement and growth.
The company says it is able to: offer system analyses and diagnostics to customers on site; measure speed over several [pipe] sections so that the various flow speeds can be taken into account; provide controlled and reliable measurements to reduce uncertainty about flow dynamics; mount probes under load; and allow for consistent repeatability of applications throughout entire projects.
Hans Kuenz GmbH specifically developed its floating bulkhead technology for the needs of Verbund Hydro Power GmbH in Austria. The power producer was seeking a system for some of its hydroelectric facilities that could be used to dewater spillway gate bays to allow for inspection, without the need for major civil work rehabilitation or new construction.
The floating bulkhead system is comprised of individual modular components that are “floated into place” to enclose the area being dewatered. The system Kuenz designed for Verbund Hydro was used for operation at the spillways of the 12 m-high by 143 m-long Mixnitz Dam and the 19 m-high by 53 m-long Moetschlach Dam, both located on the Mur River in Bruck an der Mur, Styria, Austria.
In creating the technology for Verbund Hydro, Kuenz says it now has the ability to develop multiple construction kits applicable to address varied spans and heights of intakes, affording choice to hydro project owners.
|The Kuenz floating bulkhead system can be floated in for use.|
The elements are lowered by a mobile crane upstream into water before being floated in place in front of the gate bay. Once all bulkhead elements are mounted, the bay can be dewatered.
The floating bulkhead system’s main advantages are:
- System’s elements can be lifted directly from the shore into the reservoir because they are floatable, negating the need for relatively large gantry-type cranes;
- Construction kit can cover several different types of intakes;
- System is designed for temperatures between minus 20 degrees Celsius and 40 C; and
- Expected lifecycle of system components is more than 70 years, according the European Standard DIN 19704.
Because it is not possible at the Mixnitz Dam spillway to remove the bulkhead gates using a gantry crane, the floating bulkhead system resulted in a dewatering mechanism of the gate bays with minimal civil work modification, which helped reduce overall on-site costs.
Verterra Energy is developing the Volturnus, a modular hydropower, 3 m-diameter, low-profile vertical-axis riverine turbine-generator that has a capacity of 5 to 10 kW.
The company has received three U.S. utility patents and eight foreign fillings, including within the European Union. The pioneering patent issued for this technology was issued on July 16, 2013: Turbine System and Method United States (U.S. 8,487,468 B2).
Volturnus uses the power of flowing water to generate electricity and the company says its units have minimal impact on the environment.
The device has a patented vertical axis design that allows it to operate in water at depths of less than 2 m. Its design includes the use of a parapet – a low protective wall – along its upstream edge that allows the Volturnus to deflect and self-clear debris, which is ideal for reliable operation in man-made canals and rivers.
The company has designed, developed and built three generations of prototypes over the past five years. Verterra is in talks with four cities in the U.S. and international project developers in Italy, Haiti and Tajikistan.
|The low-profile Volturnus unit has a capacity of 5 to 10 kW.|
In September 2015, the company tested a 0.5 m-diameter scale prototype in the Crow River in Rockford, Minn., and a manmade canal. The testing was performed in multiple locations over the course of six weeks. The overall water depth ranged from 20 to 30 inches with the depth over the lip of the device varying between 3 to 7 inches. Verterra saw between 29% and 50% coefficient of power depending on water velocity, as calculated by the forward swept area of the low-profile riverine turbine-generator component, which is significant.
The device recorded nearly 32% efficiency in a 1.1 meters per second (mps) flow with turbine rotation approaching 100 rpm. That velocity range of 0.5 to 1.1 mps for the scaled-prototype is the equivalent of a commercial scale turbine in flows of 1.5 to 2.5 mps.
Volturnus, V-PODS with a nameplate capacity of 50 kW each, will be deployed modularly – scaling up to 1 MW with 20 V-PODS. This is analogous to the solar industry in which solar panels are deployed in arrays rather than as one large and costly unit.
Gregory Poindexter is associate editor for HRW-Hydro Review Worldwide.