A winter visit to Austria’s beautiful capital of Vienna is a tempting prospect at any time, so the mix of desirable venue and informative conference led to an enjoyable few days in ‘the heart of Europe’, as the landlocked country is often known. The 14th International Seminar on Hydropower Plants (held at the Laxenburg conference centre just outside of the main city, as it was two years ago) was subtitled ‘Worldwide Use of Hydropower in the Future’, and below are three examples of papers that look at implementation of changes to improve specific areas of hydro power – the ecology, operation and communication.
Focusing on fish
A common concern for hydro power professionals is the effect that a project has on its surrounding environment and wildlife. In relation to the latter, the safe passage of fishlife through the turbines is a common concern – and the conference reflected this issue in the paper ‘Studies to Evaluate Delayed Mortality Associated with Passage of Downstream Migrating Fishes Through Turbines, with Implications for Future Turbine Design’, by J.W. Ferguson, D. Baldwin, H. Lundqvist, R. Peters, T. Carlson, A.N. Popper and A. Turnpenny.
The paper documents research into the ‘delayed mortality’ of fish that have travelled through turbines – the term refers not to the event of a fish dying immediately as a direct result of coming into contact with the whirling blades, but rather to the more medium/long term effects that exposure may cause, possibly leading to the fish’s demise further down the line (also known as sublethal).
The emphasis of the paper’s study was on measuring impacts on anatomy, physiology and behaviour; relating sensory system impacts to the animal’s ability to survive its environment following exposure; and relating individual fish survival to the wider fish population.
Different mechanisms that could endanger fish, and how they are monitored, are presented in the text:
• The first is a ‘strike’, which is perhaps what comes to mind immediately – the fish being hit by either a blade or stationary structures and suffering physical trauma. Many studies have been made into this mechanism, and the likelihood of turbine/fish contact is dependent on factors such as the blade’s shape, thickness and radius of curvature, along with the dimensions of the fish itself. Basic physics are well known, and conclusions as to risk and severity can be achieved with the help of laboratory testing.
• Pressure: changes in pressure for the region between the turbine’s wicket gates and exit of the turbine runner are strong, and a drop in pressure can pose a great risk to fish. There is the potential for injury to body tissues caused by a difference in pressure between an air in space inside the animal’s body and the surrounding liquid – known as barotrauma. Currently, experimental computer controlled hyperbaric chambers are used to replicate the time history of pressure changes that fish experience during turbine passage.
• Another mechanism is what is known as shear, the change in water velocity over a given distance, which occurs at boundary layers and in draft tube swirl. There have been two types of study into the effect that this phenomenon has on fish: ‘slow fish into fast water’ and ‘fast fish into slow water’, both of which can be reproduced in a tank. Unfortunately, studies are not sensitive enough to evaluate sublethal effects. It is suggested in the paper that computational fluid dynamics (CFD) could be used to better effect.
• Turbulence, the disorientating effect that being sharply dragged in different direction, is also studied. For a fish it is more common in spillways than turbines, and can result in stunning, leaving the fish vulnerable. The paper says that experimentation in this field is ‘in its infancy’, and mostly involves releasing sensors and ‘test fish’ into turbulent fish passages.
• Finally, the perhaps less obvious problem of noise. Damage from experiencing excessive noise is most likely to be an alteration of the capability or health of the mechanosensory hair cells found in the fish’s ear and lateral line. It is more common that a fish would suffer only immediate and short-term hearing loss, but, despite several approaches being used to assess the function of the ear after exposure to ‘intense sounds’, it is unclear whether such damage is temporary or permanent so this possibility cannot be ruled out.
The paper says that that the ‘subtle, yet lethal’ effects that its study reveals are shedding new light on this area of fish preservation, and hopefully the knowledge learned can be implemented by the appropriate personnel to help tackle the challenges of safe fish passage.
Operational issues
A popular subject of papers at the conference was the efficient operation and management of hydro power plants. For example, in the paper ‘Operating concept for centrally managed AHP hydropower plants and demonstration of its implementation at the Danube’, J Stickler and E Gumpenberger detail how AHP is realising the implementation of a control center-based operating concept for the management and control of its hydro plants.
AHP operates 90 hydro plants in Austria. To streamline the management structure, a hierarchical and uniformly structured management concept was developed which essentially aims to reduce the number of permanently manned power plant control stations currently in existence, optimise the internal flow of information, and expand and utilise modern information, communication and control technology.
The control centre concept and operations control point for storage power plants was as follows:
• Starting position – locally manned control stations and individual control centers.
• Target – uniformly structured control stations in line with the structure of the plant groups within AHP.
• Solution – five control centers and one operations control point with a locally integrated control center.
The five control centers had a number of different tasks including: control and monitoring of all operating equipment of the respective plant group and control of all machine units not assigned to the OCP and monitoring of building surveillance; switching operations in AHP switchyards; management tasks in special situations (eg. floods); measures relating to repairs, audits and maintenance; and data recording for reporting.
Tasks of the operations control point are: control of storage power plants according to plan that is provision of regulation reserves and allocation of available machine units on the basis of balance group management; optimisation of machine utilisation in all storage operations; coordination of measures in the event of a major fault; coordination of scheduled and unscheduled non-availability; and fault management.
The application of the management concept results in a control center with nine power plant control stations on the Danube. The centralised main control level of all Danube power plants is installed in the last Danube barrage of AHP in Freudenau power plant.
The control center (process control level I) consists of
• Centralised main control level – fully automated operation of nine power plants using control systems (level, flow and reactive power controllers) and the ancillary automated equipment in the power plants whereby the setpoints and, if applicable, commands are entered by the control center via a redundant station control system.
• Centralised emergency control level
• Manual remote control and monitoring of weir facilities and the auxiliaries system to guarantee the supply of the weir systems of all nine power plants from the control center via an autarchic visualisation system (touch panel) for each power plant with the help of the ancillary automated equipment in the power plants.
The power plant control station (process control level II) includes:
• Decentralised main control level – fully automated operation of the individual power plants using control systems (level, flow and reactive power controllers) and the ancillary automated equipment in the power plants whereby the setpoints and, if applicable, commands are entered by the power plant control station via a redundant station control system
• Decentralised emergency control level – Manual remote control and monitoring of weir facilities from the power plant control station with the help of a touch panel to guarantee water discharge and cover auxiliaries system supply.
On site control stations (process control level III) also allows manual operation and monitoring of systems in emergency and special operating situations via on-site control stations (eg. machine/unit control stations, weir control stations).
When implementing the management concept, great attention was dedicated to operational safety, and corresponding measures were carried out, says the paper.
Improvement of the direct voltage and alternating voltage supply for the weir systems and machine units was carried out. For example, redundant communication lines in power plant are laid in isolated cable routes while independent emergency control levels with separate communication channels guarantee on site process intervention in the event of extensive control system malfunction.
The paper goes on to demonstrate the water management system, with a special focus on machine utilisation under consideration of the decentralised function groups and the controller concept.
The individual power plants of the Danube chain, will, to the greatest extent possible, be fully automated in accordance with the weir operating regulation.
The individual control elements, ie the machines and the weir systems, can be allocated to the following operating modes.
• Master control, ie the control element is assigned to the primary power plant flow control system.
• Individual control, ie the control element is assigned to the manual setting of the flow setpoint.
• Manual operation, ie. The control element is not part of the control system and direct operation is possible using corresponding control commands.
The master controllers (level controller and power plant flow controller) of the automated water management system are implemented redundantly in two centrally installed automation components. The subsidiary individual controllers, in accordance with the functional group principle, are implemented decentrally in the respective automation components of the discharge elements.
The preferred operating mode is fully automated utilisation with level selection in accordance with weir operating regulation.
The level controller is designed as a traditional PI controller with feedforward control, whereby special modules use rules to calculate additional feedforward parts which take account of special circumstances in the reservoir.
To achieve fully automated operation, it is essential that machine utilisation also be automated, says the paper. For this purpose, a machine utilisation automation system will be implemented, which, depending on the inflow and the most optimal work points, automatically connects or disconnects the individual machine units from the grid.
Priorities can be assigned to the respective machines to influence the machine utilisation automation system so that the machines can be used in the fully automated mode depending on repairs and audits that are planned.
The turbine controllers, which are normally controlled by the master controllers, are linked to each power plant to an optimisation module which is fed with relevant information relating to machine states and flows.
This module has the task of optimising the output of all machine units in the power plant while taking account of the respective flow conditions by varying control of the guide vane and the runner on the basis of a static correlation when the machine flow remains constant. The cyclical optimisation runs lead to the creation of individual correlation curves which, depending on the situation, will be used to control the respective turbine controller.
When developing the operating and process control concept, safety played a central role. The safety aspect was considered at several levels of the automation project, including the enhancement of the availability of the individual plant components and the operation of these components by way of a consistent redundancy concept. Creation of functional groups also ensure that malfunctions resulting from the failure of a component will only have a limited effect on the overall process.
The paper concludes that, thanks to the hierarchical structure, the definition of the function groups with a high degree of automation, the consideration of redundancies and the provision of emergency systems, complex and widely distributed processes can be automated in such a way that they can be remotely controlled and monitored from a central location while at the same time meeting high safety requirements. Suitable operating modes and semi automatic systems for the respective plant components ensure that the operator intervention is possible thus guaranteeing that day-to-day operations can be conducted in a proper manner.
Operator intervention is possible at all times at the respective operating levels and, if required, support can also be provided by local personnel thus guaranteeing that malfunctions or special operating situations can be appropriately dealt with.
Communication is key
A particularly interesting paper presented during the event – ‘Penstock Pals: a Common Language for Hydropower Education’, by R. Stearnes and J. Femal – focused on the importance of sharing ideas and knowledge.
As the name would suggest, ‘penstock pals’ is based on the concept of letter writing between two people – pen pals. What the name also suggests is that in this case, the emphasis is on corresponding (by more modern methods of communication like email) about hydroelectric power and dams.
FWEE’s ‘Penstock Pals’ is designed to link two educational institutes, regardless of how distant the geographic location (internet access notwithstanding). A connection is established through the use of hydro power-based questions and activities, and the two classrooms can open a discussion, that often spreads to wider areas, such as social, historical, cultural and so on.
What the FWEE programme actually entails can briefly be summarised as follows. Students follow the first three units of what is known as the Nature of Water Power curriculum. Each has a title that leads to a question; the first of these is How Can Your Community Adequately Meet Future Needs For Electricity, which asks ‘what is your community water profile?’ Each set of ‘pals’ establishes this for their area and presents a summary that can be compared to their counterparts.
Unit two is named How is Flowing Water a Source of Energy?, which asks ‘Are river(s) or other waterways in your community used as an energy source?’ Things to consider here are citing evidence that the river(s) are ‘working’; taking into account the particulars of any hydroelectric facility/s; recognising if power is utilised in by any electrical generation sources other than hydro and so on.
The third unit poses the question ‘how can your community adequately meet future needs for electricity’, under the title of How Can Work Be Done With Water Power? This unit looks more to the future, considering issues such as how much electricity is needed by the region and how hydroelectricity can help with this; what choices must be made and what would the consequences of these choices be; by what means should information be collected; and how do the needs for supplying electricity differ between the two Penstock Pal groups?
In addition, the FWEE website contains various educational support resources, and includes another activity called Make Your Own Hydropower, which has its own set of considerations and includes the physical equipment to make a working micro hydro system– ideal for a science project.
The authors see FWEE’s Penstock Pals programme as an innovative and worthwhile way to educate US students into the world of hydroelectric generation, whilst at the same time using it as a means to learn about foreign communities worldwide. This broad exchanging of ideas was demonstrated by the first-ever student exchange programme in 2005, which saw students from Tacoma, US, visiting their counterparts in New Zealand, with the reverse journey taking place three months later.
Back to the future
With such papers presented, the conference proved to be an interesting and informative event. The mix of case studies and presentation of new technologies offered something for everyone, and demonstrated how hydro power is often at the forefront of developments in the power industry. The main message I took away from this conference was that the worldwide use of hydro power is likely to increase into the future.
