Tim Probert, Deputy Editor
Hydropower is enjoying somewhat of a renaissance. Orders are through the roof. Business is booming. Just ask Alstom Hydro, which has recently doubled testing capacity of its Global Technology Centre (GTC) at its global R&D headquarters in Grenoble, France, in preparation for a long boom in sales of both new hydroelectric power plants, refurbishments and other services.
The French company claims that hydropower is the world’s most important source of renewable energy, representing over 16 per cent of the global electricity production today, in turn representing just 33 per cent of the potential economic global hydropower capacity.
Alstom Hydro can boast the highest market share with over 25 per cent of global hydropower installed capacity, representing more than 400 GW for turbines and generators installed worldwide. The company is at the centre of record-breaking hydropower plants such as La Grande in Canada, with 27 turbine/generator units totaling 7843 MW, Three Gorges in China with 14 x 700 MW turbine/generator units and Itaipu in Brazil with 10 x 700 MW turbine/generator units.
By doubling its test capacity for turbines, including pumped storage turbines, Alstom Hydro expects to slash testing times and lead times. No small matter when annual sales have doubled in the past three years to €1.6 billion ($2.5 billion) led by China, which represents 50 per cent of its market.
Pumped hydropower is proving to be one of the most economic and most flexible means of storing large amounts of excess energy, and is becoming increasingly important due to the opening of international energy trading markets. In addition, pumped storage increases overall efficiency as it recovers up to 75 per cent of the energy consumed during the overall cycle. Alstom Hydro wants to capitalize on this latent demand in fast-growing countries such as India and China.
However, large hydropower plants, often seen as environmental hazards that destroy natural landscapes, have a poor reputation. But Philippe Joubert, president of Alstom Power, says times are changing. His customers’ needs for clean energy solutions that also allow them to diversify their energy production portfolio, as well as the climate change agenda, has moved the world on.
He said: “Twenty years ago when we started Alstom Hydro it was judged badly. Public opinion was against it. Now it is seen as a key part of solving climate change and I expect large hydropower [more than 20 MW] plants to become eligible for European Union Emissions Trading Scheme credits within the next decade.”
This could only enhance demand further for Alstom Hydro, which has been taking on many new employees around the world around 650, mostly young engineers to cope with the growing demand.
Pièce de résistance
Alstom Hydro’s turbine range includes Francis, Kaplan, Bulb, Pelton and Pump turbines with capacities ranging from 5 MW to 900 MW and corresponding generator capacities of up to 1000 MVA.
The extended scale model test laboratory is the pièce de résistance of the new GTC. It is equipped with six test-rigs up from four capable of simulating conditions in a hydro plant, with the most recent addition being a second pump turbine test-rig. Three types of pump turbine scale models (single, double and multiple) can be tested in both pumping and turbining mode on the vertical shaft rig.
The rig can test for a power capacity up to 450 kW, speeds up to 2400 rpm and a maximum test head of 140 m. The maximum runner diameter that can be tested is 450 mm and the highest discharge level is 1.05 m3/s.
Philippe Cochet, president of Alstom Hydro, said: “The extension and the modernization will allow us to meet customer demand more quickly while also speeding up our research on ways to improve our turbines both in terms of efficiency and environmental performance. Our GTC guarantees Alstom’s offer of clean and creative energy solutions.
Maryse Francoise, Alstom Hydro’s vice-president for global R&D and product management, and head of the Grenoble laboratory, says the ultimate aim of the GTC is to improve the capacity of their hydroelectric generators, which have a current best of 850 MW, to a round 1000 MW. Francoise says that Alstom Hydro’s extensive research covering theoretical foundations, numerical analysis, experimental measurement and field tests produces turbines designs that match perfectly specific power plant requirements.
One of the most critical steps in the hydraulic design process involves calculations, as well as the resulting computer modeling. Using calculation and software tools, Alstom Hydro simulates how the life-size turbine will operate in order to optimize turbine efficiency, overall hydraulic behaviour and the final hydraulic design.
Scale model of an Alstom Hydro pump turbine runner
These calculation tools are used to optimize the hydraulic designs for all parts of both new and refurbished turbines, including spiral case, stay vanes, distributor, runner and draft tube. Computational fluid dynamics (CFD) software simulates the flow of water through these different parts within the whole expected operating range in either pump or turbine operating mode in line with customer specifications.
Based on experience gained in this field, Alstom Hydro has developed highly accurate in-house CFD software, in addition to using the most up-to-date software available on the market.
Particular attention is paid to the hydraulic design of the runner, as it is critical to the overall performance level of the turbine. Alstom Hydro is also equipped with sophisticated 3D surface engineering tools that are fully integrated in automated optimization procedures. These tolls, referred to as ‘Genetic Optimization Algorithms’, automatically optimize the hydraulic profile using complex mathematical equations. Solutions for reducing pressure fluctuation levels within the turbine, as a well as erosion problems arising from cavitation have been identified using these tools.
Following the computer assisted optimization of the hydraulic design, a corresponding 3D mechanical design is established to evaluate the static and dynamic behaviour of the runner. If there is structural compatibility, the next step is to produce a scale model of the turbine for testing.
In the Lab: TESTing, testing
Once the turbine scale model has been manufactured, it undergoes experimental testing in the scale model test laboratory, where conditions identical to those in a hydropower plant are simulated. Both experimental and field tests are carried out to validate the forecast performance and output test results obtained from calculation methods. This stage of the hydraulic testing process provides a unique opportunity to verify the complete turbine operating range, taking into account complex operating phenomena, which are not covered in the theoretical calculation tests carried out in previous stages.
The pump turbine test rig at Alstom Hydro’s recently upgraded Global Technology Centre
This high-tech scale model test laboratory is equipped with six test-rigs capable of simulating conditions identical to those in a hydropower plant. It is a unique facility both by the number of test-rigs it houses and by its testing capacity. The addition of two new test rigs to the facility increases the maximum head size that can be tested for pump turbines to 140 m and maximum power capacity to 450 kW.
Tests on the test-rigs are carried out on either a vertical shaft for Francis, Kaplan and Pump turbines, or on a horizontal shaft for Bulb turbines.
In addition to customer contracted project testing, a considerable number of R&D tests are carried out to find new ways of producing higher performance turbines, with increased operating ranges for the future. These development tests follow methodologies and processes that go far beyond the standard design testing process.
Once optimal performance levels have been achieved and validated through the scale model testing process, the life-size turbines are manufactured in Alstom Hydro factories in Europe, Brazil, China, India and Canada. Alstom Hydro strives to build upon a level of scientific excellence by confronting theoretical models with field tests carried out at specific hydro power plants, after the equipment has been installed.
Feedback from these tests is then used to further improve turbine designs to meet market needs. Alstom Hydro also has a long history of collaboration with leading universities and other research partners around the world, conducting joint research projects and trials of cutting edge technologies.
Simulation of real-life power plant conditions
Parameters including water head, water pressure, water output and speed of runner rotation are used to simulate real-life testing conditions. The measurement of the turbine’s performance is calculated using the hydroelectricity generating principle.
In order to make a hydropower plant run one needs to have a certain head (measured in metres), representing the height the water will fall from the upper to the lower dam reservoirs, creating the water pressure. Secondly, one needs a flow of water (discharge) to rotate the turbine and thirdly, one needs a certain rotation speed to produce electricity at the network-regulated frequency.
In the scale-model test laboratory, these three conditions are simulated on the test rig using tanks to replace the upper and lower reservoirs, pumps to pressurize the water flow and variable speed generators to simulate the rotation speed.
Systematic calibration of measuring devices is carried out before each test, guaranteeing the viability of test conditions and the accuracy of results. Using weighted water tanks, flow meters are regularly controlled and timed to gauge the speed of water flow in parallel to the test-rig closed loop system.The test-rigs are designed to carryout closed loop tests on vertical or horizontal turbine scale models for the full product range.
The scale models being tested include all hydraulic parts of the turbine (all wet surfaces), including spiral case, stay vanes, distributor, runner and the draft tube, all of which have been produced on a scale of between 1:5 and 1:30, depending on the project. Model tests carried out cover aspects such as cavitation, stability, hydraulic thrust and dynamic forces.
The Universal turbine test-rig
This is described as a universal test-rig because of its capacity to test different types of turbine scale models, those on horizontal shafts such as the Bulb and those on vertical shafts such as Francis and Kaplan models.
This test-rig can handle a power capacity up to 250 kW, for speeds of up to 2400 rpm, with maximum test heads of 10 m for Bulb, 16 m for Kaplan and 40 m for Francis models. The maximum runner diameter that can be tested is 520 mm for Bulb and Kaplan and 420 mm for Francis models, with the highest discharge level at 2.5 m3/s.
Bulb and pump turbine testing
Alstom Hydro can boast one of the highest capacities for Bulb scale model testing in the industry. The dedicated Bulb test-rig can test for a power capacity up to 150 kW, for speeds of up to 2500 rpm, with maximum test heads of 10 m. The maximum runner diameter that can be tested is 520 mm and the highest discharge level is 1.4m3/s.
The most recent addition to the global test laboratory is a second Pump turbine test-rig. Three types of Pump turbine scale models (single, double and multiple) can be tested in both pumping and turbining mode on this vertical shaft test-rig.
The Pump turbine test-rig can test for a power capacity up to 450 kW, for speeds of up to 2400 rpm and a maximum test head of 140 m. The maximum runner diameter that can be tested is 450 mm and the highest discharge level is 1.05 m3/s. This test-rig is also sometimes used to test Francis scale models.
Overall quicker testing
Each test-rig is equipped with state-of-the-art measurement and instrumentation tools. Test results are retrieved using highly efficient data acquisition and processing hardware. This computer hardware, which is constantly updated, is located in high-tech control rooms, one of which is dedicated to each specific platform. The scientific precision level of the ensuing laboratory test results has an inaccuracy level of between 0.2 per cent and 0.3 per cent.
The new acquisition systems have been implemented to record more than 50 parameters simultaneously, compared with less than 20 in the past. Overall testing time is thus reduced because more tests can be carried out quicker. Using these new systems, the monitoring of additional dynamic parameters is made possible providing increased feedback on turbine behaviour.
The hydropower market has grown 40 per cent in recent years and is forecast to maintain this high level for sometime to come. With its new, improved GTC, Alstom Hydro appears well placed to play a key role in providing access to energy to populations who previously without it.