Harnessing Hydropower – Amazing Potential helping to Face the World’s Increasing Demand for Energy
Uwe Wehnhardt,Chairman of the Management Board, Voith HydroRenewable energy is undoubtedly the most sustainable answer to the rising energy demands. And hydropower plays a key role in sustainable and environment-friendly power generation from regenerative energies.
Hydropower is the leading renewable source of electricity generation globally, supplying 72 per cent of all renewable energy in the worldwide electricity mix. In summary, one can say that hydropower is renewable, reliable, affordable and beneficial for both economic and social development.
In 2015 renewables accounted for more than half of all the new electricity generation capacity globally for the first time. Reaching 1,064 gigawatts of installed capacity in 2016, hydropower generated 16.4 per cent of the world’s electricity, taking all sources into account. In comparison, a typical power station generates one gigawatt of power (one billion watts). The Hoover Dam hydropower plant in the US produces two gigawatts and the Three Gorges Dam in China holds the record for the most powerful hydropower plant on earth generating more than 18 gigawatts.
But this is just the current picture. By 2040 power generation from renewable energies will increase to a third of today’s total energy production. Hydropower will play a major role in this, as the worldwide hydropower generation will increase as well. In addition, hydropower offers the possibility of storing electricity. In this way, it can balance the power grid with high flexibility.
What is the secret of hydropower? It is the very efficient and CO2-free transformation of the mechanically stored (by nature) energy in water into electrical energy – first by the turbine into the mechanical torque of the machine’s shaft, and then through the conversion of shaft torque into electrical energy by the generator.
There are three types of hydropower stations which can be used to exploit the energy stored in water. First, there is the ‘run-of-river’ power station, where the electricity is generated from flowing water in a river. Second, there is the ‘reservoir’ energy source, where power is generated through the release of stored water. This traditional power station uses a dam to store river water in a naturally fed reservoir. A third model is the ‘pumped storage’ power plant, where stored water is recycled by pumping it back up to a higher reservoir to be released again. These types of hydropower plants provide energy for a base load operation as well as sufficient flexibility for quickly balancing power and ensuring system adequacy during periods of low production from renewable sources.
The world’s increasing demand for energy
It is no secret: the world’s demand for power is increasing. And it is not only the rise in industrial production which is rising the world’s energy demand. Take the current use of the internet as an example. Within the next two years – according to the estimates of an international software manufacturer – over one half of the world’s population will have access to the internet. Today it is only about one third.
This ongoing development is accompanied by increased usage intensity – the buzzword being ‘data streaming’. In the very near future, as early as 2019, approximately 80 per cent of the requested data volume will be the streamed data. Transmitting bytes across the internet, accounts for the bulk of energy usage and emissions when streaming videos. The increase in streaming will foreseeably increase the demand for energy and this means that we are facing a big challenge. Today, the annual average total power consumption of the human world already amounts to 1 terawatt (one trillion watts).
Using unexploited potentials at every scale
The hydropower facilities installed today vary in size from less than 100 kilowatts to more than 18 gigawatts. They are equipped with individual turbines with up to 1,000 megawatt capacity each. Voith has been a leading supplier of this technology since the very beginnings in 1870 and has been advancing the technology ever since. More than ever before, the challenge will be to build an infrastructure that delivers power to homes and businesses reliably, and also utilize the unexploited power potential across the world.
In most of the highly-developed countries the potential of technically usable hydropower is far from exhausted. Countries such as China and Brazil are the role models for improved power exploitation. China operates the world’s largest hydropower plant (Three Gorges Dam, 18,200 megawatts) and a series of large-scale plants like Xiluodu and Baihetan (approx. 12,000 megawatts). With a population of 250 million, Brazil is the most populated and economically powerful country in the southern hemisphere and it generates nearly 80 per cent of its electricity from this source of energy. So it is no surprise that it also has one of the largest hydropower plants in the world (Itaipu, 14,000 megawatts). All these power stations clearly demonstrate that hydropower has proven its usefulness and reliability, serving countless millions of people over the decades.
Today, there are many opportunities for hydropower development throughout the world and although there is no clear consensus, estimates indicate the availability of more than 10,000 terawatt hours per year of unutilized hydropower potential worldwide. A household of three consumes 3,000 kilowatt hours of power on average every year. Hence the unused potential could serve 3.3 billion households.
“Small hydro plants safeguard local and stable power supply”
But it is not only the world’s large dams that are under-unexploited. Ten thousands of existing weirs and smaller dams as well as locks and weirs could be used for hydropower generation. Small hydro plants safeguard local and stable power supply. Often, they are the only way of producing environment-friendly power. Voith is an innovator of small-scale hydro solutions and is involved in the most promising technical solutions to open up this unexploited potential. For example, the StreamDiver, a very compact turbine-generator unit, allows power to be generated at locations where conventional plants are not viable for economic or ecological reasons. It reduces costs by making use of innovative plant layouts and can be integrated easily into existing weirs and dams without gravely interfering with the environment. Voith has developed an environment-friendly solution characterized by an oil-free operation, a submersed power unit as well as a low visual and noise impact.
At the end of 2015, the leading hydropower generating countries were China, the US, Brazil, Canada, India and Russia. But the enormous potential for power generation in African countries is also being tapped. An engagement of the energy sector in Africa can result in economic and social benefits. The access to electricity is a precondition for increasing industrialization, which in turn is a prerequisite for prosperity. The appropriate location of industrial and commercial enterprises depends on an adequate power supply. At present, several very promising large-scale projects are under way in the Democratic Republic of the Congo and Liberia: they are both new power plants as well as modernization and restoration projects. Additional potential is to be found in the sub-Saharan African countries such as Angola, Cameroon and Ethiopia. The hydropower which is technically exploitable in Africa amounts to approximately 473 gigawatts. Today, the installed turbine power generates 31 gigawatts.
High efficiency, high payback
Of course, the construction of power plants is a major investment – and not only in Africa where funding is still a serious problem. Nevertheless, when viewed over the entire lifetime of the equipment installed, the operating costs are quite low. The installations are automated and standardized to the greatest degree possible. They have been designed for long lifecycles and the maintenance requirements are low. This means that investment costs can be amortized more rapidly. Compared to other renewable energy sources, hydropower will continue to be a cost-effective solution for growing energy needs. Taking the overall life cycle into account, it is important to keep in mind that hydropower offers the lowest cost of all energy generation forms and its long-term return is among the highest. Furthermore, hydropower offers an excellent, and in most cases, the best energy payback ratio.
Technically seen, the efficiency of hydropower turbines has reached an optimum of 95 per cent, which makes it the best performer among all other sources of electrical energy production. There are several reasons for this outstanding efficiency. Most important are the physical properties of water. Its combination of density and viscosity allows for comparably low flow velocities and as a consequence small losses in the hydraulic turbine. Furthermore, water in hydropower applications is cold compared to, for example, thermal power plants, thus energy losses due to heat transfer along the water ways do not occur.
But hydropower is far more than physics. The automation technology has entered the world of hydropower plants a long time ago. Electrical components go hand in hand with the mechanical parts. Now that the digital age has arrived, the level of digitization in hydropower will further increase and change it on the fundamental level. Digitization will also play a vital role in the energy sector in general – it will change the energy market.
Major advantage: storage capability
There are two important challenges which have not been adequately considered in the discussion about renewable energies: a sufficiently flexible electricity grid when the renewable power generation through wind and solar is very high. Another challenge is stabilizing the system if little energy is being generated by renewables. Against this background, pumped storage plants are the backbone of the energy transition. They are important for the successful implementation of the energy transition not only in Germany and Europe.
Pumped storage power plants are vital for the secure, sustainable and cost-effective supply of renewable energies. Their technology supports an even more efficient use of wind and solar power, permitting renewable energies to be available at any time of the day and making power supply stable and quantifiable. In total, pumped storage plants are eminently suitable for compensating fluctuations between power surpluses and power shortages. They offer the flexibility and fast reaction needed in order to reliably and quickly counterbalance inconsistent quantities of power and varying energy demands.
Pumped storage plants are a well-proven technology. Today’s modern pumped storage plants need only thirty seconds to start from a standstill and are the only system able to store energy on an industrial scale like a battery. For this reason they contribute significantly to regulating and stabilizing the power grid. This special combination of storage system, reserve power and flexibility makes pumped storage plants true multi-functional power stations for ensuring system adequacy.
“Hybrid projects signify a major step forward in the use of renewable energy, as they balance the fluctuations of power demand and supply and ensure system adequacy”
The fact that pumped storage systems can be coupled with other sources of renewable energy is another great benefit. As already mentioned, electricity is not always generated and consumed at the same time. Fluctuations in the electricity grid occur at all times. So-called hybrid plants, for example a pumped storage system with wind or photovoltaic units, will generate reliable and affordable electricity in the future. One project for hybrid plants was initiated in Germany: a natural energy storage plant combining the pumped storage hydro-electric power station with a wind farm.
The principle behind this hybrid plant with Francis turbines (total output of 16 megawatts) being used, is simple and ingenious: if there is a surplus of power, the pumped storage power station switches to pumping mode moving water from a lower reservoir to the higher storage basin in the wind towers. If the demand for electricity in the grid rises, more electricity is generated by the turbines within seconds and fed back into the electricity grid. In this way, hybrid projects signify a major step forward in the use of renewable energy, as they balance the fluctuations of power demand and supply and ensure system adequacy.
Hydropower is renewable, reliable, affordable and good for economic and social development. Its storage and base load capabilities as well as the low carbon dioxide emissions make hydropower a valuable resource in achieving current climate targets. Moreover, hydropower is versatile and offers great unexploited potential in highly industrialized countries as well as in emerging or developing regions such as Africa. The demand for pumped storage power plants will continue to grow worldwide as they pave the way to increased use of renewable energy sources. The great challenge will be the use of fluctuating renewable energies in the face of the world’s increasing demand for energy, as the use of the internet and data streaming rises and industrial production increases.
About the Author
After studying industrial engineering at Esslingen Technical University, Uwe Wehnhardt held various positions at major international companies such as Procter & Gamble or Alfred Kärcher, where he had worked abroad for a few years. He joined Voith in 2007 and has been a Member of the Management Board of Voith Hydro since 2011. Since 1 January 2016 Mr Wehnhardt has been a member of the Corporate Board of Management and Chairman of the Management Board of Voith Hydro.