The six main basics of hydropower

Water is the cleanest and most efficient energy source for electricity generation. It is therefore no coincidence that hydropower forms the backbone of Switzerland’s electricity supply, with a share of almost 60 per cent of the country’s electricity mix. With these six basics, we’ll turn you into a hydropower expert.  

Basic No. 1 – Base energy vs peak energy

Countless devices and systems need electricity 24/7. Base energy is the electricity that is produced constantly to cover basic demand. In Switzerland, this vital coverage is ensured by run-of-river power plants and nuclear energy.

Peak energy, on the other hand, is the electricity that is produced to cover anything above and beyond the basic requirements. Flexible storage and pumped storage plants ensure that your hair is in place in the morning, your coffee is hot, and your TV drama in the evening is not interrupted. These power plants can be connected quickly, and they even continue producing electricity after sunset and during wind lulls. 

Basic No. 2 – Run-of-river power: maximum efficiency

Run-of-river power plants are among the most efficient power sources. Like all hydroelectric power plants, they are also great for the environment as they don’t produce any carbon emissions. What’s more, their efficiency is an impressive 94 per cent. This figure indicates what proportion of the supplied energy is converted into the desired form of energy (i.e. electricity). Commercial solar cells achieve an efficiency of up to 20 per cent, while wind power has an efficiency of nearly 50 per cent and a gas-fired combined-cycle power plant can reach up to 58 per cent.

Overall, Swiss run-of-river power plants have a capacity of 4,132 MW and produce approximately 17,800 gigawatt hours (GWh) of electricity per year. This means that all of Switzerland’s run-of-river power plants together cover almost a third of the country’s electricity demand (2021: 58,100 GWh).

Along the High Rhine, between Schaffhausen and Birsfelden (Basel-Landschaft), eleven run-of-river power plants with an installed capacity of around 830 megawatts (MW) generate an average of 5 terawatt hours (TWh) of electricity per year.

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Basic No. 3 – Pumped storage power plants: effective protection against blackouts

Pumped storage power plants (PSPP) can take the form of massive structures like the Limmern PSPP (Glarus), or they can be rather inconspicuous like the Wägital power plant (Schwyz). They perform three important roles:

a) Grid stabilisation: The power grid must not exceed or fall below a frequency of 50 hertz. Pumped storage power plants put their pumps into action when unpredictable energy sources such as solar and wind feed more electricity than usual into the grid or when demand suddenly plummets. A lot of electricity is needed to pump water to a reservoir at a higher altitude. By extracting excess electricity from the grid, pumped storage power plants act as grid stabilisers. Grid control centres and the transmission system operator Swissgrid are responsible for maintaining the right balance. 

b) Battery function: But pumping water doesn’t just help to stabilise the power grid – the water is stored in the reservoir higher up for future electricity production. Pumped storage power plants therefore act as giant batteries.

c) Coverage during peak demand: When electricity demand increases at mealtimes, or by the time the UEFA Champions League games kick off, the pumped storage power plant releases the stored water through steep pressure pipelines to drive its turbines and generate electricity. The power plant thereby makes an important contribution to ensuring that enough electricity can be produced to cover demand at peak times. 

The huge Limmern pumped storage power plant is highly flexible. The four state-of-the-art machines in the heart of the Glarus Alps can be controlled individually and are capable of switching from pumping to electricity generation within six minutes.

Basic No. 4 – Storage power plants: winter reserves against power shortages

In the Swiss Alpine valleys, over 80 large storage power plants collect precipitation and meltwater for electricity production. The reservoirs reach their highest levels in late autumn, before shorter and colder winter days lead to a significant increase in electricity consumption. The water reservoirs reach their lowest levels before the spring snowmelt.  

The risk of power shortages in winter is expected to increase in Switzerland. The plan is to mitigate this risk by accelerating the expansion of renewable energy. Hydropower will play a key role in this. If Switzerland manages to store more water in the future, it will be better able to use its own resources to counteract winter power shortages. Under the guidance of the federal government, existing dam walls are to be raised where possible. Axpo is actively supporting this expansion.

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Basic No. 5 – Axpo: Switzerland’s biggest hydropower producer

Axpo generates more electricity from the renewable and CO₂-free resource of water than any other electricity company in Switzerland. At present, Axpo fully or partially owns around 60 hydropower plants in Switzerland, with a total capacity of over 4,000 MW. The company (including CKW) thereby produces around eight terawatt hours of electricity per year from hydropower.

Overall, Swiss hydropower plants generate an average of around 37,172 gigawatt hours (GWh) of electricity per year, accounting for almost 60 per cent of all electricity produced in Switzerland. Hydropower is the backbone of Switzerland’s electricity supply.

However, it is important to note that the substance and thus the production of hydropower can only be maintained in the long term with sufficient investment. The federal government estimates that approximately CHF 30 billion will need to be spent nationwide on renewing and maintaining hydropower plants between 2010 and 2050. At the same time, the expansion of hydropower is being hindered by stricter residual water requirements. The Swiss water management association anticipates that hydropower generation will drop by around 10 per cent by 2050. 

Basic No. 6 – Hydrogen goes digital

The concept of hydropower is incredibly simple: collected water drives a turbine, which in turn produces electricity through a generator. The basic approach and the ‘hardware’ haven’t changed much since the first power plants were built over 100 years ago.

Due to digital advancements, however, the ‘software’ has become more powerful. Modern data management makes it possible to perform calculations and trend analyses to optimise electricity production. Key information is accessible in real time through a web app on mobile phones. Last but not least, digital tools also facilitate precise planning of maintenance intervals for hydropower plants.

Drones and robots are employed in areas that can’t be reached easily by humans. An indispensable part of this is having a reliable mobile-based infrastructure that serves as a stable platform for digital expansion. With ‘Hydro 4.0’, the transformation process at Axpo is in full swing.

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