The original article can be read as “Schlumpfs Grafik 113” in the online Nebelspalter of 27 May 2024.
An ETH study was recently published on the subject of energy security in a CO2-neutral Switzerland (see here). Andreas Züttel, who is a professor at the Swiss Federal Institute of Technology Lausanne (EPFL), thus supplements and expands on an earlier study on the same topic (see here). In contrast to the first study, however, this time Züttel’s research team also includes the option of nuclear power in the calculations. And lo and behold: among the technically feasible options, the electricity generation costs of nuclear power plants are the cheapest.
What is important:
– A new study by ETH assumes that Switzerland will cover its entire energy consumption with renewable energies by 2050.
– To generate the additional electricity required for this, eight new power plants the size of the Gösgen NPP are needed in addition to the existing sources.
– Each of these model power plants must be able to supply electricity on demand at all times.
– Of all the technically conceivable options for green electricity generation, hydropower, biogas and nuclear power are the most financially favorable solutions.
The study assumes that Switzerland’s entire energy consumption will be electrified as far as possible by 2050. With the exception of aviation kerosene, all fossil fuels (oil, gas) will be replaced by climate-neutral electricity sources. In addition, the electricity from the nuclear power plants still in operation today must also be replaced. The following chart shows this substitution process, presented in monthly values of consumption and production:

The chart on the left shows the status quo in 2019, while the chart on the right shows what the mix will look like after electrification in 2050. The improvements in technical efficiency resulting from electrification alone will reduce Switzerland’s total energy consumption per year from 232 to 156 terawatt hours – even if consumers’ final energy requirements remain unchanged.
A Swiss energy system independent of electricity imports
In both graphs, consumption is shown as a black curve at the top. The differently colored bars show the cumulative electricity production of the various sources per month. The status quo of 2019 on the left shows that more electricity was generated in Switzerland in summer and less in winter than was needed, resulting in net exports and imports. The graph on the right shows the future energy model of this study, which was designed to result in a small electricity surplus in each month – in other words, the study shows what it will take for Switzerland to be energy self-sufficient by 2050.
The mix of energy producers in the study model (right-hand diagram) shows, from bottom to top, first the fixed contributions from aviation kerosene (purple) and from six power plants the size of Gösgen (gray). The electricity from these power plants is mainly used to replace the fossil energy that is lost (brown in the left-hand graph). Above this solid band energy base of bio-kerosene and electricity from six power plants are flexibly deployed energy sources: Hydropower (river power plants light blue, storage power plants dark blue) and biomass from wood (green). This means that production is adjusted to consumption in winter, when there are gaps due to solar power (yellow), and in summer, when there are solar surpluses.
“Power plant” means reliable power generator on demand
For this to be possible, the researchers assume that the following adjustments are made by 2050 (symbolized in the top right-hand diagram):
- Photovoltaic expansion on sensibly usable roof surfaces (plus 21 terawatt hours compared to today)
- Expansion of biomass to 20 terawatt hours (plus 5 terawatt hours)
- Expansion of hydropower storage capacity (plus 9 terawatt hours)
- Green kerosene from palm oil (23 terawatt hours, imported from abroad)
According to the study, the 53 terawatt hours per year still missing after the implementation of these measures will be generated by the six power plants the size of the Gösgen NPP. This refers to an imaginary model power plant that has an output of one gigawatt and is capable of reliably supplying electricity at all times. The study examines in detail which climate-neutral energy sources can be used to generate this electricity in Switzerland. Züttel et al. come to the conclusion that, in principle, seven types of power plants are possible in Switzerland:
- Hydropower plant with reservoir (HYD-S)
- Hydroelectric power plant on the river (HYD-R)
- Thermal power plant with combined cycle (THERM)
- Nuclear power plant of the future generation (NUC)
- Photovoltaics with pumped storage hydropower plant (PV-HYD)
- Photovoltaics with hydrogen production and storage (PV-H2)
- Conversion of biomass into synfuel (BioSF)
Not enough pumped storage capacity for solar energy
For each of these types of power plant, all the necessary energy conversion steps are shown, which are later decisive for the cost calculation. The next graphic shows an example of the “photovoltaic with pumped storage” power plant type, which is central to our energy transition:

Based on electricity from photovoltaics (or wind), batteries are needed for day/night storage on the one hand and a pumped storage plant for seasonal storage on the other. According to Andreas Züttel, the operation of a single power plant of this type would require a pumped-storage power plant with which half of the water from Lake Zurich could be pumped into Lake Sihl in the summer and then drained and turbined again in the winter. However, the volume of Lake Sihl is around 40 times too small for this, and the people of Zurich would probably not like the idea of emptying half of the lake: This type of power plant is therefore not possible here for capacity reasons.
Solar power costs at least three times as much as nuclear power
Let us now turn to the costs that the researchers have calculated based on the technical requirements of energy conversion at today’s prices. The next graph shows the production costs of the various types of power plant in Swiss francs per kilowatt hour of electricity generated:

The graph shows two values (orange and blue) for each type of power plant, but these only differ where power plants have to be combined with storage. For the PV-HYD and PV-H2 photovoltaic variants and the BioSF synfuel solution, the orange value shows the costs with day/night storage only, and the blue value shows the costs including seasonal storage. With the assumed seasonal storage for three winter months, the blue value is included in the total price with a share of 25 percent. This is shown with a black bar.
Solar power combined with hydrogen or synfuel is six times more expensive than nuclear power
The power plant types are listed from left to right in the order and with the symbols as I have shown them above. In addition to these seven domestic types (Swiss cross symbol), there are three variants to the right with imports of hydrogen, synfuel and synfuel from palm oil.
Thanks to the helpful idea of the “Bandstrom” power plants, all these electricity prices can now be compared without any ifs and buts. This shows that the price of electricity from hydropower, from a biogas-fired thermal power plant and from a future nuclear power plant is less than eight centimes per kilowatt hour. At 24 centimes, the photovoltaic variant with pumped storage (which does not work) is three times as expensive as nuclear power. And storing solar power with hydrogen (44 centimes) or synfuel (47 centimes) costs six times as much.
Conclusion: A major expansion of hydropower beyond the expansion of storage by 9 terawatt hours, as already assumed in the study, is completely illusory. The only economically viable options are the thermal power plant and the nuclear power plant. However, the thermal power plant also falls away because there is not enough arable land in Switzerland to produce bio-oil or biogas. The nuclear power plant option is therefore the favorite, but the legal ban on new construction must first be lifted: The road to a reliable and climate-neutral energy future is therefore still paved with many obstacles.
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