Strengthening the Swiss electricity grid with copper and brains

Switzerland has set an important course in terms of energy policy in recent months. Since the Swiss electorate clearly approved the move away from fossil fuels with the Climate Protection Act in summer 2023 and also clearly confirmed the Electricity Act for the rapid expansion of renewable energies this year, the net-zero target has now also been enshrined in law: Switzerland will no longer produce any additional greenhouse gases by 2050 at the latest.

To achieve this, it must electrify transport and heating systems, compensate for the phase-out of nuclear power and cover the increasing demand for electricity with hydropower, photovoltaics and wind power. The future of energy in this country will therefore also be climate-neutral, renewable and electric.

No energy transition without a strong power grid

If Switzerland relies increasingly on photovoltaics and wind, the grid will have to balance out the fluctuating production of renewables at all times and adapt to demand. However, the existing grids are not designed for this. A lack of grid capacity therefore quickly leads to bottlenecks.

"That's why our grids need to be expanded and converted in line with the growth in renewables," says Christian Schaffner, Head of the Energy Science Centre (ESC) at ETH Zurich. Without a strong and flexible grid, electricity from renewables simply cannot be integrated. "This makes the expansion and conversion of the electricity grid unavoidable," says Schaffner.

So how well equipped is the Swiss electricity grid for the energy transition? The question first goes to Gabriela Hug. She is a professor of electrical energy systems at ETH Zurich and heads the Energy Science Centre (ESC). "We have to differentiate between the transmission grid and the distribution grids in Switzerland," says Hug.

Well networked in the neighbourhood

As a transit country for electricity, Switzerland has a strong transmission grid, for which Swissgrid is responsible. At this highest grid level with the extra-high-voltage lines, the country is very well connected with neighbouring countries and integrated into European trade. The planned voltage increases will strengthen critical lines.

Around two thirds of the 6700 kilometre transmission grid is currently between 50 and 80 years old and will need to be replaced in the coming years.

However, Hug sees a need for action above all in the lower grid levels. "Decentralised solar power from the roof of the house and electric cars in the garage mainly place a strain on the local low-voltage grids," says the electricity grid specialist.

The energy transition is taking place in the distribution grid

Most photovoltaic systems and heat pumps as well as all electric cars are operated on the lowest grid levels, the low-voltage or distribution grid (220 to 400 V). However, these grids were not designed for a dynamic decentralised electricity feed-in.

Nevertheless, distribution grids are now increasingly connecting seemingly synchronised generation systems with powerful consumers and feeding ever larger flows of electricity in and out. If a lot of photovoltaic power is generated, overvoltage occurs locally, while higher load consumption by heat pumps and electric cars leads to undervoltage. In both cases, local overloads can occur in the grid. And that costs money.

Turhan Hilmi Demiray knows the problem only too well. He heads the Energy Networks Research Centre (FEN), which deals specifically with issues relating to the Swiss energy sector at the ESC. This summer, Demiray co-authored a study for the Association of Swiss Electricity Companies on the need to expand and modernise distribution grids.

"Our analyses of more than 60 supply areas have shown that there is the greatest need for action in the expansion and conversion of the distribution grid, albeit to very different extents," confirms Demiray. This sometimes depends on the typology of the grids, i.e. whether they cover urban, rural or peri-urban areas, but also on the individual expansion standard, which makes it difficult to make generalised statements.

Flexibility avoids grid expansion

"We currently have a lot of projects with distribution grid operators. And they all want to know how to plan their grids cost-efficiently for the future," says Demiray. There are two approaches to grid reinforcement: copper and Grips.

Copper stands for traditional grid expansion: laying new lines in the ground, reinforcing cabling and transformers as in the past. This is expensive, but effective and sometimes unavoidable. Grid operators often orientate themselves to the maximum load and oversize physical projects - this makes grid expansion even more expensive.

Grips stands for intelligence and flexibility: Digitalisation and smart concepts for controlling electricity flows play a decisive role here. Limited feed-in from photovoltaics and reduced load peaks from heat pumps and electric vehicles combined with grid-friendly home batteries ensure flexibility. This stabilises the electricity grid and substantially reduces expansion costs.

Coveted sources of flexibility

However, the principle applies to the entire electricity grid: if production here typically fluctuates from minute-by-minute to seasonal, the grid must become more flexible on these time scales.

Demiray explains: "Batteries, pumped storage, alpine storage lakes and seasonal heat storage for the winter are then ideal balancing resources. But smart grid approaches for intelligent grid and consumption control and the full integration of Switzerland into the European electricity market are also essential resources that will ease the burden," says the electricity grid specialist.

In a highly regarded study commissioned by the federal government, the Energy Grids 2022 research centre examined the security of supply in the electricity sector in Switzerland and Europe. The analysis showed that three aspects are decisive for Switzerland's security of supply: Flexible electricity production from hydropower, electricity trading (imports in winter), and the very well integrated electricity grid with Europe. "These are very valuable sources of flexibility," says

In the SFOE-funded external page SWEET-PATHFNDR project, ETH researchers from the ESC are working with utility companies and municipalities to find ways to make the best possible use of flexibility options, digitalisation and sector coupling.

In this context, they are also investigating the extent to which e-mobility could contribute to the flexibility of the Swiss electricity grid - for example, if e-cars are charged when sufficient electricity is available. Dynamic electricity prices could help to set the right incentives.

The power grid needs both: copper and brains

Demiray summarises: "The smarter and more flexible the electricity grid, the better it can balance out peaks from sun, water and wind, and the less physical grid expansion it needs."

You can't replace it completely. "Even if we utilise all the flexibilities, there will always be a need for expansion," says Hug with a grin.

"The Swiss electricity grid itself is well suited to function for a future electricity system. But it needs investment in both the physical expansion of the grid and in new control concepts. Both are important," says Schaffner.